Interleukin-10 plasma levels in the critically ill

Objective: Interleukin-10 (IL-10) is known to function as an important suppressor of the inflammatory response. Plasma levels of IL-10 were studied serially over a period of five days in critically ill patients. Design: Prospective study. Setting: Clinical investigation in a surgical Intensive Care Unit of a university hospital. Subjects: Twenty trauma patients (Injury Severity Score [ISS] > 15 points) and 40 sepsis patients secondary to major surgery were included in the study. Interventions: Standard principles of intensive care therapy were used in the management of all patients. Sepsis patients randomly received either 1.5 mg/kg/hr pentoxifylline (PTX) iv for five days (sepsis-PTX, n=20) or saline solution as placebo (sepsis-control). Measurements and main results: From arterial blood samples IL-10 plasma concentrations were measured using a sandwich enzyme-linked immunosorbent assay (ELISA) (normal values in healthy volunteers: < 5 pg/ml) on the day of admission to the Intensive Care Unit (='baseline') and during the following five days. At baseline IL-10 plasma levels in the trauma patients (14.0±6.1 pg/ml) were significantly lower than in the sepsis patients (sepsis-control: 42.4±22.0. pg/ml; sepsis-PTX: 39.0±15.1 pg/ml) (p<0.01). When eliminating all patients who died during and after the study period (trauma: n=5; sepsis-control: n=6, sepsis-PTX: n=5), IL-10 decreased in both the trauma group (from 10.1±3.5 to 4.2±2.0 pg/ml) and in the sepsis patients. In the sepsis group continuous infusion of PTX did not influence survival rate nor plasma levels of IL-10. The baseline IL-10 plasma level in the survivors (all three groups; n=44) was significantly lower (30.1±9.1 pg/ml) than that of all non-survivors (n=16; 48.5±18.9 pg/ml). In the survivors IL-10 decreased to 15.5±4.4 pg/ml at the end of the study (p<0.05), whereas it significantly increased in the non-survivors from the third day onwards (to 109.1±22.2 pg/ml). All patients showing IL-10 plasma levels >50 pg/ml over three days died. Conclusions: IL-10 appears to be an important anti-inflammatory substance. It is another marker for assessing the degree of inflammation and may even help to predict outcome. Pentoxifilline infusion failed to affect IL-10 plasma level beneficially. More controlled studies are necessary to elucidate how IL-10 can best be influenced and whether therapeutic manipulation of IL-10 plasma concentration is helpful in improving patient outcome.