THE EFFECT OF ACUTE HYPOCAPNIA ON MIDDLE CEREBRAL-ARTERY TRANSCRANIALDOPPLER VELOCITY DURING ORTHOTOPIC LIVER-TRANSPLANTATION - CHANGES ATREPERFUSION

This study examines the effects of acute hypocapnia, instituted prior to reperfusion of the graft liver, on the middle cerebral artery (MCA) Doppler blood flow velocity response to reperfusion during orthotopic liver transplantation in humans. Seventeen patients with chronic live r disease underwent continuous, noninvasive Doppler imaging of the MCA . Hyperventilation to an end-tidal Pco(2) of 25 +/- 1 mm Hg was associ ated with a decrease in mean MCA flow velocity (FVm) from 51.6 +/- 5.7 to 37.0 +/- 3.3 cm/s (P < 0.05). After reperfusion, the Paco(2) incre ased from 32 +/- 1 to 40 +/- 1 mm Hg (P < 0.05), mean arterial pressur e (MAP) decreased from 76 +/- 3 to 60 +/- 2 mm Hg, and the FVm increas ed from 37.0 +/- 3.3 to 54.0 +/- 4.7 cm/s (P < 0.05). FVm increased po streperfusion despite prior hyperventilation, decreased MAP, and abrup t increases in central venous and pulmonary artery pressures, but FVm did not exceed the prereperfusion level. In 10 of the 17 patients, the baseline FVm versus Paco(2) response slopes and Paco(2) measured post reperfusion were used to predict the FVm response to Paco(2) after rep erfusion. The slopes were similar to those reported for anesthetized p atients without liver disease. Predicted FVm exceeded measured FVm in 9 of the 10 patients. We conclude that mild hyperventilation prior to reperfusion of the graft liver prevents FVm increases above prereperfu sion baseline level.