Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients

Written by Nick Dulin, MD

Reviewed by Jonathan Kaplan, MD

Corl KA, et al. Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients. J Crit Care. 2017;41:130-137.

Full text:

  • Background
    • Both under and over resuscitation are associated with worsened clinical outcomes in critically ill patients2
    • Assessing fluid status is essential in the management of these patients however is clinically challenging
      • Vital signs and physical examination cannot reliably predict fluid responders
      • Pulmonary artery catheters (PACs) are invasive and associated with many complications3
      • Non-Invasive Cardiac Output Measuring (NICOM) produces comparable hemodynamic data to PACs and is much less invasive but requires a resource rich environment (e.g. ICU)4
      • Point of Care Ultrasound (POCUS) can estimate central venous pressure and collapsibility of the inferior vena cava (cIVC) during respiration aka the caval index however data supporting use of this practice in spontaneously breathing patients was limited prior to the publication of this article
  • Clinical Question of the Study
  • Can cIVC detect fluid responsiveness in spontaneously breathing critically ill patients undergoing IVF resuscitation?
  • Secondary goals of the study
    • Establish optimum cutoff for cIVC/compare this value to previous studies
    • Determine if passive leg raise (PLR) assists in fluid response
  • Methods
    • Prospective observational study
    • N = 124 spontaneously breathing patients in acute circulatory failure defined by
      • Hypotension (systolic blood pressure < 90 mmHg, or a mean arterial pressure < 65 mmHg for ≥30 min)
      • Decreased urine output (<0.5 ml/kg/h)
      • Persistent tachycardia (heart rate N 120 bpm for ≥30 min)
      • Serum markers suggesting organ hypoperfusion (acidosis with a serum pH <7.3 or lactic acid >2 meq/l)
    • Exclusion Criteria
      • Primary traumatic, cardiogenic, obstructive, or neurogenic shock
      • Age <18 years old; incarceration; pregnancy
      • Hospitalization for >36 h
      • Use of Non invasive positive pressure ventilation (NIPPV)
      • Active pulmonary edema
    • Patients placed supine with two 10 second clips of IVC taken 1 min apart while on NICOM
    • This was followed by 3 min of passive leg raise (PLR) then another clip was captured
    • Patient was returned to supine position for 3 min, given a 500cc fluid bolus, and another clip was obtained
    • Fluid responsiveness was defined by >10% increase in cardiac index on NICOM
  • Results
    • 61 participants (49.2%) were fluid responders
    • Primary outcome
      • Optimal (maximal sensitivity and specificity) cIVC was 24.6 however 25% was more clinically useful
      • cIVC of 25% had 87% sensitivity and 81% specificity; LR+ 4.56 LR- 0.16
      • cIVC able to detect fluid responsiveness with area under the curve (AUC) of 0.84
    • Secondary outcomes
      • cIVC of 25% had lower misclassification rate (16.1%)  than previously suggested 40-42% (34.7-36.3%)
      • Baseline maximum/minimum IVC diameters, change in cIVC after PLR, and change in cIVC after 500mL bolus were unreliable measures of predicting fluid responsiveness
      • PLR did not reliably reduce cIVC from baseline compared to IVC bolus
  • Discussion
    • cIVC measured by POCUS is able to detect fluid responsiveness and may be used to guide IV fluid resuscitation in spontaneously breathing critically ill patients
      • If a patient has a cIVC of <25% it is unlikely that that patient will benefit from additional IVF (LR- 0.16, NPV 86.4% in population with 49.2% prevalence)
      • Conversely, a cIVC of > 25% indicates a patient would likely benefit from additional fluid resuscitation (LR+ 4.56, PPV 81.5%)
      • A caveat to this assumption is a subset of patient will have cIVCs >25% and not respond to fluids
        • Reduced cardiac ejection fractions and pulmonary hypertension were examples observed in the study
      • PLR was not clinically useful in diagnosis or treatment of hypovolemia (AUC 0.68)

Receiver operator characteristic curves for baseline cIVC and for a PLR to detect fluid responsiveness (Corl et al. Fig. 2.)

  • Study Strengths and Limitations
    • Strengths
      • Largest investigation to date examining POCUS measurement of cIVC in spontaneously breathing critically-ill patients
      • Performed by non US fellowship trained providers
    • Limitations
      • Critically ill non medical patients excluded (e.g. trauma patients)
      • Cardiac dysfunction & pulmonary hypertension may limit applicability of study
      • Non standardization of respiration
      • No NIPPV limits clinical relevance

Proposed Treatment Algorithm (Fig 5: Corl et al)


  1. Corl KA, et al. Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients. J Crit Care. 2017;41:130-137.
  2. Boyd JH, Forbes J, Nakada TA, et al. Fluid resuscitation in septic shock: a positive fluid balance and elevated central venous pressure are associated with increased mortality. Crit Care Med 2011;39(2):259–65.
  3. Evans DC, Doraiswamy VA, Prosciak MP, et al. Complications associated with pulmonary artery catheters: a comprehensive clinical review. Scand J Surg. 2009;98(4):199-208.
  4. Raval NY, Squara P, Cleman M, et al. Multicenter evaluation of noninvasive cardiac output measurement by bioreactance technique. J Clin Monit Comput 2008;22(2): 113–9.

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