An observational study in Microcirculatory Diffusion, Microcirculatory Convection Capacity and Venous Congestion, sponsored by University Hospital, Basel, Switzerland. Recruiting at 1 site in Switzerland. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-25.
Sponsored by University Hospital, Basel, Switzerland · Observational
The aim of the VeMic study is to explore if venous congestion is linked with microcirculatory impairment in elective cardiac surgery patients in the postoperative ICU stay.
Cardiac surgery is associated with a significant risk of postoperative complications, including organ dysfunction such as acute kidney injury (AKI). Traditionally, clinical management in the intensive care unit (ICU) has focused on monitoring macrocirculatory parameters-such as blood pressure, cardiac output, and central venous pressure (CVP)-to guide treatment. However, adequate systemic perfusion does not always translate into sufficient tissue oxygenation at the microcirculatory level. Microcirculation, which occurs in the smallest vessels such as capillaries, is where oxygen and nutrients are actually delivered to the cells. Impairment in microcirculatory function can occur even when macrocirculatory values appear normal, leading to what is known as loss of hemodynamic coherence. Despite growing evidence of the clinical importance of microcirculation, routine bedside assessment remains limited due to technical challenges and the lack of easily applicable tools.
While elevated CVP and signs of venous congestion have been linked to worse outcomes such as AKI, the underlying mechanisms remain poorly understood. CVP alone is an imperfect marker for venous stasis and does not reliably predict microcirculatory impairment. Newer ultrasound-based tools-such as the Vexus score and femoral vein Doppler (FVD)-are emerging as promising, non-invasive methods to assess venous congestion at the bedside. However, it is currently unclear whether these sonographic signs of venous congestion are actually associated with impaired microcirculatory function. This knowledge gap limits clinicians' ability to interpret ultrasound findings in the context of microvascular health and to make informed decisions about fluid management and organ perfusion.
The VeMic study aims to investigate whether ultrasound-based indicators of venous congestion correlate with objectively measured microcirculatory impairment in patients admitted to the ICU after non-emergency cardiac surgery. By combining ultrasound assessments with advanced analysis of sublingual microcirculation using handheld vital microscopy and automated software, the study seeks to bridge the gap between macro- and microcirculatory monitoring. The findings may help determine whether these easily accessible ultrasound tools can be used to detect early signs of microvascular dysfunction and guide more targeted, physiology-based interventions in the postoperative setting.
98 studies on the registry are indexed under Hyperemia; 44 are open to participants now.
This study's planned enrollment of 40 is below the median of 100 across 46 observational studies indexed under Hyperemia.
Browse Hyperemia studies →University Hospital, Basel, Switzerland is the lead sponsor of 990 studies on the registry; 189 are open to participants now.
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Patients presenting for elective or urgent cardiac surgery. Urgent patients are defined as patients who have not been electively admitted for operation but who require intervention or surgery on the current admission for medical reasons. These patients cannot be sent home without a definitive procedure but do not require immediate emergency surgery.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Difference in red blood cell velocity: concested vs non-congested
Difference in red blood cell velocity (RBCv) between patients grouped as congested (Vexus score of 2 and 3) vs. non-congested (Vexus score of 0 and 1).
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in total vessel density: concested vs non-congested
Difference in total vessel density (TVD) between patients grouped as congested (Vexus score of 2 and 3) vs. non-congested (Vexus score of 0 and 1).
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in red blood cell velocity: physiologic femoral vein flow vs. pulsatile pattern
Difference in red blood cell velocity (RBCv) between patients with a physiologic femoral vein flow vs. pulsatile pattern
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in total vessel density between patients with a physiologic femoral vein flow vs. pulsatile pattern
Difference in total vessel density (TVD) between patients with a physiologic femoral vein flow vs. pulsatile pattern
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in RBCv between patients with different Vexus scores
Difference in RBCv between patients with a Vexus score of 0 vs. 1 vs. 2 vs. 3
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference inTVD between patients with different Vexus scores
Difference inTVD between patients with a Vexus score of 0 vs. 1 vs. 2 vs. 3
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in microcirculatory reserve capacity: congested non-congested
Difference in microcirculatory reserve capacity between patients grouped as congested (Vexus score of 2 and 3) vs. non-congested (Vexus score of 0 and 1)
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
Difference in microcirculatory reserve capacity: physiologic femoral vein flow vs. pulsatile patern
Difference in microcirculatory reserve capacity between patients with a physiologic femoral vein flow vs. pulsatile patern
Time frame: 3 measurements:T0 prior surgery, T1 first post-operative day, T2 6 hours after T1
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