A Double Blind Randomized Control study comparing the efficacy of 0.25% Isobaric Bupivacaine to 0.5% Hyperbaric Bupivacaine during Spinal Anaesthesia for Lower Limb Surgery in ASA II and ASA III patients

INTRODUCTION: Augustus Karl Gustav Bier was the first to introduce cocaine intrathecally in six patients coming for lower limb Surgery in 1898, since then spinal anaesthesia has seen many modifications from the local anesthetics to the spinal needle in use. In the last few decades, the use of regional techniques for anaesthesia and analgesia has significantly risen. This is mainly because of awareness of the benefits of regional anaesthesia particularly in an aging population riddled with a wide range of intercurrent illness. Amongst the various regional techniques, spinal anaesthesia is amongst the most commonly used, besides being easier to perform with definitive results. Though spinal anaesthesia is generally limited for procedures below the umbilicus, its usage has been in plentiful. The main advantage of spinal anaesthesia being the ability to control the level of anaesthesia and to a certain extent the duration of anaesthesia by altering the drug characteristics, dosage and patient position during and immediately after the spinal anaesthetic. The commonly used local anaesthetic for spinal anaesthesia is hyperbaric bupivacaine, though this gives good motor and sensory block it is associated with hypotension and at times bradycardia which can be detrimental in the elderly and those with intercurrent illnesses like hypertension, diabetes mellitus, ischemic heart disease as hemodynamic instability worsens already compromised organ function in this subset of people. Alteration of the drug characteristics can limit the degree of hemodynamic instability and this is what we aspire to do in this study. The challenge during a subarachnoid block lies in the ability to provide enough local anaesthetic to provide adequate anaesthesia for surgery while preventing extensive cephalad spread and unwanted adverse effects. AIMS AND OBJECTIVES: 1. To compare the efficacy of two solutions of bupivacaine, 1.5ml of 0.5% bupivacaine and 3 ml of 0.25% hyperbaric bupivacaine in providing stable hemodynamics. 2. To compare the time of onset, height of block, intensity of sensory and motor blockade, duration of analgesia as well as the incidence of side effects between the two groups. MATERIALS AND METHODS: A randomized double blinded study was conducted on ASA II and ASA III patients coming for lower limb surgery. Sample size estimation was done based on a similar study by Paul et al 2001 where the mean difference in the outcome (SD) was 11.69. For a level of significance of 5% and power of study of 80%, sample size was estimated to be 180 in each group. Inclusion criteria: 1. Age more than 20 years (adult patients). 2. ASA II and ASA III. 3. Lower limb general surgery procedures like debridement, amputation, split thickness skin grafting. Exclusion criteria: 1. Patient refusal. 2. Coagulation disorders. 3. Current treatment with antiplatelets except aspirin. 4. Sepsis. 5. Dehydration. 6. Spinal canal anomalies. 7. Height