Preoperative Ultrasound Guided Evaluation of Subclavian Vein Collapsibility Index and Inferior Vena Cava Collapsibility Index as Predictors of Hypotension After Induction of General Anesthesia in Major Onco-surgery

Investigators plan prospective study , written informed will be taken from all included patients. In the OR 5 lead ECG, NIBP,SPO2 monitors will be attached , patients will be explained about Ultrasound imaging . Preinduction using SONOSITE EDGE II ultrasonography machine and placing high frequency linear array probe (6-13 Hz) beneath the middle of the clavicle aligned in deltopectoral groove to obtain short axis view of Subclavian/Infraclavicular axillary vein in B-Mode (2-D imaging). Doppler pulse waveform and minimum and maximum diameter measurements of SVC will be obtained in M-mode , both during spontaneous breathing and after deep inspiration, using digital calipers after freezing the image. The collapsibility index CI will be calculated using the following equation SCV AV CI = (dSCV max- dSCV min)/ dSCV max ×100.

A phased array or cardiac ultrasound probe (1-5Hz) will be placed in the subxiphoid window to view IVC at the junction of IVC with right atrium .Then the transducer will be adjusted to obtain the long axis view of IVC. Doppler pulse waveform will be obtained to ensure imaging of IVC and then in the M mode the minimum and maximum diameter measurements of IVC will be obtained both during spontaneous breathing and after deep inspiration, using digital calipers after freezing the image. The collapsibility index CI will calculated using the following equation:IVC CI = (dIVCmax- dIVCmin )/ dIVCmax ×100 . In all the patients both SVC and IVC -CI will be calculated.

All patients will receive standard General Anesthesia with IV Fentanyl 1-2 mcg/kg , Sleeping dose propofol , Atracurium 0.5mg/kg and orally placed Endotracheal tube.The heart rate (HR) and mean arterial pressure (MAP) will be recorded in two phases .Intraoperative hypotension (IOH) been defined as MAP<60mmHg or >30%decrease in MAP from baseline.

1. Post induction phase: Readings will be taken at 1 min intervals from the start of induction till intubation (upto 5 minutes) and
2. Post intubation phase: Readings will be taken at 2 min intervals upto 10 min and at 5 min intervals up to 30 mins or till incision . Each hypotensive episode encountered will be treated with leg lifting first (lifting both lower extremities for 2 minutes by technical staff) , if hypotension persists then IV Ephedrine 6 mg boluses will be given . All patients will receive preloading 200ml crystalloids prior to induction of anesthesia .