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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
This review of 23 trials found a simple leg raise test helped predict whether patients were responsive to extra intravenous fluids in intensive care.
Passive leg raising—using a hospital bed to tilt a patient’s straight legs up to a 45 degree angle—increases the amount of blood returning to their heart, similar to the effect of giving them an extra 250 to 350mls of fluid. The immediate but temporary increase in heart blood flow from leg raising helped identify those most likely to benefit from extra intravenous fluids.
This test is not common practice in the UK, perhaps because it isn’t practical in some patients, such as those with major injuries requiring immobilisation or having surgery. The evidence does suggest it is useful in many intensive care circumstances and so should not be overlooked as an assessment option.
Why was this study needed?
Shock is a life-threatening medical condition which may follow serious bleeding, infection or heart damage. The amount of blood pumped around the body becomes insufficient and this deprives the tissues and organs of oxygen and energy. The treatment of shock may involve rapidly giving intravenous fluids but it is difficult to know who may respond and exactly how much fluid is needed.
Passive leg raising temporarily causes more blood to flow back to the patient’s heart, and depending how their heart responds, may help predict those most likely to benefit from subsequent fluids, called predicting “fluid responsiveness”.
This review aimed to assess the ability of passive leg raising to identify patients who would benefit from extra fluids compared with the standard “fluid challenge” tests used as a reference.
What did this study do?
The review included 23 trials comparing passive leg raises (see Definitions) with standard “fluid challenge” tests involving giving patients 500ml of intravenous fluid over 10 to 30 minutes.
The main response measures were heart output and its linked “flow” measurements as well as “pressure” measurements like pulse pressure.
The trials included 1,013 patients, mostly in intensive care units with circulatory failure due to infection (sepsis). Most studies took place in France (17/23): the locations of the rest were not reported.
Most trials included were rated as having a low risk of bias increasing our confidence in the findings.
What did it find?
- Using pooled results from all the trials, the sensitivity of the passive leg raising test for a heart response to fluid was 86% (95% confidence interval [CI] 79 to 92). This is the proportion of people who responded to extra fluid who were correctly predicted as being able to respond by the leg raising test.
- The specificity was 92% (95% CI 88 to 96). This is the proportion of people who did not need extra fluid who were correctly identified in the leg raising test.
- Passive leg raise testing showed similar performance when used on patients who were breathing independently or used a ventilator, when different types of fluid were used for the standard test, and when starting the leg raise from a lying down or semi-inclined position.
What does current guidance say on this issue?
NICE guidance from 2013 on Intravenous fluid therapy in adults in hospital states that passive leg raising tests ‘suggests fluid responsiveness’ during initial assessment of fluid needs.
What are the implications?
This simple test is already an option stated in 2013 NICE guidance but is not widely used in the UK, possibly because it isn’t practical for many patients, for example, those with head injuries or undergoing surgery. It probably has a place in some intensive care scenarios, so should not be overlooked as an assessment option.
Citation and Funding
Cherpanath TG, Hirsch A, Geerts BF, et al. Predicting fluid responsiveness by passive leg raising: a systematic review and meta-analysis of 23 clinical trials. Crit Care Med. 2016. [Epub ahead of print].
Dr Geerts’ institution received funding from Edwards Lifesciences LLC. The remaining authors have disclosed that they do not have any potential conflicts of interest.
Bibliography
Cavallaro F, Sandroni C, Marano C, et al. Diagnostic accuracy of passive leg raising for prediction of fluid responsiveness in adults: systematic review and meta‐analysis of clinical studies. Intensive Care Medicine. 2010;36(9):1475‐1483.
Monnet X, Taboul JL. Passive leg raising: five rules, not a drop of fluid! Critical Care. 2015;(19):18.
NICE. Intravenous fluid therapy in adults in hospital. CG174. London: National Institute for Health and Care Excellence; 2013.
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