Introduccion: Modified ultrafiltration (muf) in children undergoing cardiac surgery, improves cardiac function after cardiopulmonary bypass (cpb). Increase in cardiac output and blood pressure, has been described so far. The exact mechanism underlying these hemodynamic changes remains unclear. We hypothesize that changes in blood pressure after muf are mostly related to changes in viscosity, due to a rise in hematocrit. The aim of this study is to assess blood viscosity pre and post muf, and correlate those measurements with changes in both systolic and diastolic blood pressures simultaneously.

Methods: After written consent and institutional approval, 23 children scheduled for cardiac surgery with cpb and muf were prospectively studied. Plasma and blood viscosity were measured with a digital viscometer brookfield®, 37ºc (100 and 50 rpm). Systolic and diastolic blood pressures were recorded. All measurements were performed, immediately after cpb before and after muf. Anesthesia and cpb technique were uniform for all patients.

Results: (Graphics)

Conclusion: Blood pressures, and plasma and blood viscosity increases significantly after muf. However there is no correlation between changes in blood pressure and changes in blood viscosity after muf. Hemodynamic improvement after muf are not primary related to changes in viscosity, but probably to other mechanisms, not well studied as yet.