Ultrasonographic evaluation of Internal Jugular Vein collapsibility index and its association with post induction hypotension in patients undergoing Supratentorial craniotomy A Prospective Observational Study

All the patients satisfying inclusion criteria will be evaluated at least one day prior to surgery . NPO will be explained and written informed consent will be taken . No sedative premedication will be given . On the day of surgery Iv cannulation will be performed and normal saline will be given at 10 ml/hr body weight duuring study period. Ultrasonographic measurements of IJV diameter will be taken  at the level of thyroid cartilage with minimum pressure at supine and 10 degree trendelenberg position respectively  . Collapsibility index will be calculated . Standard ASA monitoring and anaesthesia technique will be used in all patients. Intraarterial cannulation will be performed after applying local anaesthesia .Fentanyl 2 mcg/kg , Propofol 1.5 - 2 mg /kg . Intubation will be done with cuffed ETT of appropriate size after administration of Inj .Vecuronium 0.1 mg/kg to facilitate endotracheal intubation . Anaesthesia will be maintained in all cases using 40 percent  oxygen in air , Sevoflurane . Ventilation will be controlled to maintain ETCO2 of 35 mmhg . Continuous IABP will be recorded at induction and 1,2,3,4,5,10,15,20 minutes post induction . Systolic blood pressure less than 80 or greater than 30 percent decrease from baseline will be defined as significant hypotension. Mephentermine 6 mg will be given if hypotension of SBP less than 80 mmHg occurs.