Comparison of spinal block characteristicsbetween height and weight based dosage versus fixed dosage of intrathecal bupivacaine for elective caesarean section

The preferred choice of anaesthesia for conducting emergency and elective caesarean section is spinal considering the various physiological changes in pregnancy. Hypotension still persists as a major problem during spinal anaesthesia.

Various strategies employed to prevent hypotension are preloading with intravenous fluid, leg elevation, prophylactic administration of vasopressors, using lower dose of local anaesthetic agents, use of additives like clonidine, opioids etc.

The dose of bupivacaine is reduced in obstetric patients due to increased sensitivity of neural tissue, alteration in CSF volume, weight gain and exaggerated lordosis. As a result of these factors which ultimately result in significant cephalad spread resulting in higher level of blockade causing maternal discomfort and hypotension.

The dose of bupivacaine for patients undergoing LSCS under spinal is around 12mg (12.78 mg for normal weight and 11.86 mg for obese population). Studies have proved that dose of bupivacaine based on height for spinal anaesthesia in LSCS patients is 0.06mg/cm.

The use of 8-10mg bupivacaine has been associated with lesser incidences of hypotension but greater intraoperative need for analgesia to dampen the pain.

This results in a wide range of dose of bupivacaine administered to these patients.

The purpose of this study is to analyze the characteristics of block achieved with height and weight adjusted dose of bupivacaine with fentanyl versus a fixed dosage of bupivacaine with fentanyl in elective caesarean section patients so as to find the optimum dose of drug required for adequate anaesthesia, which in turn will reduce the usage of vasopressors.