Role of subclavian vein collapsibilty index (SCVCI) in predicting post spinal hypotension in pregnant women undergoing caesarean section-A prospective observational study

After IEC-HR Permission, all pregnant patients fulfilling Inclusion and exclusion criteria posted for caesarean section using sub arachnoid block will be included in the study. All patients will be explained about the study and a written valid informed consent will be taken. All the basic information about the patient and preoperative evaluation will be done from the patient’s history and case sheets. The ultrasound measurements will be performed with the parturient on the transfer bed in the post-anesthesia care unit or labor ward 15 min before anesthesia. An Ultrasound device with a high frequency linear array probe (L12–5; 5–12 MHz) will be used for the measurement of SCV and SCVCI. The ultrasound examination will be performed with parturient in a supine position. It will be ensured that the SCV measurements will be completed within 10 min. Right SCV diameters will be measured in order to get the best crosssectional picture of the vein, the probe will be positioned beneath the proximal region of the midpoint of the clavicle perpendicular to the long axis of the SCV. The dynamic change in diameter will be recorded over time utilizing the M-mode to locate and quantify the minimum and maximum venous diameter during the breathing cycle once the target vein will be located. The maximum (dSCVmax) and minimum (dSCVmin) cross sectional diameters of the SCV at the end of the expiration and inspiration periods were recorded during the same respiratory cycle. The SCVCI will be calculated using the following formula: SCVCI = (dSCVmax – dSVmin)/dSCVmax × 100% All the ultrasound recordings will be performed by registered anesthesiologists and part to the examination results. The parturient will then be transferred to the operation Theater table. The routine protocol includes standard monitoring with electrocardiography, non-invasive blood pressure, and pulse oximetry will be done continuously. The baseline values of systolic blood pressure (SBP) (mmHg), diastolic blood pressure (mmHg) (DBP), mean blood pressure (MBP) (mmHg), heart rate (beats/min) and pulse oximetry will be measured and recorded. The first two resting blood pressure and HR measurements with the parturient in the supine position will be recorded, and the average value be recorded as baseline blood pressure. A quick infusion of Ringer lactate will be administered according to institutional protocol that is 5 ml/kg once the baseline vital parameters are noted. Subsequently spinal anesthesia will be induced using the Routine protocol for SAB in LSCS. The routine protocol for SAB in LSCS is as follows: After taking all aseptic measures, the skin is infiltrated with 2% lignocaine. A 25G Quincke’s spinal needle is introduced at the L3-L4 or L4-L5 intervertebral space with the patient in the sitting position. After ensuring free flow of cerebrospinal fluid, total volume of 2ml +/- 0.4ml containing 0.5% hyperbaric bupivacaine (heavy) with 10 μg) of preservative-free fentanyl is administered in the subarachnoid space over 20–30s. Patients are immediately positioned supine with a 15° left lateral tilt using a wedge under the buttock. Parturient will be withdrawn from the study if they could still feel the pinprick sensation below the T6 level at the beginning of surgery or failed spinal anesthesia. One of the member of anesthesia team will record HR, systolic blood pressure (SBP), diastolic blood pressure, and mean arterial pressure (MAP) at baseline (5 min after stabilization of patient in the OR), at the time of institution of spinal anesthesia, at every 1 min interval for 10 min, and at 3 min intervals until delivery of baby. Hypotension will be defined as a drop in SAP by > 20% from the baseline value, within 15 min after SA administration or before delivery. Patients who developed hypotension will be administered intravenous fluid (250 mL of crystalloid infusion in 10 min) and a vasopressor agent (6 mg of ephedrine or phenylephrine bolus of 50 μg at 2 min intervals) until a 20% increase in SBP or MBP is observed. and the vasopressor bolus will be administered every time if the parturient presents with hypotension before delivery. Total requirement of fluids and vasopressor dose will be noted. In the meantime, patients will be followed up for possible complications such as nausea, vomiting, allergies, etc., and managed as per standard protocol. Bradycardia will be defined as a HR below 50 beats per minute (bpm). If bradycardia is identified, 0.5 mg of atropine will be administered.

PARAMETERS TO BE NOTED

1. SCVCI.

2. Total volume of spinal drug. (ml)

3. Upper sensory level.

4. Total fluid administered before spinal anaesthesia. (ml)

5. Induction-to-delivery interval (min).

6. Total fluid before delivery of baby or post spinal hypotension

whichever is earlier (ml).

7. Total dose of vasoactive drug administered(mcg/mg).

Statistical Analysis:

Data analysis will include following steps:

• The data will be collected from desired sample population using

standard, pre-validated case record proforma.

• The collected data will be entered using M.S. Excel software.

For the normality check, the Shapiro–Wilk test will be used. The patient

and obstetric characteristics will be presented as mean ± standard

deviation or median (interquartile range), as appropriate, and will be

analyzed by an unpaired Student’s t-test (quantitative data between two

groups), Fisher’s exact probability test, or Pearson’s Chi-Square test

(categorical data), as appropriate.

The SCVCI measured by ultrasound in the supine position, will be

analyzed by multinomial logistic regression analysis to determine if they

are independently associated with the incidence of post-spinal

hypotension. The area under the receiver operating characteristic (ROC)

curves will be used to test the ability of the identified parameters to

predict post-spinal hypotension, and the area under the curve (AUC) will

be calculated. The perioperative hemodynamic parameters will be

assessed by two-way analysis of variance with the Bonferroni post hoc

test. A cut off value for SCVCI variation for the prediction of post spinal

hypotension will be determined using the ROC(Receiver Operator

Characteristic curve) and the relation between the total amount of fluid

administered and SCVCI will be analysed using Pearson’s coefficient

test. The secondary parameters associated with hypotension(like BMI,

Gestational age, Amniotic fluid index[AFI],etc) influencing the

development of hypotension, total dose of vasoactive drugs

administration in case of hypotension, total amount of fluid infused

before delivery etc will be assessed by using logistic regression analysis.

All statistical analyses will be performed using SPSS for Windows,

version 24.0 (SPSS Inc., Chicago, IL, USA). If calculated p-values found

less than 0.05, the difference will be considered as significant.