Oesophageal Doppler monitoring of descending aortic blood flow velocity during off-pump coronary artery bypass surgery

Objective

Acute haemodynamic changes occur frequently during off-pump coronary artery surgery (OPCAB). Currently used haemodynamic monitors are not satisfactory during this procedure. We assessed the feasibility of oesophageal Doppler insonation of the descending aorta to measure cardiac output and other haemodynamic indices continuously during OPCAB.

Methods

Twenty-five consecutive patients scheduled to undergo OPCAB were studied prospectively. The ethical committee waived the need for informed consent because the oesophageal Doppler monitor (CardioQ, Deltex, UK) was already in routine use in our hospital. Haemodynamic parameters were recorded at multiple intervals after anaesthetic induction; before sternotomy; before, during and after each anastomosis and at the end of surgery. Stroke volume, cardiac output (CO), corrected flow time (FTc), peak velocity(PV) and mean acceleration were measured or calculated by the Doppler monitor. Mean arterial pressure (MAP) and central venous pressure(CVP) were measured from radial artery and internal jugular venous cannulae respectively.

Results

Satisfactory Doppler signals were not obtained in one patient. Two patients were converted to standard revascularisation using cardiopulmonary bypass because of technical considerations. One, 7 and 14 patients had one, two and three vessels grafted respectively. The haemodynamic data on these 22 patients are presented in Table 1 as mean and standard deviation.

Table 1

Conclusion

The oesophageal Doppler was able to monitor cardiac output and other haemodynamic parameters continuously throughout OPCAB. Further studies are needed to determine whether or not active haemodynamic management assisted by oesophageal Doppler monitoring during OPCAB improves patient outcome.