How to manage high lactate levels in patients with Acute Kidney Injury (AKI)?

Managing High Lactate Levels in Patients with Acute Kidney Injury

In patients with acute kidney injury (AKI) and elevated lactate levels, bicarbonate should be used instead of lactate as a buffer in dialysate and replacement fluid for renal replacement therapy (RRT), especially in those with circulatory shock, liver failure, or lactic acidemia. 1

Understanding Lactate Elevation in AKI

• Elevated lactate in AKI patients is a significant predictor of mortality, with higher levels associated with worse outcomes 2
• The primary causes of elevated lactate include tissue hypoperfusion, sepsis, shock states, and trauma 3
• In AKI, altered glycolysis and gluconeogenesis significantly disturb lactate metabolic balance, impacting disease severity and prognosis 4
• Hyperlactatemia is particularly concerning in critically ill AKI patients requiring continuous renal replacement therapy (CRRT), with higher lactate levels correlating with increased mortality risk 2

Diagnostic Approach

• Measure serum lactate levels to estimate and monitor tissue perfusion status; levels >2 mmol/L indicate potential tissue hypoperfusion 3
• Perform serial lactate measurements to objectively evaluate response to therapy 3
• Consider base deficit values from arterial blood gas analysis as an indirect estimation of global tissue acidosis 3
• Categorize patients based on lactate levels: low (≤2 mmol/L), moderate (2.1-7.5 mmol/L), and high (≥7.6 mmol/L) to stratify mortality risk 2

Management Strategies

Renal Replacement Therapy Considerations

• Use bicarbonate rather than lactate as a buffer in dialysate and replacement fluid for RRT in all AKI patients (Grade 2C recommendation) 1
• This recommendation is stronger (Grade 1B) for patients with AKI and circulatory shock 1
• For patients with AKI and liver failure and/or lactic acidemia, bicarbonate is also preferred over lactate as a buffer (Grade 2B) 1
• Account for additional calories provided by lactate (3.62 kcal/g) in RRT solutions when calculating total daily energy provision to avoid overfeeding 1

Addressing Underlying Causes

• Identify and treat the underlying cause of elevated lactate, focusing on improving tissue perfusion in shock states 3
• In hypovolemic AKI, administer volume replacement (albumin at 1 g per kg body weight to maximum 100 g/day) to reduce serum creatinine 1
• For patients with significant blood loss, maintain hemoglobin at 8 g/dL while carefully monitoring volume status 1
• Consider medication effects on lactate levels, such as those caused by epinephrine through beta-2-adrenergic stimulation 3

Monitoring and Prognostic Implications

• Monitor lactate clearance time, as it is a significant predictor of survival 3
• Normalization of lactate levels within 24 hours is associated with improved survival 3
• Consider adding serum lactate levels to prognostic models like SOFA and APACHE II scores for better mortality risk prediction in CRRT patients 2
• Be aware that initial lactate concentration may not discriminate between survivors and non-survivors in patients with severe lactic acidosis receiving RRT 5

Special Considerations

• CRRT use might be associated with elevation of longitudinal lactate levels in sepsis-associated AKI patients 6
• Energy excess provided by RRT could be partially avoided by using protocols based on lower citrate concentration solutions, bicarbonate as a buffer, and citrate solutions without glucose 1
• Consider diffusive prolonged intermittent kidney replacement therapy modalities like sustained low-efficiency dialysis (SLED), which allow increased citrate removal 1
• Recent research suggests that reducing lactate levels through pyruvate dehydrogenase activation may attenuate sepsis-induced AKI 7

Pitfalls to Avoid

• Don't ignore elevated lactate in seemingly stable patients, as it may indicate occult tissue hypoperfusion 3
• Avoid using high lactate replacement fluids in AKI patients with elevated lactate levels 1
• Don't overlook the caloric contribution of lactate in RRT solutions, which can provide up to 1300 kcal/day 1
• Be aware that critically ill patients with AKI oxidize fewer carbohydrates and more lipids than expected, which may affect nutritional management 1