TRANSCRANIAL DOPPLER ULTRASONOGRAPHY WITH INDUCTION OF ANESTHESIA FORNEUROSURGERY

Intracranial hypertension can occur with induction of anesthesia; howe ver, the clinical significance of this is unclear. We used transcrania l Doppler (TCD) ultrasonography in neurosurgical patients during induc tion of anesthesia and endotracheal intubation to assess the incidence of high intracranial pressure (ICP) waveforms and to correlate TCD ob servations with specific anesthetics and anesthetic regimens. The midd le cerebral artery was monitored by TCD during induction of anesthesia and endotracheal intubation in 196 patients undergoing elective neuro surgery. Middle cerebral artery blood flow velocity (MCABFV) and physi ologic data were observed continuously and recorded at the following t imes: preinduction, induction, intubation, and postintubation. Inducti on with thiopental or etomidate decreased MCABFV, intubation increased MCABFV, and postintubation ventilation decreased MCABFV. MCABFV was h igher throughout the induction sequence in the 92 patients with tumors . Although there were numerous individual exceptions, changes in mean arterial pressure correlated statistically with changes in MCABFV. No patient had an end-diastolic flow velocity of 0. We reached the follow ing conclusions: (a) TCD is a straightforward modality that can be use d to monitor dynamic cerebrovascular events during induction of anesth esia; (b) MCABFV is increased with brain tumors; (c) thiopental and et omidate rapidly decrease and intubation rapidly increases MCABFV; and (d) routine TCD monitoring for high ICP waveforms during anesthetic in duction for routine elective neurosurgery appears to be unwarranted.