A Quick and Reliable Mental Formula to Calculate the BSA of a Patient.

A patient’s body surface area (BSA) is used throughout healthcare settings, but it usually requires a calculator due to involvement of the calculations (1). The BSA is used for an array of purposes such as determining metabolic demand, medication dosages, sizes of mechanical replacement devices (e.g., cardiac valves), and blood perfusion flows for adequate blood flow during cardiac surgery (1). Much of the purposes for BSA are for quick medical treatments. For example, when a patient suffers cardiac arrest and needs emergent cardiopulmonary bypass (CPB) support to address the underlying causes of the cardiac arrest, the perfusionist must know the patient’s BSA so they can provide enough blood flow, delivering adequate oxygen supply to the patient. Much critical time before initiating CPB is used getting the heart–lung machine ready to initiate CPB. The perfusionist also needs to make sure they are ready with proper medications and disposable devices for CPB. Because of these requirements, the perfusionist does not usually have much downtime to take out a calculator to determine the BSA and find out what an adequate blood flow is required during CPB. After calculating BSA, the perfusionist can use a cardiac index (C.I.) between 1.8 and 2.4 L/min/m to multiply by the BSA to determine the required blood flow during CPB (2). Since this situation refers to emergent cardiac surgery, the perfusionist can simply use a C.I. of 2 L/min/m multiplied by the BSA to quickly reference what the average required CPB blood flow should be. Because this calculation is required, having quick access to an accurate BSA is a useful information when valuable time is not devoted to computing the BSA on a calculator.