Inferior Venacava Ultrasound to Guide Fluid Management for Prevention of Hypotension After Spinal Anesthesia.
Condition: Hypotension; Fluid Overload
MeSH terms: Hypotension
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Inferior venacava Ultrasonography (IVC USG) guided fluid management
Intervention type(s): Other
Intervention description(s): The IVC will be visualized using a paramedian long-axis view via a subcostal approach. A two-dimensional image of the IVC as it enters the right atrium will be first obtained. Variations in IVC diameter with respiration will be assessed using M-mode imaging performed 2 to 3 cm distal to the junction of right atrium and IVC. Maximum and minimum diameter will be measured from inner wall to inner wall and collapsibility index(CI) will be calculated using formula: CI = [(dIVCmax - dIVCmin)/dIVCmax] x 100% CI of ˃36% will be accepted as predicted fluid responder and ≤36% will be regarded as predicted fluid non responders. Predicted fluid responders will receive a bolus of 500 ml of Ringer's lactate over a time period of 15 min, after which the IVC diameter variation will be reassessed. Additional 250ml of Ringer's lactate bolus will be applied until a non fluid responder pattern is observed during IVC USG. Thereafter,spinal anaesthesia will be performed.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: Collapsibility index; Inferior venacava ultrasound; Spinal anesthesia; Transthoracic echocardiography