Passive Leg Raise & Hemodynamics in the ED

Without adequate tissue delivery of oxygen, early shock states quickly progress to multi-organ dysfunction syndrome (MODS) in critically ill patients.  Early goal directed therapy (EGDT) with aggressive crystalloid resuscitation has been instrumental in halting and reversing a subset of distributive shock states.  

Adequate resuscitation is predicated on correct assessment of the patient's fluid status.  This routinely challenges ED clinicians evaluating patients early in the course of their illness – when they are without central lines and arterial lines, or when ultrasound is equivocal or technically limited.

Under-resuscitation may lead to inappropriate use of vasopressors, while over-resuscitation saddles the ICU team with extended hospital stays to remove volume once a distributive shock

state resolves.  

The shortcomings of central venous pressure (CVP) monitoring as a surrogate for preload are well-known and documented.   Studies have documented that CVP is about as good as a coin-flip with regard to assessing fluid status and responsiveness in the critically ill.

Other methods of measuring fluid-responsiveness have emerged and are seeing fair success.  These include pulse-pressure variation (PPV), bedside IVC ultrasound, plethysmography, and brachial artery peak velocity.  

One low-tech high-quality method to assess fluid responsiveness is the passive leg raise (PLR).  

Steps to performing PLR:

1. Seat the patient upright at 45 degrees with the legs flat.  
2. Hemodynamics are measured in this position (i.e., BP, PPV).  
3. Lie the patient's head flat and raise the legs to 45 degrees. 
4. Repeat hemodynamic measurements.  
5. If BP or PPV increase with the 2nd position, the patient is likely fluid responsive.

Image courtesy of  Hofer C, Cannesson M (9).

The idea behind the PLR is that, in effect, the patient is getting a reversible bolus, moving volume from their lower extremities to their thoracic compartment.  Preload is transiently increased and the Frank-Starling curve  is challenged.  

This test carries a number of characteristics that make it attractive to the ED clinician.  It may be used in patients with arrhythmias and spontaneously breathing patients (unlike pulse pressure variation).  It is reversible – patients who do not need volume will not become overloaded.  

Furthermore, it is easy to employ at the bedside, relatively inexpensive, reproducible by multiple caregivers, and retains an ability to be measured serially at any point in resuscitation.

Beyond the teleological argument, the literature seems to agree.  Changes in a large number of hemodynamic variables (aortic blood flow assessed by esophageal Doppler, continuous cardiac output monitoring, arterial pulse pressure variation) monitored during PLR correlate well with rapid fluid loading (3, 4, 5, 6, 8).

Unfortunately PLR is not usable in all patients.  In the severely hypovolemic, the volume of fluid in the lower extremities may not be adequate to have a measurable effect on preload and all related hemodynamic variables.  Likewise,PLR has also been shown to be a poor predictor of fluid responsiveness in patients with intra-abdominal hypertension (7).

-- Peter Acker MD MPH

References:

1) Marik P.  “Hemodynamic Parameters to Guide Fluid Therapy.”  Transfusion Alternatives in Transfusion Med. 2010;11(3):102-112.

2) Marik PE, Baram M, Vahid B.  “Does central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares.” Chest 2008 Jul;134(1):172-8.

3) Boulain T, Achard JM, Teboul JL, et al. “Changes in BP induced by passive leg raising predict response to fluid loading in critically ill patients.” Chest 2002; 121:12451252.

4) Monnet X, Rienzo M, Osman D, et al. “Passive leg raising predicts fluid responsiveness in the critically ill.” Crit Care Med 2006; 34:1402-1407.

5) Lafanechere A, Pene F, Goulenok C, et al. “Changes in aortic blood flow induced by passive leg raising predict fluid responsiveness in critically ill patients.” Crit Care 2006; 10:R132.

6) Preau S, Saulnier F, et al. “Passive leg raising is predictive of fluid responsiveness in spontaneously breathing patients with severe sepsis or acute pancreatitis.” Crit Care Med 2010 Mar;38(3):819-25.

7) Mahjoub Y, Touzeau J, et al. “The passive leg-raising maneuver cannot accurately predict fluid responsiveness in patients with intra-abdominal hypertension.” Crit Care Med 2010 Sept; 38 (9): 1824-1829.

8) Maizel J, Airapetian N, Lorne E, et al.  “Diagnosis of central hypovolemia by using passive leg raising.”  Intensive Care Med 2007; 33:1133–1138.

9) Hofer C, Cannesson M.  “Monitoring fluid responsiveness.”  Acta Anaesthesiologica Taiwanica Volume 49, Issue 2, Pages 59-65.