Patient Safety Emphasized at ASA Meeting:
Patient Safety Emphasized at ASA Meeting: Exhibits
Letter to the Editor :Capnography Book Correction
Prototype Workstation Has -'Expert Alarm'; Computer Finds Error, Flashes Warnings
Letters to the Editor: Vaporizer Safety Statement Draws Fire
APSF Awards Four 1989 Patient Safety Research Grants
Letter to the Editor : Questions Raised About Leaving Patient During Competing Emergency
ASA Panel Examines Future of Safety Research
Letter to the Editor: N.Y. Rules: Needed Reform
Canadian 4-Center Study Targets Patient Outcome
Extubation by PACU Nurses Stirs Major Reader Debate
Ability to Reintubate Should be the Key
The Elusive Disconnect Alarm Examined
by Bradley J. Narr, M.D., Mark A. Warner, M.D. and Stephen J. Allen, M.D.
The October meeting of the American Society of Anesthesiologists in San Francisco included several scientific and poster sessions on patient safety and risk management. These sessions included abstracts which discussed equipment, epidemiology, drugs, and various forms of monitoring. A brief summary of some selected presentations concerning patient safety is given here.
Dr. B.D. Spiess from Chicago presented data detailing the hemodynamic changes which occurred in a high risk group of patients during autologous blood donation. The use of autologous blood transfusions for patients undergoing elective surgery has increased due to public awareness of transfusion related infectious diseases. Dr. Spiess in concert with his local blood banking services sought to provide monitoring during blood donation for these patients, a high percentage of whom had significant cardiovascular disease and were on intensive medical regimens. He showed that blood donation could be done safely in the vast majority of these patients. He emphasized the expanding clinical role of contemporary anesthesiologists to assist in providing the safest cooperative service, with blood bankers, for autologous blood collection.
Dr. H.A.T. Hein from Temple, Texas, reviewed his survey of hospitals and ambulatory surgery centers to assess their ability to handle an acute, fulminant malignant hyperthermia reaction with dantrolene. Using the criteria of a stock of 12 ampules of dantrolene within five minutes of the operating rooms, he found that 9.3% of hospitals and 48% of ambulatory surgery centers were incapable of handling an initial malignant hyperthermia treatment. He further speculated, utilizing the data from his study, that the cost to supply every unsupplied operating suite and ambulatory surgery center in the United States would be approximately $229,000. Utilizing data from the Center for Disease Control study on premature mortality in the United States, Dr. Hein estimated that the rapid and efficient treatment of malignant hyperthermia with appropriate amounts of dantrolene would potentially result in a significant reduction in years of potential life lost, up to the equivalent of IO% of the mortality from diabetes mellitus or COPD. He concluded that at a relatively low cost these facilities could be equipped to prevent these fatalities and that increased efforts should be undertaken to provide the drug for treatment of malignant hyperthermia in all surgical facilities.
Dr. L.E. Teller from Philadelphia presented her study on the nasopharyngeal insulation of oxygen to prevent hypoxia in apneic patients. After anesthetic induction and muscle relaxation with succinylcholine, a 36 French nasal airway was passed and within it an 8 French catheter was passed 2 cm beyond the tip with subsequent insufflation of oxygen at 3 liters per minute. Patients were monitored with pulse oximetry. None of the patients who had nasopharynpal insufflation of oxygen with this technique had a saturation below 98% during the entire ten minute apneic study period. Dr. Teller stated that the mechanism was most certainly similar to that of apneic oxygenation. She stated that this technique might be used while teaching laryngoscopy, maintaining oxygenation during an anticipated difficult intubation, or during various other laryngoscopic exams.
Dr. D. R. Westenskow of the University of Utah presented the concept of "expert alarms" and autopilot in an anesthesia workstation. Dr. Westenskow tested an expert alarm system which, via a central display, flashed a diagram of the failed component in the anesthesia system and one of 43 possible alarm messages. The expert alarm system was tested to see if it properly identified 26 different critical events during multiple different anesthetic situations. He found that the expert alarm system did correctly identify 619 of 660 simulated critical events. He found that the workstation expert alarm system produced more information and encouraged more rapid diagnosis than did the more routine oxygen, carbon dioxide, and high and low pressure monitor alarms. He stated that the system needed further refinement to correct several problems that he found during this testing. A goal of this work is to improve the accuracy of alarms from an anesthesia workstation.
Dr. G.L. Gibby from the University of Florida presented a computerized Doppler system for standalone real-time monitoring of venous air emboli. A computerized monitor that utilizes pattern recognition analysis of Doppler signals was developed. This was tested in an animal model. The detection of venous air emboli was I 00% for all bolus sizes above 0.025 cc/kg. Dr. Gibby found that automated analysis of the Doppler signal was far more sensitive than end-tidal C02 or pulmonary artery systolic pressure He felt that such a system might be of benefit during high risk procedures either standing alone, or as an adjunct to more common monitors.
Dr. H.G. Jense from the Medical College of Georgia presented data on the effect of obesity on safe duration of apnea. Study patients were divided into groups based on comparisons of actual to ideal body weight (IBW): normal (within 20'/o of IW, obese (>20% over IBW but within 100 pounds of IBW), and morbidly obese (>I 00 pounds over IBW). Patients were preoxygenated and denitrogenated, then anesthetized with pentothal and paralyzed with succinylcholine after appropriate measures were taken to assure that the airway could be maintained. Time to 90% Sao2 was recorded. Her results demonstrate that time to desaturation varies inversely with greater obesity. She advised that awake intubation should be considered in morbidly obese patients who present for emergency procedures.
Dr. G.A. Fromme from the Mayo Clinic presented his study on the incidence of arterial desaturation In patients discharged from postanesthetic areas has been well demonstrated that patients may have arterial desaturation during transport from the OR to the recovery area and that the use of supplemental oxygen during transport and in the recovery area alleviated desaturation. Many of these patients do not, however, receive oxygen during transport to their hospital rooms despite the fact that many will receive oxygen once they have arrived. Ninety three patients undergoing a variety of procedures were followed with pulse oximetry during routine transport without oxygen to their hospital rooms; of these, 27% desaturated to Sao2 < 90% during transport while breathing room air. Dr. Fromme advised that patients with Sao2 <95% while receiving oxygen in the recovery area should be transported with supplemental oxygen.
Dr. M.A. Warner of the Mayo Clinic presented examples of the use of sentinel event analysis to discover common etiologies of major perioperative morbidities from his institution's large data base. These examples were taken from observations made prospectively on over 150,000 patients during a 30-month period. Specifically, he identified 65 cases of documented intraoperative pulmonary aspiration and 46 cases of intraoperative pulmonary edema. Common but unusual etiologies for several of these cases demonstrated the utility of a data base and continuous review of unexpected morbidities.
A number of papers dealt with the incidence of perioperative complications associated with a number of factors including type of anesthesia, the extremes of age, as well as the outpatient setting.
Dr. C. Ringsted from the University of Copenhagen reported the results of a retrospective nonrandomized study concerned with the association of postoperative pulmonary complications (POPC) and type of anesthesia. They divided the patients into groups based on age, presence of pulmonary disease, and whether the surgery was minor or major. Regardless of stratification, general anesthesia was associated with a three fold increase in POPC when compared to regional anesthesia.
Dr. M.P. Hosking from the Mayo Clinic retrospectively investigated the effect of general vs. regional anesthesia on the long term survival of patients >90 years of age undergoing either total hip arthroplasty (THA) or transurethral resection of the prostate (TURP). They found no difference in either outcome or incidence of major morbidity between the two anesthetic techniques. More importantly, they found excellent overall outcome of these very aged individuals undergoing surgery and anesthesia. Ninety-five percent of their 188 patients were discharged alive from the hospital and exhibited normal short and long term survival compared to nonsurgical age and gender matched population cohorts.
Dr. C. Bell from Yale University reported the re-suits of a prospective study of perioperative problems that occurred in a pediatric service. They divided the children into three groups based on age: <1 year, 1-2 years, and 21 0 years. They found that age had no effect on the incidence of perioperative complications. Generally, the highest incidence of complications in the post-anesthetic recovery unit were in patients undergoing ENT procedures regardless of age.
Dr. B. Gold and colleagues from San Francisco studied patients who underwent unanticipated admission to the hospital following outpatient surgery. They compiled the reasons for admission as well as the impact of certain factors. About I % of all outpatients were admitted with the most common reasons being pain, excessive bleeding, and vomiting. The use of general anesthesia was associated with a 5.8:1 chance of admission compared to other forms of anesthesia. Similarly, laparoscopy, lower abdominal surgery, OR time < I hour, and a > I hour drive home were each associated with a greater chance of admission.
Completing the studies of perioperative problem, Dr. M. Warner presented his group's retrospective analysis of the outcomes of 25,534 ASA I and 52,266 ASA 11 patients requiring anesthetic care between 1985-87 at the Mayo Clinic. Six percent received monitored anesthesia care (MAC). There was no in-hospital mortality in the ASA I patients. There were 14 deaths (0.03%) in the ASA If group; however, none of the deaths were related to anesthesia. They concluded that with the routine use of pulse oximetry and mass spectrometry, anesthesia related mortality in healthy patients is < 1:75,000.
Dr. D.M. Gaba from Stanford University, noted for his development of an anesthesia simulator, presented the response of anesthesia trainees to problems during a simulated anesthetic. The presented problems included endobronchial intubation, kinked W, atrial fibrillation, circuit disconnect, as well as cardiac arrest. Both the time to detection of problem as well as the time to correction were noted. In this study, lack of vigilance was not a factor as re-cognition that a problem existed was reasonably quick. However, the trainers did less well in instituting definitive, expeditious correction. Compliance with the ACLS guidelines for CPR was poor. This study points out the need for a more structured approach for teaching clinical anesthesia problem solving and the likely utility of simulators in this effort.
Dr. R.A. Kaplan from the Virginia Mason Clinic presented a study based on an analysis of the ASA's Closed Claims Database. The authors divided 1,000 cases into four groups classified as to high or low severity of injury and whether or not care had been judged appropriate. They then sent 48 case summaries (I 2 from each group) to 42 anesthesiologists who had participated in the Closed Claims Study and who represent a broad range of experience, practice, and geographical background. The authors asked these anesthesiologists to rate the cases as to appropriateness of care. The subjects were more likely to label care less than appropriate if the patient receiving that care had suffered a severe injury. This tendency of severity of injury to impact judgment of appropriateness of rare has obvious implications in medicolegal proceedings.
Drs. Narr and Warner (Mayo Clinic) and Dr. Allen (University
of Texas-Houston) moderated the sessions concerning patient safety and
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by John H. Eichhorn, M.D.
Patient safety was again a prominent theme of the technical and scientific exhibits at the San Francisco 1988 American Society of Anesthesiologists (ASA) annual meeting.
Among the products displayed by manufacturers of supplies and equipment, there were few genuinely new ideas. Rather, the emphasis was on new variations and combinations of established technology, especially oximetry and capnography.
Thirty-one manufacturers exhibited pulse oximeters for sale in one form or another. Size, shape, and features varied widely, but the function was universal in its application. There were several versions of "data management systems" that organize patient and monitoring information in a manner believed to facilitate interpretation and faster response to clinical developments.
Among the new products seen was a calorimetric C02 detector intended to verify the correct placement of an endotracheal tube by showing a color change when the device is attached to a newly inserted tube through which expired gas flows. Intended only for single-patient use, these are relatively expensive at about $15.00 each and seem to be primarily intended for non-OR use in places where capnography would not be available (such as in an ambulance).
Also displayed was an intracardiac Doppler device intended to give a continuous reading of cardiac output and a waveform of ventricular contractility. This complemented several other ultrasound-based cardiac output devices.
Two manufacturers offered instruments to determine hemoglobin, hematocrit, or both in the operating room using a simple system utilizing a drop of patient blood. Such measurements by anesthesia personnel are likely to be easy and very rapid.
One anesthesia machine manufacturer offered for the first time a "vigilance audit" preventive maintenance program in which the anesthesia machines covered would be certified annually as functioning correctly and in compliance with standards.
Automated anesthesia record keeping devices continue to advance, with new programs for trending, analysis, and review of captured data.
Among the scientific exhibits were several presentations of automated/computerized anesthesia quality assurance programs. One focused specifically on the PACU. There was an illustration of the application of telemetered pulse oximetry for a hospital general medical ward. One display concerned non-invasive cerebral oxygenation monitoring and another demonstrated an endotracheal tube introducer that simultaneously insufflates oxygen while measuring exhaled carbon dioxide. One major display dealt with a computer simulation of clinical anesthesia situations and featured new graphic animations and a system to analyze errors in judgment by the subject training on the simulator.
Dr. Eichhorn, Harvard Medical School, is Editor of the APSF Newsletter.
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Safety Progresses Worldwide; Assistants Play Key Role in Practice
American anesthesiologists should be aware of the great strides in the development of anesthesia patient safety in many other nations. Particularly noteworthy are the Australian undertakings described in the last issue of the APSF Newsletter, as well as the recent publication in Britain, "Recommendations for Standards of Monitoring by The Association of Anesthetists of Great Britain and Ireland '" It should also be noted that the Netherlands was probably the first nation to have promulgated standards for monitoring and that currently, significant development in safety is being undertaken in Germany and France.
In my view, one the most important methods for improving safety in anesthesia is the utilization of anesthesia technical assistants as described for both the United Kingdom and Australia in the September, 1988, APSF Newsletter.
In my own departments, we have had one assistant for every four operating rooms for a number of years and, in as much as temporally possible, the assistant is present during induction of anesthesia to help with application of cricord pressure, taping of the endotracheal tube, positioning of the patient and providing knowledgeable assistance when there is equipment failure. As in the United Kingdom and Australia, qualifications do vary. The usual route to becoming an anesthesia assistant with us is through movement from an operating room aide into the position, with on the job training and a study period at one of the anesthesia machine manufacturer's technical schools.
The rationale for such personnel is clearly described in the guideline, "Minimum Assistance Required for the Safe Conduct of Anesthesia," from the Faculty of Anesthetists of the Royal Australian College of Surgeons (September, 1988, APSF Newsletter).
In addition, in our departments, the technicians have been trained in assisting with blood transfusion management in patients with large blood loss, as well as providing knowledgeable assistance during other crisis periods. They also greatly improve efficiency in anesthesia scheduling and turnaround time. It should be stated, however, as was done by Dr. Greg Purcell, Chairman, N.S.W. Regional Committee, Faculty of Anesthetists, Royal College of Surgeons, "An inadequately trained assistant, perhaps without commitment and insight into what is happening may be more of a liability than a value."
Anesthesiologists should stress to their operating room and hospital administrations the important role these individuals play in furthering anesthesia patient safety. In 30 years of anesthesia practice, I can recall a great number of times when these hospitals employees were a major factor in preventing a significant negative outcome during an anesthesia management problem. The time for anesthesiologists to be treated differently than surgeons and other physicians in their needs for assistance has long gone
Ellison C. Pierce, Jr., M.D. President, APSF
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To the Editor:
In the September, 1988 issue of the AIISF Newsletter, Dr. Kupeli reviewed Capnography in Clinical Practice. I take exception to Dr. Kupeli's statement that this monograph is the "only current text on the subject". An educational program also entitled Capnography in Clinical Practice (Puritan-Bennett Corporation's Vita Series) has been commercially available since 1983. The objectives of this program are to:
describe the process of end-tidal carbon dioxide measurements (ETC02)
demonstrate the physiologic significance of ETE02 determinations
Show a number of clinical conditions where EM02 trending by slow speed capnography may be useful
Show some clinical conditions where high speed capnography may reveal abnormalities in carbon dioxide elimination in individual exhaled breaths.
This material provides information on "capnography and capnometry in addition to providing information concerning production and elimination of C02".
I note this in the hope that the more aware practitioner's are of educational material, the more informed they are and the safer their practice becomes. L. Robert Mogue, Marketing Education and Development Manager, Puritan-Bennett Corporation, Overland Park, KS.
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by D.R. Westenskow, Ph.D., R.G. Loeb, M.D., J.X. Brunner, Ph.D, and N.L. Pace M.D.
Editor's Note: Dr. Westenkow was a recipient of an APSF Research Grant for 1987. He reports here on a portion of his work.
An anesthesia workstation is more than just a gas machine with monitors on it. The workstation concept should help improve the safety of anesthesia by gathering data to one central location, by detecting critical events and by helping to control the delivery of anesthesia.
A prototype workstation, assembled under a grant for the Anesthesia Patient Safety Foundation, has nine pressure sensors, a pneumotach, an infrared anesthetic agent analyzer, a mainstream C02 analyzer, a polarographic oxygen monitor, a ventilator bellows position sensor, and three mass flow controllers. PASCAL programs acquire, filter and plot the data. When a critical event is found, one of the 43 heuristic rules used by the computer is employed and it actually draws a diagram of the anesthesia machine and breathing circuit to highlight the faulty component and prints an alarm message.
The prototype alarm system was tested, measuring the accuracy with which it identified 2 6 critical events. The alarm system correctly identified 94% simulated critical events. The failures occurred when the alarm system did not see fresh gas hose disconnects and an open inspiratory valve. The system did not specifically identify an "open inspiratory valve" but instead saw the "high endtidal C02". An open expiratory valve was seen as "Ventilator Failure".
The alarm system in the workstation produced alerts that are more meaningful, and more diagnostic than are the traditional oxygen, C02, agent or pressure alarms. The graphic presentation of the alarm condition and text should reduce reaction time and help in rapidly resolving critical events. The alarm thresholds are set automatically, thus averting mistakes sometimes made when setting alarm limits manually.
In the prototype workstation, the computer electronically controls the fresh gas flows to achieve the user specified fresh gas flow rate, F02 and endtidal volatile anesthetic concentration. This "autopilot" feature reached the desired end-tidal volatile agent concentration after 4.4 + 1.4 min (mean + SD). It kept the inspired oxygen concentration, within .002 vol% of the desired value. The autopilot appears to make anesthesia delivery easier to manage.
1. Loeb R, Westemkow D, Brunner 1, Feldman B, Pace N: The Utah Anesthesia Workstation. I Clin Mon 4:148-149, 1988.
Dr. Westenskow is from the Department of Anesthesiology,
University of Utah, Salt Lake City
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To the Editor:
The article "Volatile Agent Overdose is Potential Cause of Catastrophe" by R.L. Keenan M.D. (APSF Newsletter, June 1988) appears to have been written by an armchair pundit stoking our current monitoring hysteria in the name of safety.
Although the body of Dr. Keenan's article is fairly benign, his summary comments are diametrically opposed to the reality of clinical practice.
He states "in summary, volatile anesthetic gases may be administered in the absence of anesthetic gas monitoring only when the "tec" vaporizers are used in high How circle and non-rebreathing systems."
However, when "tec" vaporizers are used with any system, the maximum anesthetic concentration cannot exceed the highest dialed vaporized settings. Circuit anesthetic concentrations deviate from the dialed concentration in proportion to the size of the patient, the degree of rebreathing and inversely to the current duration of the case Commonly, in a totally closed system, the circuit concentration is far lower than the "tec" settings. Conversely, in a high flow system, airway concentrations approach the dialed settings, and an anesthetic gas monitor may then be useful in minimizing the incidence of lethal concentrations.
There is a widespread mistaken belief that knowledge of inspired anesthetic agent concentration helps in delivering an appropriate anesthetic level. This is so only when the individual patient's sensitivity and correlation between airway and brain concentration is known.
At the risk of sounding patronizing, the safest way to administer an inhalational anesthetic with any system, is to preserve the patient's physiologic responses. For example, a patient breathing halothane spontaneously through an uncalibrated drawoever or in-circle vaporizer will use his minute ventilation (which governs the amount of agent vaporized) to continuously adjust the anesthetic level commensurate with his sensitivity and surgical stimulus. Providing this system is left intact, excessive doses cannot be taken up, and monitoring agent concentration becomes superfluous.
When using other anesthetic systems, attention to clinical signs will prevent an overdose; an anesthetic monitor may compound the criticism of residents watching monitors rather than the patient. We encourage reliance on expensive monitors by using opioids and muscle relaxants, often unnecessarily, ablating valuable clinical signs of pupil size and minute ventilation. It is of little wonder that we now need yet another monitor to guard against anesthetic overdose. But then again, the trained 747 pilot who is lulled to sleep waiting for his bells and whistles to alarm should not be expected to fly an unlicensed ultralight where sagacity and vigilance are the keys to safety and exhilaration.
Hansel de Sousa, M.D. Pittsburgh, PA
To the Editor:
I would disagree with Dr. Keenan 1 that volatile agent overdosage is more likely to occur when low fresh gas flows are used. Indeed, the opposite may be true. For example, suppose the user wishes to reduce the inspired concentration of a volatile agent, but accidentally turns the vaporizer dial the wrong way so that it is in the full on position rather than off. If he is using high fresh gas flows, the inspired concentration will immediately rise to that on the dial. On the other hand, if he is using low flows, the inspired concentration will rise much more slowly giving him more time to discover his error.
This "cushioning" effect that low flow anesthesia affords is only one of its many benefits. As pointed out in another article in the same newsletter 2, low flows result in a higher temperature in the airway, an important factor in anesthetizing children.
The safety of low flow anesthesia has been demonstrated millions of times worldwide. The burden of proof that it is any less safe than high flow anesthesia must rest with anyone who makes that claim.
Susan E. Dorsch, M.D. Jacksonville, FL
1. Keenan RL: Volatile agent overdose is potential cause of catastrophe. APSF Newsletter, June, 1988, p. 13.
2. Holzman RS: Children face extra saw problems. APSF Newsletter, June, 1988, P.9.
To the Editor
In his article "Volatile Agent Overdose is Potential Cause of Catastrophe, Keenan I stated that "volatile anesthetic gases may be administered safely in the absence of anesthetic gas monitoring only when "tec" vaporizers are used in high flow circle or non-rebreathing systems." This is not necessarily correct. In fact, accidental overdosage is less likely to happen when using low flows and closed circuit, than when using high flows. Lin (2) showed that currently used (Mark III Cyprane and Dragger) "tec" type vaporizers, actually vaporized equal or lower concentrations than those shown in the dial, when the total fresh gas flow is between 0.5 and 2 1 /min.
Most cases of overdosage, including the author's series (3), have occurred when high flows were being used. Undoubtedly, continuous monitoring c)f anesthetic gas concentrations is safer than not having it, but it is no substitute for insufficient knowledge on vaporization and lack of attention by the user.
J. Antonio Aldrete, M.D., M.S., Professor and Chairman, Department of Anesthesiology & Critical Care, Cook County Hospital, Chicago, IL.
1. Keenan RL: Volatile WI overdose is Potential cause of catastrophe. IPSF Newsletter 2:13, 1988.
2. Lin CY-. Assessment of vaporizers performance in low-flow and closed -circuit anesthesia. Anesth Analg 59:359-366,1980.
3. Keenan RL, Boyan CP: Cardiac Arrest due to anesthesia. A study )f incidence and causes. JAMA 253:2373-2377, 1985.
Dr. Keenan replies:
I thank Drs. Aldrete, Dorsch, and de Sousa for their comments, many of which helpfully extend the discussion of this important issue. All three rise to the defense of low flow breathing systems. Dr. Aldrete correctly notes that delivered concentrations in low flow systems are typically lower than "tec" dial settings. Dr. Dorsch adds the useful observation that the "cushioning" effect of low flows may be a safety feature Dr. de Sousa is riot, of course, in reminding us that the maximum system concentration can never exceed the highest dialed concentration.
However, my article, which examined the place of the Copper Kettle and of gas monitoring in contemporary practice, was not meant to "bash" low flow breathing systems. Dr. Dorsch is correct; there is no published evidence that high flows are inherently safer than low flows. The issue is not whether low flow systems should be used, but whether volatile gas concentrations should be monitored when they are.
Dr. de Sousa's "armchair pundit" comment to the contrary, I have used "tecs" and "kettles" with low flow systems for almost three decades, with nothing to go on but patient response. I have also used glass syringes to squirt liquid halothane (and now isoflurane) into a closed circuit, and still do. I once did it without gas monitoring, but not anymore. I see no virtue in giving any drug without knowing what dose is being presented to the patient. Like Dr. Aldrete, I believe that knowing is always safer than not knowing; hence the necessity of gas monitoring in low flow systems.
Regarding the importance of observing patient response, of course-, I agree with Dr. Aldrete that gas monitoring is no substitute for following clinical signs. However, Dr. de Sousa would have us believe that monitors and clinical observation are somehow incompatible when he describes "residents watching monitors rather than the patient". He invokes an either/or argument which I do not accept. We cannot afford to choose between knowing the dose and following patient response. We need both, and nothing in my article argues otherwise
Richard L. Keenan, M.D., Professor and Chairman, Department of Anesthesiology, Medical College of Virginia, Richmond, VA.
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by Jeffrey B. Cooper, Ph.D.
Four Research Grant Awards totaling nearly $135,000 were announced at the annual meeting of the Board of Directors of the Anesthesia Patient Safety
Foundation in October:
1. Charles Cote, M.D. (Harvard Medical School) "A Prospective Evaluation of Combined Pulse Oximetry and Expired Carbon Dioxide Monitoring in Anesthetized Pediatric Patients." S 34,450
2. Randall Carpenter, M.D. (Virginia Mason Medical Center) "Identification of Patients at Risk for Developing Adverse Effects During Spinal Anesthesia." $30,680
3. Michael Good, M.D. (University of Florida) "Can Simulation Teach Clinical Skills?" $35,000
4. David Gaba, M.D. (Stanford University School of Medicine) "A Model Course in Handling lntra-operative Critical Incidents: Training and Practice to Prevent Anesthetic Mishaps." $34,615
Dr. Cote will be building upon his earlier work on studying the efficacy of pulse oximetry in the pediatric population. He plans to contrast the success in detecting critical events by the combination of pulse oximetry and capnography versus the absence of these two monitors. Patients will be randomized into two groups and, for the "unmonitored" patients, a trained observer win view a monitor turned away from the anesthetists, document events, and intervene according to predetermined criteria. The objectives are to examine the efficacy of the combination of the two monitors, to examine the types of events diagnosed by each, and to assess if one monitor may be superior to the other.
Dr. Carpenter's research will attempt to identify predictors of patients who are at increased risk to develop adverse side effects or complications of spinal anesthesia. A research nurse will track patient complications and the characteristics of patients who do and do not experience adverse side effects will be compared.
Dr. Good, using an anesthesia simulator successfully exhibited at several national meetings, will examine how well anesthesiology residents learn clinical skills with this teaching aid. Specifically, the investigators will test the hypothesis that residents learning on this simulator are better able to detect and correct adverse situations in the absence of monitoring instrumentation. They are addressing the concern that residents may be unable to rely solely on clinical skills if their training incorporates monitoring instrumentation. An improved patient mannequin will be a key ingredient in this effort.
Using a simulation mannequin developed by his group at Stanford, Dr. Gaba will develop and demonstrate an intensive training course for trainees and practitioners on how to prevent critical incidents during anesthesia or respond to them before patient safety is compromised. The remarkably realistic anesthesia simulator will provide the environment in which to understand and practice specific clinical skills. They will examine how well participants learn new skills from the course and whether these subjects perceive this form of training as superior to traditional continuing medical education as a means to achieve greater patient safety in anesthesia.
This is the third consecutive year that the APSF has supported investigations directed toward enhancing patient safety.
These grant awards illustrate some major foci of patient safety research in anesthesia examining the effectiveness of monitoring modalities, developing anesthesia simulators to improve skills and to examine patterns of error and identification of patterns associated with anesthesia complications and adverse outcomes.
The Anesthesia Patient Safety Foundation awards grants annually for research and patient safety. Awards are based on competing applications. An announcement of 1990 application details and deadline appears in this issue.
Dr. Cooper is Director of Anesthesia Technology, Department
of Anesthesia, Massachusetts General Hospital and the new chairman of the
APSF Committee on Scientific Evaluation.
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To the Editor:
I read with great interest pages 14 and 15 of the June, 1988 issue of the APSF Newsletter.
On page 14, Drs. Howard Zauder and Joanne Jenne answer the question as to "when, if ever, is it appropriate for an anesthesiologist to step outside the OR door for brief periods... etc?" On page IS there is a letter from a Risk Manager in a Massachusetts hospital regarding the practice of allowing Post-Anesthesia Care Unit Nurses to Extubate patients.
Drs. Zauder and Jenne are very emphatic about the fact that it is never appropriate for the anesthesiologist to leave an anesthetized patient for any reason unless replaced by an appropriate substitute. The writer from Massachusetts questioned the practice of PACU Nurses extubating patients in the recovery room.
The following incident recently took place in one of our hospitals. I have changed the names of the patients to ensure confidentiality. I would like to hear comments from Drs. Zauder and Jenne The scenario was as follows:
About 3:00 P.M., two anesthesiologists were finishing a days' work in a Single Day Surgical Facility myself and one of my associates.
In one room I was giving Monitored Anesthesia Care to a patient named "Jenne" for a cataract extraction. Mrs. Jenne was slightly sedated but awake and perfectly calm even trying to talk whenever she was allowed. In the other room a patient named "Pierce" was undergoing a laparoscopy under general endotracheal anesthesia with controlled ventilation. AU was relatively quiet until a call came from the recovery room that a patient named "Zauder" was experiencing some respiratory obstruction after having been extubated by very experienced recovery room nurses. Mr. Zauder had undergone a knee arthroscopy under general endotracheal anesthesia and had been taken to the recovery room breathing spontaneously but still intubated.
Since my associate in the next room couldn't really leave his patient with an "appropriate substitute", I asked my surgeon if I could leave Mrs. Jenne, who was actually awake and very stable, in the care of the circulating nurse, and go to the recovery room to do whatever I could to save Mr. Zauder's life. Actually, even Mrs. Jenne herself, although under the influence of sedatives, agreed I should go see what was wrong. I rushed to Mr. Zauder's side, applied some positive pressure ventilation, re-intubated him and returned to the care of Mrs. Jenne, fully confident that I had acted appropriately.
To this day, I believe I would do the same thing under the same circumstances. However, after reading the last APSF Newletter, I am beginning to wonder if it was proper to save Zauder's life in the recovery room when I really should have remained with Mrs. Jenne as long as she was in the operating room.
Miguel Figueroa, Jr., M.D. North Miami Beach, FL
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by Richard L. Keenan, M.D.
A Panel Discussion on "Needed Research in Patient Safety" attracted an audience of over 1 50 at the October ASA annual meeting. In his introduction, Dr. Arthur S. Keats of the Tom Heart Institute announced that the purpose of the Panel was to stimulate the submission of more and better grant applications to the Anesthesia Patient Safety Foundation, which awards over S I 00,000 per year in research support. Maximum support is $35,000 per year, and last year 3 of 20 applications were funded. Applications must be for applied research relating directly to patient safety in anesthesia, and, because each grant is for one year only with no provisions for renewal, proposals which could be completed within one year are considered most favorably.
"Clinical Problems" were addressed by Dr. Frederic Cheney of the University of Washington. Citing his experience with the ASA Closed Claims study, he described the high incidence of severe patient injury in malpractice actions against anesthesiologists, noting that most problems were respiratory in origin, and that most were preventable. His specific recommendations for future development include a means of predicting difficult intubation, foolproof indicators of tracheal (not esophageal) tube placement, ventilatory monitors for non-intubated patients, and predictors of sudden bradycardia and arrest during spinal as well as general anesthesia. Dr. Cheney also indicated a need for proof that pulse oximetry and capnometry really do decrease the incidence of mishaps.
Dr. William New, an anesthesiologist from Stanford who is now Chairman of the Board of the Nellcor company, discussed "Technology Questions" A major problem in the development of new technology is the fact the innovation in medicine comes from the university and not the business world, whereas in engineering the reverse is true. The trick, Dr. New believes, is to bring clinicians and engineers together. He also stressed the ',applied" nature of technologic research. Sensors and microchips are places in industry where clinicians will find exciting new developments that might be applied to patient safety.
Dr. David Gaba of Stanford addressed "Human Factors" Dr. Gaba, an active investigator in the area of simulation, observed that most mishaps involve human error. We need to study ourselves, he suggested, as well as our tools. What does an anesthesiologist do? What differentiates an expert from a novice? Better knowledge of external factors which shape performance (fatigue, environmental, psychological) is needed. Ergonomics and organizational aspects also deserve study. Problems specific to the study of human factors include heterogeneity, the fact that "we don't have Sprague-Dawley anesthesiologists". Dr. Gaba also echoed a common theme among investigators of safety: Outcome studies are difficult because bad outcomes are ram
Jeffrey Cooper, Ph.D. from Harvard, who is well known for his "critical incident" studies, discussed a "Potpourri of Research Questions". Noting the problem of small numerators over large denominators inherent in studies of mortality and major morbidity, Dr. Cooper suggested that, for all its inconsistencies and "rough numbers", epidemiology is an acceptable means of investigating anesthesia safety. A mass of data already exists in the literature which may be amenable to analysis, and from which useful information might be extracted. He suggested also that subsets of events requiring intervention to prevent damage or death can also be studied, and built into a quality assurance program as well. And perhaps the ultimate study of safety is one designed to prove whether quality assurance efforts really do work to improve safety. Accident investigation is another fruitful area of work which, while well developed in the aircraft industry, is still in its infancy in anesthesiology.
Finally, Dr. Donald Stanski, a senior faculty member from Stanford with extensive experience in reviewing grant applications for the ASA as well as the APSF, described how to get a safety grant. He noted that most applications received by the APSF in the past three years were unacceptable. Some were excellent proposals but not related directly to safety; other were meritorious projects which couldn't be completed in a year. And some were simply poorly prepared. He gave the following advice to potential applicants: First, find a mentor, a successful investigator who knows how to write a good proposal. Provide evidence that you will be successful, either by having a proven track record, or with convincing preliminary data. Make a clear statement of the importance of the study. Spend a lot of time in the preparation of the grant (Dr. Stanski suggested that it takes him six to ten months to write a grant). Finally, use what one of Dr. Stanski's colleagues calls the "mud on the wall" technique: If a proposal is rejected, keep revising and re-submitting. "If you keep throwing mud on the wall, some will eventually stick!"
In the discussion period, Dr. Cheney was asked by members of the audience whether other investigators could access the ASA Closed Claims Study data base. Dr. Cheney gave a qualified "yes". He and his colleagues would be willing to share data with other investigators, but only in a joint project.
Concern was voiced from the floor regarding possible negative liability consequences of risk studies. The panel agreed that while this might be a problem, it should not deter such studies. (It occurs to this reporter that safety studies to date have had the opposite effect; with the implementation of monitoring standards, the escalation of malpractice premiums has moderated in many jurisdictions.)
Lastly, Dr. New cited the experience in Holland, where advanced monitoring technologies have been used extensively, and where anesthetic mortality has reached very low levels. He expressed the hope that some day (assuredly not today) mortality will be so low that it will no longer be worth studying.
Dr. Keenan is Professor and Chairman of Anesthesiology
at the Medical College of Virginia, Richmond.
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To the Editor:
The New York State Regulations regarding work hours, resident supervision and anesthesia monitors are very interesting from at least two aspects. The first is that these reforms did not appear to be motivated by any compassion for the poor exhausted individual struggling to maintain some standard of quality care in the face of inadequate supervision. Rather, the motivation appears to have developed only when the problem became painfully clear in the form of poor patient outcome. What a terrible commentary on our teaching programs when they are more interested in squeezing every last bit of service from the student than in providing the best possible quality of instruction.
The second area of interest is the apparent surprise and shock that the cost of these reforms win be in the range of $200 million. For the most part, these are not new services that will have to be provided. These are services that are already provided although without compensation. So now the society that has so casually exploited the-se people in training will have the opportunity to actually put a price tag on their efforts.
New York State is to be applauded for these reforms. They demonstrate a recognition of the full responsibility of our society to train our medical people and care for our sick. In my opinion, they do not go far enough in that requiring 24 hours of continuous care is still unreasonable, although it is a start. Certainly these regulations should be made universal in the entire country.
John D. Rasmussen, M.D. Sacramento, CA
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by Marsha M. Cohen, M.D. and Peter R. Duncan, M.D.
Editor's Note: Dr. Cohen was a recipient of an APSF Research Grant for 1987. She reports here on a portion of her work.
Since mortality from anesthesia has decreased in recent years, nonfatal events have become much more important in assessing quality of care in anesthesia. Studies by Cooper (1978, 1984) looked at anesthetic "near mishaps" rather than at actual deaths or major complications. While extremely helpful, this approach cannot be used to determine the frequency of such occurrences.
Similarly, review of malpractice suits (e.g., Utting, 1979) have proven invaluable in defining deficiencies in anesthetic practices, but cannot be used to determine rates of adverse events. In addition to deaths and "major" complications, it is essential for patient comfort to determine the rate of "minor" anesthetic complications for example, nausea and vomiting, broken teeth, spinal headache and so forth as these are often an indication of poor anesthetic technique. Indeed, it is probably these " nuisance' complications that most often lead to patient dissatisfaction and contribute to medical-legal events.
According to a World Health Organization Working Group (I 985), there are several reasons to undertake a quality assurance program. The first stems from a desire for health professionals to be self-regulating to identify their deficiencies and thereby their areas for improvement. A second motive for quality assurance programs is the increasing requirement to be accountable to society for monies spent on health services and for safety to the public. In today's climate of increased expectations, the pub4c wants to be protected from harmful treatments but is also not content with inappropriate or suboptimal care. Thus quality assurance systems are needed to ensure social accountability. Last, the report suggests that quality assurance is necessary to design programs which identify problems and advance the performance of health care systems. The improvement of health care data will permit health planning to proceed based on a more adequate information base
There are three basic types of quality assurance studies those based on structure, process and outcome Donabedian (1980). In a review of the history and evolution of quality assessment programs in the U.S., Sanazaro (1980) pointed out the deficiencies of quality assessment programs based primarily on the structural and process approaches, and called for the development of methods of monitoring "the application of efficacious medical treatment and the attainment of outcomes that have been shown to be the direct results of that treatment".
The most powerful evaluation of quality care is the outcome study. This evaluates the impact on care on the patients' health status. Measures of outcome include mortality, morbidity, complication rates, infection rates and patient satisfaction (Lohr 1988). Outcome studies must have some means of controlling for patient "case-mix" such as age and sex adjustment. In a previous publication (Cohen & Duncan, 1988), we used the American Society of Anesthesiologists' physical status score combined with age, sex and emergency status as case-mix variables.
In today's medical-legal climate, there is a great need to develop outcome (quantitative) standards for anesthetic care. The Canadian Four Centre Study on Anesthetic Outcomes was designed to determine if a systematic system for surveillance of anesthetic outcomes could he developed, a system which could then be subsequently adopted for general use in most hospitals. The second goal of the study was to determine the rate of the more common adverse events attributable to anesthesia, given the advances in technology and therapeutics.
The basic program uses "occurrence screening". This means that all (or almost all) patients undergoing anesthesia are captured by the Follow-up program. For each patient undergoing surgery, anesthesiologists fill out a check-off form which includes the preoperative physical status assessment, patient characteristics, anesthetic techniques and drugs used, anesthetic monitors, and any complications occurring during the operative procedure. Anesthetists are encouraged to use the check-off items in addition to, or as a replacement for, the usual documentation.
Following the operative procedure, recovery room nursing staff record any complications which occur during the immediate postoperative recovery period. Within 72 hours (usually 24-48), a designated anesthesia nurse reviews all anesthesia records and hospital charts. Inpatients are interviewed to determine "minor" complications. The nurse also checks hospital logs to determine if deaths have occurred among surgical patients. The nurse then returns the form to the anesthesiologist for a final review and for appropriate action to be taken if needed.
After inspection by the anesthesiologists, the form is then sent for computer entry (a personal computer is used with specially designed software). A monthly report outlining patient characteristics and complication rates is then generated. This information is reviewed by the Medical Audit Committee and prints out cases for review by the committee. Parallel programs are being run in the four hospitals.
Preliminary results from the study show that after some technical problems were overcome, it was possible to set up the program in four very different hospitals, each with their own modes of operation. Some of the technical problems which we dealt with were related to the anesthesia record, compliance of the anesthetists, and hiring appropriate nursing staff.
The design of the anesthesia record was accomplished after several months consultation with several groups of interested persons. These included the anesthesia staff, the administration officers, hospital forms committees and others. After development of a prototype, the form was piloted for six months. The record had to meet the needs of the anesthetists, had to be self-explanatory and easy to use and had to be of a certain size to fit into the hospital chart at each institution. The costs of the form also had to be considered since they were somewhat more expensive than the form they replaced.
Compliance of the anesthesia staff was less of a problem than had at first been anticipated once staff were familiar with the form, compliance improved. In two hospitals, the anesthetists' billing form was part of the anesthesia record leading to improved compliance. lnservices and rounds helped to familiarize staff with the new records. Hiring of appropriate nursing staff and training took several months, but fortunately high quality personnel seemed to be attracted to these nursing positions.
Table I presents the characteristics of the four hospitals. Hospital A performed the most cases per month and the number of cases was similar in the other three centers. Hospital A had the most outpatient surgery and consequently fewer inpatients who were available to be interviewed. Outpatient charts were not accessible for review in hospitals A and B. For those patients interviewed, approximately 96 to 97% were seen within 72 hours (the time period when the majority of anesthesia-related events would occur).
The majority of cases at hospital A were under 41 years of age and were female (Table 2). Hospital B performed the most surgical procedures among the elderly. With regard to physical status, 47% of the cases at hospital A were rated as " I " (normal healthy) and hospital D had the sickest patients (10% who were ASA 4 or 5). Approximately 10% of the cases were emergency and at hospitals B, C, and D, 5% of the cases were less than 20 minutes in duration. Conversely, hospital D had 50% of its cases which were two hours or more. Hospital D also performed the most cardiac surgery (7. 1 % of cases).
Aimed at Rare Events
Thus, we are using occurrence screening to carry out an outcome study at four hospitals across Canada. While occurrence screening is probably preferable to study rare events, it may not be possible for all types of hospitals to use such an approach. The resources implicated in this type of follow-up program are not high, but still represent an investment in time and money. Approximately one full time nurse (preferably two half time nurses) are needed for follow-up. While we use data entry (and require a half-time data entry operator), possibly machine readable forms might be available in the future The forms themselves are expensive and represent an investment of resources. Finally a personal computer and someone who can operate it are needed.
The information from the follow-up prognosis can be utilized in several ways. First the individual hospital department of anesthesia could use the data to compare its performance on a monthly or quarterly basis tot hat of its performance (with regard to complication rates or resources used) in the past. Second, the system would identify any unusual patterns of complications which would alert the department to perform an investigation and either remedy the problem or institute measures to prevent the problem from recurring. Third the information ran identify cases of anesthetic related conditions which should be reviewed by the Medical Audit committee in addition to operative deaths (which tend to be the only cases reviewed by most of these committees). Last, the individual performance of any staff member could be compare-d to that of his/her peers (after adjustment for case-mix).
Our study will also help to determine if it is necessary to carry out interviews with ward patients as well as chart reviews and whether phoning day surgical patients is needed. Finally, a hospital may want to consider some combination of follow-up program with the department of surgery. If that is the case, then the optimal time for seeing patients for follow-up wig need to be determined.
Will the presence of a quality assurance program make any difference, either to patient-related morbidity or to medical-legal proceedings? Them is little doubt that documentation of success elicits pride in one's performance-, and spurs one to improve his/her attributable outcomes. However, it is not yet known if anesthetic-related complications have a minimum rate beyond which further improvements are unlikely. However, there is no evidence to date that we have achieved the ultimate standard of excellence and only sequential quality assurance surveys will confirm when that day arrives.
Cohen MM, Duncan PG. Physical status score and trends in anesthetic complications. I Clin Epidemiol 1988;41:83-90.
Cooper IB, Newbower RS, Long CD, McPeek B. Preventable anesthesia mishaps: a study of human factors. Anesthesiology 1978; 49:399AO6.
Cooper IB, Newbower RS, Kitz RI. An analysis of major errors and equipment failures in anesthesia: considerations for prevention and detection. Anesthesiology 1984;60:3842.
Donabedian A. The definition of quality and approaches to its assessment. Ann Arbor, MI, Health Administration, 1980.
Lohr KN. Outcome measurement: concepts and questions. Inquiry 1988;25:37-50.
Sanazaro PI. Quality assessment and quality assurance in medical care. Ann Rev Public Health 1980;1:37-68.
Utting JE, Gray TC, Shelly FC. Human misadventure in anesthesia. Can Anaesth Soc 1 1979;26:472-78.
WHO Working Group in the Principles of Quality Assurance.
'Me principles of quality assurance. Copenhagen, World Health Organization,
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Letters to the Editor
To the Editor:
In response to a question from Mr. Clark A. Fenn, Risk Manager of Holyoke Hospital, concerning the advisability of recovery room nursing staff extubating patients, we believe the following considerations should apply:
David J. Cullen, M.D. and Kathy Porter, R.N., Head Nurse, Recovery Room, Massachusetts General Hospital, Boston, MA.
Massachusetts General Hospital
Department of Nursing
Operating Room Nursing Service
Post Anesthesia Care Unit (PACU)
Policy for Extubation of Patient by PACU Nurses
Only Registered Nurses who have been qualified may extubate patients according to the established procedure Nurses will be qualified by the Head Nurse and Unit Teacher.
This policy will be implemented under the
I . An order must be given by a physician.
2. An anesthesiologist or their designee must be present in the unit.
3. The following patients will NOT be extubated by nurses:
A. Pediatric patients.
B. Patients who have had a difficult intubation.
C. Patients who have had thoracic surgery (i.e., tracheal reconstruction, esophagectomies, lobectomies, pneumonectomies).
D. Patients who have had upper airway, oral or nasal surgery.
To the Editor:
This is in regard to allowing Post Anesthesia Room nurses to extubate patients. In the institutions where I practice, most PAR Registered Nurses are ACLS certified. As an ACLS instructor in airway management, I emphasize the complications of extubation and instruct them in the technique of intubation. The rule is that only those that who "put them in" can take them out. To extubate the patient, the PAR nurse comes to the OR and gives a complete report on the patient's condition to the anesthesia provider. The decision is then made by that provider whether or not to have the patient extubated.
Some criteria I personally use include level of alertness, ability to swallow on command, good inspiratory and expiratory force, and the general condition of the patient. In actual practice, we have very few patients who are educated by PAR nurses. If you have nurses extubating patients, it is essential to have a policy giving strict guidelines of this procedure
Robert Laird, CRNA
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To the Editor:
The following is my personal opinion as a response to Mr. Fenn's question in the June issue of the APSF Newsletter Who Should Extubate the Patient in the PACU?
Extubation is a simple technical maneuver. The timing of extubation requires mature judgment and experience. A critical decision which the anesthesiologist must make is WHEN to extubate.
Premature extubation can eventuate in serious damage to the patient from hypoventilation, respiratory obstruction or aspiration. The decision to extubate requires professional training and experience not less than the professional qualifications to induce anesthesia and to intubate.
A patient is maintained intubated in the recovery room due to prolonged drug effect and/or medical condition. Prior to extubation, a qualified person should make an on-site determination that the condition no longer exists. Extubation by individuals lacking the appropriate qualifications can result in an increased risk for complications or in injury due to unwarranted delay in obtaining assistance when needed.
Extubation outside of the operating room should be done by the same person who is qualified to make the decision and to perform an intubation.
G. Ram Volotzky, M.D.
St. Louis, MO
An Alternate View
To the Editor:
I have heard the question discussed "Who should extubate?" since the early 1970's.
Extubation of patients in PACU should be done by the RN who is following specific established criteria approved by the Director of the Department of Anesthesia. On arrival of the patient to PACU, an anesthesiologist or CRNA should discuss with the PACU nurse any specific instructions for extubation and any intubation problem. Anesthesia should extubate patients who may have severe respiratory limitations.
The PACU nurse is expected to use professional judgment and communicate with the anesthesia person regarding any patient problems that may be encountered after they have left the room. The PACU nurse is expected to be a specialist in post anesthesia care. Not many hospitals are large enough to have an anesthesia floater available in PACU. Anesthesiologists, CRNA and PACU nurse must work cooperatively with one another and be supportive of one another.
The RN's in PACU at our hospital have been extubating patients since the early 1970's.
Utha May Morris, RN CCRN Arnarillo, TX
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by Ralph A. Epstein, M.D.
Over the last five years, the introduction of monitors which alarm unsafe conditions requiring the immediate intervention of the anesthesiologist has been largely responsible for very significant improvements in patient safety. However, along with these advances have come new dangers from an unjustified belief in the security provided by these same monitors. In part, this has been due to some confusion concerning the intrinsic limitation of such automatic devices. The confusion has even led to the misnaming of some monitors. A primary example of such a misnomer is the "disconnert alarm".
What are commonly called disconnect alarm cannot warn of all disconnects. Moreover, they may alarm in situations of no disconnect. In fact, the term "disconnect alarm" should probably be abandoned. Several different monitors are currently used in an attempt to reduce disconnect accidents. Their limitations are examined in the following discussion.
Pressure monitors: The pressure in the anesthesia machine circuit may be continuously measured and an alarm sounded if the pressure fails to reach a predetermined level periodically. This is the alarm most commonly called a disconnect alarm. There are several practical problems with this approach. First, the monitor is of little or no use during spontaneous breathing where the pressure in the circuit does not rise and fall periodically.
Second, if a disconnect is associated with an obstruction, the pressure may continue to vary periodically and the alarm may not sound. This can happen, for example, if the open end of the disconnected circuit comes to rest against the operating room table. Even the high resistance of a pediatric endotracheal tube connector, disconnected from the endotracheal tube itself, may allow sufficient pressure fluctuations in the circuit to prevent the alarm from sounding.
A problem arises in the case of certain obsolete ventilator designs which incorporate the pressure sensing point in the ventilator itself. If such a ventilator is used in conjunction with a manual selector valve which switches between the ventilator and the rebreathgin bag, no warning will be generated for the case of the selector valve being erroneously placed in the manual position during mechanical ventilation. The pressure sensing point should be as close to the airway as practical, but in any case at least as close as the absorber.
It is true that this pressure alarm, when correctly adjusted, will detect a large percent of disconnects during positive pressure ventilation. For even this to be true, the anesthesiologist must manually adjust the pressure threshold to a level which is just below the peak pressure during inspiration. This pressure will vary not only from patient to patient but even during a given case if tidal volume, inspiratory flow or pulmonary mechanics changes.
Far too often, the alarm threshold pressure is set to its lowest limit in a misguided attempt to prevent false alarms. Such a practice will predictably result in the failure to detect disconnects. Carefully and periodically readjusted, this pressure alarm is quite useful, particularly in conjunction with intelligent interpretation of the airway pressure gauge, but in no sense is it a foolproof disconnect alarm.
Expired flow monitors: A spirometer may be placed in the expiratory limb of a circle system to monitor tidal volume. Recently, units which electronically transduce flow and alarm its lack have become available. However monitors have the advantage of being useful during spontaneous breathing where the circuit pressure does not vary significantly.
However, even with total occlusion of the airway, it is possible that there may be significant flow from the compression of gas within the circuit during inspiration. If the expiratory flow alarm limit is set improperly, it may then fail to sound. Furthermore, during, spontaneous breathing, a disconnect on the machine side of either directional valve will go undetected. Finally, monitoring of flow in the expiratory limb is of limited utility in the many non-rebreathins circuits which were never designed with patient safety monitoring in mind. But most important, flow in the expiratory limb does not guarantee gas exchange First, in the case of esophageal intubation, it is possible to ventilate the stomach and have reasonably normal flow in the circuit. Second, a mechanical ventilator with descending bellows may draw in room air through a disconnect, producing a near normal flow through the spirometer.
Carbon-dioxide monitors: The capnograph is probably the single most useful monitor of ventilation and, thus, of disconnects, for it relies on the presence of carbon dioxide exchange This is particularly true if the trace is continuously displayed.
Capnography has most of the advantages of expiratory flow monitoring and suffers less from the disadvantages. For example, it can be used to help detect an esophageal intubation. Even hem there can be confusion as the stomach can contain some carbon dioxide. In general, however, with esophageal intuba6on, the capnograph will show a marked decrease in the carbon dioxide concentration over the first few breaths.
A more difficult situation arises in profound shock or cardiac arrest where there is little or no pulmonary blood flow. Here there may be no carbon dioxide exchange despite appropriate ventilation of the lungs with an intact anesthetic circuit. Despite an expired carbon dioxide level of zero, or close to zero, it would be a serious error to conclude that the patient required reintubation. Furthermore just as with expiratory flow monitors, various disconnections will so undetected in the spontaneously breathing patient.
Frank disconnects and other technical difficulties with ventilation are among the most important causes of catastrophic injury during anesthesia. Vigilance, supported by a combination of modern monitoring and display techniques, is the primary defense. However, an understanding of the limitation of our monitors is needed in order to use them most effectively.
Dr. Epstein is Professor and Chairman of Anesthesiology
at the University of Connecticut and a member of the APSF Newsletter Editorial
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Case Reports Welcomed
Case reports of "near accidents" illustrating features or principles of anesthesia patient safety are welcomed for consideration for publication in this Newsletter. Descriptions without identifiers or value judgments in standard case-report style and typed in 50-character lines should be submitted to the editor (address on the second page of each issue) by the first of the month preceding publication dates. Authors can either be credited or remain anonymous as they may desire if the report is published.
The Anesthesia Patient Safety Foundation Newsletter is the official publication of the nonprofit Anesthesia Patient Safety Foundation and is published quarterly in March, June, September, and December at Overland Park, Kansas. Annual membership: Individual $25,00, Corporate $500.00. This and any additional contributions to the Foundation are tax deductible. @Copyright, Anesthesia Patent Safety Foundation, 1988.
The opinions expressed in this newsletter are not necessarily those of the Anesthesia Patient Safety Foundation or its members or board of directors. Validity of opinions presented, drug dosages, accuracy and completeness of content are not guaranteed by the APSF.
APSF Executive Committee: Ellison C. Pierce, Jr., M.D., President; W. Dekle Rountree Jr., Vice-President; E.S. Siker, M.D., Secretary; Burton A. Dole, Jr., Treasurer; Jeffrey B. Cooper, Ph.D.; Joachim S. Gavenstein, M.D.; James E Holzer, J.D.
Newsletter Editorial Board: John H. Eichhorn, M.D., Stanley J. Aukburg, M.D., Jeffrey M. Beutler, C.R.N.A., M.S., Ralph A. Epstein, M.D., David E. Lees, M.D., Bernard V. Wetchler, M.D., Mr. Mark D. Wood
Address all general, membership, and subscription correspondence to:
Administrator Anesthesia Patient Safety Foundation
515 Busse Highway
Park Ridge, IL 60068
Address Newsletter editorial comments, questions, letter, and suggestions to:
John H. Eichhorn, M.D. Editor, APSF Newsletter; Dept. Anesthesia
Beth Israel Hospital, DA-7 1 7 Boston, MA 02215
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