From the Guidelines
A positive passive leg raise test is defined as an increase in stroke volume of more than 12% during the maneuver, indicating fluid responsiveness in a patient. This test is particularly useful in critically ill patients where assessing volume status can be challenging, such as in spontaneously breathing patients 1. The passive leg raise technique involves elevating the patient's legs to 45 degrees for 1-2 minutes, which mobilizes approximately 300 mL of blood from the lower extremities to the thorax, increasing preload without changing the patient's intravascular volume.
Key points to consider when performing a passive leg raise test include:
- The test is most reliable when performed correctly with appropriate hemodynamic monitoring
- Conditions that interfere with venous return, such as intra-abdominal hypertension, can limit the test's predictive value 1
- The test simulates a fluid bolus without actually administering fluids, making it valuable in patients where unnecessary fluid administration could be harmful
- An increase in stroke volume of more than 12% during passive leg raise is highly predictive of fluid responsiveness 1
In patients where the passive leg raise test is not feasible or reliable, alternative methods such as transesophageal echocardiography (TEE) may be considered, particularly in patients unable to obtain adequate images with transthoracic echocardiography (TTE) 1. However, TEE requires additional training and presents additional risks and expenses. The passive leg raise test remains a valuable and non-invasive tool for assessing fluid responsiveness in critically ill patients, and its results should be interpreted in the context of the patient's overall clinical condition and hemodynamic status.
From the Research
Definition of Passive Leg Raise Test
- The passive leg raise (PLR) test is a maneuver used to predict fluid responsiveness in critically ill patients 2.
- It involves lowering the head and upper torso from a 45° angle to lying supine while simultaneously raising the legs to a 45° angle, creating a transient, reversible autotransfusion that simulates a fluid bolus 2.
Purpose of the Test
- The purpose of the PLR test is to predict which hemodynamically unstable patients will increase their stroke volume in response to fluid administration, thereby avoiding deleterious effects of fluid overload 2.
- The test is used to guide fluid management and avoid fluid overload during early septic shock treatment 3.
Method of Performing the Test
- The method of performing the PLR test is crucial for interpreting the hemodynamic effects and reliability of the test 4.
- The test should be performed with the patient in a supine position, and the legs should be raised to a 45° angle while the head and upper torso are lowered to a supine position 2.
Interpretation of the Test
- The PLR test is considered positive if there is an increase in stroke volume index (ΔSVI) > 10% after the maneuver 5.
- The test can also be used to predict fluid responsiveness by measuring changes in pulse pressure variation (ΔPPVPLR) 6.
- A volume expansion-induced increase in cardiac index of >15% defines fluid responsiveness 6.