Identification of independent predictors for intravenous thiopental-induced yawning

To explore risk factors for the yawning response induced by the intravenous administration of thiopental during the induction of general anesthesia.

We analyzed data from a cohort of 1322 patients who underwent elective surgery under general anesthesia plus intravenous thiopental. The data collected were: (a) the patients' demographic findings (age, sex, height, weight, cigarette smoking, hypertension, and presence of cerebral lesion), and (b) anesthesia-related findings (the kind of preanesthetic medication, i.e., atropine, epidural lidocaine, priming dose of vecuronium, fentanyl, and the dose of intravenous thiopental). An association between an individual variable in the evaluation model and the likelihood of thiopental-induced yawning behavior was characterized by means of the odds ratio. Multiple logistic regression was used to examine the independent contribution of each candidate variable, while controlling for all variables.

After the intravenous administration of thiopental, 461 patients exhibited a yawning response. The probability of this response was decreased by the prior use of intravenous fentanyl, by female sex, and by premedication with clonidine, but the probability was unaffected by premedication with hydroxyzine, by the prior use of atropine, or by the presence of hypertension or a cerebral lesion.

Thiopental-induced yawning may be suppressed by female sex, prior use of intravenous fentanyl, and premedication with clonidine. These findings may allow insights into the physiologic and pharmacological aspects of yawning in humans, thereby leading to the development methods to prevent thiopental-induced yawning.