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Passive Leg Raise – Clinical Test Explained

The Passive Leg Raise is a clinical test used in critical care to assess fluid responsiveness. By raising the legs, venous blood is shifted toward the heart to evaluate cardiac output response.

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Things worth knowing about "Passive Leg Raise"

The Passive Leg Raise is a clinical test used in critical care to assess fluid responsiveness. By raising the legs, venous blood is shifted toward the heart to evaluate cardiac output response.

What Is the Passive Leg Raise?

The Passive Leg Raise (PLR) is a dynamic, non-invasive clinical maneuver widely used in intensive care and emergency medicine. Its primary purpose is to assess whether a critically ill patient is likely to benefit from intravenous fluid administration. Because no fluid is actually given, the PLR is considered a reversible functional fluid challenge, making it a safe and practical bedside tool.

Mechanism of Action

During the Passive Leg Raise, the patient is repositioned so that the legs are elevated to approximately 45 degrees while the upper body is simultaneously lowered to a flat position. Gravity causes venous blood from the legs and pelvis to shift toward the central circulation, temporarily increasing venous return to the heart by approximately 150 to 300 mL.

If the heart responds to this increased preload with a measurable rise in cardiac output, the patient is considered fluid responsive, suggesting that intravenous fluid therapy is likely to be beneficial. If cardiac output does not increase significantly, further fluid administration is unlikely to improve hemodynamics and may risk causing harm through fluid overload.

How the Test Is Performed

Baseline Assessment

The patient is positioned either flat or in a semi-recumbent position (approximately 45 degrees head-of-bed elevation). Baseline hemodynamic parameters are recorded, including cardiac output, heart rate, and blood pressure.

Test Procedure

The legs are passively raised to approximately 45 degrees.
The upper body is simultaneously lowered to a flat position (if it was previously elevated).
Hemodynamic parameters are reassessed within 30 to 90 seconds.
The patient is then returned to the original position, reversing the effect.

Interpretation

An increase in cardiac output of at least 10 to 15 percent is considered a positive result, indicating fluid responsiveness. Recommended methods for measuring cardiac output during the PLR include:

Pulse contour analysis (e.g., PiCCO system)
Transthoracic or transesophageal echocardiography
Non-invasive hemodynamic monitoring devices

Clinical Applications

The Passive Leg Raise is particularly useful in the following clinical settings:

Septic shock and other forms of circulatory shock
Acute circulatory failure
Perioperative hemodynamic optimization
Assessment in mechanically ventilated patients
Guiding fluid therapy decisions in the ICU

Advantages of the Test

A key advantage of the PLR over traditional static hemodynamic parameters (e.g., central venous pressure) is its reversibility. Since no fluid is administered, the test carries no risk of fluid overload. Additionally, the PLR is applicable even in patients with cardiac arrhythmias or spontaneous breathing efforts, where dynamic respiratory variation parameters such as pulse pressure variation are less reliable.

Limitations and Contraindications

The PLR test is not suitable or reliable in all clinical situations. Limitations include:

Intra-abdominal hypertension
Severe tricuspid regurgitation
Deep vein thrombosis (contraindication to leg elevation)
Unstable spinal injuries
Raised intracranial pressure (contraindication to lowering the head of the bed)

References

Monnet X, Teboul JL. Passive leg raising: five rules, not a drop of fluid! Critical Care. 2015;19(1):18. doi:10.1186/s13054-014-0708-5
Cecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and haemodynamic monitoring. Intensive Care Medicine. 2014;40(12):1795-1815.
Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2016. Intensive Care Medicine. 2017;43(3):304-377.

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