Introduction

Vitamin D deficiency seems increasingly prevalent in the community, and deficiency has been reported in almost 60% of medical inpatients [1]. Pleiotropic effects of vitamin D like immunomodulation and effects on muscle strength may be of special importance to critically ill patients. Despite this knowledge, vitamin D deficiency has only been studied in small and selected groups of ICU patients [2]. Therefore, we prospectively determined the prevalence of vitamin D deficiency and related vitamin D status to outcome in a cohort of critically ill patients.

Methods

This prospective observational cohort study was performed in a 20-bed general ICU of a teaching hospital in the city of Amsterdam between 1 March and 30 April 2009. We measured 25-hydroxyvitamin D (25-OH-D) on admission and after 48 hours in all consecutive patients admitted to our unit. Patients received enteral feeding. Additional vitamin D was not supplied. Vitamin D status was defined as: adequate: >75 nmol/l, insufficient: 50 to 75 nmol/l, deficient: 25 to 50 nmol/l, severely deficient: <25 nmol/l, undetectable: <10 nmol (to convert values for 25-OH-D to ng/ml, divide by 2.50). We compared observed and predicted mortality (APACHE IV), and standardized mortality ratio (SMR, observed/predicted number of nonsurvivors) between vitamin D cohorts.

Results

Vitamin D was measured in 111 patients at admission and in 44 after 48 hours. Mean 25-OH-D at admission was 31 nmol/l. Thirteen percent of the patients had undetectable 25-OH-D levels, 49% was severely deficient and 85% had a vitamin D <50 nmol/l. Only two patients had an adequate 25-OH-D status. During the first 48 hours of ICU admission, vitamin D decreased in 24 of 44 patients. Mean change was -2.3 nmol/l (range -32.5 to +22.5 nmol/l). Observed mortality was significantly lower than predicted in all patients (P = 0.02) and in patients with 25-OH-D >25 nmol/l (P = 0.04), but not in those <25 nmol/l (P = 0.21). See Table 1.

Table 1
Full size table

Conclusions

At the end of winter, one-half of our patients had severe vitamin D deficiency. In contrast to patients with severe deficiency, the cohort with vitamin D levels more than 25 nmol/l had a significant lower mortality than predicted by APACHE IV score. Measurements from a larger patient cohort are collected to further analyze this finding.