Relationship of blood thiamine pyrophosphate to plasma phosphate and the response to enteral nutrition plus co-administration of intravenous thiamine during critical illness.

Abstract

Hypovitamin B1 occurs frequently during critical illness but is challenging to predict or rapidly diagnose. The objective of this study were to evaluate whether plasma phosphate concentrations predict hypovitamin B1, enteral nutrition prevents hypovitamin B1 and intravenous thiamine supplementation achieves supraphysiological concentrations in critically ill patients. Thirty-two enterally-fed critically ill patients, with a plasma phosphate concentration ≤ 0.65 mmol/L, formed a nested cohort within a larger randomised clinical trial. Patients were assigned to receive intravenous thiamine (200 mg) twice daily or no intravenous thiamine (control). Thiamine pyrophosphate concentrations were measured at 4 time points (pre- and post-infusion, and 4- and 6-hours post-infusion) on days 1 and 3 in those allocated to thiamine and once in the control group. Baseline thiamine pyrophosphate concentrations were similar (intervention 88 [67, 93] vs. control 89 [62, 110] nmol/L, P=0.49). Eight (25%) patients had hypovitamin B1 (intervention 3 vs. control 5), with two patients in the control group remaining insufficient at day 3. There was no association between baseline phosphate and thiamine pyrophosphate concentrations. Intravenous thiamine achieved supraphysiological concentrations 6 hours post first infusion with concentrations increasing to day 3. In the control group, thiamine pyrophosphate concentrations were not statistically different between baseline and day 3 (mean change 8.6 (-6.0, 23.1) nmol/L, P=0.25). Phosphate concentrations did not predict hypovitamin B1, which was observed in 25% of the participants. Enteral nutrition alone prevented the development of new hypovitamin B1. Administration of a single 200 mg dose of intravenous thiamine achieved supraphysiological concentrations of thiamine pyrophosphate with repeated dosing sustaining this effect. This article is protected by copyright. All rights reserved.