Thrombocytopenia in septic shock patients--a prospective observational study of incidence, risk factors and correlation with clinical outcome.

The objectives of the study were to study the incidence of various degrees of severity of thrombocytopenia in septic shock, the risk factors for its development and the correlation with clinical outcome. Complete blood counts, chemistry panel, arterial lactate, serum cortisol, APACHE II score, logistic organ dysfunction score and SOFA score were determined in 69 septic shock patients within 24 hours of admission or onset of septic shock. We followed the patients until they died or for six months to determine the mortality rate. The incidence of thrombocytopenia in our study group was 55%. Patients with thrombocytopenia had significantly higher serum creatinine, SOFA score, vasopressor requirement, lower PaO2/FiO2 ratio and higher mortality than those without thrombocytopenia (P < 0.05). Higher SOFA score, low P(a)O2/FiO2 ratio and high vasopressor dose were independent risk factors for development of thrombocytopenia. The presence of thrombocytopenia had significant correlation with SOFA score (P = 0.008). On receiver-operator characteristic curve analysis, platelet count was found to be predictive of increased mortality (area under curve = 0.56). Thrombocytopenic patients had 1.4 times the risk of mortality and lower survival probability at six months (log rank test P = 0.03). In conclusion, thrombocytopenia is common in septic shock and is associated with worse clinical outcome. Higher SOFA score, low P(a)Os/FiO2 ratio and high vasopressor dose are independent risk factors for development of thrombocytopenia in septic shock.