Expected and observed mortality in critically ill patients receiving initial antibiotic therapy.

OBJECTIVE: To evaluate the predictors of mortality in critically ill patients receiving initial antibiotic therapy (IAT; < 48 h after admission).
METHODS: Six hundred thirty-one consecutive patients admitted to an intermediate care (IMC) unit were included. IAT was initiated in 227 patients. Laboratory markers, interventions, medications, systemic inflammatory response syndrome (SIRS) and sepsis criteria, length of stay, and hospital mortality as well as expected mortality, based on the SAPSII-expanded score, were assessed retrospectively. Failure of IAT was defined as a rise in C-reactive protein (CRP) or leukocyte count on day 3 compared with the values on admission.
RESULTS: Patients with IAT were significantly older (67 ± 14 vs. 64 ± 14 years; p = 0.006) and had a higher prevalence of chronic renal failure (33 vs. 23 %; p = 0.015), chronic obstructive pulmonary disease (COPD; 27 vs. 16 %; p = 0.002), malignoma (17 vs. 9 %; p = 0.007), acute renal failure (11 vs. 4 %; p = 0.001), respiratory failure (22 vs. 7 %; p < 0.001), and a shock index < 1.0 (21 vs. 8 %; p < 0.001). Although patients with IAT did not have significantly different expected mortality compared with patients without IAT (19.2 vs. 14.5 %; p = 0.144), they did have a significantly higher observed mortality (16.7 vs. 3.7 %; p < 0.0001). Based on the number of SIRS criteria (0, 1, 2, or 3-4) or sepsis criteria (no sepsis, sepsis, or severe sepsis) fulfilled, expected mortality (16.4, 18.2, 20.6, or 21.0 %, respectively; p = 0.955/17.5, 18.3, or 23.4 %, respectively; p = 0.689) did not differ in IAT patients. In contrast, observed mortality differed significantly (4.8, 10.6, 20.6, or 29.4 %, respectively; p = 0.029/8.3, 19.7, or 29.3 %, respectively; p = 0.013). Patients who responded to IAT did not differ regarding comorbidities, SIRS or sepsis criteria, but they had a lower observed mortality (11.9 vs. 26.3 %; p = 0.008) than patients who failed to respond to IAT. Central venous lines were more frequently present in patients with failure to IAT when compared with those with response (51 vs. 22 %; p = 0.009). In the subgroup of patients with acute myocardial infarction (AMI), those with IAT (n = 41) were treated less frequently according to the current cardiac guidelines than those without (n = 124)
CONCLUSIONS: Patients with IAT have a high morbidity burden and higher observed than expected mortality. The SAPSII-expanded score does not seem to precisely estimate the risk of in-hospital mortality in these patients. Failure of response to IAT was associated with an even higher mortality. Whether central venous lines and nonadherence to cardiac care guidelines influence the mortality of patients with IAT should be investigated in further studies.