Introduction and Aims: Lactate accumulation / lactic acidosis are associated with poor clinical outcome in critically ill patients. Treatment of the underlying condition as tissue hypoxia is essential in the care of these patients. However, since bicarbonate infusion may be harmful due to intracellular acidification and pH related hypocalcaemia, hemodialysis provides an important treatment modality in lactic acidosis. The effect of hemodialysis on lactate clearance rates and serum levels seems important in a lactate-guided intensive care therapy, while the role of hyperlactatemia itself remains unclear. To our knowledge, this is the first study, that measures total lactate removal in extended dialysis.
Methods: We enrolled 20 critically ill patients with renal replacement therapy dependent AKI on our ICU. All patients or their legal representatives gave written informed consent. Every patient received an extended dialysis treatment (blood flow and dialysate flow ranged from 180-250/min) with the GENIUS dialysis batch system and the F60 dialyzer (polysulphone, 1.3 m2, FMC, Germany). Blood lactate levels were measured at the beginning, after 15 min, 30 min, 60 min, 120 min, 240 min and at the end of every dialysis session as well as 15 after dialysis. Blood flow was adjusted over a short-term to 100 and 300 ml/min for dialyzer clearance measurements. Lactate levels in the total spent dialysate were measured to calculate the total removed lactate mass.
Results: Extended dialysis decreased blood lactate levels with a lactate reduction ratio of 61.5 ± 19.5 %. A total amount of 130 ± 125 mg lactate was eliminated during a single dialysis treatment. Removed total lactate mass was significantly increased in patients with serum lactate levels of > 2.5 mmol/l (2.5 mmol/l: 29.1 ± 6 vs. 300 ± 87.8 mmol/l, p=0.0005) and correlates with serum lactate levels at the begin of treatment (Figure 1).
Dialyzer lactate clearance was significantly increased during hemodialysis with higher blood flow rates (100 vs. 300 ml/min: 39.8 ± 2.7 vs. 111.7 ± 6.5 ml/min, p<0.0001). Lactate rebound 15 min after dialysis was 27.7 ± 83.3 % (Figure 2).
Results are given in mean ± SEM.
Conclusions: Extended dialysis can remove a substantial amount of lactate, although the quantity produced in severe sepsis may be much higher. The mass of lactate removed is related to the burden of lactate at the start of the treatment. Lactate dialyzer clearance is highly dependent on blood flow rates and raises directly proportional with its increase. Due to the marked rebound of serum lactate a continuous treatment would be necessary to control the blood levels of lactate. The clinical significance of this intervention remains to be determined.
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