Thread by @DepthAnesthesia

Tweetorial time! 🚨🚨

1/ What is the passive leg raise test and how do you properly perform it?

Spoiler...physically lifting and holding the patient's leg might not be ideal.

#Tweetorial #meded

2/ Do you use the passive leg raise test as a measure of fluid responsiveness?

3/ Before we get started, what exactly is fluid responsiveness?

Contrary to popular opinion, fluid responsiveness is defined as an increase in stroke volume with a fluid challenge and not an increase in blood pressure.

4/ PLR testing is particularly attractive as a predictor of preload responsiveness without the need to administer fluid.

Monnet and Teboul describe five rules for optimizing a passive leg raise test.

5/ Rule 1:

What is the ideal starting position of the patient prior to passive leg raise testing?

6/ Interestingly, Jabot et al. found that PLR from a semi-recumbent baseline increased cardiac preload and index more than from a supine baseline in septic patients.

It was thought that the semi-recumbent baseline was able to better recruit the splanchnic reservoir.

7/ Perhaps the most important finding from the study was that 40% of the patients in the supine baseline group would have falsely been classified as fluid non-responders if a 10% increase in cardiac index was defined as a positive response.

8/ Rule 2:

PLR effects are best assessed with a direct measurement of cardiac output and not simply blood pressure.

A meta-analysis of PLR-induced changes in pulse pressure found a pooled sensitivity and specificity of only 59.5% and 86.2%, respectively.

9/ The pooled sensitivity and specificity, however, of PLR-induced changes in cardiac output (or surrogates) was 89.4% and 91.4%, respectively. Not bad!

10/ Rule 3:

Techniques to measure cardiac output must be able to detect short-term and transient changes.

This may require more complex or invasive monitoring. Some measurement strategies from the meta-analysis include esophageal Doppler, TTE, PiCCO, and Vigileo.

11/ Rule 4:

Cardiac output should be measured not only before and during PLR but also after to check that it has returned to baseline.

12/ The thought is that a return to baseline suggests that any variation was more likely related to changes in cardiac preload than to spontaneous variations of the inherent disease.

This rule seems to be less evidence-based and more “stands to reason”.

13/ Rule 5:

Precautions must be taken to minimize pain, cough, discomfort, or awakening.

A significant increase in heart rate might suggest adrenergic stimulation and confound the results of the PLR.

14/ It turns out that aggressively lifting the legs of my hypotensive 85-year old patient with chronic lower back pain and watching for an increase in blood pressure was probably not the right way to do it...

15/ Five rules!

📌 Baseline position semi-recumbent (45°)
📌 Directly measure cardiac output (or surrogate)
📌 Expect results to be short-term and transient
📌 Measure before and during but also after
📌 Minimize adrenergic stimulation

16/ How do you perform the test and do you find it useful?

Thanks again to Dr. Xavier Monnet and Dr. Jean-Louis Teboul.