Wednesday, May 9, 2012

Miffed at the Myth of MIVF and nonplussed by nil per os (NPO)

I will have to consult with physicians from a former generation to determine from whence came the concept of "maintenance intravenous fluids" or MIVF.  Early in medical school, especially during the pediatrics and surgery rotations, medical students are taught how to calculate fluid deficits and ongoing losses with the goal of selecting the optimal electrolyte solution and rate with which to replace them.  (Internists generally just select some base-10 friendly number such as 100 or 150 cc/hour and call it a day.)  This is a worthy enough goal, because dehydration is indeed one of the easiest and most worthwhile things to correct in the acutely ill patient.  (If you've ever puked your guts out for a day and then gotten a liter of intravenous fluid, you know what I mean.)

But the whole practice begs the question:  If there is a fluid deficit, why not just correct it once and be done with it?  If the average deficit in diabetic ketoacidosis (DKA) is 5 liters, why not just give 5 liters and stop?  I used to chide the residents during their ICU rotation:  "Bolus is for resus, rates are to maintain" to reinforce the notion that deficits should be repleted quickly.  But now I have come to question the second clause in that aphorism - do we need rates to maintain?