id ▁or ▁cry stal lo id , ▁it ▁is ▁imper ative ▁to ▁think ▁about ▁all ▁the ▁components ▁of ▁the ▁star ling ▁equation : ▁ ▁To ▁identify ▁the ▁minimum ▁safe ▁h emat oc rit ▁des irable ▁for ▁a ▁given ▁patient ▁the ▁following ▁equation ▁is ▁useful : ▁ ▁where ▁E B V ▁is ▁the ▁estimated ▁blood ▁volume ; ▁ 7 0   m L / kg ▁was ▁used ▁in ▁this ▁model ▁and ▁Hi ▁( initial ▁h emat oc rit ) ▁is ▁the ▁patient ' s ▁initial ▁h emat oc rit . ▁From ▁the ▁equation ▁above ▁it ▁is ▁clear ▁that ▁the ▁volume ▁of ▁blood ▁removed ▁during ▁the ▁AN H ▁to ▁the ▁H m ▁is ▁the ▁same ▁as ▁the ▁B L s . ▁How ▁much ▁blood ▁is ▁to ▁be ▁removed ▁is ▁usually ▁based ▁on ▁the ▁weight , ▁not ▁the ▁volume . ▁The ▁number ▁of ▁units ▁that ▁need ▁to ▁be ▁removed ▁to ▁hem od il ute ▁to ▁the ▁maximum ▁safe ▁h emat oc rit ▁( AN H ) ▁can ▁be ▁found ▁by ▁▁ ▁This ▁is ▁based ▁on ▁the ▁assumption ▁that ▁each ▁unit ▁removed ▁by ▁hem od il ution ▁has ▁a ▁volume ▁of ▁ 4 5 0   m L ▁( the ▁actual ▁volume ▁of ▁a ▁unit ▁will ▁vary ▁somewhat ▁since ▁completion ▁of ▁collection ▁a is ▁dependent ▁on ▁weight ▁and ▁not ▁volume ). ▁The ▁model ▁assumes ▁that ▁the ▁hem od il ute ▁value ▁is ▁equal ▁to ▁the ▁H m ▁prior ▁to ▁surg ery , ▁therefore , ▁the ▁re - trans f usion ▁of ▁blood ▁obtained ▁by ▁hem od il