Predictors of intra-operative recall of awareness: Thai anesthesia incidents study (THAI Study): A case-control study

Abstract

Background: The authors determined predictors of intra-operative recall of awareness in the Thai Anesthesia Incidents Study (THAI Study). Objective: To study a multi-centered registry of anesthesia in 20 hospitals across Thailand. Material and Method: Structured data collection forms of patients who underwent general anesthesia and experienced intra-operative recall of awareness between March 1, 2003 and February 28, 2004, were reviewed by three independent anesthesiologists. One case of awareness was matched to four controls by age, gender, and level of hospitals. Univariate analysis (p < 0.1) and logistic regression (p < 0.05) identified characteristics associated with intra-operative recall of awareness. Results: Eighty-one cases were matched with 324 controls in the nested case control study. From univariate analysis, risk factors were cardiac surgery, cesarean delivery, upper abdominal surgery, IV anesthetics, depolarizing muscle relaxant, non-depolarizing muscle relaxant, and nitrous oxide (p < 0.1). The predictors from multivariable logistic regression were cesarean delivery p < 0.001, OR 6.48 (95% CI 2.03, 20.71), and cardiac surgery p < 0.001, OR 10.37 (95% CI 3.37, 31.89). Decreased risk was associated with intra-operative use of nitrous oxide p = 0.02, OR 0.42 (95% CI 0.20, 0.88). Conclusion: In the THAI Study, predictors of intra-operative recall of awareness were cesarean delivery and cardiac surgery. Use of nitrous oxide attenuates the risk of awareness.