Association of Serum Serotonin and Pain in Patients with Chronic Low Back Pain before and after Spinal Surgery.

Introduction: In this study we are aiming to evaluate the changes of serum serotonin and its association with pain in patients suffering from chronic low back pain before and after lumbar discectomy surgery.

Patients and methods: A prospective study was performed on the patients referring to the outpatient clinic in Besat hospital, Hamadan University of Medical Sciences, Hamadan, Iran, during 2016. A 2 mL fasting blood sample was collected from each patient at preoperative day 1 and postoperative day 14 and they were measured for level of serum serotonin. Besides, all patients were asked for severity of their low back pain in preoperative day 1 and postoperative day 14 and scored their pain from zero to ten using a Numerical Rating Scale.

Results: Forty patients with the mean age of 47 ± 13 yrs/old (range 25-77) including 15 (37.5%) males were enrolled into the study. The overall mean score of preoperative pain was significantly decreased from 7.4 ± 2.18 (range 4-10) to the postoperative pain score 3.87 ± 2.92 (range 0-10) (P < .001). The overall levels of pre- and postoperative serum serotonin were 3.37 ± 1.27 (range 1.1-6.4) and 3.58 ± 1.32 (range .94-7.1) ng/mL, respectively, with no significant difference (P = .09). The levels of pre- and postoperative serum serotonin were significantly higher in males and patients older than 50 yrs/old compared to the females and patients younger than 50 yrs/old, respectively (P = .03 and .005, respectively). A significant inverse correlation between the postoperative levels of pain and serum serotonin was observed (r = -.36 and P = .02).

Conclusion: A negative medium strength linear relationship may exist between the postoperative serum serotonin and low back pain.