Does yawning represent a transient arousal-shift during intravenous induction of general anesthesia?

UNLABELLED: Although yawning occurs frequently during the IV induction of general anesthesia, the significance of this response remains unknown. In this study, we induced 30 surgical patients with 4 mg/kg thiopental IV, and 30 patients with 2 mg/kg propofol IV. Thereafter, the occurrence of yawning was continuously assessed, as the only clinical end-point, for 1 min. The electroencephalographic bispectral index was monitored throughout the observation period. The criterion for an arousal response was a transient increase during a continuing decrease in the bispectral index value. On the basis of this criterion, the sensitivity and specificity of the yawning response as an arousal sign were 77% and 80%, respectively. If a patient exhibited a yawning response, the chance of arousal was 84% (positive predictive value). With no yawning response, the chance of nonarousal was 71% (negative predictive value). According to simple logistic regression, the yawning response was predictive of a transient arousal-shift with an odds ratio of 13.5 (95% confidence interval: 3.8-48; P < 0.001). The occurrence of a yawning response during IV induction may be a clinical indicator of a transient arousal-shift during progressive loss of consciousness.

IMPLICATIONS: Yawning elicited by IV anesthetic induction was related to a transient increase during the continuing decrease in the electroencephalographic bispectral index value (sensitivity and specificity, 77% and 80%, respectively). This type of yawning may be a clinical indicator of a transient arousal-shift during progressive loss of consciousness.