Acute fluid shifts influence the assessment of serum vitamin D status in critically ill patients.

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Acute fluid shifts influence the assessment of serum vitamin D status in critically ill patients.

Crit Care. 2010 Nov 26;14(6):R216

Authors: Krishnan A, Ochola J, Mundy J, Jones M, Kruger P, Duncan E, Venkatesh B

ABSTRACT: INTRODUCTION: Recent reports have highlighted the prevalence of vitamin D deficiency and suggested an association with excess mortality in critically ill patients. Serum vitamin D concentrations in these studies were measured following resuscitation. It is unclear whether aggressive fluid resuscitation independently influences serum vitamin D. METHODS: Nineteen patients undergoing cardiopulmonary bypass were studied. Serum 25(OH)D3, 1alpha,25(OH)2D3, parathyroid hormone, C-reactive protein (CRP), and ionised calcium were measured at five defined timepoints: T1 - baseline, T2 - 5 minutes after onset of cardiopulmonary bypass (CPB) (time of maximal fluid effect), T3 - on return to the intensive care unit, T4 - 24 hrs after surgery and T5 - 5 days after surgery. Linear mixed models were used to compare measures at T2-T5 with baseline measures. RESULTS: Acute fluid loading resulted in a 35% reduction in 25(OH)D3 (59+/-16 to 38+/-14 nmol/L, P < 0.0001) and a 45% reduction in 1alpha,25(OH)2D3 (99+/-40 to 54+/-22 pmol/LP < 0.0001) and i[Ca](P<0.01), with elevation in parathyroid hormone (P<0.0001). Serum 25(OH)D3 returned to baseline only at T5 whilst 1alpha,25(OH)2D3 demonstrated an overshoot above baseline at T5(P<0.0001). There was a delayed rise in CRP at T4 and T5; this was not associated with a reduction in vitamin D levels at these time points. CONCLUSIONS: Hemodilution significantly lowers serum 25(OH)D3 and 1alpha,25(OH)2D3, which may take up to 24 hours to resolve. Moreover, delayed overshoot of 1alpha,25(OH)2D3 needs consideration. We urge caution in interpreting serum vitamin D in critically ill patients in the context of major resuscitation, and would advocate repeating the measurement once the effects of the resuscitation have abated.

PMID: 21110839 [PubMed - as supplied by publisher]

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