Monnet

PLR

Passive leg-raising and end-expiratory occlusion tests perform better than pulse pressure variation in patients with low respiratory system compliance

Monnet. Critical Care Med. 2012; 40:152-157

Clinical Question

  • In patients who are mechanically ventilated, does the tidal volumes or compliance, affect the performance of pulse pressure variation to predict volume responsiveness? In addition, in patients with ARDS can a passive leg raise test or end-expiratory occlusion test predict fluid responsiveness?

Design

  • Prospective observational study
  • Blinding not stated
  • Use of consecutive patients not stated
  • Statistics
    • Data pre + post fluid challenge compared using paired Student t test or Wilcoxon paired test, as appropriate
    • Comparison of data between different groups performed using two-sample Student t test or a Mann-Whitney U test, as appropriate
    • Comparison of ROC curves tested with Hanley-McNeil test

Setting

  • Single medical ICU, Paris
  • Dates of data collection not stated

Population

  • Inclusion criteria: Mechanically ventilated patients with circulatory failure who required a fluid challenge
    • Circulatory failure:
      • BP ≤90mmHg (or decrease of ≥50 in known hypertensive)
      • And at least 1 of the following
        • Urinary flow ≤0.5ml/kg/min for ≥2 hours
        • HR ≥100
        • Skin mottling
    • Need for fluid challenge as determined by attending physician
    • Mechanical ventilation in assist control mode
    • Absence of cardiac arrhythmias and spontaneous triggering of ventilator, as assessed by 2 investigators using airway pressure curve
  • Exclusion criteria:
    • <18 years
    • Moribund
    • Passive leg raise contraindicated (head trauma, venous compression stocking)
  • All patients sedated, and 5 patients paralysed
  • 54 patient included
    • 44 septic patients
    • 27 patients had ARDS, Compliance was 22ml/cmH20 in these patients
    • 27 patients did not have ARDS, Compliance was 45ml/cmH2O in these patients

Tests of Interest

  • Pulse pressure variation (PPV)
    • Measured pre and post-fluid challenge
  • Passive leg raise (PLR)
    • Patient transferred from 45° semirecumbent position to supine with legs raised to 45°
    • Cardiac output studies recorded when changes induced by PLR were maximal i.e. within 1 minute
  • End-expiratory occlusion (EEO)
    • End-expiratory hold for 15 seconds
    • Cardiac output studies recorded at end of EEO

For both PLR and EEO, baseline cardiac output measurements performed at baseline and 1 minute post test of interest.

Gold Standard Investigation

  • Fluid challenge
    • Following PLR and EEO tests, patient given 500ml normal saline over 20 minutes

In all patients cardiac output studies performed using a PiCCO2 device. Measurements taken at baseline, post-test of interests and post-fluid challenge. Volume responder defined as increase in Cardiac index (CI) ≥15%

Outcome

  • Volume responders
    • Fluid challenge significantly increased CI ≥15% (+44% ±39%) in 30 ‘volume responders’
    • In patients with ARDS there were 16 responders and 11 non-responders
    • In patients without ARDS there were 14 responders and 13 non-responders
  • Primary outcome: Pulse pressure variation
    • Significantly correlated with compliance (r=0.55, p=0.0001)
    • Not correlated with tidal volume (r=0.21, p=0.13)
    • Significantly higher in volume responders with compliance >30ml/cmH20 vs. ≤30ml/cmH20 (18% vs. 8%). Whereas in non-responders there was no significant difference
    • All patients that had a PPV of >12% were found to be fluid responsive regardless of the compliance. The poor performance at predicting fluid responsiveness in patients with a low compliance was due to the false negative results.

Passive Leg Raise

  • Changes in CI induced by PLR not significantly correlated with compliance (r=-0.09) or with tidal volume (r=0.14)
  • Significant increase in CI induced by PLR in volume responders with both low and high compliance (28% and 24% respectively)
  • In non-volume responders no significant increase in CI with PLR

End-expiratory occlusion

  • Changes in CI induced by EEO signficantly correleated with compliance
  • Significant increase in CI induced by EEO in volume responders with both low and high compliance (9% and 10% respectively)
  • In non-volume responders no significant increase in CI with EEO

PLR and EEO copy

 

Authors’ Conclusions

  • Pulse pressure variation is less accurate at predicting fluid responsiveness in patients with low compliance, but passive leg raising and End-Expiratory Occlusion test remain valuable in these circumstances.

Strengths

  • Clear inclusion and exclusion criteria
  • Analysed for effects of both tidal volume and compliance
  • 3 tests of interest compared with results from fluid challenge

Weaknesses

  • Not stated if consecutive patients enrolled
  • No sample size calculation
  • Single centre
  • Authors on advisory board of Pulsion Medical Systems

The Bottom Line

  • Pulse pressure variation performed poorly at predicting fluid responsiveness in patients with a low compliance, irrespective of lung volumes. This was due to to a high false negative rate.
  • Increases in cardiac index induced by passive leg raising and end-expiratory occlusion performed well at predicting fluid responsiveness in patients with both a high and low compliance.

External Links

Metadata

Summary author: @davidslessor
Summary date: 27th April 2016
Peer-review editor: @avkwong

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