Transcutaneous Electrical Nerve Stimulation for Local Anaesthesia

Patients undergoing a split skin graft harvest will be selected from theatre lists and will be given complete information regarding the nature of trial, possible complications, risks and advantages by sending them a Patient Information Sheet at least a week prior to the procedure when they are send an appointment. On the day of procedure, either the Chief Investigator or one of the other two Investigators will see the patient in the Theatre Arrivals Area and have a full discussion on the details of the trial and will answer all their questions. Patients willing to take part and are within the inclusion criteria and does not have any of the exclusion criteria will be randomised to either the study group or the control group after obtaining informed consent.

The trial group will have the TENS to the area planned for injection for 30 minutes before injection of the local anaesthetic (a combination of 0.25% levobupivacaine and 1% lignocaine with 1/200,000 adrenaline). The control group will have EMLA applied on the site planned for local anaesthetic injection and after 1 hour , will be removed and immediately injected with the same anaesthetic solution (this is already a procedure practised by some of the surgeons).

Pain perception will be evaluated using two Numeric Pain Rating Scales in the study and control groups- one to assess the pain of needle penetration and the second to assess the pain of local infiltration. The Numeric pain scale is filled in by the doctor as indicated by the patient. Pulse rate and Blood Pressure monitoring will be carried out as an objective measurement of response to pain (these are routinely recorded when patient is in the theater for a procedure). Patient involvement in the study ends at this point.

Analysis of the outcome will be done at the end of the trial period.

• TENS machine (Device): The trial group will have the TENS to the area planned for injection for at least 30 minutes before injection of the local anaesthetic solution. Pain perception will be evaluated using two Numeric Pain Rating Scales in the study and control groups- one to assess the pain of needle penetration and the second to assess the pain of local infiltration.
• EMLA cream (Combination product): The control group will have EMLA applied on the site planned for local anaesthetic injection and after 1 hour, will be removed and immediately injected with the same anaesthetic solution (this is already a procedure practised by many of the surgeons). Pain perception will be evaluated using two Numeric Pain Rating Scales in the study and control groups- one to assess the pain of needle penetration and the second to assess the pain of local infiltration.

Primary outcomes

• The primary outcome is pain of local anaesthetic injection after application of TENS or LA cream as measured by two Numeric Pain Rating Scale [10 minutes]: Pain perception will be evaluated using two Numeric Pain Rating Scales in the study and control groups. One scale will assess the pain caused by needle piercing the skin and the second will do so for the pain caused by infiltration of local anaesthetic agent. The scale used is "Numeric Pain rating scale" which shows a transverse line with values from 0 to 10 from left to right where 0 indicates no pain and 10 worst possible pain. The middle, which is 5 indicates moderate pain. Outcome of the intervention is better towards the left indicating less pain and worse towards the right indicating more pain. No sub scales are used.

Secondary outcomes

• Changes in blood pressure in response to injection of local anaesthetic [10 minutes]: Blood Pressure (BP) monitoring will be carried out as an objective measurement of response to pain. The unit of measurement is mm of Hg (millimetres of Mercury). This measurement is to assess if there is a rise in BP in response to the local anaesthetic injection after application of either TENS or EMLA and if present, to what extent. The changes will be analysed with respect to the baseline BP recording of the patient.
• Changes in heart rate in response to injection of local anaesthetic [10 minutes]: Heart rate (HR) monitoring will be carried out as an objective measurement of response to pain. The unit of measurement is number per minute. This measurement is to assess if there is a rise in HR in response to the local anaesthetic injection after application of either TENS or EMLA and if present, to what extent. The changes will be analysed with respect to the baseline HR recording of the patient.

Sex: All, ages: 18 Years to 90 Years

Both interventions will be carried out in adult patients. For the purpose of standardisation and avoiding the variations from different sites in the body, and different surgical procedures, the site will be the thigh in both groups which is the donor site for a split skin graft.

Inclusion criteria:

• Adult patients aged 18 to 90 years undergoing a split skin graft harvest under local anaesthesia

Exclusion criteria:

* Patients below 18 and above 90 years of age
* Patients with dementia or other mental abnormalities causing incapacity.
* Pregnant ladies
* Patients with pace maker or ICD
* Patients with history of epilepsy or aneurysm
* Patients with undiagnosed skin or pain conditions

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• Study Protocol (PDF, 2018-10-29)
• Informed Consent Form (PDF, 2019-02-17)

• Rajshree Jayarajan, Principal investigator, University Hospitals, Leicester