Cerebral arterial blood flow velocity during induction of general anesthesia: rapid intravenous induction versus awake intubation.

Changes in middle cerebral arterial flow velocity (MCAV) during rapid intravenous induction and awake intubation using transcranial Doppler sonography were investigated. The study involved 20 patients without disorders of the central nervous or cardiovascular systems who were scheduled for maxillofacial surgery. In the intravenous induction group, anesthesia was induced with sodium thiopental, and orotracheal or nasotracheal intubation was facilitated with succinylcholine chloride or alcuronium chloride. In the awake intubation group, orotracheal or nasotracheal intubation was performed under intravenous sedation with diazepam and topical anesthesia with 4% lidocaine. Arterial blood pressures, heart rate, and MCAV were monitored at specific intervals. During intravenous induction, blood pressures decreased after the administration of thiopental and muscle relaxants and increased during endotracheal intubation. MCAV was remarkably slowed after the administration of thiopental and during mask ventilation. During awake intubation, blood pressures were increased by endotracheal intubation. MCAV was decreased from the administration of diazepam to the transtracheal injection of lidocaine, but returned to the control value from endotracheal spray to endotracheal intubation. These results suggest that smooth awake intubation may be the safest method of induction for patients with cerebrovascular disorders.