Difference between elderly and non-elderly patients in using serum lactate level to predict mortality caused by sepsis in the emergency department

Elderly people are more susceptible to sepsis and experience more comorbidities and complications than young adults. Serum lactate is a useful biomarker to predict mortality in patients with sepsis. Lactate production is affected by the severity of sepsis, organ dysfunction, and adrenergic stimulation. Whether the predictive ability of serum lactate will be different between non-elderly and elderly patients is unknown. A retrospective cohort study was conducted to compare the prognostic value of hyperlactatemia in predicting the mortality between elderly (≥65 years) and non-elderly (<65 years) patients with sepsis. This is a single-center retrospective observational cohort study conducted from January 2007 to December 2013 in southern Taiwan. All patients with sepsis, who used antibiotics, with blood culture collected, and with available serum lactate levels in the emergency department, were included in the analysis. We evaluated the difference in serum lactate level between the elderly and non-elderly septic patients by using multiple regression models. A total of 7087 patients were enrolled in the study. Elderly and non-elderly patients accounted for 62.3% (4414) and 40.2% (2673) of all patients, respectively. Statistically significant difference of serum lactate levels was not observed between elderly and non-elderly survivors (2.9 vs 3.0 mmol/L; P = .57); however, elderly patients had lower lactate levels than those within the 28-day in-hospital mortality (5.5 vs 6.6 mmol/L, P < .01). Multiple logistic regression revealed higher adjusted mortality risk in elderly and non-elderly patients with lactate levels of ≥4.0 mmol/L (odds ratio [OR], 4.98 and 5.82; P < .01, respectively), and lactate level between 2 and 4 mmol/L (OR, 1.57 and 1.99; P < .01, respectively) compared to that in the reference group with lactate levels of <2.0 mmol/L in each group. In receiver operating characteristic curve analysis, sensitivity rates for predicting mortality were 0.80 and 0.77 for non-elderly and elderly patients, respectively, by using serum lactate levels higher than 2.0 mmol/L. Septic elderly non-survivors had 1 mmol/L lower serum lactate level than those of the non-elderly non-survivors. Lactate >2 mmol/L still could provide enough sensitivity in predicting sepsis mortality in elder patients.