Aspects of patient safety were once again the focus of a significant number of scientific presentations at the annual meeting of the American Society of Anesthesiologists in New Orleans October 21-23.
In the Monday morning poster session, Dr. M. Jaheri and his group from the Shock Trauma Center of the University of Maryland School of Medicine showed how they utilized the Australian Incident Monitoring Study (AIMS) crisis management algorithm and applied it to their operating rooms and resuscitation areas as criteria for identifying critical incidents. They wanted to see if the current AIMS algorithm was actually useful. From a series of 110 videotapes of actual patient management, 12 were found which had critical incidents. Critical incidents are incidents which would have led to harm to the patient if an intervention had not taken place. In reviewing the tapes, they felt that the 20-item AIMS algorithm, if applied, would certainly have prevented any mishap. However, they also concluded that simply applying the 4-item ABCD (airway, breathing, circulation, drugs) portion of the AIMS algorithm would have accomplished the same result and taken much less time and effort.
In another poster discussion, two abstracts presented teaching programs for trainees. Dr. P. McQuillan at Penn State in Hershey discussed an intense workshop on regional anesthesia, using cadavers. The workshop lasted one morning and residents were tested pre, post and three weeks after the workshop to measure learning and retention. The residents who participated in the workshop did significantly better in the three-week post test than did those who had not participated. There was no control group. Dr. P. Fish at Stanford and Dr. Brendan Flanagan discussed their program’s medical student clerkship, which includes a simulator. During the two-week clerkship, students spend two half-day sessions on the simulator. The first is learning about the anesthesia machines and monitors, and then about oxygenation, hypoxia, and drugs and their physiologic effects. The second is spent actually formulating and implementing an anesthetic plan for a particular patient. The feelings of the participants were that they had a chance to think and perform without the pressure of a live situation, and yet felt they had a chance to manage the total patient as opposed to just mastering the technical aspects of anesthesia. There was no measure of student performance or retention presented.
Fasting for 8 hours preoperatively may increase aspiration risk factors, increase gastric volume, and decrease patient dissatisfaction, according to Dr. A. Mathieu from the University of Cincinnati. Using a meta-analysis of 25 studies, he presented evidence that adults who ingested clear liquids (100-450 ml) 2 or 3 to 8 hours prior to surgery were less likely to have gastric volumes greater than 0.4 ml/kg and/or gastric ph less than 2.5 when compared with adults who fasted for 8 hours. These patients were seven times less likely to experience thirst and three times less likely to experience hunger.
Gastric volumes greater than 0.4 ml/kg were not found in fasting insulin-dependent diabetic patients without neuropathy presenting for elective surgery. Dr. V. Kartha from the University of Chicago suggested that routine aspiration prophylaxis with metoclopramide is not necessary in this patient population.
The water content of Baralyme, normally 10-15%, may be reduced to 5% in the lower canister of the CO2 absorber by high gas flows. Under these conditions the production of compounds B and C, degradation products of sevoflurane, is 1000 times greater than from wet Baralyme, but only trace amounts of compound A are formed. Dr. H. Woehlck from the Medical College of Wisconsin stated that although toxicity studies have been performed for compounds A (toxic) and B (non-toxic), none have yet been published for compound C.
Also suggested were the points that using the anesthesia machine as an oxygen source during MAC may dry out the absorbent even more. Another study by Dr. E. Frink et al. seemed to confirm previously reported data regarding the production of CO by the interaction of halogenated ethers with dry Baralyme.
Stress in anesthesia care providers while anticipating and performing emergency intubation in a trauma care setting was studied by Dr. Xiao and colleagues from the University of Maryland. They found the heart rates of providers peaked one minute before the endotracheal tube cuff was inflated in emergency and on emergency intubations alike, and that heart rates were higher throughout the airway management period when the intubations were considered emergencies.
Drs. Battito and colleagues from the University of Alabama applied Utstein Style, the recording of time until a certain task is performed, to endotracheal intubation during management in hospital CPR. They defined five minutes as the time in which non-face mask ventilation should be initiated and monitored 123 intubations in adult resuscitations. Only 46% were intubated within 5 minutes; anesthesia residents arrived within 5 minutes in only 42% and cricoid pressure was never being applied when they arrived. Logistical problems preclude more timely arrival of anesthesiologists and so the institution has begun airway management courses for the medical residents.
Dr. M. O’Connor and the liver transplant anaesthesia team at the University of Chicago reported that esophageal varices are not a contraindication to transesophageal echocardiography during transplants based on a retrospective review of 364 adult patients. There were no complications noted in the 9.6% of this sample who were monitored with this technology.
Complications of TEE in cardiac surgery patients were explored by Drs. London, Shroyer and Grover from the University of Colorado. They reported no clinically significant increase in gastrointestinal sequelae from this technology.
Drs. Burton and Zornow reviewed 99 patients who had received spinal or general anesthesia for elective inguinal herniorrhaphy at the University of Texas, Galveston, and reported that complications resulting from either anesthetic did not differ statistically. While induction, recovery and total times were slightly longer in the spinal group, pharmacy costs were higher in the general anesthesia group.
Damage to several types and sizes of spinal needles incurred by contact with bone during their placement was reported by Drs. Sharma, Parker and White from the University of Texas Southwestern and Tufts University. They illustrated flattening and shredding of needle tips, fractures and barbs, and bending of shafts. The least damaged needles were the Sprotte and Gertie Marx 26 gauge. This is part of an ongoing, larger study that will eventually determine the clinical significance of these findings. At present, this group discards spinal needles after bony contact.
Sleep Deprivation Revisited
Dr. R. Geer and colleagues from the Departments of Anesthesia and Psychiatry of the University of Pennsylvania expanded on their 1995 abstract in which anesthesiology resident performance was shown to deteriorate on-call. They studied on-call performance of anesthesia faculty, again employing the psychomotor vigilance task (PVT), an instrument which has been validated in studies of shift work and sleep loss. Their results suggested that faculty did not suffer decreased vigilance during call, and postulated that older age and decreased sleep requirements of the faculty might play a role in the findings. Other contributing factors may be that residents lost disproportionately more sleep than faculty from pre- to post-call, and subjectively they tended to be sleepier overall, even pre-call.
Dr. M. Weinger and colleagues from the University of California, San Diego, and the VA Medical Center, San Diego, studied five senior-level anesthesia residents, comparing their performance during day time cases with performance during night time call cases. At night, the resident mood was found to be more tired/drowsy and temperatures were lower. Of 35 task categories of intraoperative activities that were measured, higher workload values and less “efficiency” were noted, although “spare capacity,” measured by response to a simulated alarm light, was unchanged.
Difficult Airway Simulations
Dr. R. Gonzalez and colleagues from the University of Pittsburgh described their use of a CAE simulator modified to produce a variety of difficult airway configurations, including restricted mouth opening, limited neck extension, tongue swelling, pharyngeal swelling, laryngospasm, and poor pulmonary compliance. The neck and cricothyroid membrane of the mannequin is also amenable to transtracheal jet ventilation. The difficult airway scenarios have been incorporated into an airway management curriculum for the institution. The scenarios have been used for training of practicing anesthesiologists in a CME program, and for residents and fellows as well. An anonymous exit survey suggests very high trainee satisfaction and perceived educational value.
Several abstracts presented dealt with issues previously examined by the Closed Claims Study. Dr. J. Rosenberg and colleagues examined data on cardiac arrest and death within 48 hours of anesthesia to determine factors associated with these adverse outcomes. Records from a hospital database at the University of Michigan Medical Center covering 69,083 total (all ASA classes) anesthetics administered over a 25-month period included 91 intraoperative cardiac arrests and 60 intraoperative deaths. The overall anesthetic mortality in this data set was 8.6 per 10,000 anesthetics with the risk increasing from 0.015% in ASA Class I or II patients to 90.48% in Class V-E. The investigators noted that reversible factors were more commonly associated with these adverse events in healthy patients.
Another observational study was derived from incidents reported to the Australian Incident Monitoring Study. A database of 4,159 incidents was searched for reports of endobronchial intubation to determine associated factors and outcome. The database included 154 episodes of endobronchial intubation (3.7% of all incidents). Most of the episodes were diagnosed by a decrease in oxygen saturation (66%) while capnography was unremarkable during 87% of the endobronchial intubations. The factor most commonly associated with this complication was flexion of the patient’s head. According to the authors, Drs. McCoy and Russell from The Royal Adelaide Hospital, approximately 60% of the incidents could have been prevented by having measurement markers on the distal end of the endotracheal tube to indicate depth of tube placement below the vocal cords.
Delayed Ulnar Palsy
Following up on a previous report of factors associated with postoperative ulnar neuropathy, Dr. M. Warner and colleagues from Mayo Clinic performed a prospective evaluation of 1,506 adult surgical patients undergoing noncardiac surgery. Serial neurologic examination and EMG testing were used to detect 7 perioperative ulnar neuropathies. Of note was the fact that no patient developed symptoms within the first 48 hours after surgery suggesting that the etiology was not in the intraoperative period. This indicates that measures taken in the operating room have been successful and that the focus for preventing ulnar neuropathies now should address postoperative factors.
Ocular injuries after non-ophthalmologic surgery were assessed by Dr. S. Roth and colleagues from the University of Chicago. The investigators found 34 cases of eye injury in a database of 60,965 patients having surgery over a four-year period. Factors significantly associated with eye injury include a long surgical procedure, lateral position during surgery, operation on the head or neck, general anesthesia, and surgery on Monday. Since this was an observational study, the specific cause for these risk factors was not elucidated. Further work will focus on identifying strategies for prevention of ocular injuries.
Airway management as an important factor in patient safety was stressed in presentations. The decision to extubate a patient who has been difficult to intubate or in whom postoperative airway patency is questionable poses a significant challenge. The current difficult airway algorithm suggests extubation over a tracheal tube exchanger to permit reintubation if necessary. Unfortunately, many awake patients do not tolerate the tube exchanger. Dr. J. Denny and colleagues from UMDNJ-Robert Wood Johnson Medical School assessed the safety and effectiveness of leaving a 0.038 inch diameter, 145 cm guidewire in the trachea after extubation. In this study of 20 patients, the wire was tolerated for up to 48 hours. Successful reintubation occurred in 7 of 7 patients where it was attempted. The technique involved placing a tube exchanger over the guidewire and then reinserting the endotracheal tube over the tube exchanger. The long wire was used to permit the option of reinserting the endotracheal tube by passing the wire through a flexible fiberoptic scope with the tube loaded on the scope. Dr. J. Parmet suggested that practice with retrograde intubation techniques on elective patients dramatically increased the effectiveness and success of utilization of this technique in emergency airway situations.
An electronic esophageal detector device and preliminary results (which appear promising) of its use were presented by Dr. P. Schafer and colleagues; further studies are underway.
Prospectively standardized data collection is an important aspect of medical care. The process allows physicians precisely to define and to solve intricacies related to patient care. Two abstracts presented at the 1996 ASA convention in New Orleans used large, well-organized databases to answer important questions. Dr. James Duke and colleagues from the University of Colorado reviewed self-reporting, quality assurance data to determine the frequency of cardiovascular, respiratory and airway difficulties in trauma patients. Three different groups totaling approximately 9500 patients were used in the analysis: Trauma patients (study group), Non-trauma emergency patients; Scheduled non-emergency, non-trauma patients. Trauma patients experienced the highest mortality with exsanguination the most common cause of death. Major airway and respiratory events were found in all groups. However, they were most common in the trauma group. This abstract points out that although we have made progress, trauma centers must continue to refine procedures to care for these patients in order to eliminate these problems.
The North American Malignant Hyperthermia Registry is the well-known national database that accounts for every patient who has a malignant hyperthermic type of reaction to general anesthesia, Dr. M.G. Larach at Pennsylvania State University used this database to review masseter muscle spasm (MMS) with and without malignant hyperthermia (MH). 391 patients were studied with 118 of these patients experiencing MMS alone without MH. The study looked at a variety of parameters including demographics, usculoskeletal abnormalities, operative procedure, etc. The investigators found that males were 2.8 times more likely than females to develop MMS combined with MH. Orthopedic procedures were more commonly performed in patients who eventually developed the clinical picture of MMS plus MH. Muscle biopsies found that 30.8% of 91 patients who had MMS alone to be MH susceptible. Overall, the review of the information in this national database found that MMS plus MH compared to MMS alone were more likely to be males undergoing orthopedic procedures.
The safety of acute normovolemic hemodilution was discussed in three abstracts. Dr. O. Kick used a mathematic model to suggest that only suitable patients expected to lose more than half their blood volume were candidates. Dr. U. Kreimeier and associates concluded that dilution to Hb of 7.5 grams was safe and avoided transfusion in appropriate cases while Dr. D. Pulley advocated combining preop autologous donation with hemodilution.
Dr. A. Bowdle observed that disordered sleep following outpatient surgery occurs just as it does in inpatients previously studied and he suggests further studies to investigate any morbidity and outcome implications of these postoperative sleep disturbances.
Infiltration of an extremity soft tissue by intravenous cannulae connected to pressure infusors for IV fluid was presented by Dr. P. Schoenwald and associates from the Cleveland Clinic using quite dramatic photographs of an infiltrated hand.
Reviewed here were only a small fraction of the 134 abstracts presented in the meeting section on patient safety and related topics. Interested readers are referred to the September 1996 abstract supplement of Anesthesiology, Abstracts 913-1047.
Dr. Liu is Professor and Chair of Anesthesiology at the New Jersey Medical School. Dr. Curry is from Columbia Presbyterian Medical Center. Dr. Berry is in the Department of Anesthesiology at Emory University Hospital in Atlanta. Dr. Bready is from the Department of Anesthesiology, University of Texas Health Science Center, San Antonio. Dr. Harper is from Emory University, Atlanta. Dr. Roy is Chair of the Department of Anesthesiology, University of Virginia School of Medicine, Charlottesville. Dr. Polk is with the Department of Anesthesia and Critical Care at the University of Chicago. Dr. Zaidan is from the Department of Anesthesiology, Emory University, Atlanta.