Can saline injection protect phrenic nerve? - A randomised controlled study.

Area of Science:

• Anesthesiology
• Regional Anesthesia
• Ultrasound-Guided Procedures

Background:

• Phrenic nerve palsy is a known complication of interscalene brachial plexus nerve blocks.
• The presumed mechanism involves local anesthetic spread anterior to the anterior scalene muscle.
• Preventive strategies are needed to mitigate this risk.

Purpose of the Study:

• To investigate the efficacy of a pre-block saline injection in reducing phrenic nerve palsy during ultrasound-guided interscalene brachial plexus nerve blocks.
• To test the hypothesis that saline injection anterior to the anterior scalene muscle can prevent anesthetic spread and subsequent diaphragmatic dysfunction.

Main Methods:

• A double-blinded, randomized controlled trial involving 36 patients undergoing interscalene block.
• Patients were randomized to receive either a conventional block or a block preceded by a 10 ml saline injection anterior to the anterior scalene muscle.
• Diaphragmatic ultrasound and spirometry were used to assess phrenic nerve palsy and pulmonary function, respectively.

Main Results:

• The incidence of diaphragmatic paresis was significantly lower in the saline group (44%) compared to the conventional group (94%) (P = 0.002).
• No significant differences were observed between groups regarding post-operative pain, dyspnea, or patient satisfaction.
• Ultrasound confirmed a marked reduction in diaphragmatic palsy with the saline pre-injection technique.

Conclusions:

• Pre-procedural injection of saline anterior to the anterior scalene muscle is an effective method to reduce the incidence of diaphragmatic palsy following interscalene brachial plexus nerve blocks.
• This technique offers a safe and simple adjunct to improve the safety profile of interscalene blocks.
• Further research may explore the long-term implications and broader applicability of this method.