Septic shock of early or late onset: does it matter?

STUDY OBJECTIVES To determine possible differences in morbidity and mortality between early and late onset of septic shock in ICU patients. DESIGN Systematic data collection. SETTING Thirty-one-bed, mixed, medicosurgical ICU in a university hospital. PATIENTS All 65 patients who acquired septic shock after admission to the ICU between February 1999 and April 2000. INTERVENTIONS None. MEASUREMENTS AND RESULTS Forty-one of the 65 patients presented with septic shock within 24 h of admission to the ICU (early septic shock [ESS]); the other 21 patients acquired septic shock > 24 h after ICU admission (late septic shock [LSS]). Eleven patients had a second episode (7 patients in the ESS group, and 4 patients in the LSS group), and 1 patient in the LSS group had a third episode of septic shock. Patients with ESS had higher APACHE (acute physiology and chronic health evaluation) II (mean +/- SD, 26 +/- 6 vs 20 +/- 6; p = 0.002) and sequential organ failure assessment (SOFA) scores (11 +/- 3 vs 7 +/- 3, p < 0.001) on ICU admission, and a higher blood lactate concentration at the onset of shock (median 3.70 mEq/L; interquartile range, 2.6 to 6.6 mEq/L; vs median, 2.50 mEq/L [interquartile range, 1.8 to 4.0 mEq/L], p = 0.03) than patients with LSS. However, the duration of septic shock (median, 42 h [interquartile range, 21 to 97 h] vs median, 93 h [interquartile range, 32 to 241 h], p = 0.058) and the length of ICU stay after the onset of septic shock (median, 75 h; [interquartile range, 38 to 203 h] vs median, 321 h [interquartile range, 96 to 438 h], p = 0.018), was shorter in patients with ESS than patients with LSS. The ICU mortality rate was 63% (26 patients) in the ESS group, and 88% (21 patients) in the LSS group (p = 0.071). At the onset of the first episode of shock, patients with ESS had higher SOFA scores (11 +/- 3 vs 9 +/- 3, p = 0.045), lower pH (7.24 +/- 0.15 vs 7.33 +/- 0.12, p = 0.01), and were treated with higher doses of dopamine (median, 20 microg/kg/min [interquartile range, 14 to 20 microg/kg/min] vs median, 12 microg/kg/min [interquartile range, 8 to 20 microg/kg/min], p = 0.028) than patients with LSS. CONCLUSIONS Septic shock is more severe when of early onset, as reflected by more severe organ dysfunction, greater lactic acidosis, and higher vasopressor requirements, yet the outcome is better, as reflected by a shorter duration of the shock episode, shorter ICU stay, and slightly lower mortality rates. These differences may influence clinical trials of therapeutic agents for sepsis, and should be taken into account when analyzing the results.