Continuous hemodiafiltration with bicarbonate- and lactate-buffered replacement fluids in septic shock

Introduction

Acid-base imbalances are an important aspect while using continuous renal replacement techniques in critically ill patients. The quality of replacement fluid needs to be considered regarding to the acid-base requirements especially in septic patients. Commonly used replacement fluids contain lactate as buffer. Whereas lactate has to enter the Cori- or Citrate-Cycle to become effective as a buffer, bicarbonate can act immediately. The metabolism of lactate in addition is depending on the impaired liver function of patients with septic shock and represents an oxygen consuming process.

Methods

We investigated the metabolic effects of lactate- and bicarbonate-buffered hemofiltration substitution fluids in a clinical follow-up design in 13 patients (mean age 67 ± 9 years [± SD]) with acute renal failure during septic shock. All patients received continous veno-venous hemodiafiltration (CVVHDF, Prisma ^® Hospal). Seven patients have been treated with bicarbonate- (Schiwa Combi-Pac ^®, Schiwa) and 6 patients with conventional lactate-buffered replacement fluid (Biosol ^®, Hospal). We evaluated individual course of pH, HCO₃–, BE and lactate levels within the first 5 days after start of CVVHDF by linear regression analysis (Excel ^® regression-procedure). The slopes of the regression equations for bicarbonate- and lactate-buffered hemodiafiltration were compared by t-test (SPSS ^®).

Results

The use of bicarbonate replacement fluids for CVVHDF leads to a significant improvement of acid-base balance in the course of acute renal failure in septic shock. Linear regression equations for bicarbonate- and lactate CVVHDF are shown in the following table (mean ± SEM):

Discussion

Lactate buffered CVVHDF leads to the removal of large amounts of endogenous bicarbonate per day (600-1.000 mmol). Its impact on the acid-base balance in septic shock is considerable. The approach with bicarbonate replacement fluid for the treatment of acute renal failure in septic shock seems to be advantageous to normalize an impaired acid-base balance.

Table 1