Risk and protective factors for chronic pain following inguinal hernia repair: a retrospective study.

Purpose: A large proportion of patients experience chronic post-surgical pain (CPSP) following inguinal hernia repair surgery. The aim of this study was to investigate the predictive risk factors and protective factors for CPSP following inguinal hernia surgery.

Methods: After institutional ethics approval was obtained, we conducted a retrospective observational case-control study including a total of 236 adult patients undergoing elective inguinal hernia repair at a single tertiary medical center from 2014 to 2015. Preoperative and postoperative variables were collected from electronic medical records. Binary logistic analysis was used to determine the association between CPSP and clinical factors and built a CPSP risk model.

Results: The incidence of CPSP was 14.4%. Bilateral inguinal hernia repair (OR 4.44; 95% CI 1.62 to 12.17; p = 0.004), preoperative pain (OR 2.57; 95% CI 1.14 to 5.79; p = 0.023), preoperative anxiety (OR 1.05; 95% CI 1.01 to 1.09; p = 0.018), and relatively high intensity of acute pain at 1 week after the surgery (OR 1.40; 95% CI 1.03 to 1.91; p = 0.031) were the risk factors for CPSP while low-dose ketamine at anesthesia induction (OR 0.42; 95% CI 0.18 to 0.98; p = 0.044) was the protective factor for CPSP in patients undergoing inguinal hernia repair.

Conclusions: These results indicated that bilateral inguinal hernia repair, preoperative pain, preoperative anxiety, and acute pain at 1 week after the surgery were the independent risk factors for CPSP while low-dose ketamine was the protective factor. These findings may assist with primary prevention by allowing clinicians to screen for individuals with the risk of CPSP.