A randomized control trial to compare effectiveness and the safety of Isobaric (plain) Bupivacaine with Hyperbaric (heavy) Bupivacaine in patients undergoing caesarean sections.

INTERVENTION: Study setting: This will be carried out as a single centre study at main operating theatre and obstetric wards at Teaching Hospital Peradeniya. Method of Randomization: Block randomization method will be used to divide them into Isobaric and Hyperbaric Bupivacaine groups. Accordingly, the first five subjects, who come for the sections will be given Isobaric and the next five subjects will be given the hyperbaric bupivacaine. An independent nursing officer, who is not involved in the study or subsequent patient management will be assigned to this task. Intervention: In the operating theatre, blood pressure will be measured on the supine position. The mother will be cannulated with 18G cannula and a running drip with 500ml normal saline will be started. A lumbar puncture using a 25G pencil pointed needle will be used to give the drugs in to the intrathecal space at L3‐4 or L4‐5 intervertebral space when the patient is in the seated position. The dose of Isobaric and Hyperbaric bupivacaine will vary according to the height of the patient. Accordingly, 3 patient categories will be identified. Height of those 150cm or below, 151‐159cm, 160cm and above will be given 1.5ml (7.5mg), 1.75ml (8.75mg) and 2ml (10mg) Isobaric Bupivacaine respectively. The same three height groups who receive Hyperbaric bupivacaine will receive 2.5ml(12.5mg), 2.75ml(13.75mg) and 3ml(15mg) respectively. The subjects who receive Isobaric will be kept flat with a pillow to head while the Hyperbaric group subjects will be positioned in a slight head up position using a pillow to the upper chest. CONDITION: Caesarian sections PRIMARY OUTCOME: Time taken to achieve satisfactory level of anesthesia and the level of sensory block intra‐operatively. [Intra‐operative period]; The duration of anesthesia (sensory block) ‐ assessed by the time for the first pain post‐operatively [Intra‐operative period]; The degree of cardiovascular stability (systolic blood pressure drop less than 20mmHg, heart rate variability of 60 to 100) and the respiratory rate of 10 to 20) will be considered normal and stable) ; [Intra‐operative period]; SECONDARY OUTCOME: Presence of non‐specific complications such as; shivering, abnormal sensations like “pins and needles”, itchiness, nausea & vomiting.; [Intraoperative and post operative period]; INCLUSION CRITERIA: Pregnant women undergoing elective caesarean section, above 18 years of age.