[Effect of rapid mannitol infusion on middle cerebral artery blood flow velocity and pulsatility index--a transcranial Doppler ultrasonography study in monkeys].

Hemodynamic changes immediately after the administration of mannitol were investigated in monkeys (Macaca Fuscata) using transcranial Doppler ultrasound (TC2-64) and were compared with those after CO2 loading. The CO2 loading group was hyperventilated to an end-tidal PCO2 of 36.5 +/- 2.21 and hypoventilated to an end-tidal PCO2 of 46.3 +/- 2.69. Mean flow velocity in the middle cerebral artery (MCA-FV), Pulsatility index (PI) and blood flow in the internal carotid artery (IC-BF) studies were performed twice before and after hypercapnea. In the Mannitol group, Mannitol (2 g/kg) was infused at a rate 20 to 30 ml/min. MCA-FV, PI, IC-BF and intracranial pressure (ICP) studies were performed twice before administration and 10 minutes after administration of Mannitol. In the Mannitol group (n = 8), MCA-FV and IC-BF and ICP increased significantly after administration of Mannitol (p < 0.005, p < 0.005, p < 0.025), but there was no significant difference in the PI. In the CO2 loading group (n = 15), MCA-FV and IC-BF increased significantly (both p < 0.005) and PI decreased significantly (p < 0.005). These results indicated that, in the presence of normal autoregulation without intracranial hypertension, there was no change in the resistance of the peripheral cerebral vessels, while a decrease in viscosity after administration of Mannitol caused an increase in cerebral blood flow. Hence, according to Poiseuille's law, peripheral vasoconstriction occurred in the early period after administration of Mannitol. This change was considered to be due to autoregulation of the cerebral vessels.