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* From the Department of Anesthesiology and
Critical Care "A" and Department of Medical Information, Lapeyronie University Hospital, Montpellier, France.
Address correspondence to: Dr. Ph. Biboulet, Département d'Anesthésie Réanimation A, Hôpital Lapeyronie, 34295 Montpellier cedex, France. Phone: 33-4-6733-8256; Fax: 33-4-6733-7960; E-mail: p-biboulet{at}chu-montpellier.fr
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Abstract |
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 TOP Abstract Patients and methodsResultsDiscussionReferences |
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Methods: All patients undergoing anesthesia over a six year period were included in a prospective study. The cardiac arrests encountered during anesthesia and the first twelve postoperative hours in the PACU or ICU were analysed. For each arrest, partially or totally related to anesthesia, the sequence of events leading to the accident was evaluated.
Results: Eleven cardiac arrests related to anesthesia were identified among the 101,769 anesthetic procedures (frequency : 1.1/10,000 [0.44-1.72]). Mortality related to anesthesia was 0.6/10,000 [0.12-1.06]. Age over 84 yr and an ASA physical status > 2 were found to be risk factors of cardiac arrest related to anesthesia. The main causes of anesthesia related cardiac arrest were anesthetic overdose (four cases), hypovolemia (two cases) and hypoxemia due to difficult tracheal intubation (two cases). No cardiac arrests due to alveolar hypoventilation were noted during the postoperative periods in either PACU or ICU. At least one human error was noted in ten of the eleven cardiac arrests cases, due to poor preoperative evaluation in seven. All cardiac arrests totally related to anesthesia were classified as avoidable.
Conclusion: Efforts must be directed towards improving preoperative patient evaluation. Anesthetic induction doses should be titrated in all ASA 3 and 4 patients. The prediction of difficult tracheal intubation, and if required, the use of awake tracheal intubation techniques, should remain a priority when performing general anesthesia.
THE causes of anesthesia related mortality have been examinated in many epidemiological studies, allowing the proposal of preventive measures. Since the most recent publications,1–7 anesthetic practice has evolved, taking these proposals under consideration, specific to each of the operative periods.8,9 The INSERM study revealed a high incidence of early postoperative hypoxemic cardiac arrest.2 In consequence, our institution has adopted systematic postoperative supervision in a postanesthesia care unit (PACU), and the use of pulse oximetry and capnography has become widespread. Since our last epidemiological publication,5 we have regularly examined all anesthesia- related cardiac arrests, allowing follow-up of their evolution. The purpose of this study was to determine the incidence and to analyse the causes of anesthesia-related cardiac arrest, in order to discuss the need of new preventive measures for anesthetic security.
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Patients and methods |
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TOPAbstractPatients and methodsResultsDiscussionReferences |
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Anesthesia practice
All patients were examined by an anesthesiologist prior to anesthesia. Basic safety monitoring included: continuous electrocardiogram display, automatic non invasive blood pressure, and pulse oximetry. When regional anesthesia was associated with sedation, or general anesthesia was performed, capnography, oxygen concentration, and delivered anesthetic vapour concentration were measured. Since 1992, larygeal mask airway devices (LMA) were progressively used in our institution. Postoperative supervision was systematically performed in either a PACU or intensive care unit (ICU). Obligatory postoperative monitoring included pulse oximetry. An anesthesiologist's authorisation was required for all releases from the PACU or ICU.
Data collection
An information form was edited on which details of the anesthesia were reported by the anesthesiologist: patient identification, age, ASA physical status, elective or emergency procedure, anesthetic techniques, surgical procedures, complications encountered during anesthesia and the first twelve postoperative hours in the PACU or ICU. Surgery was classified as an emergency procedure when not scheduled, and either performed within the first 24 hr of admission, or later if urgently indicated. When regional and general anesthesia were combined, only regional anesthesia was retained. The forms were regularly checked by a senior anesthesiologist, verifing the quality and completeness of the information. In order to minimize the risk of under-recording cardiac arrests, this information was cross-checked with regular medical staff interviews, ICU admission records, and hospital administrative files.
Analysis of cardiac arrests
For each reported cardiac arrest, the patient's medical record and, when applicable, the autopsy report, were analyzed by two of the authors. The classification of the cardiac arrests used in the INSERM2 and our previous5 studies was applied. When requiring external cardiac massage or electric defibrillation, asystole, ventricular fibrillation and electro-mechanical dissociation were considered as cardiac arrests. Recovery was defined as an alive and non-comatose patient 24 hr after the arrest. The cardiac arrest was assigned to one of three groups: (1) totally related to anesthesia when anesthesia was the only or the major contributive factor, (2) partially related to anesthesia when patient condition or surgical procedure were major contributive factors, but anesthesia represented an additional factor, or (3) unrelated to anesthesia. The causes of the cardiac arrests were classified according to the primary responsible mechanism.2,5 Cooper's classification10 was then applied to qualify and quantify the errors associated with each procedure. Finally the arrest was classified as avoidable or not.
Statistical analysis
Event incidences are expressed for 10,000 anesthesias (0/000) with their 95% confidence intervals in brackets. Univariate analysis was used to test risk factors for cardiac arrest: ASA 1 and 2 vs ASA 3 and 4, age < 85 vs age > 84 yr, emergency vs elective. Statistical significance was retained when P < 0.05.
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Results |
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TOPAbstractPatients and methodsResultsDiscussionReferences |
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Of the 11 anesthesia related cardiac arrests, 1.1/10,000 [0.44 - 1.72], three were considered totally, and eight partially related to anesthesia. Risk factors for anesthesia related cardiac arrest were age > 84 yr (P < 0.01), ASA 3 and 4 (P < 0.001). Emergency surgical conditions were not retained as a risk factor (Tables I, II
). Five patients recovered following cardiac arrest. Anesthesia related mortality was 0.6/10,000 [0.12-1.06]. Cardiac arrests related to regional anesthesia were noted only during spinal anesthesia (Table III).
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). In two cases, (patient #7 and #11), the exact cause of the cardiac arrest could not be determined. However, the arrest was retained as partially anesthesia related as an anesthetic overdose was identified in patient #7 and patient #11 was hypovolemic.
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Discussion |
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TOPAbstractPatients and methodsResultsDiscussionReferences |
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Affirming the exhaustive inclusion of all data in this type of epidemiological study is impossible. When considering the denominator, the number of anesthesias recorded was regularly compared to the number of surgical procedures registered in the administrative files. A possible under-reporting in the number of anesthesia related cardiac arrests was reduced by limiting the study to only one department of anesthesia. Regular contacts with all staff, as well as checking the ICU admission registers identified two anesthesia related cardiac arrests not retained in the computer files. Moreover, as recovery was defined as a live non-comatose patient 24 hr after the arrest, we ignored later outcomes. Finally, cardiac arrests which occurred just after departure from the PACU where not retained.
It is difficult to compare the incidence of anesthesia related cardiac arrests and deaths reported in this work with those of previous studies, as the methods differ greatly among studies. Some were based on the voluntary declaration of incidents,3,7 others on case series,1,2,4–6,11 of which only two were prospective studies.2,12 Some include only critical incidents occurring during the intraoperative period,1,4 while others include only those totally related to anesthesia.3,11 The patient populations differ considerably among studies. Consequently, it seems hazardous to compare the incidence of anesthesia related cardiac arrests and anesthesia related mortality among studies.13 In contrast, the analysis of the causes of these arrests seems instructive.
Hypoxemia is classically considered the most frequent cause of anesthesia-related cardiac arrest, estimated to be between 0.4 and 1.1/10,000 in the intraoperative period,1,2,4,5 and 1.1/10,000 in the postoperative period when only 40% of patients were supervised in a PACU or ICU.2 In our study, hypoxemia was retained as the cause in only two anesthesia related cardiac arrest (0.2/10,000). Both cases involved difficult tracheal intubation, and were considered to be a result of poor preoperative assessment, leading to the use of inappropriate anesthetic induction techniques. In contrast with the literature, the two most common causes of hypoxemic cardiac arrests, inadequate ventilation and esophageal intubation,1,4,14 were not observed in our study. Furthermore, no hypoxemic arrests were noted in the postoperative period in either the PACU or ICU. It is tempting to explain this result by the systematic use of pulse oximetry and capnography, and the systematic supervision in a PACU or ICU. The ASA closed claim study reported that 57% of anesthesia related deaths were avoidable by the use of pulse oximetry and capnography.15 With the use of such monitoring in more than one million anesthetics, the anesthesia-related arrests decreased from 0.13/10,000 to 0.04/10,000 anesthetics.16 To reach statistical significance, this study would have required the inclusion of more than seven million anesthetics.17 Furthermore this study included only ASA 1 and 2 patients, evaluating only the intraoperative period. As such, further studies are necessary to confirm the low incidence of hypoxemic cardiac arrest noted in our study using systematic pulse oximetry, capnography, and PACU or ICU postoperative supervision. The role of LMA in anesthetic safety is difficult to assess. In this study, the two hypoxemic arrests secondary to a "cannot ventilate, cannot intubate" situation were due to a laryngeal tumour in one case, and tracheal compression by a mediastinal mass in the other. The LMA was not used in either. Though pathology below the vocal cords is considered to be a relative contraindication to the use of LMA,18 some anesthesiologists do not retain this notion.19 With the generalisation of the intubating LMA use, further studies are necessary to analyse these hypoxemic cardiac arrests.
In the present study, anesthetic overdose was the primary cause of anesthesia-related cardiac arrest and death. Arrests due to spinal anesthetic overdoses are particularly frequent, 3/7,656 spinal anesthesia, occurring in elderly patients in two of the cases. Spinal anesthesia overdosage is a well known cause of cardiac arrest in the elderly,4,5,13,20 with doses as low as 5 mg of either isobaric or hyperbaric bupivacaine, reaching sensory levels of T421 / T2.22 Accordingly, single shot spinal anesthesia should be avoided in the elderly, favouring techniques which allow for dose titration, such as continuous spinal anesthesia.21,22 In contrast, no cardiac arrests were noted during other regional anesthesia techniques, including those with a risk of local anesthetic toxicity. Similar results were reported in two recent publications examining 25,69723 and 51,69120 epidural or nerve block procedures.
Human error has long been identified as a major factor leading to anesthesia-related cardiac arrest.1,3,4,7,12 In this study, anesthesia-related cardiac arrest resulted from the association of numerous common human errors, previously called the chain of accident evolution.24 In accordance with an Australian study,7 poor preoperative preparation was the human error most often identified in this work. Human error has more consequences on patients with higher ASA scores as their ability to adapt to aggression is limited.10,12 As all identified errors did not lead to cardiac arrest, one can suppose that the incidence of errors is far greater than that noted in this work. Preventing human error is a complex task. In anesthesia, research based on models derived from aeronautics has started.25,26 Continued education of anesthesia practitioners is fundamental, however some studies demonstrate that it is poor practical application rather than a lack of knowledge that leads to critical incidents.27 Training programs based on simulations of critical anesthetic scenarios have been proposed.28,29 However, the errors identified in this study were encountered in ordinary situations such as anesthesia in the elderly, in hypovolemic patients, and when a difficult intubation had been predicted; not exceptional situations. These findings do not minimize the need of regular training to meet the needs of exceptional situations, but rather underline the interest of regular epidemiological surveillance of the causes of the critical incidents.
In conclusion, this study highlights several simple means of improving anesthetic safety. Preoperative patient evaluation must be thorough. Anesthetic induction doses should be titrated in all ASA 3 and 4 patients. Predicting difficult tracheal intubation followed, when necessary, by the use of awake intubation techniques, should remain a priority when performing general anesthesia.
Accepted for publication December 3, 2000.
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References |
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2 Tiret L, Desmonts JM, Hatton F, Vourc'h G. Complications associated with anaesthesia - a prospective survey in France. Can Anaesth Soc J 1986; 33: 336–44.[Medline]
3 Lunn JN, Delvin HB. Lessons from the confidential enquiry into perioperative deaths in three NHS regions. Lancet 1987; 12: 1384–6.
4 Olsson GL, Hallén B. Cardiac arrest during anaesthesia. A computer aided study in 250 543 anaesthetics. Acta Anaesthesiol Scand 1988; 32: 653–64.[Medline]
5 Aubas S, Biboulet Ph, Daurès JP, du Cailar J. Incidence and aetiology of cardiac arrests occuring in operating and recovery rooms during 102,468 anaesthetics. (French) Ann Fr Anesth Réanim 1991; 10: 436–42.[Medline]
6 Tikkanen J, Hovi-Viander M. Death associated with anaesthesia and surgery in Finland in 1986 compared to 1975. Acta Anaesthesiol Scand 1995; 39: 262–7.[Medline]
7 Warden JC, Horan BF. Deaths attributed to anaesthesia in New South Wales 1984-1990. Anaesth Intensive Care 1996; 24: 66–73.[Medline]
8 Standards and Guidelines. American Society of Anesthesiologists 1999 Directory of Members 64th ed. Park Ridge, IL: ASA Ed, 462–76.
9 Les référentiels en Anesthésie-Réanimation. Société Française d'Anesthésie et de Réanimation. Paris: Elsevier Ed, 1997.
10 Cooper JB, Newbower RS, Kitz RJ. An analysis of major errors and equipment failures in anesthesia management: considerations for prevention and detection. Anesthesiology 1984; 60: 34–42.[Medline]
11
Harrison GG. Deaths attributable to anaesthesia. A 10-year survey (1967-1976). Br J Anaesth 1978; 50: 1041–6.
12 Pedersen T, Johansen SH. Serious morbidity attributable to anaesthesia. Considerations for prevention. Anaesthesia 1989; 44: 504–8.[Medline]
13
Keats AS. Anesthesia mortality in perspective. Anesth Analg 1990; 71: 113–9.
14 Caplan RA, Posner KL, Ward RJ, Cheney FW. Adverse respiratory events in anesthesia: a closed claims analysis. Anesthesiology 1990; 72: 828–33.[Medline]
15 Tinker JH, Dull DL, Caplan RA, Ward RJ, Cheney FW. Role of monitoring devices in prevention of anesthetic mishaps: a closed claims analysis. Anesthesiology 1989; 71: 541–6.[Medline]
16 Eichhorn JH. Prevention of intraoperative anesthesia accidents and related severe injury through safety monitoring. Anesthesiology 1989; 70: 572–7.[Medline]
17 From RP, Pearson K, Tinker JT. Did monitoring standards influence outcome? (Letter) Anesthesiology 1989; 71: 808–9.
18 Benumof JL. Management of the difficult adult airway. Anesthesiology 1991; 75: 1087–110.[Medline]
19
Rosenblatt WH, Wagner PJ, Ovassapian A, Kain ZN. Practice patterns in managing the difficult airway by anesthesiologists in the United States. Anesth Analg 1998; 87: 153–7.
20 Auroy Y, Narchi P, Messiah A, Litt L, Rouvier B, Samii K. Serious complications related to regional anesthesia. Anesthesiology 1997; 87: 479–86.[Medline]
21 Biboulet Ph, Capdevila X, Aubas P, Rubenovitch J, Deschodt J, d'Athis F. Causes and prediction of maldistribution during continuous spinal anesthesia with isobaric or hyperbaric bupivacaine. Anesthesiology 1998; 88: 1487–94.[Medline]
22 Biboulet Ph, Deschodt J, Aubas P, Vacher E, Chauvet Ph, d'Athis F. Continuous spinal anesthesia: does low-dose plain or hyperbaric bupivacaine allow the performance of hip surgery in the elderly? Reg Anesth 1993; 18: 170–5.[Medline]
23 Brown DL, Ransom DM, Hall JA, Leicht CH, Schroeder DR, Offord KP. Regional anesthesia and local anesthetic-induced systemic toxicity: seizure frequency and accompanying cardiovascular changes. Anesth Analg 1995; 81: 321–8.[Abstract]
24 Gaba DM, Maxwell M, DeAnda A. Anesthetic mishaps: breaking the chain of accident evolution. Anesthesiology 1987; 66: 670–6.[Medline]
25
Arnstein F. Catalogue of human error. Br J Anaesth 1997; 79: 645–56.
26
Helmreich RL, Davies JM. Anaesthetic simulation and lessons to be learned from aviation (Editorial). Can J Anaesth 1997; 44: 907–12.
27 Sigurdsson GH, McAteer E. Morbidity and mortality associated with anaesthesia. Acta Anaesthesiol Scand 1996; 40: 1057–63.[Medline]
28
Gaba DM, DeAnda A. The response of anesthesia trainees to simulated critical incidents. Anesth Analg 1989; 68: 444–51.
29
Doyle DJ, Arellano R. The Virtual AnesthesiologyTM Training Simulation System. Can J Anaesth 1995; 42: 267–73.
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