Effect of cardiac arrest on cerebral circulation. An experimental investigation.

The effect of 2 to 15 min of cardiac arrest on cerebral circulation was investigated in dogs and Rhesus monkeys. When circulatory arrest lasted longer than 5 minutes, angiographic changes of the no-reflow phenomenon were observed between 3 and 4 h after resuscitation in dogs but not in monkeys. These findings were (1) marked prolongation of the arterial phase in both intracranial and extracranial arteries; followed by (2) occasional evidence of dilatation of the proximal intracranial arteries with non-filling of the distal intracranial arteries; and (3) faint demonstration of the venous phase.

Mechanisms of contractile response of cerebral artery to externally-applied fresh blood.

The authors report and analyze the in vitro contractions of fresh bovine cerebral artery on exposure to blood. The vessel does not contract significantly until blood clots on its surfaces; the contraction begins at the moment of clotting and is maintained as long as extracellular calcium is available. Comparative studies with vasoconstrictor amines suggest that serotonin, liberated from platelets by the clotting process, is responsible for this contraction and that the adherent clot itself concentrates the serotonin of the surface of the vessel.