Efficacy of Inferior Vena Cava Collapsibility Index, Internal Jugular Vein Collapsibility Index and Caval Aorta Index in predicting the incidence of hypotension after spinal anaesthesia

After obtaining approval from Institutional Ethics Committee and written informed consent from the participants, patients will be recruited in accordance with the predefined inclusion and exclusion criteria.

These pre – operative parameters will be recorded

1.     Age

2.     Gender

3.     Weight

4.     Height

5.     BMI

6.     ASA grade

7.     Baseline BP and MAP

8.     Baseline HR

9.     Baseline oxygen saturation

All patients will be fasting as per standard protocol (6 hrs for solids and 2 hrs for clear liquids). On the day of surgery, USG measurement of IVC, IJV and aorta diameters will be done in the preoperative holding area by a trained operator, with the patients in supine position. A phased array probe of a standard USG machine will be used for the study.

Inferior Venacava Measurement:

With the transducer kept in the subxiphoid region, IVC measurements will be taken lateral to the IVC - hepatic vein junction. In one respiratory cycle IVC AP diameter during expiration (IVCmax) and inspiration (IVCmin) will be measured.

Aorta Measurement:

The transducer will be kept in the subxiphoid region. Aorta will be identified and maximum aorta internal diameter at systole will be measured.

Internal Jugular Vein Measurement:

The transducer will be kept lateral to the middle level of thyroid cartilage and a clear transverse view of the IJV will be obtained. In one respiratory cycle, IJV diameter during expiration (IJVmax) and inspiration (IJVmin) will be measured.

Procedure for spinal anaesthesia:

Intraoperatively, non-invasive blood pressure (NIBP) to measure the systolic, diastolic blood pressures and mean arterial pressure, heart rate, 5 lead ECG and oxygen saturation will be monitored. Availability of IV access with appropriate gauge IV canula in a peripheral line will be ensured. After the administration of spinal anaesthesia, intraoperative infusion of crystalloid solution at the rate of 10ml/kg/hr will be started.

Sub arachnoid block (SAB) will be administered to the patient positioned as sitting, with 25G Quincke – Babcock needle, at the L3-L4 or L4-L5 intervertebral space, and 3ml, 0.5% Hyperbaric Bupivacaine will be instilled in the space. Patient will be kept supine after SAB throughout the study period (30 mins). After recruitment, if level of anaesthesia achieved is above T5, then that patient will be excluded from the analysis.

NIBP, HR and SpO2 will be recorded every 2 minutes for the first 10 minutes and every 5 minutes until 30 mins after SAB. Post spinal anaesthesia hypotension is defined as fall in SBP by more than 20% of baseline OR absolute value of SBP < 90 mm Hg OR MAP less than 60 mm Hg. Any episode of hypotension will be noted and managed with 6 mg IV Mephentermine or Ephedrine to keep BP within 20% of baseline. Complications like bradycardia, nausea or vomiting will also be noted and managed accordingly.