Predicting fluid responsiveness with the passive leg raising test: don’t be fooled by intra-abdominal hypertension!

Abstract

Fluid therapy is often used as first line therapy in critically ill patients in shock. Among the methods currently available to detect preload responsiveness, the PLR test has been demonstrated to be reliable in many studies and a recent meta-analysis (1,2). According to Monnet and Teboul, five rules need to be taken into account, when performing a PLR (3). First, PLR should start from the semi-recumbent and not the supine position. Second, the PLR effects must be assessed by a direct measurement of cardiac output and not by the simple measurement of blood pressure. Third, the technique used to measure cardiac output during PLR must be able to detect short-term and transient changes since the PLR effects may vanish after 1 min. Fourth, cardiac output must be measured not only before and during PLR but also after PLR when the patient has been moved back to the semi-recumbent position, in order to check that it returns to baseline. Fifth, pain, cough, discomfort, and awakening could provoke adrenergic stimulation, resulting in erroneous interpretation of cardiac output changes. We would like to add a sixth rule: confounding factors and underlying conditions that may influence the PLR must be assessed before performing the test, these include increased intrathoracic pressure [high PEEP, presence of autoPEEP, thoracic compartment syndrome (e.g., tension pneumothorax)], cardiac tamponade, right ventricular infarction or failure and intra-abdominal hypertension

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