Nearly half (~45%) patients report severe pain in the immediate postoperative period after shoulder surgery. With the majority of these procedures being performed in the ambulatory setting, providing effective postoperative analgesia has become paramount in promoting quicker recovery and rehabilitation of these patients.
Nerve block (NB) anesthesia is an alternative or an adjunct to general anesthesia (GA) as a means for adequate pain control postoperatively. There are compelling reasons to avoid GA in outpatients and older patients, such as short-term cognitive impairment, postoperative nausea and vomiting, and delayed recovery. Adequate postsurgical pain control is critical as postoperative pain can interfere with initial rehabilitation.
NB is a superior choice to opioid analgesics, which are associated with nausea, vomiting, somnolence, constipation, urinary retention, respiratory depression, sleep disturbances, and most significantly high addiction potential.
There are two main varieties of nerve blocks administered for shoulder surgery:
- Interscalene brachial plexus block (ISB) – provides complete regional anesthesia for shoulder surgery. It can be used as the sole anesthetic, but it is more commonly administered in conjunction with GA primarily for postoperative analgesia. ISB provides optimal analgesia for these patients. It reduces pain scores for at least 8 hours and decreases opioid consumption for between 8 and 12 hours postoperatively. ISB is associated with a high risk of transient and potentially long-term respiratory complications, most notably phrenic nerve paresis and unilateral diaphragmatic paralysis. it is associated with a number of significant adverse effects. Other temporary side effects include Horner’s syndrome and hoarseness. More serious complications include shoulder girdle paralysis.
- Suprascapular nerve block (SSB): The suprascapular nerve is a branch of the superior trunk of the brachial plexus. Its courses postero-laterally towards the suprascapular notch on the upper border of the scapula to the supraspinous groove, where it lies beneath the tendon of supraspinatus. It then winds around the greater scapular notch to terminate within infraspinatus. It provides 70% of the sensory input to the glenohumeral joint and also innervates the infraspinatus and supraspinatus muscles. SSB is a safe and effective method to treat postoperative shoulder pain. The technique consists of injecting anesthetics in supraspinatus fossa of affected shoulder, with the patient sitting down and upper limbs pending besides the body. Blocking the suprascapular nerve has been proposed to produce sufficient analgesia for shoulder surgery. Many studies have shown SSB to be as effective as ISB for adequate postoperative pain for shoulder surgery, and have found it to have fewer complications as compared to ISB. NB does not anaesthetize all five nerves supplying the shoulder joint, supplemental opiate can be administered intraoperatively. Mostly all patients will find their pain recedes significantly over the first two hours postoperatively. Pain arising from surgery to the shoulder joint structures is well controlled by combined suprascapular and axillary nerve blockade.
In order to reduce postoperative neurological complications associated with both nerve blocks, ultrasound-guidance can be considered. Ultrasound has gained popularity for peripheral nerve blockade because it allows the anesthesiologist to directly visualize the nerves of interest, the needle tip itself, and the spread of the local anesthetic in the desired location. It also visualizes blood vessels and lungs that we wish to avoid. This can improve the overall performance characteristics of nerve blocks.