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 epidemiology.