NIHR Signal Simple leg raise test may help in assessing patients’ fluid needs in intensive care

Published on 12 April 2016

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.

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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.

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.

Predicting Fluid Responsiveness by Passive Leg Raising: A Systematic Review and Meta-Analysis of 23 Clinical Trials

Published on 8 January 2016

Cherpanath, T. G.,Hirsch, A.,Geerts, B. F.,Lagrand, W. K.,Leeflang, M. M.,Schultz, M. J.,Groeneveld, A. B.

Crit Care Med , 2016

OBJECTIVE: Passive leg raising creates a reversible increase in venous return allowing for the prediction of fluid responsiveness. However, the amount of venous return may vary in various clinical settings potentially affecting the diagnostic performance of passive leg raising. Therefore we performed a systematic meta-analysis determining the diagnostic performance of passive leg raising in different clinical settings with exploration of patient characteristics, measurement techniques, and outcome variables. DATA SOURCES: PubMed, EMBASE, the Cochrane Database of Systematic Reviews, and citation tracking of relevant articles. STUDY SELECTION: Clinical trials were selected when passive leg raising was performed in combination with a fluid challenge as gold standard to define fluid responders and non-responders. DATA EXTRACTION: Trials were included if data were reported allowing the extraction of sensitivity, specificity, and area under the receiver operating characteristic curve. DATA SYNTHESIS: Twenty-three studies with a total of 1,013 patients and 1,034 fluid challenges were included. The analysis demonstrated a pooled sensitivity of 86% (95% CI, 79-92), pooled specificity of 92% (95% CI, 88-96), and a summary area under the receiver operating characteristic curve of 0.95 (95% CI, 0.92-0.98). Mode of ventilation, type of fluid used, passive leg raising starting position, and measurement technique did not affect the diagnostic performance of passive leg raising. The use of changes in pulse pressure on passive leg raising showed a lower diagnostic performance when compared with passive leg raising-induced changes in flow variables, such as cardiac output or its direct derivatives (sensitivity of 58% [95% CI, 44-70] and specificity of 83% [95% CI, 68-92] vs sensitivity of 85% [95% CI, 78-90] and specificity of 92% [95% CI, 87-94], respectively; p < 0.001). CONCLUSIONS: Passive leg raising retains a high diagnostic performance in various clinical settings and patient groups. The predictive value of a change in pulse pressure on passive leg raising is inferior to a passive leg raising-induced change in a flow variable.

Passive leg raise test

Most of the leg raise procedures in this review started in a semi-reclined position with the patient’s torso lifted 45 degrees on a hospital bed. Although not described in the review, the bed is then typically flattened before the patient’s straightened legs are raised to a 45 degree angle using the bed, while their torso remains horizontal. Their heart output is measured in real time for any effects, before they are returned to the semi-reclined position.

A 2015 Critical Care editorial shows a picture of the procedure and describes five principles for carrying out the passive leg raise test:

  1. The patient should start in the semi-recumbent position.
  2. The effect of the passive leg raise on circulation should be measured by cardiac output, not by pulse blood pressure.
  3. As the change in circulation measurements may last for only a minute, the measurement technique should be capable of capturing this.
  4. The patient’s cardiac output should be measured before, during and after the test, in order to fully assess the changes.
  5. The patient should not be in pain, in discomfort, coughing or awakening during the test. The patient’s legs should not be lifted directly. All these factors could produce misleading test results.

Source: Monnet X, Taboul JL. Passive leg raising: five rules, not a drop of fluid! Critical Care. 2015;(19):18.

Available at: http://ccforum.biomedcentral.com/articles/10.1186/s13054-014-0708-5

Expert commentary

This is an interesting review which confirms that the passive leg raising manoeuvre can be used to test whether patients need more intravenous fluid. However, this involves quite a significant change in the patient's position, more than simply passively lifting their legs. The test has been slow to catch on for practical reasons.

Rupert Pearse, NIHR Research Professor & Consultant in Intensive Care Medicine, Queen Mary University of London