Validation of an Oesophageal Doppler Cardiac Output Monitor (ODM) versus a Transpulmonary Thermodilution Cardiac Output Monitor (PiCCO).

Cardiac Output (CO) monitoring is an important tool in advanced hemodynamic
monitoring and provides important information to guide hemodynamic therapy in
patients with circulatory problems. In contrast to research performed with CO
monitoring in adults, only few information about validation of CO monitoring
in children is available . Size of great vessels, vascular elasticity and
ventricular compliance differ between children and adults. The variety of these
parameters is strongly dependent of age . This makes it difficult to compare CO
measurements between adults and children in part based upon nomograms for all
age categories.
Currently, the Transpulmonary Thermodilution Technique (TPTD) and the
pulmonary thermodilution technique (Pulmonary Artery Catheter PAC) both count
as the gold standard for CO monitoring in children . The use of PAC in children
has become less popular because of the risk of serious complications and the
unsuitability in neonates and small children.
During the last decade non invasive technologies have become available to
measure CO. One of the advantages of these monitors is the low risk of serious
complications as seen in the invasive CO techniques. Much research has been
done to test reliability of the non invasive CO techniques in adults, but not
in children. Promising non invasive techniques for CO monitoring in children
use ultrasonography; transthoracic through the suprasternal notch (USCOM,
Australia) or transoesophageal (CardioQ, Deltex UK) .

Goal of our study is to compare the CO measuments by the Oesophageal Doppler
Monitor (ODM, Cardio Q) with the TPTD technique (PiCCO) and to determine
reliability of the ODM in absolute CO values and as a trend monitor. A
validation study comparing these two techniques has not been done before.
Validation of the non-invasive ODM against the gold standard TPTD as CO monitor
in children can provide a reliable alternative CO monitor for children with a
lower complication risk.

All included patients will be sedated, ventilated and have a PiCCO catheter in
situ before oral placement of an esophageal Doppler probe. Each patient will
have three CO measurements of both TPTD and ODM. All measurements are done in a
hemodynamic stable period. CO measurements by TPTD (PiCCO) are performed by
the attending nurse as is daily practice. The mean of three consecutive
measurements is taken as CO value and counts as reference value. Within a time
frame of maximally one hour, without hemodynamic changes, this is followed by
three consecutive ODM measurements done by one of the two trained researchers.
The mean of these three is taken as ODM-CO value. Minimal interval between two
paired measurements (TPTD and ODM) is one hour. In between two measurements
the esophageal Doppler probe is removed. The depth at which Doppler flow was
optimal will be marked for subsequent measurements.

CO monitoring by TPTD (PiCCO) is standard of care in pediatric intensive care
and in our hospital.
Also, ODM is an internationally known and used CO monitor.
Placement of de oesophageal Doppler probe is not associated with adverse events
when positioned by mouth and left in situ for less than 24 hours.
In this study the probe will only be left in place for less then 30 minutes.