Identifying pre-operative predictors of post-surgical pain in adolescents using quantitative sensory testing
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Objective: Research on the role of acute post-surgical pain in children is extremely important in order to have a positive influence on pre-surgical preparation and post-surgical care and to prevent pain from becoming chronic, which can extend decades into adulthood. This project aims to identify predictors of acute post-surgical pain in adolescents with idiopathic scoliosis undergoing spinal fusion by utilizing sensory thresholds obtained through quantitative sensory testing (QST). Methods: Eligible candidates were Adolescent Idiopathic Scoliosis (AIS) patients ages 10-17 who have been recommended to receive elected spinal fusion surgery at Boston Children's Hospital (BCH). 9 successfully recruited and enrolled participants underwent a full series of QST tests on their palmar thenar eminence (non-surgical site), and their lower back (surgical site). Patients' Light Touch Detection Threshold (LTDT) and Pain Detection Threshold (PDT) scores were determined using Von Frey Hairs. Patients' Pressure-Pain Sensation Threshold (PPST) scores were determined using a pressure algometer. Patients' Warm/Cool and Hot/Cold Pain Detection Thresholds were detected using a calibrated thermode strapped to the skin. Following the full-series of QST tests, and after the patient was discharged from the hospital, a retrospective chart review was conducted to determine the patients': Age at Surgery, Gender, Number of Vertebrae Fused (Fusion Length), Length of Surgery, Pre-Operative Self-Identified Pain Level (NRS 0-10), Average Post-Operative Acute-Phase Self-Identified Pain Level (NRS 0-10), and daily Pain Medication Doses (Opiate Vs. Non-Opiate Vs. Total). Correlation calculations were done between each variable, including those determined through QST as well as retrospective chart review. For every QST test, each patient's individual score was compared to the cohort's median score, which helped determine whether the patient was either hyper- or hyposensitive for that particular test. For each QST test, these hyper- and hyposensitive groups were then compared to see if there were any significant differences in post-operative pain experienced. Results: Due to the low number of participants (N = 9), the results should be considered preliminary. Correlation studies demonstrate that pre-operative pain was significantly positively correlated with post-operative pain (r = 0.81, p <0.05), indicating that patients who are pre-operatively already in pain, will consequently experience the most pain post-operatively. Additionally, fusion length had a strong positive correlation to acute post-operative opiate pain medication administration (r = 0.71, P < 0.05), indicating that patients who had more vertebrae fused were given more opiates. Through the use of QST, we discovered that patients hypersensitive in the LTDT-Spine QST test experienced significantly less pain post-operatively (3.22 NRS 0-10) than that experienced by hyposensitive patients (5.52 NRS 0-10) from the same test. Identical results were discovered in patients determined hyper- and hyposensitive using the PPST-Spine test, respectively. Retrospective chart review data show that these hyposensitive patients were experiencing greater pain pre-operatively (0.75 NRS 0-10) than that experienced by the hypersensitive patients (0 NRS 0-10), which may have contributed to the hyposensitive cohort's greater post-operative pain. Although insignificant, patients hypersensitive in the Hot Pain - Spine QST test experienced greater post-operative pain (4.72 NRS 0-10) than that experienced by hyposensitive patients in the same test (4.06 NRS 0-10). Conclusions: The goal of this study was to determine a substantiated hypothesis to test in the future, using larger pediatric cohorts. Even though it initially appears that the hyposensitive patients, as determined by the LTDT-Spine and PPST-Spine QST tests, experienced greater post-operative pain, one must consider the fact that this hyposensitive group experienced a significantly greater amount of pre-operative pain. Not only has pre-operative pain been proven to have a strong correlation to post-operative pain in this study, it has also been proven in other larger studies as well. Other studies have identified a test similar to the Hot Pain - Spine QST test as a potential predictor of post-operative pain. The present study's results, although insignificant, share the same conclusion that hypersensitive patients determined through Hot Pain - Spine QST test experience greater post-operative pain. Therefore, the hypothesis to test in the future in pediatric cohorts should read: AIS patients with no pre-operative pain who demonstrate increased sensitivity to hot pain on their surgical site via thermal stimulation (QST) will experience greater post-operative pain in the acute-recovery phase.