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The thrombogenicity of membrane oxygenators as well as clotting parameters profiles, using standard human clotting tests, was analyzed in calves and pigs during 6 h perfusion. Three calves and 3 pigs were connected to extracorporeal circulation with standard heparinization. Blood samples were taken for coagulation variables throughout perfusion, and oxygenators were examined for clot deposits at the end of the experiment. Two out of 3 oxygenators of the calf group presented clot deposits while none in the pig group did. Baseline coagulation variables of pigs showed values similar to those of humans while neither extrinsic nor intrinsic pathways could be activated in calves with standard human coagulation tests. The calf model, in conclusion, was confirmed to be a difficult model for the testing of extracorporeal circulation device resistance to thrombus formation, which is, however, not reflected by standard human coagulation tests. The pig model is a better model in which both coagulation pathways could be activated with standard human coagulation tests.

In a calf model, 3 standard and 3 heparin coated intraaortic balloons (IAB) were inserted and left deflated in the descending aorta during 20 min to simulate balloon rupture. At the end of the experiment, the IAB were examined, and 3 samples of each were collected for scanning electron microscopy (SEM) analysis. None of the heparin coated IAB showed any sign of clot or deposit whereas all 3 standard IAB exhibited clots. SEM revealed no deposit on the heparin coated samples while 8 of the 9 standard samples disclosed deposits (p < 0.001). Morphometrically, 16.1+/-21.4% of the surfaces of the standard samples were covered with deposits whereas all the heparin coated samples were free (p = 0.004). The presence of clots on every standard IAB supports the hypothesis that other than local factors of the insertion site can play a role in the vascular complications of IAB. The absence of clots and deposits on the heparin coated IAB suggests a promising role of such devices in circumventing the tendency of clot formation on deflated balloons while avoiding the drawback of systemic anticoagulation.

The AB-180 is a new implantable centrifugal pump with a low volume dome (10 ml) and a local heparin delivery system which avoids systemic heparinization. This study focuses on its hemodynamic performance. We analyzed 3 anesthetized calves (71.0 +/- 2.5 kg), equipped with arterial pressure (AP), and Swan-Ganz and left atrial pressure (LAP) catheters. The AB-180 pump was installed through a left thoracotomy, with a transmitral left ventricular (LV) inflow cannula inserted via the left appendage and an outflow tract sutured to the descending aorta. LAP, AP, and blood flow across the pump were recorded for various pump speed and in different preload conditions (right atrial pressure = 4, 7, and 10 mm Hg, respectively). The pump significantly unloaded the left heart cavities and was able to increase the mean AP. For an RAP of 10 mm Hg, running the pump at 4,500 rpm decreased the LAP from 11.0 +/- 0.8 mm Hg to 3.0 +/- 0.8 mm Hg (p < 0.001) and augmented the mean AP from 48.2 +/- 6.4 mm Hg to 80.8 +/- 12.1 mm Hg (p < 0.001). A maximal pump flow of 5.6 +/- 0.2 L/min was obtained under these conditions. In addition to the advantage of its particular design, the AB-180 can be considered as an efficient left ventricular assist device (LVAD). It significantly unloads the left heart cavities and ensures efficient systemic AP and blood flow.

Because of the risk of vein collapse, the benefits of using a centrifugal pump to assist venous drainage for cardiopulmonary bypass are limited when the tips of peripheral cannulas are maintained within the vena cava. Using a mock circuit including 20 mm diameter latex tubing to mimic a vena cava, we compared the performance of 6 commercially available peripheral venous cannulas and attempted to determine potential factors influencing maximal flow drainage before vein collapse. A close correlation was observed with the total hole area of the cannula. Best performance (5.10 ′ 0.08 L/min) was obtained with an 8 mm internal diameter (ID) cannula and 343 mm 2 total hole area. A larger cannula (ID 9.2 mm) with only 209 mm 2 total hole area drained 5.03 ′ 0.05 L/min whereas a smaller cannula (ID 6.7 mm) with a total hole area of 586 mm 2 also allowed a similar flow of 5.03 ′ 0.12 L/min. Therefore, the total hole area appears to be a critical factor in designing peripheral cannulas used in restricted chambers such as vena cavae.