Is hypothermia a benefit? Von Willebrand factor in pediatric cardiopulmonary bypass

The use of cardiopulmonary bypass (CPB) is associated with the risk of development of postpump syndrome. Thrombocyte activation leads to microembolism, endothelial damage and necrosis with release of various substances, such as the von Willebrand factor (vWf). High levels of vWf increase the risk of postoperative complications and mortality. Our objective was to find a correlation between CPB and plasma levels of vWf in pediatric patients operated on for congenital heart defects.

Twenty patients with congenital heart defects (ventricular septal defect, atrial septal defect/partial anomalous pulmonary vein drainage, Bland White Garland syndrome) were operated on with the use of CPB. The arterial blood was sampled after induction of anesthesia, 5 minutes after commencing CPB, 1 hour and 3 hours after surgery. The plasma levels of vWf were measured and compared to selected clinical findings.

There was no early mortality. There were no significant differences in CPB and aortic cross clamp times when compared in patients with various defects. vWf plasma levels were significantly elevated in all patients 1 hour and 3 hours after surgery. We found no correlation between vWf levels and type of defect, CPB duration, aortic cross clamp as well as reperfusion time. However, we were able to demonstrate that the observed elevation of vWf levels was almost 4-fold higher in patients cooled down to lower temperatures (15 patients; mean rectal value 27.64+/-0.7 degrees C) than in 5 patients (mean rectal temperature 30.74+/-1.56 degrees C) where only slight elevation was found. There were no differences in the postoperative course of these patients. All patients were discharged from hospital 10+/-3 days after operation (mean value 9 days).

vWf plasma levels are significantly elevated after pediatric hypothermic CPB. It seems that the augmentation of vWf values could be independently associated with rate of hypothermia.