Purpose of review: It has recently become evident that administration of intravenous fluids following initial resuscitation has a greater probability of producing tissue edema and hypoxemia than of increasing oxygen delivery. Therefore, it is essential to have a rational approach to assess the adequacy of volume resuscitation. Here we review passive leg raising (PLR) and respiratory variation in hemodynamics to assess fluid responsiveness.
Recent findings: The use of ultrasound enhances the clinician's ability to detect and predict fluid responsiveness, whereas enthusiasm for this modality must be tempered by recent evidence that it is only reliable in apneic patients.
Summary: The best predictor of fluid response for hypotensive patients not on vasopressors is a properly conducted passive leg raise maneuver. For more severely ill patients who are apneic, mechanically ventilated and on vasopressors, point of care echocardiography is the best choice. Increases in vena caval diameter induced by controlled positive pressure breaths are insensitive to arrhythmias and can be performed with relatively brief training. Most challenging are patients who are awake and on vasopressors; we suggest that the best method to discriminate fluid responders is PLR measuring changes in cardiac output.