Background and aim: Acidosis is able to induce negative changes of different organs that increase progressively with aging. At present it is not known whether the levels of lactate may differently influence the prognosis of younger and older patients. Thus, the aim of this study is to evaluate the prognostic value of lactate levels after admission of younger and older patients to an acute intensive care unit.
Methods: Younger (<65 years, n = 118) and older (≥65 years, n = 165) patients admitted to an acute intensive care unit were prospectively enrolled and classified according to diagnosis of acute heart or/and respiratory failure. For each patient, APACHE II score, time of hospitalization and mortality, blood levels of lactate were collected.
Results: Both in-hospital mortality and lactate >2.5 mmol/L at the admission was higher in the older than in the younger patients (42.4 vs. 20.3 %, p < 0.01 and 57.8 vs. 31.9 %, p < 0.01, respectively). Lactate level was higher in older than in the younger patients both at admission and after 24 h (3.9 ± 3.4 vs. 2.4 ± 2.2 mmol/L and 2.4 ± 2.0 vs. 1.4 ± 1.3 mmol, p < 0.01, respectively). Accordingly, multivariate analysis shows that lactate was predictive of mortality in younger (OR = 2.65, 95 % CI 1.62-5.24, p = 0.03) and even more in the older (OR = 4.74, 95 % CI 2.10-6.70, p < 0.01) patients.
Conclusions: Lactate concentration increase is associated with increased mortality in younger patients but, even more so, in older patients admitted to an acute intensive care unit. These results confirm the experimental evidence showing acidosis has a greater effect of leading to organ failure and higher mortality with increasing age.
Keywords: Elderly; Lactate; Mortality.