Intracranial pressure and venous cannulation for cardiopulmonary bypass.

Abstract

The onset of cardiopulmonary bypass (CPB) is a period of changing hemodynamics, and during this transition, the position of the aortic and venous cannulas is assessed. Increased arterial line pressures may indicate a malposition of the aortic cannula, whereas reduced venous return to the reservoir of the CPB circuit suggests suboptimal position of a venous cannula. Classically described signs of compromised venous drainage, such as engorgement of the head and neck, are rare, and incomplete obstruction of the superior vena cavae may be difficult to detect clinically but can significantly alter cerebral physiology. Impedance to superior vena caval (SVC) flow may increase intracranial pressure (ICP) and decrease cerebral perfusion pressure (CPP) (CPP 5 mean arterial pressure [MAP] 2 [ICP] (1). In the experimental setting, we have incidentally, but repeatedly, observed this effect. The same physiologic phenomenon is of relevance in the operating suite and may bear on practice. The purpose of this article is to briefly describe the influence of venous cannula position on ICP during CPB.