Sequential Organ Failure Assessment in H1N1 pandemic planning

Abstract

Objective: The H1N1 pandemic has highlighted the importance of reliable and valid triage instruments. A Sequential Organ Failure Assessment score of >11 has been proposed to exclude patients from critical care resources quoting an associated mortality of >90%. We sought to assess the mortality associated with this Sequential Organ Failure Assessment threshold and the resource implications of such a triage protocol.

Design: Retrospective cohort.

Setting: Three multisystem intensive care units.

Patients: Consecutive patients admitted from January 2003 to December 2008. Subsequently, a comparison H1N1 cohort was assembled consisting of all patients admitted in 2009 with confirmed H1N1.

Interventions: None.

Measurements and main results: Sequential Organ Failure Assessment was collected daily by use of an electronic bedside clinical information system (n = 10,204 patients, 69,913 patient days). Mean admission Acute Physiology and Chronic Health Evaluation was 19.1. 13.4% of the cohort (9% of total patient days) had an initial Sequential Organ Failure Assessment of >11. Mortality in patients with an initial Sequential Organ Failure Assessment score of >11 was 59% (95% confidence interval: 56%, 62%). The mortality associated with an initial Sequential Organ Failure Assessment >11 across diagnostic categories varied from 29% for poisoning to 67% for neurologic patients. Hospital mortality exceeded 90% only when initial Sequential Organ Failure Assessment was >20 (0.2% of patients). H1N1 patients were younger, had a longer intensive care unit length of stay, and more commonly had a respiratory admission diagnosis than the nonH1N1 cohort. Hospital mortality in H1N1 patients with an initial Sequential Organ Failure Assessment score of >11 was 31% (95% confidence interval: 5%, 56%).

Conclusions: A Sequential Organ Failure Assessment score of >11 was not associated with a hospital mortality of >90% at any time during intensive care unit stay. Only a small proportion of patients have the extreme initial Sequential Organ Failure Assessment values associated with a hospital mortality of >90% limiting the usefulness of Sequential Organ Failure Assessment as a triage instrument for pandemic planning. Application of a Sequential Organ Failure Assessment threshold of >11 to the recent H1N1 pandemic would have excluded patients with a markedly lower mortality than seen in a large regional cohort of intensive care unit patients.