Objective evaluation of the efficacy of various venous cannulas

Six venous cannulas (USCI No. 32, USCI No. 40, USCI No. 44, Sarns No. 40, Sarns two-stage cavoatrial, and Ferguson Argyle No. 40) were tested for efficiency of venous flow during cardiopulmonary bypass, with and without aortic cross-clamping. Each cannula was tested six times in dog models (twice in each of three dogs) and the data were averaged. The tip of the cavoatrial Sarns catheter was positioned as recommended. Two No. 32 USCI caval cannulas were placed either with or without caval snaring. The other cannulas were placed in the right atrium. Arterial flow was constant at 80 ml/kg/min, and aortic pressure averaged 84 mm Hg. Central venous pressure and the right ventricle excluded from the pulmonary artery so that blood which was not drained via the venous cannula was measured. Each single atrial cannula decompressed the right atrium (right atrial pressure 0 to 1 mm Hg) better than two caval cannulas (right atrial pressure 0 to 2 mm Hg). Caval snaring did not empty the right atrium (right atrial pressure 2 to 5 mm Hg) as well as any single cannula. The cavoatrial Sarns catheter did not empty the right atrium as well (right atrial pressure 2 to 4 mm Hg), but drained blood from the inferior vena cava (central venous pressure 0 mm Hg) better than other atrial cannulas (central venous pressure 1 to 5 mm Hg). All of the atrial cannulas performed equally well. The right ventricular vent flow varied between 63 and 70 ml/min with each of the atrial cannulas but rose to 85 ml/min with the cavoatrial Sarns catheter and 190 and 74 ml/min during caval cannulation with and without snaring, respectively. Aortic cross-clamping eliminated coronary sinus flow and decreased right ventricular vent flow. Therefore, a single atrial cannula is more efficient in draining blood from the right side of the heart than are two caval or a cavoatrial cannula. This advantage is negated by aortic cross-clamping.