Aspects of cerebral perfusion in open-heart surgery

A selected series of 25 patients undergoing open-heart surgery were subjected to continuous monitoring of arterial blood pressure (BP), central venous pressure (CVP) and intracranial epidural pressure (EDP). This gave continuous information on the cerebral perfusion pressure (CPP = BP-EDP). In all patients the start of the extracorporeal perfusion caused a rapid fall in CPP (30 mmHg or less in 22 patients, less than 10 mmHg in 5 patients). The combination of grave systemic hypotension and increased EDP contributed to these low CPP states, which varied in duration from 2 to 15 min. Spontaneous, as well as vasopressor-induced BP recovery was accompanied by a concomitant increase in EDP in 15 patients. This prolonged the low CPP state, making an evaluation of CPP from BP alone misleading under such conditions. Increasing EDP secondary to a rise in BP was also observed during termination of the extracorporeal circulation, particularly in 6 patients requiring an intra-aortic balloon pump in addition to large doses of vasopressors to obtain an acceptable BP. An increase in CVP to levels above EDP is transmitted intracranially, thus reducing the CPP. The recordings may improve insight into pathogenic mechanisms leading to harmful effects on the brain in connection with open-heart surgery.