Sensorial and Physiological Mechanism-based Assessments of Perioperative Pain

The overall goal of this proposal is to determine if quantitative sensory testing (QST) assessing pain modulation can be used as a clinical tool to optimize perioperative pain management. The central hypothesis is that the identification of patient's sensory pain profile allows personalizing therapeutic approaches to improve individualized pain management and thus prevents pain chronicity.

The primary objective of this study is to evaluate if pre-operative QST can identify if patients will have high pain intensity peri-operatively and at 6 months post-operatively. Evaluation of the intensity and chronicity of pain and the function of the descending inhibitory system through a short QST procedure before surgery and six months after surgery will be carried out. In addition, evaluation of the patient's physical and emotional functioning, and exploration of the potential biological underlying mechanisms will also be assessed at the same time points.

The secondary objective of this study is to determine if the peri-operative use of an alpha-2 adrenergic receptor agonist enhances the efficacy of the descending inhibitory system of patients with sub-optimal CPM efficacy before surgery by decreasing pain after surgery. Consequently, this pharmacological intervention may also reduce the incidence of acute and chronic pain after surgery. Evaluation of the pain intensity and the function of the descending inhibitory system through a short QST procedure six weeks after surgery and six months after surgery in patients receiving Clonidine or placebo during the perioperative period will be done. In addition, evaluation of the patient's physical and emotional functioning, and exploration the potential biological underlying mechanisms at the same time points will be assessed.

Lastly, evaluation of potential biomechanical alterations in 3D related to pain in children reporting presence of back pain pre and post spine surgery will be looked at.

The hypothesis is that patients undergoing spine surgery with poor inhibitory pain response will have less pain in the immediate and long-term period when treated prophylactically with Clonidine in the perioperative period.

Eligibility Criteria:
Inclusion Criteria:

* Females\* aged between 10 and 21 years old
* Scheduled to undergo anterior or posterior spinal fusion surgery for AIS with instrumentation
* Ability to adequately understand and respond to outcome measures
* No previous major orthopedic surgery
* Any ethnic background

Exclusion Criteria:

* Children with history of allergies to Clonidine or it's excipients in either injection or tablet formulation (see respective monograph)
* Children with history of galactose intolerance
* Children with history of myocardial disease, arrhythmias, cerebrovascular disease, Raynaud's/Thromboangiitis obliterans or chronic renal failure diagnosis based on history and physical
* Children taking anti-hypertensive agents (diuretics, vasodilators, beta-blockers, ace-inhibitors)
* History of depression
* Inability of the child to speak English or French
* Diagnosed with developmental delay that would interfere with understanding the questions being asked (autism, mental retardation)
* Children with major chronic medical conditions (ASA status III or higher)
* Pregnancy excluded by an in hospital testing the night before surgery