Question 17

Discuss the advantages and disadvantages of the following three techniques for assessing fluid responsiveness:

a)    Pulse pressure variation.    (40% marks)

b)    Passive leg raising.    (30% marks)

c)    Fluid bolus.    (30% marks)

(Note to candidates: details of how the techniques are performed are not required.)

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College answer

Not available.


  Advantages Disadvantages
Pulse pressure variation
  • Readily available in critical care, where arterial lines are common
  • Some monitoring systems even display PPV as standard
  • Highly sensitive - a threshold of 12% predicts fluid responsiveness with an AUROC curve of 0.94.
  • Fewer errors in calculation than SVV (easier to calculate)
  • Limited validity in spontaneously breathing patient (in fact , validated only for mandatory ventilation, with tidal volumes of 8ml/kg)
  • Impossible to use during a cardiac arrhythmia
  • Unreliable with valvular heart disease, especially aortic
  • Not going to work with cardiogenic shock (with poor LV function), as stroke volume may not increase in response to increased preload
  • Intracardiac shunts, AV fistulae and severe peripheral vascular disease  can all affect the pulse pressure
Passive leg raise
  • A reversible fluid challenge
  • This method of testing fluid responsiveness is well validated; sensitivity and specificity is 89% and 91%, respectively (Cavallaro et al, 2010)
  • Easy to do at the bedside, and gives rapid results with high sensitivity and specificity to identify fluid responders
  • When measuring cardiac output during this test, the AUC is about 0.95
  • Validated only for the use of cardiac output monitoring devices (AUC for  using pulse pressure variation was only 0.76)
  • You need a patient with both legs intact
  • You rely on an intact pelvis, so this excludes a lot of messy trauma patients (in whom it would be very useful)
  • It can't be done if you have a balloon pump in situ, or post angiography (because you need to lie flat) - and thus a lot of low-cardiac-output cardiogenic shock patients are excluded, which is a pity
  • It can't be done if you are even slightly concerned about your intracranial pressure.
Fluid bolus
  • Gold standard for fluid responsiveness testing
  • Does not have to be very large, and it can be ceased abruptly if it is clearly not improving the cardiac output
  • Statistically speaking, a number of patients being assessed for fluid responsiveness will actually require fluid resuscitation, which this technically is.
  • The whole point of assessing fluid responsiveness is that you do it before you give the fluid
  • This is an irreversible fluid challenge
  • There is little agreement on what the volume for such a challenge should be (JL Vincent suggests 200ml over 10min)
  • The response to one challenge does not predict the response to the next challenge
  • Repeated multiple challenges can lead to an undesirably positive fluid balance


Cavallaro, Fabio, 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 36.9 (2010): 1475-1483.

Teboul, Jean-Louis, et al. "Arterial pulse pressure variation with mechanical ventilation." American journal of respiratory and critical care medicine 199.1 (2019): 22-31.

Vincent, Jean-Louis, and Max Harry Weil. "Fluid challenge revisited." Critical care medicine 34.5 (2006): 1333-1337.

Vincent, Jean-Louis, Maurizio Cecconi, and Daniel De Backer. "The fluid challenge." (2020): 1-3.