MINIMAL INVASIVE MONITORING OF VOLUME STATUS IN PATIENTS AFTER MAJOR ABDOMINAL SURGERY.

Determining volume status is important in critically-ill patients. Currently no
gold-standard is available to accurately assess a patient*s volume status and
physicians use clinical signs and hemodynamic parameters (like cardiac output)
to estimate volume status.
Currently, the Pulmonary Artery Catheter (PAC) is one of the standards to
monitor major abdominal surgery patients. Its use, however, is related to
complications upsetting its value in other subpopulations like septic patients.
The primary aim of this study is to evaluate the use of less invasive
techniques to determine cardiac output (with pulse contour) compared to
thermodilution cardiac output measurement with a pulmonary artery catheter. If
proven accurate less invasive techniques could replace the PAC in the
perioperative monitoring of major abdominal surgery patients.

The primary objectives of this study consist of:
1. To assess the accuracy of different pulse contour methods to measure CO
compared to thermodilution CO measured with a PAC in major abdominal surgery
patients.
2. To assess the effect of propofol sedation and different hemodynamic
challenges (PEEP increase, fluid challenge and passive leg raising) on the
accuracy of the measurement of stroke volume variation (SVV), pulse pressure
variation (PPV) and CO with different techniques.
3. To assess the accuracy of a novel method to estimate mean systemic filling
pressure against two validated methods.

Secondary objectives consist of:
1. To study the effect of propofol sedation on mean systemic filling pressure.
2. To study the effect of propofol on systemic, venous and arterial resistance.
3. To assess the value of dMAP, dCO, dCVP due to 30° PLR, 5 and 10 cm H2O PEEP,
50 and 100 cc volume challenges to predict fluid loading responsiveness.
4. To assess the value of baseline CO, SVV, SPV, PPV and Pmsf to predict fluid
loading responsiveness.

Prospective intervention and measurement study

Hemodynamic measurements are performed during propofol infusion at a blood
concentration of 4, 2 and 1 µg•mL-1. Subsequently measurements are repeated
prior to, 30 seconds after start and 2 minutes after returning to baseline
conditions for 30° passive leg raising, PEEP +5 cmH2O and PEEP +10cmH2O.
Finally, 500 mL of Voluven is administered in 50 mL bolus with intermediate
measurements.

Propofol
Propofol is a GABAA agonist that is widely used as intravenous hypnotic for
surgical anesthesia and for sedation during loco-regional anesthesia and at the
ICU and PACU. We have experience with propofol in the PACU at the dose range
studied and expect minimal hemodynamic side effects in the patients studied.
These hemodynamic depressant effects of propofol are the result of peripheral
vasodilatation and direct myocardial depression.

Pulmonary Artery Catheter
The standard of perioperative anesthetic care for patients scheduled for major
abdominal surgery in the LUMC includes central venous catherisation with or
without pulmonary artery catherisation. The insertion of a pulmonary artery
catheter is left to the judgment of the attending anesthesiologist. The
acquisition of venous access for both the central venous catheter and the PAC
is associated with similar complications (id est arterial puncture, bleeding at
the injection site, pneumothorax, air- or thrombo-embolism, arrhythmias,
infections. Catheterization with a PAC may lead to more specific complications
like mild tricuspid insufficiency, pulmonary artery rupture and pulmonary
infarction. In a general ICU population the beneficial effects of the
monitoring characteristics of the PAC is upset by its complications.. Several
subpopulations, however, have shown to have improved survival due to the
monitoring capabilities of the PAC, for example high-risk cardiac surgery.
Patients undergoing major abdominal surgery also have an indication for
pulmonary artery catheterization for its use is associated with an improved
outcome in patients after planned major surgery like those included in our
study.