Severe hyperlactatemia with normal base excess: a quantitative analysis using conventional and Stewart approaches.

Area of Science:

• Critical Care Medicine
• Nephrology
• Acid-Base Physiology

Background:

• Critically ill patients can exhibit complex acid-base disorders despite normal pH, PCO2, bicarbonate ([HCO3-]), and base excess ([BE]) levels.
• Severe hyperlactatemia, an acidifying process, may be masked by concurrent alkalinizing conditions that normalize [BE].

Purpose of the Study:

• To quantify complex acid-base disorders in critically ill patients with severe hyperlactatemia.
• To investigate the masking effect of alkalinizing processes on hyperlactatemia-induced acidosis using Stewart and conventional approaches.

Main Methods:

• Prospective evaluation of 1,592 intensive care unit (ICU) patients upon admission.
• Stratification of patients with severe hyperlactatemia (lactate ≥ 4.0 mmol/l) into low [BE] (<-3 mmol/l) and normal [BE] (> -3 mmol/l) groups.

Main Results:

• Severe hyperlactatemia was identified in 11% of patients (n=168).
• Patients with normal [BE] and severe hyperlactatemia exhibited lower plasma chloride ([Cl-]) and higher differences between anion gap and [HCO3-] changes, suggesting hypochloremic alkalosis.
• Shock was more prevalent in the low [BE] group, while COPD was more common in the normal [BE] group.

Conclusions:

• Severe hyperlactatemia can coexist with normal pH, [HCO3-], and [BE] in critically ill patients.
• Associated hypochloremic alkalosis frequently masks the acidifying effects of severe hyperlactatemia, leading to normal [BE] values.
• Accurate quantification of acid-base disorders requires advanced approaches beyond conventional parameters.