Phentolamine administration increases blood S100B protein levels in pediatric open-heart surgery patients

Phentolamine administration during open-heart surgery shortens the cooling and rewarming phases of cardiopulmonary bypass (CPB) and hastens weaning from mechanical ventilation and extubation. Data on the effects of phentolamine on cerebral circulation and function in this setting are lacking. This study reports the cerebral effects of phentolamine using blood S100B protein levels and the middle cerebral artery pulsatility index (MCA PI).

Sixty pediatric patients undergoing congenital heart disease repair were randomly assigned to receive either phentolamine 0.2 mg kg(-1) i.v. (n = 30) or placebo (n = 30) before the cooling and rewarming phases of CPB. Samples for S100B measurement were collected at seven predetermined time-points before, during and after surgery. MCA PI values were recorded at the same times as sampling.

S100B blood levels were higher in the phentolamine-treated group than in controls after rewarming (3.53 +/- 1.88 vs 1.58 +/- 0.53 microg l(-1); p < 0.001), remained persistently higher at the end of surgery (2.95 +/- 0.91 vs 0.79 +/- 0.21 microg l(-1); p < 0.001) and returned to normal ranges 12 h later than in the placebo group (p > 0.05). MCA PI values were also significantly higher at the end of surgery in the phentolamine-treated group (1.83 +/- 0.50 vs 1.22 +/- 0.34; p < 0.01). Cooling and rewarming times were shorter in the phentolamine-treated group (p < 0.01, for all).

Despite improved peripheral vasodilatation and perfusion, phentolamine administration in pediatric open-heart surgery is correlated with increased cerebrovascular resistance and brain damage.