Predicting Fluid Responsiveness in on Pump Coronary Artery Bypass Graft Using Extra Systoles

From induction of anaesthesia to cardioplegia we will serve two fluid challenges. Before and after each challenge we will collect hemodynamic data and use this to asses our two hypotheses.

Fluid responsiveness (the outcome to predict) will be defined as a 15% increase in stroke volume(SV) from immediately before fluid infusion is initiated (baseline) to after the full fluid infusion. Stroke volume is derived from the gold-standard pulmonary artery catheter measurement of cardiac output(CO), which is standard monitoring for these patients (SV = CO/heart rate). From subsequent offline analysis of the extracted curve data we will investigate if post-ectopic characteristics from identified extra systoles during the baseline period can predict fluid responsiveness (i.e. the SV change). This analysis addresses the primary hypothesis. Also, we will analyse the arterial waveform related to the mini fluid challenge for morphologic changes (comparing heart beats before the infusion with heart beats during the infusion) and see if such transient changes, e.g. in systolic blood pressure, are able to predict fluid responsiveness. This analysis addresses the secondary hypothesis.

Inclusion criteria

• Predominant sinus rhythm (No atrial fibrillation, trigemini, 2nd and 3rd degree atrioventricular block also if pacing is present etc.)

Exclusion criteria

• Ejection fraction < 35% (Safety limit minimising risk of fluid overload)
• Haemodialysis (safety precaution for patients with end-stage kidney failure)
• Pregnancy
• Mentally retarded (due to lack of capability to sign an informed consent)