Two Mathematical Methods to Estimate Arterial Occlusion Pressure and Tourniquet Effectiveness in Lower Limb Surgery

January 20, 2019 updated by: Samaa A. Kasem, Beni-Suef University

Comparison Between Two Mathematical Methods to Estimate Arterial Occlusion Pressure and Tourniquet Effectiveness in Lower Limb Surgery: Randomized Comparative Study

Pneumatic tourniquets are widely used not only to reduce blood loss and to ensure optimal operating conditions during extremity surgery, but also in regional anesthesia (local intravenous) vein puncture and to control life or limb threatening conditions. However, compression of the tissues under a tourniquet is associated with soft tissue damage involving the skin, vessels, muscles, and most importantly, nerves, and are commonly pressure related and can be affected by tourniquet time as well. Therefore, the "minimal tourniquet inflation pressure" necessary to provide a bloodless field has been suggested to minimize the risk of complications from excessive inflation pressure. Arterial occlusion pressure (AOP) is the lowest pneumatic tourniquet inflation pressure required to stop the arterial blood flow into the limb, and its usage has been shown to be useful in optimizing tourniquet cuff pressures. The pressure to which a pneumatic tourniquet cuff should be inflated depends on a number of variables, including the patient's age, skin, blood pressure and the shape and size of the extremity in question, as well as the dimensions of the cuff. One of the estimation method for AOP is based on systolic blood pressure (SBP) and tissue padding coefficient (KTP) values (AOP=[SBP+10]/KTP) according to extremity circumferences. Unver B. et al., used this method to estimate effective tourniquet pressure in total knee replacement under hypotensive general anesthesia tourniquet pressure achieved was 169.7±7.9 mmHg, while Tuncali et al., tested it again in different lower limb surgeries under general or neuraxial anesthesia with normotensive techniques and the achieved maximal tourniquet pressures used was 173.3±15.6 mmHg. Hong-yun Liu et al., established a new occlusion pressure mathematical model for the upper limb based on the correlation analysis between several possible influencing parameters and the minimal pneumatic tourniquet pressure.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

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Intervention / Treatment

Intervention / Treatment

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Detailed Description

After ethical committee approval and informed consent from the patients, 80 adult patients 18-40 years old, (ASA I-II), scheduled for knee arthroscopy under general anesthesia with pneumatic tourniquet around the thigh, will be randomly allocated (using closed opaque envelop) into one of two groups:

  • Group (A): where the pneumatic tourniquet inflated 20 mmHg above the arterial occlusion pressure which will be estimated using the equation of Unver B. et al., [1]: (AOP=[SBP+10]/KTP)
  • Group (B): where the pneumatic tourniquet inflated 20 mmHg above the arterial occlusion pressure which will be estimated using the equation of Hong-yun Liu et al., [2]: (AOP = 17.986 + 3.158X1 + 0.408X2) Patients will be excluded from the study if they are outside the age range, hypertensive, diabetic, complaining of any lower limb claudications, any vascular disease, hemolytic blood disorders or hypercoagulability.

Upon arrival to the operating room, standard monitoring will be attached (5 lead ECG, pulse oximeter and non-invasive blood pressure) followed by a wide-bore canula will be inserted a big vein in the upper limb. General anesthesia will be induced using fentanyl 1 mcg/kg and propofol 2-3 mg/kg laryngeal mask airway device will be inserted after atracurium 0.5 mg/kg and lungs will be mechanically ventilated to maintain end-tidal CO2 at 36-40 mmHg and maintenance of anesthesia will be achieved using isoflurane 1-2 volume %. Hemodynamic stabilization will be assured and systolic blood pressure will be maintained within the pre-induction values ± 20% using intravenous fluid infusion and titration of inhalational anesthetics.

In all patients, the thigh circumference will be measured 20 cm proximal to the superior pole of the patella then, pneumatic the tourniquet cuff will be placed (deflated) around the thigh with the distal edge 15 cm proximal to the proximal pole of the patella. The tissue padding coefficients based on limb circumferences will be calculated in all patients of group (A) according to table (1) [3].

After three successive stable systolic blood pressure reading (5 minutes apart), an initial systolic blood pressure [initial SBP] reading will take and estimated arterial occlusion pressure (AOP) will be quickly calculated according to one of the previously mentioned equation followed limb exsanguination using an Esmarch bandage, then the tourniquet cuff will be inflated to a safety margin pressure 20 mmHg above the calculated (AOP) [3] which will be the [initial tourniquet pressure]. The time between the initial SBP taking and tourniquet inflation will be measured [initial SBP-to- tourniquet inflation time]. The absence of arterial flow in the lower limb is assured using Doppler probe (HD, Philips) positioned, by an independent anesthetist, at either the dorsalis pedis artery or the posterior tibial artery on the foot to monitor arterial flow distal to the tourniquet. If any arterial flow sound will be heard, the estimated tourniquet pressure will be considered insufficient and the patient will excluded from the study. When no arterial blood flow is secured, the surgeon (blinded to the groups) will allowed to start and will be asked to rate the bloodless surgical field using a 4-point scale [1 (Excellent) = No blood in the surgical field, 2 (Good) = Some blood in the surgical field but no interference with surgery, 3 (Fair) = Blood in the surgical field but no significant interference with surgery, 4 (Poor) = Blood in the surgical field obscures the view] [3] at the beginning, in the middle, and at the end of the surgical procedure.

During the surgery, systolic blood pressure will be measured every 5 minutes and the tourniquet inflation pressure will be always kept 20 mmHg above the SBP.

Surgical procedure and anesthetic management were performed by the same surgical and anesthesia teams respectively. The attending anesthesiologist was aware of the allocated group, but the data analyst, surgeon and the patients were blinded to group allocation.

All the patients will be examined one day after surgery for any complications associated with the tourniquet, (e.g. tissue damage, nerve palsy, lower limb blood flow).

The following will be measured:

  • Patient's age, weight and gender and lower limb circumference?
  • Operative duration and tourniquet time.
  • Initial SBP-to- tourniquet inflation time
  • Primary outcome: initial and maximal SBP, initial and maximum tourniquet inflation pressure.
  • Secondary outcome: surgeon rating of the bloodlessness of the surgical field.
  • Any tourniquet associated complications.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
77

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Egypt
      • Banī Suwayf, Egypt, 62511
        • Beni Suef University, Faculty of medicine

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

14 years to 36 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • adult patients 18-40 years old, (ASA I-II), scheduled for knee arthroscopy under general anesthesia with pneumatic tourniquet around the thigh,

Exclusion Criteria:

  • outside the age range, hypertensive, diabetic, complaining of any lower limb claudications, any vascular disease, hemolytic blood disorders or hypercoagulabilty.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Tourniquet inflation pressure method 1
the pneumatic tourniquet inflation pressure at 20 mmHg above the arterial occlusion pressure which will be estimated using the equation of Unver B. et al.,: (AOP=[SBP+10]/KTP)
Procedure: Pneumatic tourniquet inflation pressure
Pneumatic tourniquet inflation pressure estimation using two different mathematical equations
Active Comparator: Tourniquet inflation pressure method 2
the pneumatic tourniquet inflateion pressure at 20 mmHg above the arterial occlusion pressure which will be estimated using the equation of Hong-yun Liu et al.,: (AOP = 17.986 + 3.158X1 + 0.408X2)
Procedure: Pneumatic tourniquet inflation pressure
Pneumatic tourniquet inflation pressure estimation using two different mathematical equations

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Systolic Blood Pressure,
Time Frame: baseline and maximum inflation
initial and maximal Systolic Blood Pressure,
baseline and maximum inflation
tourniquet inflation pressure.
Time Frame: baseline and maximum inflation
initial and maximum tourniquet inflation pressure.
baseline and maximum inflation

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
surgeon rating of the bloodlessness of the surgical field.
Time Frame: middle and end of surgery
surgeon rating of the bloodlessness of the surgical field.
middle and end of surgery

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Beni-Suef University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

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Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 12, 2018

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
November 12, 2018

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
November 15, 2018

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 9, 2018

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 11, 2018

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 16, 2018

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
January 23, 2019

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 20, 2019

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
January 1, 2019

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • FM-BSU REC 005/2018

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

Undecided

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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