In extracorporeal membrane oxygenation (ECMO), blood is drawn out of the body via tubes, oxygenated in an artificial lung; and then pumped back into the blood vessels. This allows the supply of oxygen-rich blood to the organs (brain, heart, lungs, kidneys, liver, intestines, etc.) to be maintained. Continuous monitoring of cardiac function and circulatory status (blood pressure, blood flow to organs) is very important in intensive care medicine in order to control the administration of circulation-supporting medication and infusions. Various devices are routinely used for this task. However, in the specific situation of ECMO treatment, the measurements of these devices could be affected due to the artificial circulation; outside the body. The purpose of this study is therefore to test the accuracy of different methods of circulation monitoring during ECMO treatment.
Patient receiving VA ECMO support
Age 18 - 75 years
Pregnancy
Conditions not allowing for passive leg raising maneuvers, e.g. "open abdomen", known or suspected elevation of intracranial pressure, recent leg or spinal trauma or orthopedic conditions not permitting leg raising
Known ischemic or hemorrhagic stroke within 3 months prior to study enrollment.
Single group
Transthoracic Echocardiography
DeviceTransthoracic echocardiography (TTE) is used for intermittent non-invasive stroke volume (SV) measurements. It is calculated by multiplication of left ventricular out flow tract (LVOT) and LVOT velocity time integral (VTI), obtained in a parasternal long axis view and apical five chamber view, respectively.
Uncalibrated Pulse Contour Analysis
DevicePulse Contour Analysis allows an automated and continuous measurement of stroke volume (SV). Its underlying principle is that the integral of the systolic arterial pressure curve directly correlates with stroke volume.
Transpulmonary Thermodilution/Calibrated Pulse Contour Analysis
DeviceTranspulmonary thermodilution (TPTD) involves the administration of a cold saline bolus into a central venous catheter. A special thermistor catheter placed in the femoral or brachial artery detects the successive changes in blood temperature. The resulting heat dissipation curve is analyzed to estimate stroke volume, cardiac output and other hemodynamic variables such as intrathoracic thermal volume (ITTV), pulmonary thermal volume (PTV), global end-diastolic volume (GEDV), intrathoracic blood volume (ITBV) and extravascular lung water (EVLW). Intermittent TPTD-derived cardiac output measurements (typically performed 1-3x/d) are used to calibrate pulse contour analysis.
Esophageal Doppler
DeviceIn esophageal Doppler, a thin ultrasound probe, coated with aqueous ultrasound gel, is orally or nasally inserted into the esophagus and orientated towards the aorta. By emission and detection of continuous wave Doppler signals, real time spectral waveforms of red blood cell velocity in the aorta are obtained, from which cardiac indices can be derived.
Bioreactance
DeviceBioreactance is a noninvasive hemodynamic monitoring technique, in which four double electrode sensors are placed on the skin of the chest. A high frequency sine wave is transmitted across the thorax. Pulsatile flow in the aorta causes phase shifts and amplitude changes of this signal, which are measured across the different electrodes and used to compute cardiac output.
Passive Leg Raising
Diagnostic testPassive Leg Raising (PLR) is a maneuver that mimics a fluid challenge by shifting about 300 ml of venous blood from the lower body to the heart. Thereby, it can help to predict fluid responsiveness without actual fluid infusion. To start with, the patient is placed in a semi-recumbent position. Then, the bed is adjusted so that the patient's torso is moved to a horizontal position and the lower limbs are raised to an angle of 45°. Hemodynamic effects occur and can be measured within one minute.
Vena Cava Ultrasound
Diagnostic testInferior Vena Cava (IVC) Ultrasound has become a popular technique for assessing volume status. IVC diameter is measured in a subcostal long-axis IVC view 1-2 cm from the junction with the right atrium. The magnitude of distensibility during mechanical ventilation cycles or collapsibility during spontaneous breathing has been proposed to correlate with fluid responsiveness
End-expiratory /-inspiratory occlusion test
Diagnostic testIn preload-dependent patients, mechanical ventilation induces periodic changes in cardiac output. Standardized maneuvers of end-expiratory or end-inspiratory interruption over 15 seconds may increase or decrease stroke volume, respectively, which is a valid predictor of fluid responsiveness
Fluid bolus
DrugTo verify fluid responsiveness, 500 ml of balanced crystalloids will be infused over a time of 15-20 min (25-33.33 ml/min) after completion of passive leg raising and restoration of baseline patient positioning
Agreement of receiver operating characteristic (ROC) curves for predicting fluid responsiveness using the passive leg-raising test between different cardiac output measurement techniques (echocardiography, pulse contour analysis, thermodilution).
Cardiac Output (L/min) will be measured using transthoracic echocardiography, uncalibrated pulse contour analysis, and thermodilution before, during, and after a passive leg-raising test, as well as after administration of a fluid bolus of 500 ml balanced crystalloids over 15-20 min. A cardiac output increase of \> 15% will be the cut-off for defining fluid responsiveness. Receiver operating characteristic (ROC) curves will be generated for each cardiac output measurement technique and compared using the Hanley-McNeil method. The agreement between the ROC curves (Hanley-McNeil test statistic) will serve as the primary outcome.
Diagnostic performance (receiver operating characteristic (ROC) area under the curve) of an inspiratory and expiratory occlusion test in conjunction with pulse contour analysis for the prediction of fluid responsiveness during ECMO.
Cardiac Output (L/min) will be measured using calibrated and uncalibrated pulse contour analysis before, during, and after an end-inspiratory and end-expiratory occlusion test (15 s), as well as after administration of a fluid bolus of 500 ml balanced crystalloids over 15-20 min. A cardiac output increase of \> 15% after fluid infusion will be the cut-off for defining fluid responsiveness. Receiver operating characteristic (ROC) curves will be generated to assess the performance of the end-inspiratory and end-expiratory occlusion tests and the best threshold for predicting fluid responsiveness during ECMO.
Changes of cardiac output (L/min) over the course of ECMO therapy
Cardiac output (L/min) will be measured at different time points (at least at the beginning of ECMO therapy and after ECMO removal) throughout ECMO therapy using transthoracic echocardiography, uncalibrated pulse contour analysis, and thermodilution.
Changes of tricuspid annular plane systolic excursion (TAPSE, mm) over the course of ECMO therapy
Tricuspid annular plane systolic excursion (TAPSE, mm) will be measured at different time points (at least at the beginning of ECMO therapy and after ECMO removal) throughout ECMO therapy using transthoracic echocardiography.
Changes of tissue doppler imaging tricuspid annular velocity (cm/s) over the course of ECMO therapy
Tissue doppler imaging tricuspid annular velocity (cm/s) will be measured at different time points (at least at the beginning of ECMO therapy and after ECMO removal) throughout ECMO therapy using transthoracic echocardiography.
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