the MICCS study: the complex relation between the microcirculation and macrocirculation in patients after cardiothoracic surgery with and without circulatory shock

In patients after cardiothoracic surgery, changes in the microcirculation will
occur. Causes of these changes in the microcirculation can be tissue trauma,
activation of the inflammatory response and haemostatic system, anaesthesia,
hypothermia and formation of micro-embolisms. An impaired microcirculation
results in a decreased tissue oxygenation or even organ damage if a situation
of low tissue oxygenations persists.
Monitoring on the Intensive Care Unit (ICU), is mainly focused on
microcirculatory and macrocirculatory parameters, such as blood pressure,
cardiac output and saturation. The hemodynamic coherence between the
macrocirculation and the microcirculation is the condition under which
resuscitation procedures aimed at correcting macrocirculatory parameters are
also effective in correcting microcirculatory perfusion and cellular
oxygenation. Different studies in patients with sepsis or septic shock show
that a loss of hemodynamic coherence can occur. This means that during
resuscitation, macrohemodynamic parameters improve to normal values while
microcirculation is still altered, a condition that is associated with
increased morbidity and mortality 3. This loss of coherence may also be present
in patients after cardiothoracic surgery. Routinely measuring the
microcirculation with the CytoCam may therefore be valuable in monitoring
patients after cardiothoracic surgery.

In this study, we aim to investigate the postoperative time course of
microcirculatory parameters in patients admitted to the ICU after
cardiothoracic surgery with and without circulatory shock.

Secondary objectives:
* To study the postoperative time course of macrocirculatory parameters in
patients admitted to the ICU after cardiothoracic surgery with and without
circulatory shock.
* To investigate the relationship (i.e. coherence) between microcirculatory
parameters and macrocirculatory parameters in patients admitted to the ICU
after cardiothoracic surgery with and without circulatory shock.
* To study the relationship between the microcirculation and vital organ
(dys)function, particularly the need for vasopressors and/or inotropic therapy
or duration of mechanical support.
* To study the relationship between postoperative microcirculatory parameters
and clinical outcomes (i.e. acute kidney injury, the need for continuous
veno-venous hemofiltration, Iength of stay ICU and ICU mortality).

Prospective single-centre cohort study.

Included patients will undergo treatment after cardiothoracic surgery according
to current clinical practice. Microcirculation measurement with the CytoCam
will be performed as soon as possible after ICU admission (within 24 hours
(T0)), then within 24 hours (T1) after admission to the
ICU, and if possible >48 hours (T2) after T0. No delay of treatment will take
place. Data collection, including circulatory, respiratory and inflammatory
data, as well as blood samples and fluid balance, will occur at the same time
as the microcirculatory measurements. Simultaneously with To, demographic data
will be collected.

If a patient develops shock (a condition in which there is a lack of effective
circulating volume resulting in insufficient tissue perfusion) or the need to
receive mechanical support while on the ICU, microcirculation measurements will
be measured according to the current Shock protocol of LUMC.

All devices used in this study are minimal-invasive, easy to use, and
electrically safe. The use of the devices is risk-free. For the participating
patients, there are no advantages or disadvantages to the study. The study is
about gaining insight into the microcirculation in relation to the
macrocirculation in cardiothoracic surgery patients, with or without
circulatory shock. These results may contribute to the understanding and more
effective treatment of circulatory shock after cardiothoracic surgery. The
patient is measured a maximum of 3 times for several minutes. These
measurements are completely painless and of short duration.

In conclusion, we believe that this is a valuable study for post cardiothoracic
surgical patients, with almost no risks and some potential benefits for future
patients. We therefore believe that this study is ethical.