Middle cerebral artery transcranial Doppler velocity monitoring during orthotopic liver transplantation: changes at reperfusion--a report of six cases.

ABSTRACT

STUDY OBJECTIVE: To determine the effect of reperfusion of the grafted liver on transcranial Doppler blood flow velocity in the middle cerebral artery in humans during orthotopic liver transplantation. DESIGN: Clinical study. SETTING: University hospital. PATIENTS 6 patients scheduled for orthotopic liver transplantation. INTERVENTIONS: Middle cerebral artery blood flow velocity (MCAVm) was monitored continuously using a transcranial Doppler (TCD) probe. The TCD measurements were noninvasive. MEASUREMENTS AND MAIN RESULTS: The EME TC2000S TCD probe (Nicolet, Inc., Memphis, TN) was secured to the head using a strap providing continuous measurement of MCAVm. All other data were recorded by a patient monitoring system and a respiratory gas analyzer. Averaged MCAVm increased significantly in 5 of 6 patients (p < 0.001) when pre-reperfusion and post-reperfusion values were compared. Maximum post-reperfusion values for MCAVm, pulsatility index (PI), and systolic Doppler velocity (Vs) were greater than the corresponding immediate pre-reperfusion values (p < 0.05, p < 0.05, and p < 0.001, respectively). The increases in MCAVm cannot be explained on the basis of hypercarbia alone and were observed in the presence of systemic arterial hypotension and abrupt increases in central venous pressure, particularly at the time of graft reperfusion. CONCLUSIONS: MCAVm increased with reperfusion of the grafted liver. These data suggest that multiple factors--including hypercarbia, lactic acidosis, or multiple vasoactive substances released by the grafted liver--may contribute to the observed increases in MCAVm, Vs, and PI.