Lactic acidosis epidemiology and demographics
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saud Khan M.D.
Overview
Lactic acidosis is a common event in the high dependency units of a hospital, however the exact prevalence is difficult to estimate, as it usually occurs in critically ill patients.
Epidemiology and Demographics
Incidence Among type 2 diabetics, lactic acidosis is a rare event, with an estimated incidence of 4.3 cases per 100,000 person-years in metformin users. The occurrence in type 2 diabetes is alarming as the mortality can be up to 50%. A secondary analysis of more than 41,000 person-years in type 2 diabetes showed that the incidence of LA in diabetic patients not exposed to metformin was between 9.7 and 16.7 per 100,000 person-years. Lactic acidosis often occurs in patients with acute severe asthma, most likely due to fatiguing respiratory muscles and subsequent inadequate oxygen delivery to the muscles and liver ischemia. Severe lactic acidosis also occurs in sedated mechanically ventilated patients without respiratory muscle activity. Hyperlactatemia is also associated with antiretroviral therapy. In a large study, incidence was found to be 18.3 per 1000 person-years with antiretroviral therapy and 35.8 per 1000 person-years for stavudine (d4T) regimens.
Case Fatality Rate Jung et al. found that of the studied population of 2550 patients, severe lactic acidosis occurred in 6% . Among those treated with vasopressors, mortality was 57%, with a pH of 7.09 (+-0.11) and high lactic acid values. The higher the level and the longer the time for normalization, the greater the mortality. Shock and severe lactic acidosis (pH less than 7.2) are often comorbid, and this carries a mortality rate of about 50%. No survival has been reported for severe lactic acidosis with shock when the pH had fallen under 7.0. Interestingly, this contrasts to lactic acidosis associated with non-shock states, as in metformin-induced lactic acidosis producing pH values of 7.0 where observed mortality was only 25%. Patients who have an arterial lactate level of more than 5 mmol/L and a pH of less than 7.35 are critically ill and have a very poor prognosis. Multicenter trials have shown a mortality rate of 75% in these patients. A stepwise logistic regression model identified serum lactate, anion gap acidosis, phosphate, and age as independent predictors of mortality in patients with lactic acidosis compared to patients with metabolic acidosis. In patients with suspected sepsis, lactate levels between 2.0 and 3.9 mmol/L were associated with a moderate-to-high risk of mortality, independent of the patients blood pressure. Overall, there is a high mortality rate (70%) among patients with a serum lactate level greater than 2 mmol/L which persists after 24 hours with an associated acidemia.
Gender The prevalence and incidence of lactic acidosis does not vary by gender.