Role of ultrasonographic Inferior Vena Cava collapsibility index in predicting spinal anaesthesia induced hypotension in elective lower abdominal surgeries.

Written informed consent will be taken. Patients will be kept nil by mouth as per standard protocol. In the operating theatre, 18G cannula will be secured in a peripheral vein, standard monitoring will be applied and baseline HR, SBP, DBP, MAP & SpO2 will be recorded before administering SA in supine position.

Ultrasound guided IVC diameter measurements will be done by an experienced anaesthetist using a curvilinear probe of 1-8 MHz during spontaneous breathing through subxiphoid view lateral to the IVC-hepatic vein junction. IVC anterioposterior diameter which is maximum during expiration (IVCmax) and minimum during inspiration (IVCmin) will be taken in one respiratory cycle using M-mode of ultrasound. IVCCI will be calculated using the formula: [{IVCmax-IVCmin}/IVCmax]*100.

No fluid preloading will be done and the infusion of Ringer’s Lactate solution at a rate of 10ml/kg/hr will be started only after administration of SA in a sitting position at L3-L4 intervertebral space with a dose of 3.5 ml of 0.5% hyperbaric bupivacaine through 25G spinal needle to achieve spinal blockade of T8.

Patients will be kept supine after SA and the pin prick test will be used to evaluate the level of sensory blockade. HR, SBP, DBP, MAP and SpO2 will be recorded every 2 minutes for 10 minutes and every 5 minutes for 30 minutes after the administration of SA.

SAIH (spinal anaesthesia induced hypotension) will be defined as a decrease in SBP by more than 20% of the baseline value or MAP <60 mmHg.

Any episode of hypotension will be noted and managed with 6mg i.v. mephentermine to keep BP within 20% of baseline. Any complications like bradycardia, nausea or vomiting will be noted and managed accordingly

All the factors known to affect SAIH i.e. age, gender, height, weight, BMI, IVCCI will be included in the final multivariate model for finding the single most useful SAIH predicting variable..