Q Is it appropriate to adjust body surface area (BSA) and intravenously administered vasoactive medication dosage against daily weight changes in the intensive care unit (ICU)? Because of these significant changes, is admission weight acceptable? Is there such a thing as “dry weight”? If so, how is it defined and measured?

A Nancy Faulkner, RPh, BS, replies:

BSA is not an appropriate parameter by which to calculate or modify inotropic and vasopressor drug infusion doses in the ICU. BSA is not a kinetic variable; it remains nearly constant regardless of changes in patient weight. Weight is a good kinetic variable for predicting drug concentration, dose, and therapeutic response. It better reflects changes in volume of distribution of the “size of the tank” into which drugs are distributed. Drug doses for the inotropic vasopressor agents, which have wide therapeutic ranges...

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