What is the maximal allowable blood loss for this procedure, according to current guidelines and assuming the patient remains hemodynamically stable? A 76 yo m with PMHx of ACS with 2 stents placed 5 years ago presents for an elective cholecystectomy.  He is 6'2 and weighs 73 kg.  His pre-procedure hematocrit is 35.  

780 ml

The maximum allowable blood loss is a function of the patients pre-procedure blood volume, hematocrit, and minimum allowable hematocrit. This patient has a history of myocardial infarction, so the minimum recommended hematocrit for him is 30. The first step toward this calculation is knowing the patients pre-procedure blood volume. For a man, blood volume is approximately 75ml / kg. As this man weighs 73 kg, his blood volume is 73 x 75 = 5475. Now, the hematocrit is 35, and as this patient has a history of coronary artery disease, the minimum hct allowable for him is 30. The formula is [Hct(original) - Hct(minimal)] / Hct(original), so (35 - 30 ) / 35 = 0.143. This fraction x blood volume = 0.143 x 5473 = 0.782. Miller RD and Pardo MC, Basics of Anesthesia 6th Edition, Elsevier Publishers, Philadelphia PA, 2011.