Passive leg raise (PLR)

PASSIVE LEG RAISE (PLR)

The PLR test is a bedside assessment to determine fluid responsiveness. The test involves raising a patient’s legs (to at least 45 degrees) to induce a gravitational transfer of venous blood from the legs into the central circulation. The resulting effect is a transient increase in cardiac preload of ~150-300 mL. If the patient is fluid responsive, there will be an increase in right ventricular preload, right CO, left ventricular filling, and consequently CO [1].

A PLR test is a brief and reversible ‘self volume challenge’. However, because the potential effects are not always sustained, the haemodynamic effects of the challenge should be assessed in the 30-90 s following the onset of the test.

 

When assessing the haemodynamic response to a PLR test it is important to use a technology that directly measures CO, with sufficient precision to measure a 10-15% change in SV/CO. It should not be assessed by the simple measurement of BP. Oesophageal Doppler-measured changes in SV/CO have been shown to be more accurate at predicting fluid responsiveness than arterial pulse pressure [2] and [3].

When conducting a PLR, it is important to consider the following [1]and [3]:

  • Avoiding pain-induced sympathetic stimulation and therefore changes in HR is important to ensure validity. Movement from the 45 degree semi-recumbent to the PLR position does not induce hip flexion and is the simplest way to preform the test.
  • PLR should be performed using the bed mechanism and not by manually lifting the patient’s legs.
  • Not moving the thorax to below the horizontal position to avoid gastric inhalation.
  • Avoiding PLR in patients with head trauma in case of increases in intracerebral pressure.
  • Consider the effect of elastic compression stockings on reducing the venous reservior recruited by the PLR.
  • CO should be measured before, during and after the PLR.
  • The decision to give intravenous fluid based on PLR must be made on an individual basis depending on the clinical situation and is likely to include the following: haemodynamic instability, signs of circulatory shock, preload responsiveness and where there are limited risks of overload. 
  • ​PLR is likely to be more labour intensive than a fluid challenge.
  • ​When assessing preload responsiveness to a PLR, the monitoring tool needs to be both highly precise and FAST. ODM is precise [4] and also displays beat to beat changes. 
  • PLR has not been studied in terms of its impact on outcomes.​

References

  1. Monnet, X. and Teboul, J.L. Passive leg raising. Intensive Care Med, 2008. 34(4): p. 659-63.
  2. Monnet, X., et al., Passive leg raising predicts fluid responsiveness in the critically ill. Crit Care Med, 2006. 34(5): p. 1402-7.
  3. ​Money, X and Teboul J. L.,  Passive leg raising: five rules, not a drop of fluid! Critical Care 2015. 14;19:18.
  4. ​Singer, M. and Bennett, D. ​Continuous hemodynamic monitoring by oesophageal Doppler. ​Critical Care Medicine 17(5): p. 447-452.