Lidocaine is used for suppressing circulatory responses to endotracheal intubation. In this study the investigated changes of middle cerebral artery blood flow velocity (Vmca) before and after intravenous lidocaine injection by transcranial doppler.

Fifteen healthy volunteers received a bolus dose of intravenous lidocaine 1.5 mg/kg. Vmca's were measured on the temple using a bidirectional 2-MHz transcranial doppler probe before and after lidocaine injection. Vmca's were recorded continually every 10 sec for 10 minutes after lidocaine injection.

Mean Vmca was 67.6 ± 7.6 cm/sec before lidocaine injection. Maximal Vmca's (70.7 ± 7.5 cm/sec, P<0.05) occurred 35 ± 16 sec after lidocaine injection, and then the Vmca decreased gradually. Minimal Vmca's (56.6 ± 7.4 cm/sec, P<0.05) were measured at 164 ± 40 sec after lidocaine injection.

We suggest that lidocaine generally causes the decreases in Vmca, excepting the temporarily increase in Vmca about 35 sec after a single bolus administration of intravenous lidocaine.