Evaluating the accuracy and reliability of sublingual micro-circulation measurements as an adjunct to fluid management in Cardiac Surgery patients

Open cardiac surgery leads to severe inflammation and is related with a wide
range of micro- and macro-circulatory derangements which may correspond to
reduced tissue oxygenation. Improvement of tissue oxygenation is important to
decrease post-surgical morbidity and mortality. Fluid and/or
vasopressor/inotrope therapies are used in order to restore tissue perfusion.
Fluid administration is the first step in the resuscitation of perioperative
patients displaying signs of impaired organ perfusion. Inadequate fluid therapy
leads to hypovolemia and consequently inappropriate use of vasopressor therapy.
Conversely, excessive fluid administration during the perioperative period
leads to a positive cumulative fluid balance and is regarded as one of the most
common clinical problems in post-intensive care unit (ICU) cardiac surgery
patients. Fluid overload can cause several complications which result in a
longer recovery period, increased length of hospital stay, increased morbidity
and decreased quality of life after surgery. The volume of administered fluid
is often excessive and no real end points for its administration are currently
available. The *de-escalation phase* follows fluid administration and describes
the event where fluid is removed from the patient. Several options are
available, but the common methods are the use of diuretics and ultrafiltration
if required.
Unfortunately, global macro-hemodynamic parameters like systemic blood
pressure, heart rate and urine output may not reflect microcirculatory
dysfunction. The microcirculation may remain deteriorated despite the global
hemodynamic parameters are improved. Direct visualization of the sublingual
microcirculation with hand-held vital microscopy (HVM; Cytocam-IDF (Braedius
Medical, Huizen the Netherland) may provide the clinician to monitor fluid
therapy by potentially preventing the unnecessary and inappropriate
administration of large volumes of fluids and monitor the success of
de-escalation therapy thereby allowing more physiologically based approaches
for the diagnosis and treatment of cardiac surgery patients.

The primary aim of the study is to determine how microcirculation is affected
at the bedside during fluid resuscitation and de-escalation phase of fluid
therapy during surgery and in post-ICU cardiac surgery patients. The secondary
aims of the study are to determine how the microcirculation changes in parallel
with macro-circulation during these phases of fluid administration, to
determine the usability of Nexfin® (BMEYE, Amsterdam, The Netherlands) for
non-invasive cardiac output measurement and Bioimpedance (Body Composition
Monitor (BCM), Fresenius Medical Care, Bad Homburg, Germany) for non-invasive
measurement of tissue water and weight in association with macro-hemodynamic
parameters such as blood pressure and oxygen saturation during fluid
resuscitation and de-escalation phase of fluid therapy .

Observational cohort study.

There are no risks associated with the use of the Cytocam. The burden is
minimal, the measurments are painless, patients do not need to come back to the
hospital for extra examinations. They endure measurements at three different
time points, each time it costs approximately 30 minutes to complete the
measurements.