How much thiamine is enough in malnourished patients receiving total parenteral nutrition?

Thiamine deficiency manifests as two conditions: cardiac (wet) beriberi, or Wernicke’s encephalopathy. Furthermore, it can potentiate lactic acidosis through failure of pyruvate to enter the Kreb’s cycle. Patients who are malnourished are at risk of thiamine deficiency, and traditionally, replacement is given for patients at risk (patients on TPN without micronutrients, those with history of alcohol abuse, starvation states). Thiamine levels are not routinely checked in usual practice, but instead, supplementation is provided based on risk. The current guidelines give different recommendations (excluding for treatment of beriberi/Wernicke’s, in which the dose is 200-500mg intravenously three times a day for 5-7 days followed by 100mg for 1-2 weeks) 1. For those at high risk of thiamine deficiency, therapeutic guidelines suggests giving 300mg intravenously for 3 days and then 100mg daily for 1-2 weeks 2. In re-feeding syndrome 100mg intravenously for 7-10 days Clinical Question Is 3 days of intravenous thiamine replacement in patients receiving TPN AND at risk of refeeding syndrome, sufficient to restore and maintain thiamine levels when measured at day 7? Hypothesis In patients at risk of refeeding syndrome, thiamine levels are sufficiently restored with 3 days, as opposed to 7 days, of supplementation. Methodology Patients randomized to receive 3 days of intravenous thiamine or 7 days of intravenous thiamine. Standard dose will be given, 250mg b dose forte intravenous. Thiamine levels will be measured at day 0, 3 and 7 to ensure adequate blood levels are reached.