Postoperative Pain Management and the Incidence of Ipsilateral Shoulder Pain After Thoracic Surgery at an Australian Tertiary-Care Hospital: A Prospective Audit

Abstract

Objectives: Ipsilateral shoulder pain (ISP) is a common but variably occurring (42%-85%) complication after thoracic surgery. Multiple potential treatments, including upper limb blocks, intrapleural local anaesthetic infiltration, and systemic opioids, have undergone trials, with limited efficacy. Phrenic nerve infiltration is a potential intervention that may prevent ISP. The aim of this study was to assess the incidence and severity of ISP after thoracic surgery at the authors' institution, where phrenic nerve infiltration is commonly used.

Design: Observational cohort study.

Setting: A single- center study in a tertiary referral center in Brisbane, Australia.

Participants: This study comprised all adult patients undergoing thoracic surgery at a tertiary- care referral center from May to July 2018.

Measurements and main results: Surgical procedures were divided into open thoracotomy, video-assisted thoracic surgery (VATS) and VATS-guided mini-thoracotomy. The primary outcome was a comparison of incidence of ISP among the 3 types of surgical procedures. Data were analyzed using Stata (StataCorp), with significance testing by Kruskal-Wallis equality of populations rank test. A p value of < 0.05 was deemed significant. Sixty thoracic surgeries were performed during the audit period. Nineteen patients had thoracotomies performed for lobectomy or pneumonectomy, all of whom received phrenic nerve infiltration. The incidence of moderate-to-severe ipsilateral shoulder pain among the thoracoctomy cohort was 15.8% (3/19). Of the 36 VATS procedures audited, 7 patients (19.4%) received infiltration of their phrenic nerve, none of whom reported postoperative ISP. Of the remaining twenty-nine patients who did not receive phrenic nerve infiltration, there were 4 cases of moderate-to-severe ipsilateral shoulder pain (11.1%). Four of the 5 patients (80%) who underwent VATS-guided mini-thoracotomies received phrenic nerve infiltration intraoperatively. Three patients reported moderate-to-severe ISP and of these 3 patients, 2 patients had phrenic nerve infiltration, and 1 patient did not receive infiltration. Overall, there were no statistically significant differences in rest or dynamic pain scores across the surgical groups at any time point. Mann-Whitney test revealed that the participants with ISP were significantly older than those without ISP (p = 0.006). However, there were no significant differences in sex or body mass index between those with and without ISP.

Conclusion: The authors observed a lower (15.8%) incidence of moderate-to-severe ISP among their thoracotomy patients than reported in prior literature. Injection of local anesthetic into the phrenic nerve fat pad at the level of the diaphragm appeared to be an effective and safe surgical intervention that may eliminate a significant cause of ISP. None of the VATS patients who received phrenic nerve infiltration experienced ISP. Postoperative pain in VATS is expected to be reduced by avoiding the use of a rib spreader, severing of the intercostal nerves, and division of muscle tissue, which may account for the lower observed rates of ISP in the VATS cohort who did not receive phrenic nerve infiltration. Further randomized controlled trials are warranted to establish if patients undergoing various VATS procedures benefit from this intervention.

Keywords: Thoracotomy; acute pain; phrenic nerve; shoulder pain; thoracic surgery.