Sublingual microvascular changes in perfused vessel density and boundary region during an intravenous fluid challenge.

During anesthesia and surgery, patients receive fluids to maintain system
hemodynamics and to compensate for blood loss. Inadequate fluid resuscitation
in the intraoperative period may not only result in perioperative hypovolemia
or postoperative fluid overload, but may also change the integrity of the
vascular wall. Animal studies suggest that the glycocalyx serves as a competent
barrier for water and colloids, but may also be damaged by fluid infusion.
However, evidence for this phenomenon in patients is limited, which is mainly
due to the lack of measurement devices. With the introduction of a novel
technique for evaluation of microvascular changes it has recently become
possible to study glycocalyx dimensions in patients. In the present study we
will investigate the effects of a fluid challenge on microcirculatory vessel
perfusion and the glycocalyx thickness in order to gain more insight in the
effects of fluid therapy on microvascular perfusion and the perfused boundary
region.

I) Is the infusion of crystalloid fluids in healthy subjects associated with a
reduction in microcirculatory perfused vessel density and increase in perfused
boundary region?

II) Does colloid administration attenuates the crystalloid-induced alterations
in the microcirculatory perfused vessel density and increase in perfused
boundary region in healthy subjects?

III) What is the relation between the volume of intraoperative fluid infusion
and the level of microcirculatory perfused boundary region in patients
undergoing surgery?

An intervention study in 19 healthy volunteers, and an observational study in
26 surgical patients in VU University Medical Center, Amsterdam, the
Netherlands.

In healthy subjects, the intervention includes two fluid boluses (crystalloid
and colloid) of 300 ml each.

Healthy subjects: healthy subjects will be exposed to an intravenous punction,
two fluid boluses, 6 sublingual microcirculatory measurements and Nexfin
hemodynamic measurements, which are all associated with minimal discomfort.
Healthy subjects have no benefit from the present study.

Patients: Nexfin and microcirculatory measurements will be mostly performed
during anesthesia, and the burden for the patient is minimal. Intraoperative
fluid management is part of the standard anesthesia procedure. There are no
benefits from the present study for the patient.