THE BLOCKING EFFECT OF BUPIVACAINE ON THE LARYNGEAL CHEMOREFLEX AND THE TRIGEMINAL DIVING REFLEX IN NEWBORN LAMBS

Abstract

The laryngeal chemoreflex (LCR) and the trigeminal diving reflex (TDR) responses in the unanesthetized newborn lamb and the changes in these responses produced by administration of i.v. bupivacaine were studied. Both 1 mg and 10 mg bupivacaine significantly reduced the LCR. The responses to water and saline stimulation were similar after bupivacaine suggesting a complete blocking effect on the chemoreceptors. When the LCR was initiated by electrical stimulation of the cut superior laryngeal nerve, the response was not reduced by bupivacaine, indicating that the most likely site of action of bupivacaine is the chemoreceptors in the laryngeal mucosa. The trigeminal diving reflex was significantly reduced after 10 mg bupivacaine, 1 mg was ineffective. Implications for maternal-fetal bupivacaine transfer and human fetal toxicity were discussed.