From the Guidelines
To perform a passive leg raise (PLR) test, start with the patient lying flat on their back in a semi-recumbent position at approximately 45 degrees, then lower the head of the bed to a flat position while simultaneously raising the patient's legs to a 45-degree angle and hold this position for 30-60 seconds, as this method has been shown to be effective in predicting fluid responsiveness in patients with postoperative hypotension 1.
Key Steps for the PLR Test
- Measure baseline hemodynamic parameters such as blood pressure, heart rate, and ideally cardiac output or stroke volume using available monitoring equipment.
- Lower the head of the bed to a flat position while simultaneously raising the patient's legs to a 45-degree angle.
- Hold this position for 30-60 seconds.
- Reassess the same hemodynamic parameters during this maneuver.
Interpretation of the PLR Test
- A positive PLR test is indicated by an increase in cardiac output or stroke volume of at least 10%, suggesting that the patient is fluid responsive 1.
- The PLR test works by temporarily shifting approximately 300mL of blood from the lower extremities to the central circulation, mimicking a fluid bolus without actually administering fluids.
Considerations for the PLR Test
- The test is most reliable when cardiac output is directly measured rather than using blood pressure alone as a surrogate.
- Ensure the patient doesn't experience discomfort during the maneuver and return them to their original position after completing the assessment.
- The PLR test can be useful in detecting whether inadequate preload is contributing to hypotension, and if the test does not correct hypotension, further management should focus on vascular tone and chronotropy/inotropy 1.
From the Research
Performing a Passive Leg Raise (PLR) Test
To perform a PLR test, follow these steps:
- Elevate the patient's legs to 45 degrees while they are in a supine position 2, 3, 4
- Measure the patient's cardiac output, stroke volume, and blood pressure before and after the leg elevation 5, 2, 3, 4
- The test can be performed using a non-invasive cardiac output monitor, such as the NICOM 3
- The patient's response to the PLR test can be used to predict fluid responsiveness and guide fluid management 2, 4, 6
Key Considerations
- The PLR test should be performed in a controlled environment, such as an intensive care unit or emergency department 2, 3, 4
- The test may not be suitable for patients with certain medical conditions, such as arrhythmias or spontaneous breathing activity 4
- The results of the PLR test should be interpreted in conjunction with other clinical data and used to guide fluid management decisions 6
Predicting Fluid Responsiveness
- A PLR increase of aortic blood flow > 10% predicts fluid responsiveness with a sensitivity of 97% and a specificity of 94% 4
- A PLR increase of pulse pressure > 12% predicts volume responsiveness with significantly lower sensitivity and specificity 4
- The changes in aortic blood flow induced by PLR predict preload responsiveness in ventilated patients 4