Effect of Preloading on Inferior Vena Cava Collapsibility Index: A Comparative Observational Study of Ringers Lactate versus Sterofundin

AIM OF STUDY

To compare response of IVCCI to preloading between Ringer lactate and sterofundin.

   OBJECTIVES

PRIMARY OBJECTIVE:

To compare reduction in percentage of IVCCI between two groups RL and sterofundin, In fasting after giving 500ml fluids and 15 and 30 minutes of spinal anaesthesia.

 SECONDARY OBJECTIVE:

To compare incidence of hypotension between two groups.

The requirement for inotropes and the resulting hemodynamic changes.

 STUDY PROTOCOL:

·       ETHICAL CONSIDERATION: This study will be conducted after obtaining ethical approval by local ethical committee of GMERS MEDICAL COLLEGE AND HOSPITAL, Vadodara and topic being registered with CTRI (clinical trial registry of India)

·       STUDY DESIGN: This is a prospective, comparative observational study will be conducted in the pre-operative recovery area and the operation theatre of GMERS Medical College, Gotri, Vadodara. The study will compare the effects of Ringer’s Lactate (Group RL) and Sterofundin (Group SF) on the inferior vena cava collapsibility index (IVCCI) and the incidence of spinal-induced hypotension in fasting patients undergoing elective lower limb surgeries under spinal anaesthesia.

 Group RL: Patients will receive Ringer’s Lactate (RL).

Group SF: Patients will receive Sterofundin (SF).

 Â·       STUDY PLACE: Orthopaedic surgery operating unit in a tertiary care teaching hospital (GMERS Medical college and Hospital, Vadodara)

STUDY PERIOD: Over the period 3 -5 months after the approval from ethical committee.

·        STUDY POPULATION: Adults consenting for checking IVC posted for Lower limb orthopaedic surgery with comparable demographic profile.

·        SAMPLE SIZE: We would like to derive the sample size from a study comparing RL and SF (different from ours), taking into consideration the IVCCI for the assessment of fluid responsiveness in spontaneously breathing preoperatively fasting patients or from the pilot cases after discussion with Statistics department.

 INCLUSION CRITERIA:

1         Patients posted for lower limb orthopaedic surgery under spinal anaesthesia in supine position.

2         patients aged between 18 to 65 years.

3         patients with American society of anaesthesia physical status I and II

4         Patients listed for elective surgery.

5         Fasting for more than 8 hours.

 EXCLUSION CRITERIA:

1         patients with American society of anaesthesia physical status III and more.

2         Pregnant women.

3         Patients with abdominal mass or ascites.

4         Patients posted for emergency surgery.

5         Contraindication for spinal anaesthesia.

6         BMI >30kg/m2

7         Patients who are on drugs which is affecting vascular status and tone. Eg: Diuretics, Vasodilators and alpha blockers etc.

8         Patients who are requiring over night hydration.

Pre-Study Preparation:

After proper informed written consent, patients of ASA- I & II physical status posted for Lower limb orthopaedic Surgeries will be recruited to participate in the study. Baseline vitals, including heart rate, blood pressure (BP), mean arterial pressure (MAP), and fasting duration, will be recorded for each patient. All patients will receive premedication and antibiotic prophylaxis as per institutional protocol.

 Ultrasound-Guided IVC Measurements:

Using a curvilinear probe of 3-5 MHz on an ultrasound (USG) machine, inferior vena cava (IVC) diameters will be measured in the subxiphoid view (long axis) 2 cm distal to the junction of the right atrium (RA) and IVC. Pulse-wave Doppler will be used to differentiate between the aorta and IVC.

• Measurement Technique:

• Place the patient in a supine position.

• Obtain a clear B-mode image of the IVC.

• The image will be frozen after normal inspiration and expiration.

• IVC diameters will be measured using the caliper feature of the ultrasound machine during both inspiration and expiration.

• This process will be repeated for both time points (before and after fluid administration).

The IVC Collapsibility Index (IVCCI) will be calculated as follows:

IVCCI = (IVC diameter in expiration - IVC diameter in inspiration / IVC diameter in expiration ) * 100

Fluid Administration Protocol:

Each patient will receive 500 ml of either Ringer’s Lactate (Group RL) or Sterofundin (Group SF) within 10-20 minutes, following the initial IVC measurements.

Spinal Anaesthesia:

After fluid administration, spinal anaesthesia will be administered using 0.5% hyperbaric bupivacaine (15-18 mg) combined with 200 mcg of butorphanol. A 23G Quincke needle will be used for the spinal block, performed in the sitting position at L2 – L3 or L3 – L4 intervertebral space.

• Timing: Spinal anaesthesia will be given immediately after fluid preloading.

• T0 (Time Zero): The timer starts immediately after the administration of spinal anaesthesia.

• The maintenance fluid rate is calculated according to the Holiday-Segar formula. For a 50 kg patient fasting for 10 hours, the formula is applied as follows:

• Maintenance Fluid (MF) = 90 ml.

• Deficit Fluid = MF × Fasting Hours = 90 × 10 = 900 ml.

• Third Space Loss = Weight × 2 = 50 × 2 = 100 ml.

• Total Fluid Requirement (1st hour) = 640 ml.

Fluids are administered at a calculated rate:

• For a 50 kg patient: 106 mL per 10 minutes.
• For a 60 kg patient: 120 mL per 10 minutes.
• For a 70 kg patient: 134 mL per 10 minutes.

Monitoring:

Vitals (heart rate, BP, MAP) will be recorded at the following time points:

• T15 (15 minutes post-spinal): Vitals and IVC measurements will be repeated.
• T30 (30 minutes post-spinal): Vitals and IVC measurements will be repeated.

Intervention for Hypotension:

If hypotension (MAP < 65 mmHg) occurs within the first 30 minutes post-spinal anaesthesia, an intramuscular injection of ephedrine 5 - 10 mg will be administered. Any changes in hemodynamic parameters following ephedrine administration will be recorded.

Study End Point:

The study concludes 30 minutes after the administration of spinal anaesthesia. No further observations will be made after this time point.

Data Collection and Analysis:

• IVCCI will be calculated before and after fluid administration and after spinal anaesthesia at T15, and T30.
• Incidence of spinal-induced hypotension will be recorded.
• The primary objective is to compare the reduction in IVCCI between Group RL and Group SF.
• The secondary objective is to compare the incidence of spinal-induced hypotension between the two groups and the requirement for inotropes and the resulting hemodynamic changes.

Statistical Analysis:

Data will be analysed using appropriate statistical tests to determine significant differences between the two groups. A p-value of < 0.05 will be considered statistically significant.