Comparative Evaluation of Conventional Anatomical Landmark Guided, Perineural Ultrasound Guided and Perivascular Colour Doppler Guided Brachial Plexus Block In Sheep

Abstract

Thirty six adult sheep irrespective of sex, randomly allotted to six groups i.e., A, B, C, D, E & F with six animals each formed the subjects of study with the objectives to identify the window most feasible and an alternative site to conventional site for localization of brachial plexus in adult sheep and its subsequent blockade under ultra sonographic guidance; to compare the perineural brachial plexus blockade (BPB) using ultrasound guidance and perivascular BPB using color doppler and to ascertain possible dose regimen variation and anesthetic effect with and without ultrasound guidance. All the animals received 0.75% ropivacaine hydrochloride @ 3mg/kgBW. Perineural ultrasound guided BPB was performed in animals of group A & B, in which group A animals received ropivacaine whereas group B animals received additional 4mg isoflupredone, perivascular colour doppler guided BPB was performed in groups E & F, in which received ropivacaine and ropivacaine plus 4mg isoflupredone respectively. BPB in groups C & D was performed using landmark approach using ropivacainein group C and additional 4mg isoflupredone in group D. We identified the ultrasound scanning window. The perivascular and perineural BPB allowed a feasible and accurate access to BP and significantly shortened the onset and prolonged the duration of anesthesia as compared to conventional technique of BPB. By incorporating 4mg isoflupredone, ropivacaine dose was reduced by 15mg. Therefore, it could be concluded that this anesthetic regimen can provide a very good anesthesia for forelimb surgery upto four hours duration in sheep.