Effects of high-volume hemofiltration on alveolar-arterial oxygen exchange in patients with refractory septic shock

BACKGROUND: High-volume hemofiltration (HVHF) is technically possible in severe acute pancreatitis (SAP) patients complicated with multiple organ dysfunction syndrome (MODS). Continuous HVHF is expected to become a beneficial adjunct therapy for SAP complicated with MODS. In this study, we aimed to explore the effects of fluid resuscitation and HVHF on alveolar- arterial oxygen exchange, the Acute Physiology and Chronic Health Evaluation II (APACHE II) score in patients with refractory septic shock.METHODS: A total of 89 refractory septic shock patients, who were admitted to ICU, the Provincial Hospital affiliated to Shandong University from August 2006 to December 2009, were enrolled in this retrospective study. The patients were randomly divided into two groups: fluid resuscitation (group A, n=41), and fluid resuscitation plus high-volume hemofiltration (group B, n=48). The levels of O₂ content of central venous blood (C_cvO₂), arterial oxygen content (C_aO₂), alveolar-arterial oxygen pressure difference P_(A-a)DO₂, ratio of arterial oxygen pressure/alveolar oxygen pressure (P_aO₂/P_AO₂), respiratory index (RI) and oxygenation index (OI) were determined. The oxygen exchange levels of the two groups were examined based on the arterial blood gas analysis at different times (0, 24, 72 hours and 7 days of treatment) in the two groups. The APACHE II score was calculated before and after 7-day treatment in the two groups.RESULTS: The levels of C_cvO₂, C_aO₂ on day 7 in group A were significantly lower than those in group B (C_cvO₂: 0.60±0.24 vs. 0.72±0.28, P<0.05; CaO₂: 0.84±0.43 vs. 0.94±0.46, P<0.05). The level of oxygen extraction rate (O₂ER) in group A on the 7th day was significantly higher than that in group B ( 28.7±2.4 vs. 21.7±3.4, P<0.01). The levels of P_(A-a)DO₂ and RI in group B on the 7th day were significantly lower than those in group A. The levels of P_aO₂/P_AO₂ and OI in group B on 7th day were significantly higher than those in group A (P<0.05 or P<0.01). The APACHE II score in the two groups reduced gradually after 7-day treatment, and the APACHE II score on the 7th day in group B was significantly lower than that in group A (8.2±3.8 vs. 17.2±6.8, P<0.01).CONCLUSION: HVHF combined with fluid resuscitation can improve alveolar- arterial-oxygen exchange, decrease the APACHE II score in patients with refractory septic shock, and thus it increases the survival rate of patients.