A prospective study of thrombocytopenia and prognosis in intensive care

Introduction

To study the incidence and prognosis of thrombocytopenia in an adult critically ill population. 329 patients consecutively admitted during a 5-month period to the medical intensive care unit (ICU) of a university hospital (212 patients) and a medical-surgical ICU of a regional hospital (117 patients), were prospectively surveyed. The primary outcome measure was ICU mortality.

Results

One hundred and thirty-six patients (41.3%) had at least one platelet count < 150 × 10⁹/l. These patients displayed a higher APACHE (Acute Physiology and Chronic Health Evaluation) II, SAPS II (new Simplified Acute Physiology Score) and MODS (Multiple Organ Dysfunction Score) at admission, longer ICU stay (8 versus 5 days median (interquartile range)) and a higher mortality rate (crude odds ratio, OR = 5.0, 95% confidence interval, CI 2.7–9.1) than those who never developed thrombocytopenia (P < 0.0005 for all comparisons). Bleeding incidence rose from 4.1% in non-thrombocytopenic patients to 21.4% in patients with minimal platelet counts between 101 and 149 × 10⁹/l (P = 0.0002), and to 51.9% in patients with minimal platelet counts < 100 × 10⁹/l (P < 0.0001). 19.5% of the study population died in the ICU following the index admission. Eighteen of 193 patients (9.3%) who never became thrombocytopenic died, versus 31 of 89 patients who were thrombocytopenic at admission (OR = 5.2, 95% CI 2.7–9.8, P < 0.0001) and versus 15 of 47 patients (31.9%) who developed thrombocytopenia later on during ICU stay (OR = 4.6, 95% CI 2.1–10.0, P = 0.0002). In addition we found that a drop in platelet count to ≤ 50% of admission was associated with higher death rates (OR = 6.0, 95% CI 3.0–12.0. P < 0.0001). In a linear regression analysis, adjusting for admission APACHE II. SAPS II and MODS, admission thrombocytosis and the occurrence of bleeding, nadir thrombocytosis remained significantly related to ICU mortality.

Conclusion

Thrombocytopenia is a simple and readily available risk marker for ICU mortality, independent of and complementary to established severity of disease indices. Both a low nadir thrombocytosis and a significant fall of platelet count predict a poor vital outcome in adult ICU patients.