Fractionated Dose Versus Bolus Dose for spinal anaesthesia in adult and elderly patients

INTERVENTION: Intervention1: Nil: Nil Control Intervention1: : CONDITION: Health Condition 1: O‐ Medical and Surgical PRIMARY OUTCOME: To compare the trends in mean arterial pressure in adults and elderly patients receiving fractionated dose and bolus dose of hyperbaric bupivacaine ; Timepoint: to note intraoperative vitals at 0,5,10,15,20,25,30,45,60,90,120 mins ; SECONDARY OUTCOME: To compare the onset, maximum level & duration of sensory blockade between the groups ; To compare the onset, duration of motor blockade using modified Bromage scale between the groups ; To compare the need for vasopressors ; Timepoint: baseline,0,5,10,15,20,25,30,45,60,120 mins INCLUSION CRITERIA: Adult Patients aged between 18‐59 years Elderly patients aged 60yrs and above Patients of either se Xundergoing elective lower limb surgery under SA ASA physical status I and II BMI between 18.5 and 24.9kg/m2 Height between 150 to 180cm Patient willing provide written informed consent