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TECHNOLOGY, COMPUTING, AND SIMULATION

Online Monitoring of Pulse Pressure Variation to Guide Fluid Therapy After Cardiac Surgery

Jose Otavio Auler, Jr., MD, PhD^*, Filomena Galas, MD, PhD^*, Ludhmila Hajjar, MD^*, Luciana Santos, MD^*, Thiago Carvalho, MD^*, and Frédéric Michard, MD, PhD

From the *Department of Anesthesia and Critical Care, Heart Institute, INCOR, Hospital das Clinicas, University of Sao Paulo, SP, Brazil; and Department of Anesthesia and Critical Care, Béclère Hospital-University Paris XI, Paris, France.

Address correspondence and reprint requests to Frédéric Michard, MD, PhD, Department of Anesthesia and Critical Care, Hopital Antoine Béclère, 157 rue de la porte de Trivaux, 92141, Clamart, France. Address e-mail to michard.frederic{at}free.fr.

BACKGROUND: The arterial pulse pressure variation induced by mechanical ventilation (PP) has been shown to be a predictor of fluid responsiveness. Until now, PP has had to be calculated offline (from a computer recording or a paper printing of the arterial pressure curve), or to be derived from specific cardiac output monitors, limiting the widespread use of this parameter. Recently, a method has been developed for the automatic calculation and real-time monitoring of PP using standard bedside monitors. Whether this method is to predict reliable predictor of fluid responsiveness remains to be determined.

METHODS: We conducted a prospective clinical study in 59 mechanically ventilated patients in the postoperative period of cardiac surgery. Patients studied were considered at low risk for complications related to fluid administration (pulmonary artery occlusion pressure <20 mm Hg, left ventricular ejection fraction 40%). All patients were instrumented with an arterial line and a pulmonary artery catheter. Cardiac filling pressures and cardiac output were measured before and after intravascular fluid administration (20 mL/kg of lactated Ringer’s solution over 20 min), whereas PP was automatically calculated and continuously monitored.

RESULTS: Fluid administration increased cardiac output by at least 15% in 39 patients (66% = responders). Before fluid administration, responders and nonresponders were comparable with regard to right atrial and pulmonary artery occlusion pressures. In contrast, PP was significantly greater in responders than in nonresponders (17% ± 3% vs 9% ± 2%, P < 0.001). The PP cut-off value of 12% allowed identification of responders with a sensitivity of 97% and a specificity of 95%.

CONCLUSION: Automatic real-time monitoring of PP is possible using a standard bedside monitor and was found to be a reliable method to predict fluid responsiveness after cardiac surgery. Additional studies are needed to determine if this technique can be used to avoid the complications of fluid administration in high-risk patients.

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