Predictors of Intra-operative Recall of Awareness: Thai Anesthesia Incidents Study (THAI Study): A Case-Control Study
Mali Rungreungvanich MD*, Somboon Thienthong MD**, Somrat Charuluxananan MD***, Varinee Lekprasert MD*, Aksorn Pulnitiporn MD****, Ungkab Prakanrattana MD*****
Affiliation : * Department of Anesthesiology, Ramathibodi Hospital, Mahidol University, Bangkok ** Department of Anesthesiology, Khon Kaen University, Khon Kaen *** Department of Anesthesiology, Chulalongkorn University, Bangkok **** Department of Anesthesiology, Khon Kaen Regional Hospital, Khon Kaen ***** Department of Anesthesiology, Siriraj Hospital, Mahidol University, Bangkok
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.
Materials and Methods : 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, depo-
larizing 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.
Keywords : Awareness, Recall, Anesthesia, Complication, Risk factors
