The “banana bag” is a colloquial term referring to isotonic crystalloid fluid premixed with thiamine, folic acid, and a multivitamin (which creates the characteristic yellow coloration). Some clinicians classically opt for a banana bag when treating acute alcohol intoxication due to the associated vitamin and mineral deficiency.
Flannery et al. conducted a review study in 2016 (PMID 27002274) looking at the evidence for the vitamin and electrolyte deficiencies noted with alcoholism in ICU patients. They found that replacing thiamine with the banana bag approach does not optimize timing of delivery to the nervous system. If you think about it… the typical dose of 100 mg diluted in a liter of fluid run over several hours is… very… very… slow. Folate and magnesium repletion should also be considered, but the evidence is not as strong as that for thiamine replacement. Furthermore, there was no evidence supporting the use of a multivitamin.
Personally, I’m not a huge fan of this form of resuscitation and alimentation. I’d rather replete thiamine aggressively up front especially if I suspect Wernicke’s encephalopathy. The data shows that serum folate can acutely vary based on nutrition and alcohol intake (ethanol impairs the absorption), but when weighing the risks and benefits, I tend to replace folate early during the hospital admission as well. Hypomagnesemia can occur due to increased renal excretion from secondary hypoaldosteronism, so I’m quick to replace this important electrolyte as part of normal electrolyte sliding scales in the ICU as well.
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