Patient Safety Featured in Presentations at ASA Meeting
At the annual meeting of the American Society of Anesthesiologists in Atlanta October 22-25, aspects of patient safety were again the focus of a significant number of scientific presentations.
For example, two posters in the October 23 poster-discussion dealt with surgical techniques and their effects on the hemodynamic status of the patients. Dr. F. Miller and colleagues from the Departments of Anesthesiology of the Medical College of Pennsylvania and Hahnemann University used a transesophageal echo to observe for possible emboli during total knee arthroplasty. They questioned whether a pneumatic tourniquet could cause these emboli. In 20 patients in whom the surgeon used the tourniquet, 14 patients experienced emboli when the tourniquet was deflated. Emboli >1 cm in size occurred in 10 of these 14 patients. Of the 16 patients who did not have a tourniquet, only three demonstrated emboli during cementing procedures. This paper appears to indicate that use of a tourniquet is associated with a high incidence (70%) of large emboli. While absence of a tourniquet did not eliminate emboli, the incidence was only 10%.
In a second poster dealing with surgical technique, Dr. N. Fahmy from the Department of Anesthesiology at the Massachusetts General Hospital studied ventilatory and hemodynamic effects of three methods of removing cement during total hip revision. Sixty patients were randomly assigned to three groups: (l) osteotome, (2) high speed burr, (3) ultrasonic power tool. PaO2, end-tidal CO2, heart rate and blood pressure significantly decreased when bone cement was removed with an ultrasonic device. The other devices were associated with minimal changes. Dr. Fahmy points out that since the ultrasonic power tool is associated with high intramedullary pressure and hemodynamic and pulmonary changes reminiscent of pulmonary emboli, and since the osteotome can cause bone fractures, that the high speed burr is the best device for removing bone cement relative to potential patient complications. These two articles show not only the importance of surgical techniques on hemodynamic stability, but also the vital importance of anesthesiologists and surgeons working together to improve patient care.
Dr. P. Lee and associates from the University of Michigan found that the incidence of accidental dural puncture while administering epidural anesthesia did not vary significantly among residents over the three years of training, and averaged about 1% overall. Their data were gathered from an institu-tional quality assurance database and were possibly underreported. Dr. Wei-Te Hung and colleagues from Chung Shan Medical and Dental College in Taiwan and the University of Chicago reported on a remarkably clever combination of fiberoptic bronchoscope and a disposable laryngoscope blade used to provide instructor monitoring of endotracheal intubation by novices. Either by direct vision through the bronchoscope or use of a videocamera and monitor, the instructors were able to guide the intubation attempts and increase the success of the learners’ attempts.
Dr. P. Craigo and colleagues from the University of Chicago surveyed anesthesia residency programs to determine the provisions they made for failed intubations outside the operating rooms. Most often mentioned was needle crycothyrotomy by anesthesia personnel, followed by surgical crycothyrotomy by surgical personnel. Disturbingly, the plan for ventilation after needle crycothyrotomy was with bag ventilation in 51% of those who mentioned that needle crycothyrotomy was their plan. Fifty-six percent chose jet ventilation and one person chose passive oxygen insufflation (the respondents were able to choose more than one option). It was suggested that contingency plans are not well thought out in some programs that send residents out into the hospital for intubations.
Using a videocamera and microphone to analyze verbal interchange and compare it to the ability of expert systems to work with humans, Dr. R. Cook and colleagues from the University of Chicago and Ohio State University investigated communication between problem solvers in neurosurgical procedures. Expert systems are unable to communicate effectively with humans because of the lack of a common ground (a base of knowledge of dynamic situations that is shared by humans but unprogrammable in expert systems at present).
Dr. S. McNulty and associates from Jefferson Medical College explored the incidence of dysrhythmia caused by electrocautery in patients with right ventricular ejection fraction pulmonary artery catheters in place during surgery. They found that grounding the reference electrode resulted in a significant reduction of current through the catheter electrode and suggest that microshock hazard with this catheter would be minimized by grounding the reference electrode in patients.
More Safety-Related Posters
Dr. Y. Beilin and associates of Mount Sinai School of Medicine found via survey that the bleeding time is still frequently used by obstetric anesthesiologists prior to regional anesthesia despite recommendations that it is of no value.
The group from the University of California, Irvine, led by N. Shah, compared false alarms during patient motion between the Masimo SET prototype and the Nellcor N-3000 and N-200 pulse oximeters. The Masimo SET prototype was much more accurate during patient motion. The Masimo is not yet commercially available.
Dr. B. Inman and associates of The Medical College of Virginia found that EEG monitoring during carotid endarterectomy did not affect the incidence of post-op neurological defects nor the frequency of reintubation in the PACU.
In an effort to decrease decision-to-delivery times for C-sections, Dr. M. Souders and others of the Albert Einstein Medical Center in Philadelphia are conducting C-section drills involving persons from the nursing, anesthesia and obstetrical services. Performance evaluations are conducted after the drill. They hope to optimize outcomes in difficult situations.
Dr. E. Sia-Kho and colleagues from the New York Hospital-Cornell Medical Center cultured laryngoscope handles and blades. Even though the blades had been washed and soaked in Cidex, there was 16%-18% contamination. The handles which were not disinfected showed 60% contamination. The authors suggest that disposable handles and blades would eliminate the problem of cross contamination.
Pre- and Postoperative Visits
Drs. C. Klopfenstein, A. Villiger, J. Bolle, A. Forster, University Hospital, Geneva, Switzerland, compared a group of patients scheduled for elective surgery who received a preanesthetic visit in an outpatient setting two weeks prior to hospitalization followed by a second visit on the evening before surgery (Group A – two visits) with a second group of patients who received only the preoperative visit on the evening before surgery (Group B). Using two different subjective measures of anxiety, the group that was seen twice (Group A) had significantly less anxiety about their impending surgery (P<0.0l) when interviewed on the night before surgery (after the second preanesthetic visit) than did Group B (one visit).
In another study of the importance of the postoperative anesthetic visit, D.A. Zvara and colleagues from The Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, investigated the question: do repeated visits improve patient satisfaction and physician recognition? The investigators analyzed the impact of repeated postoperative visits on patients’ satisfaction with their anesthetic care and with the patients’ ability to recall their anesthesiologist’s name. Patients who received only one postoperative visit had a very high level of satisfaction and this did not change with two or three postop visits (on consecutive days). Regardless of the number of postoperative visits, patients still had very poor recall of the specific anesthesiologist who cared for them.
Drs. M. Lipp, M. Daublander, A. Thierbach, W. Dick, University of Mainz, Mainz, Germany, conducted a fascinating study on dependence of postoperative temporomandibular joint dysfunctions on muscle relaxants’ route and conditions of intubation. Using a randomized, controlled, partially blinded design, they examined the impact of the type of muscle relaxant and the route of intubation on the incidence of postoperative temporomandibular joint dysfunction. The authors demonstrated that succinylcholine (vs. vecuronium for intubation) and nasal (with a Magill forceps using a Macintosh blade vs. oral) intubation were associated with significantly more TMJ dysfunction in the immediate postoperative period. The TMJ dysfunctions resolved by three days postop.
Influence on postoperative hypoxemia from induction of anesthesia with thiopentone vs. propofol was reported by Drs. A. Rheineck-Leyssius and C. Kalkman, Twenteborg Hospital, Almelo and the Academic Medical Center, Amsterdam, The Netherlands. Using a randomized, prospective, double-blind design, the authors compared the incidence of postoperative hypoxemia after anesthetic induction with either of the two drugs. Anesthetic management was otherwise the same in the two groups. Induction with propofol was associated with a significantly lower frequency of hypoxemic episodes (24% vs. 45%) compared with thiopental although, otherwise, there were no differences in perioperative morbidity.
The incidence of post traumatic stress disorder (PTSD) after prolonged intensive care treatment for severe ARDS was reported by Dr. C. Stoll and colleagues, Ludwig-Maximilians University, Munich, and Department of Psychosomatic Medicine, Philipps University, Marburg, Germany. This paper described a previously unrecognized complication of prolonged ICU management. They identified all patients who had been hospitalized in their ICU for ARDS over a seven-year period and contacted all survivors (only 33%). Of these 48 patients, 44 responded to a questionnaire which allowed the authors to make a diagnosis of post-traumatic stress disorder (PTSD) according to DSMIII criteria in 23% (compared with 12% in a matched control group of postoperative patients and 0.5% in two other control groups). Note that all patients had received routine sedation during their ICU care. This study demonstrated notable implications for management of all critically ill patients.
Preoperative discomfort score predicting postoperative pain was the topic of a presentation by Dr. K. Papier, and colleagues, Wilford Hall Medical Center, San Antonio. The authors investigated the preoperative factors which might predict the magnitude of postoperative pain. After preoperative assessment, the patients received a standardized anesthetic and their pain was quantitated in the postoperative period. The factor which correlated most strongly with postop pain was preoperative anxiety.
Shorter NPO Intervals
How patients respond to proposed changes in NPO ordering practices by anesthesiologists was reported by Dr. A. McKinley and associates, Bowman Gray School of Medicine, Winston-Salem, NC. A survey was given to parents of preoperative pediatric patients regarding their feelings about and compliance with NPO orders prior to surgery. Eighty-three percent were comfortable with the traditional “NPO after midnight” prescription. However, when asked if they would rouse their children in the middle of the night to administer clear fluids, only 31% stated that they would and 49% felt that it was not “worth interrupting their sleep.”
Failure to recognize DNR orders prior to anesthesia and surgery was studied by Dr. K. Schwenzer, University of Virginia, Charlottesville. In a retrospective chart review, the author demonstrated that of those patients in that institution who came to the operating room with “Do Not Resuscitate” orders, the DNR status of the patients was not recognized in 69% and the anesthesiologists did not suspend those orders in 92%.
Cost Effectiveness Issues
Several investigators studied the costs and benefits of some common anesthetic safety practices. Dr. S. Scharf and colleagues, University of Mississippi, reviewed the recommendation of the ASA Subcommittee on Infection Control that all endotracheal tubes (ETTs) be kept sterile until the time of use. Daily discarding of all opened, but unused, ETTs costs the investigators’ hospital $17,910 per year. They could not culture bacteria from ETTs stored in open wrappers in anesthesia carts for up to 14 days, and they recommend further study and review of this policy.
Similarly, JCAHO surveyors have required hospitals to stipulate that syringes filled with drugs in the OR be discarded within 24 hours as an infection control policy. To study this, P. Langevin and colleagues from the University of Florida inoculated S. aureus into IV bags and syringes containing normal saline, 5% dextrose in lactated Ringer’s, or 5% dextrose in saline. The microorganism count in all preps declined sharply over time. The investigators describe these fluids as bacteriostatic because the fluids lack many of the substrates bacteria require. The investigators recommend further studies and re-evaluation of routine 24-hour syringe discard policies.
Airway Management Safety
At the October 25 poster-discussion session, there were ten abstracts related to airway management safety.
Dr. D. Sklar and colleagues from the University of Chicago presented a retrospective study on the incidence of difficult intubation in obese patients. Their findings are in agreement with prior reports showing an incidence of 6% in this group. This is much higher than the 0.5-1.5% incidence of difficult intubation in the general population.
The use of a self-inflating bulb to help confirm tracheal intubation (compressed rubber bulb inflates quickly when ETT is correctly in the trachea) in the morbidly obese was presented by Dr. D. Lang of the Illinois Masonic Medical Center in Chicago. He and his colleagues were able to reduce the high incidence (21%) of false negatives (absence of reinflation in case of tracheal intubation) to 11% by compressing the bulb after it was connected to the tube rather than compressing it prior to placement on the tube adaptor. This incidence of false negatives was further decreased to 4% by giving three breaths of 400 ml each before conducting the test.
Dr. Y. Xiao and colleagues from the University of Maryland, Baltimore, presented two papers in relation to stress and airway management. They conducted video analysis of tracheal intubation during emergency and non-emergency situations. It was demonstrated that the anesthesia care provider made more inappropriate decisions during emergency airway management as compared to during elective cases. The purpose of the second study was to identify stressors during airway management. Regressional analysis identified three stressors (time, workload, and uncertainty) which contributed more to overall stress than the three factors of noise, anesthesia care provider interaction, and non-anesthesia care provider interaction.
Dr. E. Davies, et al., from the National Hospital for Neurology and Neurosurgery in London, presented their study which showed that the Mallampati oropharyngeal classification and interdental distance were significantly affected by preventing cranio-cervical extension by the patient. The study was conducted on 100 healthy volunteers who were all Mallampati class 1 when the head was extended on the neck. The Mallampati class changed to class 2 (41%) and class 3 (34%) with limited interdental gap when measurements were repeated with the head maintained in a fixed, nonextension position. They concluded that the Mallampati classification is likely to be a valuable test in patients with cervical disease who may not be able to extend their necks.
The use of three dimensional computerized tomography measuring the effect of head and neck position on pharyngeal patency in awake volunteers was reported by Dr. M. Popitz and colleagues from Beth Israel hospital in Boston. Seven volunteers were studied with the head and neck in four different positions. The “sniff” position increased, while cervical flexion decreased, pharyngeal antero-posterior diameters.
Drs. R. Glassenberg and N. Vaisrub from Northwestern University reported their findings on the incidence of failed intubation in obstetrical patients. They reviewed 2,222 charts of patients subjected to Cesarean section under general anesthesia from 1975 to 1984, and 1,356 charts from 1985 to 1994. Prior to 1985, there were eight cases of failed intubation. After 1984, failed intubation occurred in three cases. The fiberoptic bronchoscope was used in 18% of intubations since 1984 in patients suspected to be difficult intubations. The differences in failed intubation in the two reported time periods were not statistically significant. The authors raise the question that there may be an irreducible minimum of failed intubation in this population of patients, due to the presence of a subgroup of patients presenting with normal external appearance of the airway.
Dr. J. Parmet and colleagues from Hahnemann University reported on a method of teaching alternative airway techniques that was tried in their department. They created an Airway Awareness Week, dedicated to airway training via invited experts, mannequin training, and encouraging use of alternative airway management strategies. This aggressive teaching approach resulted in an increased number of fiberoptic intubations, elective retrograde intubation in some patients, organizing of a difficult airway cart, and equipping of each operating room with jet ventilating system and a cricothyrotomy set.
Dr. L. Foley, et al., from Beth Israel Hospital in Boston reported on an in-hospital difficult airway/intubation registry. Once a patient is identified as a difficult airway, a fluorescent orange “Difficult Airway/Intubation” bracelet is placed on the wrist and on the patient’s medical record and also entered into a central hospital computer. Upon any subsequent admission, the same bracelet is placed on the patient.
Emergency intubation of 189 congestive heart failure patients was prospectively evaluated and reported by Drs. T. Mort and C. Foster from Hartford (CT) Hospital. Hypotension, bradycardia, tachycardia, and hypertension were common. Three cardiac arrests were recorded; two were associated with airway difficulty, the other with ventricular tachycardia upon laryngoscopy. The authors conclude that the incidence of major cardiovascular complications is high in this group of patients and that a judicious approach to airway management is critical.
The Color of Blood
During vessel cannulation, it is important to discern whether the cannula is in an artery or a vein. Examining the color of the forthcoming blood was studied by Dr. M. Young, et al., of St. Louis University who found that experience facilitates making the distinction between arterial and venous blood, recognition was more difficult at a 80% Hb saturation, and color of draping backgrounds did not affect recognition.
Visual inspection is also important in determining the amount of blood that is lost during a procedure. Papers by Dr. I. Gratz, et al., from Robert Wood Johnson Medical School and Dr. R. Calicott from Wilford Hall Medical Center addressed this issue. Both groups concluded that anesthesiologists and surgeons overestimate the amount of blood loss.
Training helps to reduce this overestimation by 50%. In general, therefore, it is suggested not to rely on estimation of blood loss alone to decide when to administer blood, focusing instead on objective measures.
To the many reasons for being conservative when deciding to transfuse blood, Dr. A. Rosenberg, et al., of New York University have added that older patients undergoing surgery for hip fracture are at an increased risk for developing a postoperative infection after perioperative transfusion of red blood cells. Nine percent of transfused patients developed a postoperative infection compared to four percent of nontransfused patients.
Two abstracts were presented concerning the problem of malignant hyperthermia. Dr. J. Antognini of the University of California, Davis suggested that increase in creatinine kinase may not be an accurate indicator of the presence of MH. For example, of patients with malignant hyperthermia, 73 percent of who received succinylcholine had peak CK measures <20,000, and 84% who did not receive succinylcholine had peak CK measures <10,000. Requests for information from the Malignant Hyperthermia Association of the United States (MHAUS) hotline from 1990-1994 most often concerned patients undergoing ENT surgery.
Dr. C. Greenberg and colleagues from several institutions summarized statistics from this patient group. Tonsillectomy and/or adenoidectomy was the most frequently performed surgery (68%). Halothane, either alone, or with other inhalation agents, was the most commonly used anesthetic (69%); succinylcholine was used in 75% of these patients. Jaw rigidity was the most frequent cardinal symptom.
Dr. P. Langevin and colleagues from the University of Florida investigated the growth characteristics of Staphylococcus aureus in propofol and intralipid. This issue has been in the news particularly since the publication of the New England Journal of Medicine article based on the CDC report of infections. These investigators found that there was a significant lag phase (approaching 8 hours) for bacterial growth in propofol which was temperature related. Further, the addition of more than 1 mM bicarbonate slowed the growth of the bacteria.
An abstract by Dr. J. Badgwell and colleagues from Texas Tech University examined the cutaneous heat loss in 23 patients undergoing surgery and general anesthesia for abdominal and thoracic procedures. Utilizing techniques which could examine cutaneous heat flux, they were able to discriminate between heat loss from cutaneous, IV, respiratory, and blood loss causes and also measure metabolic heat production. Using this methodology, the authors concluded that the most significant component of intraoperative heat loss was cutaneous, which was greater than loss through fluid infusion or the respiratory tract.
A presentation detailing the high prevalence of undiagnosed residual neuromuscular blockade following atracurium usage was presented by Dr. A. McShane and colleagues from St. Vincent’s Hospital in Dublin, Ireland. These investigators studied 45 patients undergoing general surgery. The anesthetist was blinded to the detailed neuromuscular monitoring performed using a Myograph 2000, but utilized a peripheral nerve stimulator, often applied on the face. Fifteen patients who received relaxant reversal agents from the clinicians were noted to have TOF = 0 on the myograph at the time of reversal, suggesting the possibility that some patients have undiagnosed residual paralysis at the time of extubation. Patients with shorter procedures and less spontaneous recovery of TOF, as well as those with more recent atracurium dosage, were more likely to demonstrate evidence of TOF <0.7 following extubation, and thus, be at risk for ventilatory complications.
Mindful of all the recent discussion of carbon monoxide generation by CO2 absorbant, Drs. M. Dunning, et al., from the Medical College of Wisconsin investigated the utilization of clinical gas monitors to detect inhaled anesthetics and carbon monoxide.
In this study, the authors tested enflurane, isoflurane, and desflurane with three gas monitors. They noted the trifluoromethane molecule and CO signal can be confused by the monitors. Thus, the electronic instruments have the possibility of misidentifying the potent volatile anesthetic as a consequence of carbon monoxide interference. Also, a sudden change on the monitor to a signal for an anesthetic not being used should suggest the possibility of the presence of a significant amount of carbon monoxide.
Dr. C. Rosow and colleagues from the Massachusetts General Hospital studied the possibility of airway obstruction during propofol sedation. Twenty volunteers received propofol (some with 30% N2O) via a computer-controlled infusion to produce sedation. The degree of sedation from unresponsive to fully responsive was assessed by an observer. Four subjects experienced clear evidence of airway compromise within 1 to 2.5 minutes after an appropriate response to voice. Three of these subjects required airway support. A fifth subject, receiving propofol and 30% nitrous oxide in oxygen, manifested apnea.
The investigators conclude that caution should be utilized when administering propofol sedation, as it is very easy to go from a period of responsiveness to respiratory obstruction. Thus, propofol sedation by individuals not trained in airway management may lead to significant risk of respiratory obstruction.
An additional presentation on possible nitrous oxide hazards during a laparoscopy was presented in an animal study by Dr. P. Giemunch and colleagues from Strasbourg, France.
These investigators utilized a porcine model of pneumoperitoneum and a specialized chemical methodology to ascertain nitrous oxide and CO2 concentration. Recent articles have suggested that the concentration of nitrous oxide in the pneumoperitoneum could pose a significant explosion hazard. The authors ascertained that over a period of ten hours, the nitrous oxide concentration plateaued unless additional CO2 was added. As laparoscopic procedures become more complicated and longer, it is important to be aware of possible high levels of nitrous oxide developing in the abdomen. While the actual risk of such explosions is unknown, the physical chemistry suggests they can occur.
An additional study was presented by G. Nemesdy and colleagues from the Beth Israel Medical Center in New York. These investigators studied the time course of gastric acid neutralization by Bicitra in 40 randomly selected surgical patients receiving general anesthesia. Effective neutralization of gastric acidity occurred only for the first 30 minutes. This study suggests the need to readminister Bicitra if, for some reason, the surgery is delayed after the initial dose.
Only a fraction of the interesting safety-related presentations are outlined here. Overall, safety clearly continues to be one of the major topics of the scientific sessions at the ASA.
Andranik Ovassapian, M.D., is Professor of Anesthesia at Northwestern University Medical School, Chicago;Robert E. Johnstone, M.D., is Professor and Interim Chair, Anesthesiology at West Virginia University, Morgantown;James R. Zaidan, M.D., is from Emory University School of Medicine in Atlanta;Matthew B. Weinger, M.D., is Associate Professor of Anesthesiology at the University of California, San Diego; J. Lance Lichtor, M.D., is Professor of Anesthesia and Critical Care at the University of Chicago; B. Wayne Ashmore, M.D., is from Pensacola, FL;Jonathan Moss, M.D.,Thomas Cutter, M.D., and Susan Polk, M.D., are also from the Department of Anesthesiology, University of Chicago.