ABSTRACT:The term unilateral spinal anaesthesia is used when block is off operating side only and the operative side will be dependent side and absence of block on non-operative i. e. nondependent side. So when surgery involving in one limb, especially below knee surgery such block is very advantageous as it minimizes cardiovascular effects, avoids motor block of non-operative limb and facilitates early discharge. For this purpose we used 1.2ml of (6mg) of hyper baric Bupivacaine 0.5%+0.2ml (10microgram) of fentanyl to produce exclusively unilateral spinal anaesthesia. CASE REPORT: A 62 years old obese patient (80Kgs), 5 feet 10 inch height patient with known history of hypertension and diabetes mellitus posted for below knee orthopedic surgery (Bimalleolar Screws + Fibular plating). This patients 2D Echo showed chance finding of atrial septal defect (ASD) of ostium secundum type with 26mm in size and asymptomatic with left to right shunt. Ejection fraction is 48%. CONCLUSION: In this case we used 0.5% Bupivacaine 1.2ml (6mg) and 0.2ml of fentanyl (10microgram) which has provided predominantly unilateral block. 15-20 minutes taken to keep the patient in lateral decubitus position to establish the block completely. The advantages are hemodynamic stability, patient satisfaction and faster anaesthesia recovery.

No abstract