Central Sensitisation and Postoperative Pain

Study Overview
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Brief Summary
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One out of 10 patients undergoing surgery develops persistent post-surgical pain (PPSP). Unfortunately, available therapies for treating this pain have limited success. It is therefore of great importance to find strategies to prevent PPSP. The goal of this project is to find new screening tools that identify patients that are at risk for developing PPSP. Tissue injury and inflammation following surgery increase the excitability of spinal nociceptive neurons (central sensitisation, CS) with pain hypersensitivity as consequence. It is thought that CS plays an important role in persistent pain. The first objective of this project is to assess in human patients if the propensity to develop CS manifested as secondary hyperalgesia before surgery is predictive for PPSP. In addition, we will test if the frequency content of the resting-state EEG reflecting the initial state of the brain will be related to the propensity for developing CS and to the presence of PPSP at two months after surgery.

Official Title
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Behavioural and Neurophysiological Measurements for the Assessment of Central Sensitisation and Postoperative Pain

Conditions
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Thoracotomy, Hyperalgesia, Hyperalgesia, Secondary, Central Sensitisation, Electroencephalography, Persistent Postsurgical Pain, Humans

Intervention / Treatment
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* Other: electroencephalography (EEG)
* Other: questionnaires
* Other: high frequency electrical stimulation of the forearm skin (HFS)
* Other: cutaneous mechanical pinprick stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Scheduled for a lateral thoracotomy as treatment for primary lung cancer Ability to provide written informed consent Exclusion Criteria: Evidence for a clinically-significant alteration of the skin of the volar forearms Pregnancy Having a pacemaker or implanted cardiac defibrillator

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 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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Design Details

Primary Purpose: Screening
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: patients undergo lateral thoracotomy for primary lung cancer<br>Electroencephalography (EEG) will be acquired before surgery Questionnaires assessing psychological status of the patients before and after surgery High frequency electrical stimulation of the skin (HFS) will be delivered before surgery Quantification of mechanical sensitivity after HFS and after surgery | Other: electroencephalography (EEG)<br>* recording of resting state EEG using 64 surface electrodes<br>Other: questionnaires<br>* Hospital Anxiety Depression Scale (HADS) Neuropathic Pain questionnaire (DN4) Brief Pain Inventory (BPI) Fatigue Assessment Scale (FAS)<br>Other: high frequency electrical stimulation of the forearm skin (HFS)<br>* HFS consists of transcutaneous electrical stimuli delivered as 42 Hz trains (pulse width: 2 ms) lasting 1 s. The trains are repeated 12 times. Each train is separated by 10 seconds.<br>Other: cutaneous mechanical pinprick stimulation<br>* Mechanical pinprick stimuli will be applied manually by the operator on the skin using a mechanical stimulator (maximum weight 128 mN).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| mechanical pinprick perceived intensity | magnitude of the increase in sensitivity to mechanical pinprick stimuli after HFS | 1 day before surgery | 
| area of increased mechanical pinprick sensitivity | spatial extent of the increased sensitivity to mechanical pinprick stimuli after HFS | 1 day before surgery | 
| resting state EEG | frequency content of the resting state EEG | 1 week before surgery |