Patient safety was prominently featured in several scientific sessions at the Annual Meeting of the American Society of Anesthesiologists (ASA) in Orlando in October. Interested readers can review abstracts 1172-1244 in the Anesthesiology supplement "Abstracts of Scientific Papers, 1998 Annual Meeting", published in September, 1998. Findings presented in a few of these abstracts with particular patient safety implications are summarized in this Newsletter.
Potential danger of dissemination of tuberculosis bacillus via anesthesia breathing circuits was evaluated by Dr. PB Langevin and associates from the University of Florida. They concluded that while the CO2 absorbant is bacteriocidal to Staph and Pseudomonas, it is not to TB and that there may be a danger of TB organisms "transiting" the breathing system if the fresh gas flow is not interrupted for at least one hour between uses of the absorber.
Dr. MM Kurrek and colleagues from University of Toronto used an anesthesia simulator to correlate response times in clinical scenarios with performance quality. They showed that participants with shorter response times tended to achieve higher scores. While the authors alluded to the use of simulators as potentially valuable tools in assessing competency in anesthesiology, they did not go so far as to suggest using simulator response time as a screening tool among applicants to anesthesiology residencies.
Another performance study employing a simulator was presented by Dr. CN Herndon of the University of California, San Diego and associates. Fatigue and sleep deprivation were created by 25 hours of continuous activity (equivalent to a busy Saturday call) in subjects who were compared to well-rested controls. An issue was whether the fatigued subjects altered their behavior because of being in the study. Results surprised the investigators in that the expected shifting of attention and increased response time was not seen. The fatigued anesthesiologists did do more "busy-work," presumably as a way to stay alert and engaged. The authors plan a repeat study with more stressful simulated cases to see if that brings out the known deleterious cognitive effects of sleep deprivation.
The Stanford simulator group represented by Dr. SK Howard (a past ASPF research grant recipient) studied fatigue in anesthesia residents who were either in sleep-deprived or sleep-extended states. Their performance on the simulator was continuously monitored by video camera. Residents with extra sleep were always more alert than those sleep deprived, who were nearly falling asleep up to 30% of the time of the experiment. (It was also noted that sleepiness increased immediately after lunch.) Regarding the main findings, the risk of a "catastrophic" sleep episode putting a patient or the resident (e.g. driving home after call) at risk was considered a real possibility. EEG studies to confirm these findings are being conducted.
Dr. K Ellinger of Germany reported a new nasogastric tube with a balloon large enough to occlude the cardia of the stomach in a deliberate attempt to prevent reflux and gastric content aspiration upon induction of general anesthesia. It is offered as an alternative to rapid sequence IV induction. Its use in 250 patients at high risk for aspiration yielded no complications and no aspirations.
Ulnar nerve issues were again discussed. Dr. DA Rusy and associates of the University of Wisconsin Medical School showed that during routine isoflurane anesthesia, nerve conduction velocity and muscle activity both decreased at both the wrist and elbow – independent of the position of the arm on the arm board. No ulnar neuropathies occurred in the study population but the finding suggest that a degree of potential compromise is inherent in the anesthetic situation itself. Dr. RC Morell and colleagues from Wake Forest University (in research supported by a grant from the APSF) measured pressures at the ulnar groove itself and found that supination minimized direct pressure on the nerve and that pronation of the forearm with 30° abduction produced the greatest pressure. In another approach, Dr. LC Jameson of the University of Wisconsin reported initial experience with using SSEP as a study tool to examine arm nerve function during anesthetics. In addition, the Wake Forest group used SSEP to study functional correlation with recognized arm paresthesias in awake volunteers. They detected ulnar nerve SSEP decrements in virtually all subjects after their arms rested on a hard surface but only half reported any sensation of paresthesia, leading to the suggestion that even in awake patients, this endpoint is not useful in protecting against ulnar nerve compromise.
Dr. R Greif of Austria and associates from University of California, San Francisco suggested in their presentation that supplemental oxygen in the immediate postoperative period reduced postop
nausea and vomiting by 40%. No clinically significant atelectasis resulted from the oxygen therapy. Also regarding the potential for aspiration, Dr. RL Harter and associates from Ohio State did a new study that contradicted prior findings regarding the impact of diabetes on fasting gastric volume. They discovered a significantly greater gastric volume in diabetics and suggest that maximum aspiration prophylaxis is indicated in these patients.
Bacterial contamination of the forced warm-air heating blankets was discovered by Dr. DC Sigg et al. of the University of Minnesota and, therefore, their reuse for second and subsequent patients was advised against. Disturbed sleep among patients on their first postop night was investigated by Dr. AJ Cronin of Hershey Medical Center and correlated with decreased plasma melatonin levels. It was suggested that, possibly, supplemental melatonin may mitigate the sleep disturbances widely seen among postanesthetic patients. Although not directly related, another type of disturbance was reported in the same session. Dr. H. Mikkelsen and associates from Denmark revisited their earlier work showing that 10% of elderly patients persisted in suffering cognitive decline three months after major noncardiac surgeries under general anesthesia. In this study, the same patients were tested one to two years later. Cognitive dysfunction was seen at approximately the same 10% rate but half those patients developed a deficit after the testing at three months postop. It was concluded that postoperative cognitive decline may be reversible or it may persist.
Dr. L Foley of the Beth Israel Deaconess Medical Center/Harvard reported the results of use of an in-hospital registry of difficult airway patients and noted that prospective identification of these patients did in a significant fraction of cases alter subsequent approaches to airway management – with the implication of enhanced patient safety. The ultimate potential remedy for an "impossible airway" – cardiopulmonary bypass – was the subject of a presentation by Dr. T McDonald of the University of Chicago who suggested adding this last-ditch strategy to the ASA Difficult Airway Practice Parameter algorithm.
While logical, it had not been previously demonstrated that maintaining the OR temperature consistently at a higher level (26° C/79° F) prevented unintentional patient hypothermia. Dr. N El-Gamal of Egypt did this study with patients of varying ages undergoing orthopedic surgery and reported these results, which may also suggest the greatest impact of this strategy is among the elderly.
Intraoperative medication errors were studied in a new way by Dr. G Blike of Dartmouth. Rates of self-reported errors were calculated using hours of anesthesia time as the denominator and consistently in a small sample, there were 0.44 medication errors per 100 hours of anesthesia time.
The papers briefly reviewed here only scratch the surface of the body of patient safety related research presented at the 1998 ASA Annual Meeting.