The Effects of Prolonged Head-Down Tilt Lithotomy Position on Lower Limb Haemodynamics

Study Overview
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Brief Summary
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During certain bowel surgeries for cancer (colorectal surgery), individuals frequently have to be placed in a head-down position to enable surgeons have optimal access to the cancer site. This position usually also involves bending the hips and knees while supporting the legs in stirrups. However, lying in this position for long periods of time can lower the flow of blood to the legs, which can potentially cause injury. A rare but severe consequence is called Well-Leg Compartment Syndrome (WLCS). If WLCS is not diagnosed quickly, it can lead to other difficult complications and a significant delay in recovery. Unfortunately, because the individual is under anaesthesia, diagnosis is delayed in many cases. There is very little information in the medical literature about how this damage to the legs progresses over the course of the surgery. To better understand how WLSC, how well blood vessels work during surgery will be assessed. The flow of blood and oxygen in the calf muscle will be assessed in 25 individuals placed in a head-down position during colorectal surgery. Likewise, blood samples will be obtained in order to measure the biological markers that may contribute to the development of WLCS.

Detailed Description
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The development of lower limb compartment syndrome in the absence of trauma (known as well-leg compartment syndrome, WLCS) is a severe complication reported during prolonged pelvic surgery. WLCS is characterised by muscular ischaemia and secondary necrosis from the increase in hydrostatic pressure in a closed fascial compartment. The aetiology of WLCS appears to be primarily related to ischaemia of the lower limbs after a prolonged period in the head-down tilt lithotomy (HDTL) position, which is commonly used to access the pelvis and perineum during urological, colorectal, and gynaecological surgery. Elevation of the lower limbs above the heart results in a  2 mmHg drop in mean arterial pressure at the mid-calf for every 2.5 cm that the limbs are raised. These hemodynamic changes are accompanied by an increase in compartment pressures associated with limb elevation and are further exacerbated by a steep (>15°) head-down tilt. The outcome of these changes ultimately leads to the development of significant and (often unrecognised) intraoperative ischemia in the lower limbs. Prolonged reductions in lower limb perfusion during HDTL can cause the development of localised tissue oedema, leading to marked intracompartmental hypertension, which is further exacerbated once the limbs are lowered and reperfusion of ischemic muscle occurs. This is a consequence known as ischaemic-reperfusion injury (IRI), a phenomenon where reperfusion per se may result in a local and systemic inflammatory response that may augment tissue injury in excess of that produced by ischaemia alone. Microvascular injury is considered one of the major determinants of IRI, particularly due to increased permeability of capillaries and arterioles that lead to an increase in diffusion and fluid filtration across the tissues. Subsequently, activated endothelial cells produce more reactive oxygen species and less nitric oxide, and this imbalance results in a corresponding inflammatory response and increased oxidative stress, which if sufficiently severe lead to further lower limb muscle and nerve injury. The incidence of WLCS is unpredictable and as the individual is anaesthetised, the diagnosis is delayed in many cases, so the residual motor-sensory deficit may be severe, even after fasciotomy. Although there are many published case reports of this condition, it is likely that many cases of WLCS go unreported, and some may be mild and escape clinical detection. However, in cases that have been reported, the incidence of permanent disability after the development of WLCS ranges from ≈30% to ≈100%. The paucity of detailed observational studies into the effects of HDTL on lower limb haemodynamics and tissue oxygenation has restricted the ability of the clinical and scientific society to construct clinical strategies to minimise this complication. Identifying individuals with risk factors and increasing surveillance during surgery in these people may allow for early detection and decrease the morbidity and potential mortality associated with intraoperative WLCS. The study aims to assess lower limb haemodynamics by measuring cutaneous blood flow, muscle and brain tissue oxygenation, inflammatory and oxidative stress biomarkers during pelvic surgery in patients placed in HDTL. This study has the potential to provide a better understanding of the pathogenesis of WLCS and add novel knowledge regarding its early diagnosis.

Official Title
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The Effects of Prolonged Head-Down Tilt Lithotomy Position on Lower Limb Haemodynamics in Adults Undergoing Minimally Invasive Abdominopelvic Surgery: An Intraoperative Observational Study

Conditions
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Compartment Syndrome Nontraumatic Lower Extremity

Intervention / Treatment
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* Device: NIRS monitoring
* Device: Laser Doppler flowmetry
* Other: Inflammatory and Oxidative stress biomarkers


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adults scheduled to undergo colorectal surgery in the HDTL position Exclusion Criteria: History of myocardial infarction or cerebro-vascular events in the last 12 months Previous revascularisation procedure in their lower limbs BMI > 40 kg/m2 Inability to give informed consent Other serious medical conditions, which in the opinion of study investigators, would interfere with safety or data interpretation

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Colorectal surgery<br>Individuals scheduled for colorectal surgery in the HDTL position | Device: NIRS monitoring<br>* All participants will undergo NIRS monitoring of muscle and cerebral tissue oxygenation intraoperatively.<br>Device: Laser Doppler flowmetry<br>* Cutaneous blood flow will be assessed intraoperatively via Laser Doppler flowmetry in all participants<br>Other: Inflammatory and Oxidative stress biomarkers<br>* Blood samples will be taken to measure biomarkers of inflammation and oxidative stress at specific time points<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cutaneous blood flow | Change over time in cutaneous blood flow in the legs relative to a vascular occlusion test (VOT) during surgery in the HDTL position. | baseline, during the surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Muscle tissue oxygenation | Change over time in muscle tissue oxygenation in the lower limb relative to a vascular occlusion test (VOT) during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma interleukin-6 (IL-6) concentration | Change over time in [IL-6] during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma Tumour Necrosis Factor Alpha (TNF-α) concentration | Change over time in [TNF-α] during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma Superoxide Dismutase (SOD) concentration | Change over time in [SOD] during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma Protein Carbonyl concentration | Change over time in [protein carbonyl] during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma nitrate concentration | Change over time in [nitrate] during surgery in the HDTL position. | baseline, during the surgery | 
| Plasma nitrite concentration | Change over time in [nitrite] during surgery in the HDTL position. | baseline, during the surgery | 
| Mean arterial pressure (MAP) | Change over time in MAP during surgery in the HDTL position. | baseline, during the surgery | 
| Skin temperature | Change over time in skin temperature during surgery in the HDTL position. | baseline, during the surgery | 
| Brain tissue oxygenation | Change over time in brain tissue oxygenation during surgery in the HDTL position. | continuous measurement during the surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Head Down Tilt Lithotomy, Minimally Invasive Surgery, Ischaemia Reperfusion Syndrome, Pathophysiology, Near Infrared Spectroscopy, NIRS, Robotic Assisted Laparoscopic Surgery, Well leg Compartment Syndrome