Echocardiography and passive leg raising in the postoperative period

BACKGROUND: Signs of hypovolaemia are frequent in the postoperative period, but not all patients need or respond to fluid administration. An increase in cardiac output (CO) after passive leg raising (PLR) has been demonstrated to be useful as a volume response predictor in non-surgical, spontaneously breathing patients. OBJECTIVE: The objective of this study was to evaluate the accuracy of transthoracic echocardiography after PLR to predict fluid responsiveness in post-surgical patients. DESIGN: A prospective observational study. SETTING: A tertiary hospital between January and July 2015. PATIENTS: Fifty-one spontaneously breathing postoperative patients with suspected hypovolaemia (arterial hypotension, oliguria, tachycardia or delayed capillary refill) were considered for the study. INTERVENTION: Demographic and personal data were collected, as well as heart rate variations, mean arterial pressure during PLR and after administering 500 ml of Ringer's lactate solution. CO was measured by transthoracic echocardiography. MAIN OUTCOME MEASURES: The primary outcome was measurement of CO before and after PLR and Ringer's lactate administration. RESULTS: Forty-one patients were included in the study (six patients were excluded because of a poor echocardiographic window and four because of misalignment of the Doppler and outflow tract of the left ventricle). Twenty-two patients (54%) were considered responders to fluid therapy, with an increase of stroke volume greater than or equal to 15% after 500 ml lactated Ringer's infusion. The highest area under the curve was found for an increase in CO (0.91 ± 0.05; 95% confidence interval 0.78 to 0.97). An increase in CO greater than 11% after the PLR manoeuvre predicts a volume response with 68% sensitivity and 100% specificity. CONCLUSION: This is the first study showing that measurement of CO after PLR can predict volume response in spontaneously breathing postoperative patients.