Challenging Dogma: The banana bag

The dogma

Patients with alcohol use disorders (AUD) are at risk for nutritional and vitamin deficiencies and may suffer from linked disease states, including Wernicke’s encephalopathy. These conditions may be underrecognized; for instance, an autopsy study suggests that Wernicke’s encephalopathy may have a prevalence rate of 12.5% among alcoholics.¹

Dr. Raj Sehgal

When patients with AUD are hospitalized, they have often already received a standard IV solution (100 mg of thiamine, 1 mg of folate, 1-2 g of magnesium, and a multivitamin dissolved in saline or dextrose). The practice is common enough that the solution is informally referred to as a “banana bag,” due to the yellow hue imparted by thiamine and multivitamin. These fluids might then be readministered daily during the inpatient stay. But what is the evidence supporting this widespread practice?

The evidence

While the banana bag (or “rally pack”, as it’s also colloquially known) hanging at the patient’s side may look cool, it may not be helping her. Let’s break down the ingredients:

Dr. Joshua Hanson

• Folate: Patients with alcohol use disorder are at higher risk for folate deficiency (attributable to poor intake and decreased absorption), but overall rates of folate deficiency are still quite low.² In addition, most oral and parenteral multivitamins already contain at least 400 mcg folate – the benefit of adding further intravenous folate is not clear.
• Magnesium. Patients with AUD are also at higher risk for magnesium deficiency attributable to increased excretion. While decreased magnesium levels could theoretically increase the risk of alcohol withdrawal symptoms, a Cochrane review found no evidence to support routine supplementation.³
• Multivitamin. Despite theoretical advantages in these (often) malnourished patients, there are no published studies on the benefit or harm of administering a “pan-vitamin” injection. The standard IV formulation is slightly different than an oral vitamin (the IV contains vitamin K, for instance, and lacks calcium), but the bioavailability should be roughly the same, except in rare patients with intestinal malabsorption.⁴
• IV fluids. Pharmacies typically mix these ingredients in a liter of normal saline or 5% dextrose. Once again, though, individual patients will have different needs. A dehydrated patient would benefit more from normal saline, a patient with alcoholic ketoacidosis would benefit more from dextrose, and a patient with alcohol-related cardiomyopathy likely shouldn’t be getting large volume IV fluids at all.
• Thiamine. Thiamine deficiency is likely the most common and most concerning vitamin deficiency in this patient population. The typical banana bag contains 100 mg of thiamine, which has been the traditional recommended daily amount for Wernicke’s treatment. This dosage, however, was apparently chosen arbitrarily in the 1950s (based on what the authors considered to be a high dose) and current recommendations suggest higher doses given more frequently because of the relatively short half-life of parenteral thiamine.⁵