Inferior Venacava Ultrasound to Guide Fluid Management for Prevention of Hypotension After Spinal Anesthesia.

Hypotension is common during spinal anesthesia and contributes to underperfusion and ischemia. Severe episodes of intraoperative hypotension is an independent risk factor for myocardial infarction, stroke, heart failure, acute kidney injury, prolonged hospital stay and increased one year mortality rates. Empiric fluid preloading can be done to decrease the incidence of hypotension but carries risk of fluid overload especially in elderly and cardiac patients. Inferior venacava ultrasonography (IVC USG) has been used in spontaneously breathing critically ill patients for volume responsiveness but there is limited data regarding its use for volume optimization in perioperative setting. The aim of this study is to evaluate the use of inferior venacava ultrasound to guide fluid management for prevention of hypotension after spinal anesthesia.

Introduction:

Hypotension is common during spinal anesthesia and contributes to underperfusion and ischemia. It occurs due to reduction in both cardiac output and systemic vascular resistance. Even short duration of intraoperative MAP less than 55 mmHg has been found to be associated with Acute kidney injury (AKI) and myocardial injury. Severe episodes of intraoperative hypotension is an independent risk factor for myocardial infarction, stroke, heart failure, acute kidney injury, prolonged hospital stay and increased 1 year mortality rates. Predictive variables for spinal anesthesia induced hypotension includes peak sensory level, chronic alcohol consumption, emergency surgery, age more than 40 years, hypertension, combined spinal/general anaesthesia(GA), spinal puncture at or above lumbar 2 lumber 3 (L2L3) interspace. Preoperative volume status is an important factor determining patient's hemodynamic status. Traditional static parameters such as central venous pressure have been criticized for invasiveness and lack of accuracy. Newer noninvasive dynamic parameters like inferior venacava diameter and Collapsibility index(CI), acoustic echocardiography, stroke volume variation and pulse pressure variation etc are being used widely for assessing volume status.

Study Objective: To evaluate the use of inferior vena cava ultrasound to guide fluid management for prevention of hypotension after spinal anesthesia.

Design: A randomized prospective interventional study

Sample size: 92

Place: Operating theatres of Tribhuvan University Teaching Hospital (TUTH), Maharajgunj Medical Campus (MMC), Institute of Medicine (IOM).

Interventions: A total of 92 patients undergoing lower limb orthopedic surgery will be enrolled in the study. They will be randomized into USG group and Control group. In the USG group, IVC ultrasound will be done and collapsibility index (CI) will be calculated. Depending upon the value of calculated CI, fluid management will be done by infusing Ringer's Lactate (RL). Thereafter spinal anesthesia will be performed. In the control group, spinal anesthesia will be performed without IVC USG assessment. In both the groups, incidence of hypotension and amount of fluid and vasopressors administered will be recorded.

Eligibility Criteria:
Inclusion Criteria:

1. Age ≥16-65 years
2. American Society of Anaesthesiology physical status (ASA PS) I and II
3. Requiring elective spinal anaesthesia for lower limb orthopaedic surgery

Exclusion Criteria:

1. Patients with pre-procedural hypotension, defined as two consecutive measurements of systolic arterial pressure (SAP) less than 90 mmHg or mean arterial pressure (MAP) less of 60 mmHg.
2. Contraindication for Spinal Anaesthesia

   * Platelet counts ˂100,000 per microlitre of blood
   * International normalized ratio (INR) ≥1.5
   * Bleeding disorders
   * Infection at injection site