Phrenic Nerve Infiltration vs SNB for Acute Ipsilateral Shoulder Pain
One common theory is that acute ipsilateral shoulder pain is transmitted by the phrenic nerve.
According to a recent study published in the Journal of the Egyptian National Cancer Institute, phrenic nerve infiltration is significantly more effective than suprascapular nerve block in preventing acute ipsilateral shoulder pain that can occur after thoracic surgery.
One common theory is that acute ipsilateral shoulder pain, which affects 21% to 97% of patients who undergo open thoracotomy, is transmitted by means of the phrenic nerve.
Thus, researchers predicted ipsilateral shoulder pain could be better treated by the application of intraoperative phrenic nerve infiltration and set out to compare the pain reduction efficacy of phrenic nerve infiltration with that of preoperative suprascapular nerve block.
In the study, 135 patients with lung cancer scheduled for thoracic surgery were randomly assigned to 3 equal groups. The control group received thoracic epidural with general anesthesia, the suprascapular nerve block group received 10 mL bupivacaine plus thoracic epidural with general anesthesia 1 hour before surgery, and the phrenic nerve infiltration group received 10 mL bupivacaine plus thoracic epidural with general anesthesia during surgery. Baseline characteristics were similar for all groups.
Every 6 hours for 48 hours after surgery, visual analogue score of ipsilateral shoulder pain, rescue therapy with ketorolac for breakthrough shoulder pain, peak expiratory flow rate, and arterial blood gases were assessed. The first 3 measurements were significantly lower (P <.05) for the phrenic nerve infiltration group than for the other groups. There was no statistically significant difference among the 3 groups for arterial blood gas level (P >.05).
Furthermore, the incidence of postoperative ipsilateral shoulder pain in the phrenic nerve infiltration group (15.60%) was much lower compared with the control and suprascapular nerve block groups (66.75% and 64.40%, respectively).
Researchers believe the decreased incidence and severity of pain in the phrenic nerve infiltration group demonstrates the role the phrenic nerve plays in the transmission of ipsilateral shoulder pain. They concluded that phrenic nerve infiltration is “more effective than preoperative, ultrasound-guided SNB as regards the management of acute post-thoracotomy [ipsilateral shoulder pain],” and added, “in spite of its depressing effect in postoperative [peak expiratory flow rate] values, [phrenic nerve infiltration] is considered clinically safe in terms of maintaining postoperative respiratory function.”
Elfokery BM, Tawfic SA, Abdelrahman AM, Abbas DN, Abdelghaffar IM. Comparative study on the analgesic effect of acute ipsilateral shoulder pain after open thoracotomy between preoperative ultrasound guided suprascapular nerve block (SNB) and intraoperative phrenic nerve infiltration (PNI) in cancer lung patients [published online January 13, 2018]. J Egypt Natl Cancer Inst. 2018;30:27-31