Perfusion of lower limbs Circulatory System
Conditions
Interventions
1. Infusion of phenylephrine to induce peripheral vasoconstriction
2. Infusion of glyceryl trinitrate (GTN) to induce peripheral vasoconstriction
3. Tourniquet applicat
Sponsors
University of Oxford
Eligibility
Sex/Gender
All
Inclusion criteria
Inclusion criteria: Healthy males and females between the ages of 18 to 65
Exclusion criteria
Exclusion criteria: 1. Patient whose anatomy, condition, or other required monitoring precludes the use of the camera equipment or thoracic bioimpedance monitor kit. Examples include skin disorders such as eczema, scleroderma or psoriasis 2. Allergy to silver chloride ECG sensors 3. Hyperthyroidism (intravenous phenylephrine contraindicated) 4. Any regular medication except combined oral contraceptives 5. Pregnant or breastfeeding 6. History or current psychiatric illness 7. History or current neurological conditions (e.g. epilepsy) 8. History of cardiovascular disease making phenylephrine or GTN unsafe
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Skin perfusion pattern at rest and change to the pattern post-exposure to phenylephrine and glyceryl trinitrate (GTN). Measured using composite measures from three different cameras measuring in visible, near-infrared, and infrared spectrum. Measures taken will include the strength of pulsatile signal measured at skin surface, absolute skin colour change when under constant lighting and angle, skin surface temperature gradient from proximal to distal areas, blood flow measurement using laser speckle contrast imager. Measurements will be taken at baseline, at one-minute intervals with increasing dose of phenylephrine and GTN, and at stable infusion maximal dose. | — |
Secondary
| Measure | Time frame |
|---|---|
| Current secondary outcome measures as of 17/02/2020: 1. Pulse transit time between proximal and distal regions of interest estimated from the photoplethysmographic signal using the camera set up as described for the primary outcome measure at baseline, at one-minute intervals with increasing dose of phenylephrine and GTN, and at stable infusion maximal dose 2. Surface temperature gradient between proximal and distal regions of interest measured using the camera set up as described for the primary outcome measure at baseline, at one-minute intervals with increasing dose of phenylephrine and GTN, and at stable infusion maximal dose 3. Proportions of visible skin surface with pulsatile photoplethysmographic component measured using the camera set up as described for the primary outcome measure at baseline, at one-minute intervals with increasing dose of phenylephrine and GTN, and at stable infusion maximal dose 4. Colour changes with increasing phenylephrine and GTN infusion measured using the camera set up as described for the primary outcome measure at baseline, at one-minute intervals with increasing dose of phenylephrine and GTN, and at stable infusion maximal dose 5. Description of the chronological order of skin perfusion when the lower limb is reperfused following the application and removal of a lower limb tourniquet, measured using the camera set up as described for the primary outcome measure continuously during the planned one-minute tourniquet application and in the 5 minutes following tourniquet release Previous secondary outcome measures: Chronological order of skin perfusion when lower limb is reperfused following application and removal of a lower limb tourniquet. Measured using the same camera set up as primary outcome measure, across all exposed regions of skin of lower limb (from mid-thigh to mid-shin). Measurements will be taken continuou | — |
Countries
United Kingdom
Outcome results
None listed