Frequency of Events Requiring Active Intervention by the Anesthetist

The preceding analysis of Figure 83-2 suggests that anesthetists must be prepared to react dynamically to changing events. How frequent is this requirement? In the Multicenter Study of General Anesthesia,^[197] 86% of patients had at least one undesirable outcome. Although most events were minor and caused no injury to the patient, more than 5% of patients had one or more severe events requiring "significant therapy, with or without full recovery." This incidence is probably a lower limit for severe events because the entry criteria of the study precluded the enrollment of critically ill patients or emergency surgeries for which the likelihood of severe problems requiring intervention would be expected to be high.

In another study by Cooper and associates,^[198] impact events, defined as "undesirable, unexpected, and which could cause at least moderate morbidity," occurred in 18% of patients either in the OR or in the PACU, and 3% of all cases involved a "serious" event. These figures are also probably lower limits because, for technical reasons,

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Moller and colleagues^[199] reported 4439 "impact events" out of 10,312 patients either in the OR (2441) or in the PACU (1998). Here again, some patients had several events whereas others had none. The investigators did not compute the frequency of severe events, but overall, these data appear to be consistent with those from earlier studies.