A clinical study to compare Continuous Arterial-pressure-based (FloTrac), Transoesophageal doppler ultrasound, thoracic bioreactance (Nicom) Cardiac Output Measurements in low cardiac output states

Individualized treatment of hemodynamic instability is thought to improve
patient outcome. Therapy is based on exact measurement and monitoring of
hemodynamic parameters amongst cardiac ouput is an important one. Pulmonary
artery catheter based cardiac output measurement is considered the gold
standard but is an invasive procedure. Other non-invasive methods have been
developed and they seem to have a good correlation with invasive measurements
but within the normal range. Although there are conflicting results and
questions are raised about the used methodology. Because decision making
depends on the reliability of data we set out to investigate the reliability of
different non invasive cardiac output measurements in low output states in
coronary artery bypass graft surgery.

The primary objective of this trial is to investigate the bias, limits of
agreement and percentage error of cardiac output measurements with Vigileo
FloTrac, transoesophageal doppler ultrasound, thoracic bioreactance (NICOM)
with the CO obtained from pulmonary artery catheter thermodilution measurements
in low cardiac output states.

mono centre interventional study.

CPAP manoeuvres consisting of 3 cycles of 5 minutes of 10, 15 and 20 cm H2O
respectively. A pulmonary artery catheter will be inserted transjugularly.

There is a risk associated with insertion of a pulmonary artery catheter. The
risk of persistent ventricular arrhythmias requiring lidocaine is 3%. None of
whom suffer hemodynamic instability. Other arrhytmias are very rare. There is a
5% chance of developing transient right bundle branch block, placing patients
with a left bundle branch block at risk of a complete hart block. Knotting of
the catheter can occur during insertion if loops are allowed to form within one
of the cardiac chambers. This can generally be avoided if the individual
passing the catheter is careful not to exceed the expected distance from the
insertion point to the right ventricle or pulmonary artery. When knotting
occurs, the catheter can usually be removed transvenously. However, some
patients require placement of a guidewire, venotomy, or even surgical
extraction. The most dangerous complication with pulmonary artery catheters is
associated with wedging of the pulmonary artery to determine pulmonary artery
wedge pressure (PAWP) as a representative/surrogate of the left ventricle end
diastolic pressure (LVEDP). The incidence of this rare complication is about
0.03%. In this study no PAWP will be determined. There is no pulmonary risk
associated with CPAP manoeuvres up to 20 cm H2O in patients with no pulmonary
disease. In lung recruitment studies airway pressures up to 40-50 cm H2O are
probably harmful but in lung protective ventilation studies pressures up to 30
cm H2O are considered to be safe. In studies using CPAP manoeuvres to influence
venous return similar pressures (20 cm H2O) have been used with no adverse
effects. Transesophageal ultrasound probe insertion is a common procedure and
complications are infrequent provided care is exercised and contraindications
are respected. Reported complications are: odynophagia (0,1%), upper
gastrointestinal haemorrhage (0,03%), oesophageal perforation (0,01%), dental
injury (0,03%) and endotracheal tube malposition (0,03%).