patients will be enrolled for the study after detailed preoperative assessment and relevant investigation as per inclusion & exclusion criteria after obtaining written informed consent .

Anaesthesia will be given as  per usual standard protocol ,as per discretion of in charge anaesthetist . In the operative room, routine noninvasive monitoring, electrocardiogram, pulse oximete , Noninvasive Arterial Blood Pressure (NIBP) and nasal capnometer will be used. Baseline Pulse, BP, Respiratory rate, SpO2 will be checked and noted down. An intravenous access will be established and co loading with slow infusion of RL or NS 10 ml/kg will be started. Spinal anaesthesia will be given with 0.5% bupivacaine[H]) 15-17.5 mg with 10 ug fentanyl as per height and weight of patient & as per discretion of treating anaesthetist . SA will be  given in sitting position with 25-gauge Quincke spinal needle in L3–L4 or L4–L5 interspace after skin infiltration with lignocaine (2 ml, 2%) . After aspiration of cerebrospinal fluid, injection bupivacaine will be given either as single bolus dose technique in which patients will  receive a single bolus dose of bupivacaine over 10 s while in fractionated spinal anaesthesia technique , two-third of the total calculated dose will be given initially followed by one-third dose after 30 s gap , both doses given at a rate of 0.2 ml/s. .After injection of initial two-third dose, the syringe will be kept attached to the spinal needle for remaining 30 s, after which remaining one-third dose will be administered. Patients in both technique will be made supine immediately after spinal anesthesia . Then patient will be  monitored  for vital signs (heart rate and blood pressure)  continuously every 2 minutes till 10 minutes & then every 5 minutes for  30 minutes and then every 15 minutes till end of surgery .Sensory block will be  assessed by blunted needle method .Dermatome level tested every five minutes till thirty minutes, then every fifteen minutes until the point of regression of sensory level reached to L3 .At the end of 15 minutes of spinal anaesthesia , if sensory block failed to reach T8 level or if patient had pain due to inadequate block, it will  considered as failed block and general anaesthesia will be given and these patient will withdrawn from further analysis. patients who will receive single bolus dose spinal anaesthesia will be taken as Group B and patients who will receive fractionated spinal anaesthesia will be taken as Group F. We recorded various variable like  Anaesthesia readiness time: as time from the end of injection of spinal drug to the time sensory block reached T8 level and patient anaesthesia wise ready to be handed over to surgeon for surgery Degree of motor block: will be evaluated using a Modified Bromage scale (Bromage O: Free movement of limb at hip, knee and ankle joint. Bromage 1: Free movement of limb at knee and ankle joint. Bromage 2: Free movement limb at ankle joint. Bromage 3: No movement of limb at hip, knee and ankle joint).  Duration of motor block: noted as time from the onset of grade 3 motor block to complete resolution of motor block.

Duration of sensory block: will be noted as time from the onset of T8 sensory block to regression of sensory level to L3.  If patient required analgesia for mesenteric pull intraoperative ,will be given with IV fentanyl    1-2ug /kg  & it will noted as supplementation of analgesia intraoperative .  Clinically significant hypotension will be defined as decrease in systolic arterial pressure by 20% or more from baseline values or systolic < 90 mm of Hg or < 65 mean BP  .  Hypotension will be treated with IV ephedrine 5 mg or phenylephrine 50 ug incremental boluses dosages and the total amount of ephedrine or phenylephrine required will be noted down .   The number of hypotensive episodes and total vasopressor used will be recorded for each patient.  Clinically significant bradycardia is defined as a heart rate less than 50 beats per min and it will treated with IV atropine 0.5 mg boluses.  Incidences of clinically significant hypotension and bradycardia will noted as incidence of haemodynamic adverse event  All the patients will be monitored in post anaesthesia care unit till they will be shifted to general ward after they will fulfill PACU discharge criteria.  Time to demand first rescue analgesia after completion of surgery from the onset of T8 sensory level will noted as duration of analgesia .Rescue analgesia will be provided with IV tramadol 1-2 mg/Kg . Other adverse events like nausea or vomiting will be noted down will be treated with iV dexamethasone or with Inj. Ondansetron 4 mg i.v. Intraoperative blood loss will be noted down