A study to evaluate the efficacy of USG guided inferior vena cava collapsibility index and caval aorta index in predicting the incidence of hypotension after spinal anaesthesia in S.M.S Medical College, Jaipur

Spinal anaesthesia-induced hypotension (SAIH) is a frequent side effect of spinal anaesthesia (SA), seen more commonly in hypovolemic patients which is due to sympathetic blockade and activation of cardioinhibitory fibres. Thus, fluid optimization becomes an important part in anaesthsia management. With the advent of Ultrasonography (USG), non invasive parameters such as inferior vena cava (IVC) diameters, IVC collapsibility index (IVCCI), caval aorta index (CAI) have shown promising results in terms of fluid optimization.  This study assesses and compares the efficacy of IVC collapsibility index (IVCCI) and caval aorta index (CAI) in predicting hypotension after spinal anaesthesia to allow timely and targeted intervention based on preoperative risk assessment.

Patients will be selected according to inclusion and exclusion criteria. Monitors will be attached and baseline vitals recorded. Ultrasound measurements will be performed in the preoperative room with the patient in the supine position. Measurements of the inferior vena cava (IVC) will be taken lateral to the IVC–hepatic vein junction. The internal anterior–posterior diameter, which is maximum during expiration (IVCmax)  and minimum during inspiration  (IVCmin) will be recorded. Maximum aortic diameter(Ao) on the left side of the IVC, 1 cm above the level of the celiac trunk, will be recorded during systole.

The IVC collapsibility index ( IVCCI ) will be calculated using the formula- ( (IVCmax-IVCmin) / IVCmax ) x 100

The caval aorta index will be calculated using the formula-  IVCmax / Ao

Spinal anesthesia will be administered under all aseptic precautions at the L3–L4 intervertebral level, with the patient in the sitting position, using 0.5% hyperbaric bupivacaine through a 25-gauge Quincke needle. Following the injection, the patient will be positioned supine. Infusion of Ringer lactate will be initiated only after the administration of spinal anaesthesia, at a rate of 10 mL/kg/hour. No preloading of fluid will be performed. Patients will be excluded from the study if the level of sensory block rises above the T5 dermatome.  Vital parameters will be recorded non-invasively at 0, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 45, 60, 75, 90, and 120 mins after spinal anesthesia.

If hypotension is observed, it will be managed with an intravenous bolus of 3 mg mephentermine. Any other complications, such as nausea or vomiting, will be managed appropriately.