Venoarterial modified ultrafiltration versus conventional arteriovenous modified ultrafiltration during cardiopulmonary bypass surgery
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INTRODUCTION: The role of modified ultrafiltration (MUF) in removing inflammatory mediators, reducing the need for homologous donor blood and decreasing pulmonary vascular resistance after cardiopulmonary bypass (CPB) has already been established. Different types of MUF systems evaluated illustrated that none of the MUF techniques adhered to the normal venous to arterial blood flow dynamics. OBJECTIVES: This experimental study compared a conventional arteriovenous modified ultrafiltration (AVMUF) system to a custom designed venoarterial modified ultrafiltration (VAMUF) system. This technique of VAMUF was designed to mimic the pro-grade flow pattern of the body and cardiopulmonary bypass circuit as compared to the conventional retrograde AVMUF systems. METHODS: Sixty patients that underwent MUF were divided into two groups, the AVMUF (n = 30) and the VAMUF (n=30) groups. Modified ultrafiltration was performed for a mean time of 12 minutes in both groups. In AVMUF blood was removed from the aorta, haemoconcentrated and infused into the right atrium (RA). In VAMUF blood flow was from the RA through a haemoconcentrator and re-infused into the aorta. RESULTS: There was no significant difference in any of the demographic variables, CPB or crossclamping time. Results showed significant difference in the ventilation times, with the VAMUF requiring a shorter ventilation time than the AVMUF group. Intensive care unit (ICU) stay, Hospital stay and discharge days were all significantly lower in the VAMUF group as well. The VAMUF also showed a lower percentage fluid balance than the AVMUF. The systolic and mean blood pressure was significantly higher after VAMUF with a decrease in heart rate, and central venous pressure (CVP). The VAMUF group showed a significantly greater decrease of Creatinine, serum lactacte and uric acid over time with no significant differences in oximetry. CONCLUSION: Results prove that VAMUF is more effective compared to the conventional AVMUF regarding the haemodynamics and clinical parameters of the patient and is more physiological with regards to blood flow dynamics. The VAMUF is, therefore, a more physiological technique than AVMUF.