Mechanism of lactic acidosis in children with acute severe asthma

OBJECTIVE:: Hyperlactatemia and lactic acidosis are common in adults with acute severe asthma however only a few cases have been reported in children. Type A lactic acidosis is associated with impaired oxygen delivery; type B occurs in the presence of normal oxygen delivery and has been described to occur with excessive adrenergic stimulation. Type A and B lactic acidosis can be distinguished by the blood lactate/pyruvate ratio. Our objectives are to 1) investigate the incidence of hyperlactatemia and lactic acidosis in children with acute severe asthma, and 2) determine whether lactate elevation is type A or B. DESIGN:: Prospective observational study. SETTING:: University-affiliated tertiary care children's hospital. PATIENTS:: All children (n = 105) with acute severe asthma admitted to the pediatric intensive care unit between May 1, 2008 and November 30, 2009 were included. INTERVENTIONS:: Blood lactate concentration was measured on a blood gas analyzer for all blood gas assessments obtained for clinical care. Hyperlactatemia was defined as lactate >2.2 mmol/L and lactic acidosis as lactate >5 mmol/L and pH <7.35. If lactate concentration was >5 mmol/L, consent was requested for measuring blood lactate and pyruvate using enzymatic laboratory methods. Lactate/pyruvate ratio >25:1 indicated type A lactic acidosis. MEASUREMENTS AND MAIN RESULTS:: Eighty-seven (83%) children had lactate >2.2 mmol/L and 47 (45%) had lactate >5 mmol/L. Of those with lactate >5 mmol/L, 33 (70%) had corresponding blood pH <7.35. Lactate/pyruvate ratios were obtained for 16 patients. Of these, lactate/pyruvate ratio was <10 in three patients; 10-25 in 11; >25 in one; and indeterminate in one. CONCLUSIONS:: Lactic acidosis is common in children with acute severe asthma and is primarily type B occurring in the presence of normal oxygen delivery.