From the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan.
Accepted for publication September 21, 2009.
Address correspondence and reprint requests to George A. Mashour, MD, PhD, Department of Anesthesiology, University of Michigan Medical School, 1H247 University Hospital, SPC-5048, 1500 East Medical Center Dr., Ann Arbor, MI 48109-5048. Address e-mail to firstname.lastname@example.org.
Intraoperative awareness with explicit recall is a dreaded complication of anesthetic practice and can lead to long-term psychological sequelae such as posttraumatic stress disorder (PTSD). The study of rare events such as postawareness PTSD is challenging, especially when the fear of trauma cues related to surgery may lead patients to avoid further interaction with anesthesiologists or other health care providers. As such, various approaches have been used to study the incidence of PTSD in victims of awareness, with disparate results (Table 1).1–8 When evaluating the literature on the subject, it is therefore important to consider the methodology as well as the distinction between general psychological sequelae and a formal diagnosis of PTSD.
The B-Aware trial was a landmark study of patients at high risk for awareness. Of the 2463 patients studied prospectively, 13 were identified as having a confirmed awareness event.9 In this issue of Anesthesia & Analgesia, Leslie et al.8 report the long-term psychological follow-up of patients who experienced awareness in the B-Aware trial. In doing so, the authors faced a methodological challenge: How can PTSD due to awareness be distinguished from PTSD due to high-risk surgery itself? To address this, they used a matched cohort design, taking nonawareness patients from the B-Aware trial as controls to compare the incidence of PTSD. There are limitations to this approach, but the alternative of not accounting for the confounders of major surgery and intensive care unit (ICU) experiences is also problematic for an accurate assessment of the psychological consequences attributable to intraoperative awareness.
Leslie et al. found that 5 of 7 awareness patients (71%) who were available for follow-up met criteria for a diagnosis of PTSD. This high incidence of severe long-term psychological sequelae reinforces the need for preventing intraoperative awareness. These data, however, may not be the most striking finding of the study: the incidence of PTSD in the control population of 25 patients was 12%. Extrapolating to the 2450 nonawareness patients of the B-Aware trial, this incidence would suggest that almost 300 patients developed PTSD after their high-risk surgery. Is this possible?
As the authors allude to in the discussion of their findings, surgical interventions and ICU experiences can be associated with psychological trauma. For example, rates of PTSD after cardiac surgery, a high-risk situation for intraoperative awareness, range between 11% and 18%.10 One prospective study of heart transplant recipients at 3-yr follow-up revealed the cumulative risk of PTSD to be 17%.11 In another prospective study of postcardiac surgery admissions to the ICU, 15% of the cohort patients met criteria for PTSD.12 Furthermore, other patient populations traditionally considered high risk for awareness may also be at risk for psychological sequelae caused by the surgical intervention itself. In a study of women undergoing emergency cesarean deliveries, 76% perceived the event as traumatic. Although none of these 25 women met formal criteria for PTSD at follow-up, 33% had severe posttraumatic intrusive stress reactions.13 Thus, given the overlapping conditions that may result in PTSD, Leslie et al. were justified in their approach. The incidence of 12% found in the control group is not inconsistent with the literature, especially given the fact that all 3 of the patients had mechanical lung ventilation during the course of ICU treatment.
However, there are important considerations regarding PTSD in surgical patients. First, as the authors note, this was a high-risk surgery group; the incidence of PTSD in patients undergoing routine surgical procedures is unknown. In the postawareness PTSD study by Osterman et al.,5 a control group of nonawareness patients was also included. Of these 10 individuals who underwent surgery (including 1 cardiac surgery patient), none developed PTSD.
Second, we cannot specifically ascribe the observed PTSD in the control group to the surgery, or even to the perioperative experience. The 3 control patients, who had diagnoses of neoplastic, rheumatic heart, and vascular disease, may have had a number of psychologically traumatic experiences during the course of their illness. Medical events, such as myocardial infarction, can be associated with PTSD14; similarly, the diagnosis or treatment of cancer itself may result in PTSD.15 Furthermore, other traumatic events (additional medical problems and personal or socioeconomic consequences of the illness) could have occurred in the intervening years preceding psychiatric follow-up.
Third, the patients in this study were all at high risk for awareness and were compared on the basis of demographic data rather than on psychological risk factors for PTSD. The premorbid psychiatric histories of the patients in this study were not reported. It is important to consider that high-risk surgery patients may already have a psychiatric diagnosis at the time of presentation. In one study of cardiac surgery patients and psychological sequelae, 41.2% of the patient population met criteria for a psychiatric disorder at their preoperative baseline, which included a PTSD incidence of 8.8%.16
Investigating the psychological sequelae of intraoperative awareness is challenging. The prospective study of the patients in the B-Aware trial by Leslie et al. demonstrates that a high proportion of patients develop PTSD after awareness events. These data are important, especially considering the suggestion that prospective approaches to the study of postawareness PTSD may be associated with a lower incidence compared to other methodologies.7 The presence of a control group in this study facilitated the discrimination of PTSD due to awareness versus high-risk surgery or ICU experiences. Although the incidence of PTSD in the control population may be surprising, it is not inconsistent with previous studies. However, it must be remembered that there was no control group for the control group; the data regarding PTSD in the surgical population should therefore be interpreted cautiously. Given the risk of PTSD in a significant proportion of high-risk surgical patients, as well as the association of PTSD with the subsequent development of inflammatory17 and cardiovascular disease,18 further study is warranted.
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