Anesthesiology

Subacromial decompression

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What the Anesthesiologist Should Know before the Operative Procedure

Subacromial decompression is performed for treatment of shoulder impingement syndrome. This condition occurs in people of all ages, particularly in those exposed to repetitive arm elevation activities such as overhead lifting or throwing. Recurrent inflammation of the bursa that lies between the acromion and the rotator cuff eventually produces pain, edema, fibrosis, and tendinitis of the rotator cuff and osteophyte formation on the underside of the acromioclavicular arch. If severe enough, an associated tear of the rotator cuff can be present, usually in the older cohort of patients (>40 years).

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Subacromial decompression is typically an elective procedure. However, in cases where the shoulder impingement is associated with a tear of the rotator cuff and symptoms are refractory to conservative therapy, it is often recommended that early rather than delayed surgical management is undertaken to avoid muscle atrophy and adhesive capsulitis, and to improve functional outcome. This should not, however, delay appropriate preoperative evaluation.

Elective: Because of the elective nature of this procedure, there should be few barriers to a complete preoperative evaluation and optimization of the patient's medical status.

2. Preoperative evaluation

Most patients presenting for subacromial decompression are either healthy or have well-controlled medical problems that do not require intervention. However, a history of pulmonary and/or neurologic disease should raise warning flags. For example, patients with severe restrictive or obstructive pulmonary disease may not tolerate the reduction in FEV1 and FVC (approximately 27% each) that accompanies interscalene brachial plexus blocks, if this is the desired anesthetic technique.

Similarly, patients should be questioned and examined carefully for evidence of preexisting neurologic dysfunction in the ipsilateral arm and hand, since perioperative nerve injury is possible due to surgical (e.g., traction) or anesthetic (e.g., related to the nerve block) causes.

  • Medically unstable conditions warranting further evaluation include severe COPD, reactive airways disease, active cardiac conditions (e.g., unstable coronary syndromes, decompensated heart failure, significant arrhythmias, severe valvular disease).

  • Delaying surgery may be indicated if there is severe COPD, reactive airways disease, or active cardiac conditions (e.g., unstable coronary syndromes, decompensated heart failure, significant arrhythmias, severe valvular disease).

3. What are the implications of co-existing disease on perioperative care?

Subacromial decompression is a low-risk procedure that involves minimal physiologic trespass. As such, there are few implications of mild to moderate coexisting disease on perioperative care. However, there are some unique aspects to the procedure that must be kept in mind. For example, positioning may impact the hemodynamic status of the patient, especially if there is coexisting vascular disease.

The "beach-chair" position is frequently employed, and this may predispose to a reduction in right ventricular preload and subsequent arterial hypotension and/or the Bezold-Jarisch reflex. Profound bradycardia and/or periods of asystole have been reported. In addition, concerns have been raised about the negative effect of the upright beach chair position on cerebral and spinal cord perfusion pressure. Controversy exists as to whether this actually leads to postoperative neurologic events, but it bears pointing out that the mean pressure in the circle of Willis may be substantially lower than that of the brachial artery while in the sitting position.

b. Cardiovascular system

Patients with evidence of acute or unstable cardiac conditions (e.g., unstable coronary syndromes, decompensated heart failure, significant arrhythmias, severe valvular disease) should be evaluated and managed prior to undergoing this (or any) elective procedure.

The vast majority of the remaining patients do not require further cardiac evaluation, according to the 2007 ACC/AHA guidelines for perioperative care during noncardiac surgery, since this procedure is considered low-risk, and further cardiac testing would be unlikely to alter management. This includes patients with stable coronary disease or those with compensated heart failure. Clinical judgment must always be incorporated into the interpretation of guidelines. Preoperative 12-lead EKGs are not indicated in asymptomatic patients undergoing subacromial decompression.

The goals of management for patients with stable coronary artery disease or myocardial dysfunction are to prevent significant reductions in preload and afterload (as heralded by arterial hypotension), and to prevent extremes of heart rate.

The Bezold-Jarisch reflex is a physiologic response that occurs when blood pools in the lower extremities (as in the beach-chair position). This is thought to occur in up to 20% of patients undergoing shoulder surgery in the beach chair position. Hypotension from the decreased preload results in a reflex increase in contractility. However, as the underfilled right ventricle contracts, mechanoreceptors are activated, which increase vagal tone and cause bradycardia, promoting a further decrease in cardiac output.

Treatment involves prompt administration of ephedrine or, if necessary, epinephrine. Atropine may not be effective, and in some cases of asystolic arrest during shoulder surgery in the sitting position, cardiopulmonary resuscitation was necessary. Paradoxically, the use of epinephrine in the local anesthetic or irrigation solution may predispose to this (increased contractility), and pretreatment with beta-blockers following interscalene block appears to be preventative.

c. Pulmonary

Most patients with mild to moderate pulmonary disease tolerate this procedure well. Severe COPD, asthma, or restrictive disease may not tolerate the reduction in FEV1 and FVC (approximately 27% each) that accompanies interscalene brachial plexus blocks, if this is the desired anesthetic technique. However, this side effect is only as long lasting as the duration of the nerve block, and, with reassurance and monitoring, many patients are able to tolerate the subtle feeling of breathlessness that they may experience following the block.

With a continuous catheter technique, however, this side effect may be so disconcerting that removal of the catheter may be required. Of note, emphysematous patients with air-trapping and flattened diaphragms may not become dyspneic to the degree expected because of the limited, additional effect of a diaphragmatic paresis.

Clinical questioning about exercise tolerance is all that is usually required to screen patients with a history of pulmonary disease. If symptoms appear severe, preoperative spirometry can provide a baseline with which to estimate the temporary reduction in forced expiration. A "post-block"–predicted FEV1 below 40% of baseline might raise concern about the choice of interscalene block as an anesthetic/analgesic technique, as extrapolated from the thoracic surgical data. A chest radiograph is often of little value unless pneumonia is suspected.

Acute exacerbations of COPD or asthma should be treated and should take priority over proceeding with the case. Courses of beta-2 agonists, inhaled or oral corticosteroids, and anticholinergics may be indicated, as well as antibiotics if an infectious component of the COPD exacerbation is suspected. Consultation with an internist or pulmonologist may be indicated in patients with refractory disease.

The end-point to therapy is a normal chest exam with no audible wheezing, a return to baseline forced expiratory flow rates, and a patient history of feeling at their best.

d. Renal-GI:

Patients undergoing subacromial decompression should be screened for history of acute or chronic renal disease and for gastroesophageal reflux (GERD). The latter is a common problem and can be risk-stratified by enquiring about the frequency of symptoms, triggers, and whether the GERD occurs when lying down at night to sleep.

Those with more severe symptoms may benefit from preoperative gastric acid volume reduction with administration of metoclopramide 10 mg IV and famotidine 20 mg IV, if not contraindicated. In addition, sodium citrate/citric acid (Bicitra) 30 mL, p.o., can be used to raise gastric pH preoperatively.

e. Neurologic:

Anesthesiologists should perform a routine neurologic history on this population of patients, with a focus on identifying pre-existing conditions of the peripheral nerves that may put the patient at risk for postoperative neurologic dysfunction. These include diabetic neuropathy, vascular neuropathy, or any compressive etiology of sensory or motor change. It is important to evaluate both the ipsilateral and contralateral limb for comparison and document any findings.

An examination of the patients' neck – its range of motion and symptoms on movement is warranted; many cervical radiculopathies can mimic or be masked by the pain the patient experiences in the shoulder. Any sign that a spinal component to the patient's pain exists should be brought to the surgeon's attention, and consideration given to obtaining cervical imaging prior to the procedure. This is particularly important with shoulder surgery, as both the beach-chair and the lateral decubitus position can result in dangerous amounts of traction on the roots and trunks of the brachial plexus, especially when the head is in a fixed position while the arm is being manipulated by the surgeons.

The finding that a neuropathy exists in the ipsilateral limb does not necessarily rule out brachial plexus anesthesia/analgesia. This is evidenced by the large number of patients with compressive ulnar neuropathy that have nerve transpositions under brachial plexus blockade. However, a frank discussion with the patient is warranted regarding the possibility that such a technique may worsen (even temporarily) their symptoms.

The possibility of a chemical "double crush" syndrome exists in at-risk populations; some experts advocate the avoidance of epinephrine in the local anesthetic solution in these patients in order to reduce the likelihood that an ischemic neuropathy will result.

f. Endocrine:

Patients with diabetes mellitus should be evaluated clinically for symptoms and signs of autonomic neuropathy that might predispose them to hypotension during the operation, when the patient is in the upright position. The patient should be evaluated for signs and symptoms of peripheral neuropathy (as explained above).

g. Additional systems/conditions that may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

None, other than what is discussed above.

4. What are the patient's medications and how should they be managed in the perioperative period?

The majority of medications can be continued on the evening prior or day of surgery, with a sip of water. Exceptions frequently include drugs that interfere with effective coagulation (e.g., warfarin) or antiplatelet agents (e.g., clopidogrel).

ACE inhibitors are a class of antihypertensive agents that are frequently held on the morning of surgery due to the refractory hypotension that can occur with their use. This may be especially relevant in the beach-chair position.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Patients presenting for subacromial decompression are commonly on NSAIDs. Nonspecific NSAIDs such as ibuprofen, aspirin, or diclofenac result in platelet inhibition. While this rarely affects the anesthetic plan, increased bleeding intraoperatively may obscure the arthroscopic visualization of the subacromial space and prolong the procedure.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac medications

Beta-blockers and alpha-2 agonists should be continued perioperatively to avoid withdrawal effects. If the patient is not already on a beta-blocker, there is little evidence to support initiating a perioperative course of treatment, and in fact may cause harm. Less evidence is available regarding the continuation of calcium channel blockers, but, in general, for antihypertensive effect, they should be continued.

ACE inhibitors and ARB drugs should be discontinued on the day before surgery due to the risk of hypotension, especially with the sitting position. Provided the patient is not hypotensive postoperatively, these can be resumed immediately afterwards. Diuretics should be withheld on the morning of surgery (hypotension). Statin drugs should be continued throughout the perioperative period in order to benefit from their anti-inflammatory effect.

Pulmonary medications

All pulmonary agents (e.g., beta-agonists, anticholinergics, leukotriene inhibitors, corticosteroids) should be administered per the usual schedule, with the exception of theophylline, which should be held the night before surgery due to concerns surrounding arrhythmias and interactions with other drugs.

Neurologic medications

Patients with active seizure disorder should continue antiepileptic therapy perioperatively. Management of anti-Parkinson agents is complicated, as the effect on dopamine increases the risk of arrhythmias and hemodynamic perturbations. However, abrupt withdrawal can precipitate neuroleptic malignant syndrome. A gradual tapering of the agents to the lowest effective dose over the 2 weeks prior to surgery is recommended.

Antiplatelet medications

The decision to continue aspirin perioperatively can be difficult, and the indication (e.g., coronary stents) must be taken into account, as it can reduce the rate of adverse perioperative vascular events. If coronary stents are the issue, then consultation with the patient's cardiologist to arrange appropriate perioperative management is indicated. Although subacromial decompression is a low-risk procedure from the point of view of excessive blood loss, the procedure may be difficult to perform if the joint space is particularly bloody, and most surgeons will seek to stop aspirin 10 days ahead of time. Similarly, NSAIDs should be held 3 days ahead of time, and clopidogrel 7 days.

Psychiatric medications

TCAs (tricyclic antidepressants) and psychostimulants should be held before surgery. Benzodiazepines, buspirone, antipsychotics, lithium, and SSRIs (selective seratonin reuptake inhibitors) can generally all be continued throughout the perioperative period. MAO (monoamine oxidase) inhibitors can be continued cautiously if the mood disorder is severe, but, otherwise, these drugs are best held.

j. How To modify care for patients with known allergies

Patients with known or suspected allergies to ester local anesthetics should receive an amide local anesthetic instead, or consideration should be given to a nonregional anesthetic. Likewise, if a known allergy to a common anesthetic drug (e.g., neuromuscular blocking agent, antibiotic) is encountered, an alternative drug and/or plan should be put in place.

k. Latex allergy: If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

Most surgical and anesthetic supplies are now latex-free, with the exception of some latex rubber disposable tourniquets, and latex gloves. Patients with known type I hypersensitivity reactions to latex should have their procedure as the first case of the day, after thorough preparation of the operating room to eliminate any potential latex exposure.

l. Does the patient have any antibiotic allergies?

Penicillin is a common declared drug allergy. Patients should be questioned about the type of reaction, the severity of the reaction, when it occurred, and to what drug. While the often quoted cross-reactivity with first-generation cephalosporins is 8% to 10%, the actual rate of allergic reactions to cefazolin in penicillin-allergic patient is unknown.

This is partly due to the fact that, in the past, cephalosporins contained trace amounts of penicillin as a contaminant, which may have overestimated the rate of cross-reactivity. Nonetheless, if a patient gives a clear history of allergy to beta-lactam drugs such as penicillin, especially if the symptoms are indicative of a type-I hypersensitivity reaction (e.g., hives, airway swelling, wheezing, hypotension), it is prudent to avoid cephalosporins and substitute clindamycin 600 to 900 mg or vancomycin 1000 mg.

m. Does the patient have a history of allergy to anesthesia?

In the case of a known or suspected personal or family history of malignant hyperthermia, strong consideration should be given to performing the subacromial decompression under regional anesthetic alone. If a general anesthetic is required or requested, total intravenous anesthesia using propofol and opioids is appropriate, with the strict avoidance of triggering agents such as the inhaled volatile anesthetics and succinylcholine.

The operating room should be prepared in such a way that an accidental exposure to these agents is unlikely. This may involve taping over the vaporizers or, in fact, removing the vaporizers altogether from the anesthetic machine. A fresh circuit should be used and the low pressure system flushed with high-flow (e.g., 10 L/min) of oxygen for 10 minutes to remove any residual anesthetic.

A malignant hyperthermia cart complete with dantrolene should be available in the operating room.

5. What laboratory tests should be obtained and has everything been reviewed?

There are no specific laboratory or imaging tests that are routine for this procedure due to its low-risk profile. Any investigation should be ordered as a confirmation of a clinical suspicion of a disease process and should be specific to each individual patient as the need arises.

Intraoperative Management: What are the options for anesthetic management and how do I determine the best technique?

For practical reasons, there are three options for anesthetic management: general anesthesia (with any number of airway devices), brachial plexus block (i.e., interscalene block), or combined brachial plexus block plus general anesthetic. Some clinicians choose to perform the interscalene block purely as a postoperative analgesic technique following the procedure as well. Subacromial decompression has been described, using local anesthesia plus sedation, but it is not a widely performed option.

Regional anesthesia

Regional anesthesia alone for subacromial decompression is a common technique and is well suited to this relatively brief procedure on the upper extremity.

The clear benefit of performing an interscalene brachial plexus block is the quality of pain control during and after the procedure. Arthroscopic subacromial decompression, while relatively noninvasive, can still be associated with a moderate amount of postoperative pain. For this reason, many clinicians choose to use long-acting local anesthetics (e.g., ropivacaine, bupivacaine) to maximize the duration of analgesia.

The interscalene approach is preferred over other brachial plexus approaches due to the reliable blockade of the superior trunk (C5-6, which supplies the axillary and suprascapular nerves), as well as consistent, added coverage of the C3 and C4 roots of the cervical plexus. This is important as these form the supraclavicular nerve that supplies the skin of the supraclavicular fossa laterally out to the acromion. More distal approaches (e.g., infraclavicular) tend to miss this nerve.

A continuous interscalene technique can provide even longer postoperative analgesia, although it may be associated with longer insertion time and the need for 48- to 72-hour follow-up management.

Another benefit is the avoidance of general anesthesia with its requirement for endotracheal intubation (or laryngeal mask insertion), increased risk of postoperative nausea and vomiting, and increased length of stay in the PACU before discharge.

Most patients prefer to be sedated throughout the procedure, especially since the surgical action takes place so close to the patient's ear. A combination of midazolam, short-acting opioids, and a low-dose propofol infusion is useful for this purpose. However, this can also be a drawback. For example, many patients (and many surgeons) simply do not like the idea of the patient not being completely "under." Airway management can be difficult once the patient is positioned and the drapes are in place, especially in cases where a block is not complete. Conversion to general anesthesia in the beach chair position, while considerably easier with the development of laryngeal masks, is not straightforward in these cases.

Other drawbacks to interscalene block alone exist. This block is associated with one of the highest rates of postoperative neuropathy, up to 14% in some studies. These are, for the most part, transitory, and recovery is almost universally complete. The cause is likely multifactorial, but the prevailing thought is that the nerve trunks in this location, due to the high ratio of neural to connective tissue elements within the epineurium, are particularly at risk for mechanical injury.

In addition, blocks require expertise, equipment, and time to perform. While regional anesthesia probably does not delay the case throughput in centers where the infrastructure is good and clinicians are experienced, the potential exists for significant delays if time is spent between cases by clinicians struggling to perform these block procedures. Moreover, if long-acting local anesthetics are used, there may be a delay in starting the case with regional anesthesia alone while the block "sets-up."

Other drawbacks to this option relate to patient comfort. The brachial plexus does not cover the territory of T2 (proximal medial arm), and this must frequently be supplemented by either the anesthesiologist or the surgeon. Also, if the procedure is prolonged, the patient may become restless from remaining in one position for a long time, and management of sedation and analgesia can become complicated.

General anesthesia

General anesthesia is a very common technique for subacromial decompression.

The benefit of general anesthesia is the definitive management of the airway at the outset of the case. Access to the face is not easy in the beach-chair position with the drapes in place, and airway interventions such as mask ventilation and endotracheal intubation are difficult, if not impossible. Laryngeal masks have made airway management in this position much easier, in that they are easy to place in nearly every position, giving some clinicians confidence to attempt other techniques such as regional first, with general as a backup.

Another benefit is that general anesthesia can make up for a "patchy" block or for the delayed onset of long-acting local anesthetics, the procedure is combined. General plus interscalene block may be the most common method of anesthesia for these cases in order to gain the benefits of both: excellent analgesia from the block, good airway control, and ability of the surgeon to start the procedure quickly from the GA.

Drawbacks include the need for airway intervention (sore throat, risk of dental damage), an increased incidence of postoperative nausea and vomiting, and a prolonged discharge from the PACU.

Monitored anesthesia care

This is not applicable to subacromial decompression.

6. What is the author's preferred method of anesthesia technique and why?

The author prefers to perform interscalene block as the primary technique for subacromial decompression. When combined with mild sedation, it provides excellent intraoperative and postoperative analgesia, improved patient satisfaction, and a reduction in common side effects associated with general anesthesia, such as postoperative nausea and vomiting and delayed discharge from the recovery room. We use 20 to 25 mL of ropivacaine 0.5%, which provides analgesia well into the postoperative period. Because 10 to 15 minutes is usually the length of time required to position, prep, and drape the patient and ready the instruments, there is rarely a problem with starting the procedure before the sensory block has been established.

What prophylactic antibiotics should be administered?

Cefazolin 1-2 g (SCIP guidelines 2004).

What do I need to know about the surgical technique to optimize my anesthetic care?

Historically, decompression of the subacromial space was performed via an open approach. However, this has been almost universally replaced in the past several decades with the arthroscopic technique. This offers several advantages. Chief among them is the reduction in postoperative pain and deltoid muscle dysfunction that results from the reduced surgical trauma, which leads to accelerated recovery.

In addition, because shoulder impingement is a clinical diagnosis and other sources of shoulder pain may be present (e.g., rotator cuff or labral tears), the ability to conduct a thorough assessment of the subacromial and glenohumeral joints via the arthroscope is beneficial.

Most surgeons utilize three portals (posterior, lateral, and anterior) through which the arthroscope and instruments are placed. Placement of the posterior portal in particular can be associated with discomfort if brachial plexus block alone is the anesthetic technique, as this cutaneous area may not be covered. Local anesthetic infiltration of the portal sites prior to insertion is an easy solution to this problem.

The suprascapular, axillary, and musculocutaneous nerves are all located in close proximity to the portal sites and can be injured during portal placement. This must be kept in mind when evaluating a patient presenting with postoperative neuropathy. The procedure consists of using electrocautery and shavers or burrs to remove inflamed bursae and bone spurs from the underside of the acromion, thereby enlarging the subacromial space.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Bleeding into the joint space can obscure the surgeon's visual view of the structures and prolong the procedure. The degree to which bleeding occurs is often related to the arterial blood pressure, and lowering it judiciously through the use of antihypertensive agents or anesthetic agents can accomplish this goal. However, the benefit of this intervention must be weighed against the risk of hypoperfusion of critical organs, particularly the brain. It is estimated that in the beach-chair position, the mean arterial pressure may be as much as 20 to 25 mmHg less than that in the brachial artery. If general anesthesia alone is employed, adequate muscle relaxation is required to allow for full range of motion of the shoulder joint during the decompression.

What are the most common intraoperative complications and how can they be avoided/treated?

Although a relatively simple procedure, catastrophic events can occur. Venous air embolism has been reported (although extremely rarely), either from the deliberate use of air as a distention agent in the joint, or from the accidental influx of air from the arthroscopic fluid bag. The use of liquid-only arthroscopy and vigilant monitoring of end-tidal carbon dioxide and hemodynamic data is essential.

Another rare complication related to the instillation of fluid into the joint space under pressure is the subcutaneous tracking of fluid and potential for airway compromise, which has been reported. Patients complaining of dyspnea should be examined for this potential complication.

Bradycardia is more common and may be related to venous pooling in the legs and the Bezold-Jarisch reflex. Extreme cases have resulted in asystolic cardiac arrest. Treatment should include beta and alpha-adrenergic agonists, such as ephedrine and/or epinephrine.

Arterial hypotension is the most common complication and is also related to the positioning. This can be treated by the judicious use of fluids and vasopressors.

  • Cardiac complications

- Venous air embolism has been reported (although extremely rarely), either from the deliberate use of air as a distention agent in the joint or from the accidental influx of air from the arthroscopic fluid bag. The use of liquid-only arthroscopy and vigilant monitoring of end-tidal carbon dioxide and hemodynamic data is essential. Bradycardia is more common and may be related to venous pooling in the legs and the Bezold-Jarisch reflex. Extreme cases have resulted in asystolic cardiac arrest. Treatment should include beta and alpha-adrenergic agonists such as ephedrine and/or epinephrine. Arterial hypotension is the most common complication, and is also related to the positioning. This can be treated by the judicious use of fluids and vasopressors.

  • Pulmonary–interscalene brachial plexus block

- Also associated with a hemidiaphragmatic paresis and a reduction in FEV1 and FVC of approximately 27%. However, this is rarely an issue with patients unless there is underlying severe pulmonary disease. Patients with respiratory disease should be advised that they may experience a subtle feeling of breathlessness following the procedure, but this disappears when the block resolves.

  • Neurologic

- Peripheral nerves can be injured as a result of surgical trauma from the port insertion particularly through the suprascapular, axillary, and musculocutaneous nerves. In addition, traction on the shoulder throughout the course of the case can result in a brachial plexus injury, particularly since the head is often kept in a fixed position. Vigilance with respect to the patient's upper body position and potential slipping of the torso laterally is a must. Finally, if a brachial plexus block is performed, the potential for transitory or even permanent nerve damage is present, although rare.

a. Neurologic:

Unique to procedure

Peripheral nerves can be injured as a result of surgical trauma from the port insertion, particularly through the suprascapular, axillary, and musculocutaneous nerves. In addition, traction on the shoulder throughout the course of the case can result in a brachial plexus injury, particularly since the head is often kept in a fixed position. Vigilance with respect to the patient's upper body position and potential slipping of the torso laterally is a must. Finally, if a brachial plexus block is performed, the potential for transitory or even permanent nerve damage is present, although rare.

b. If the patient is intubated, are there any special criteria for extubation?

The patient's neck and shoulder area should be examined briefly for signs of excessive fluid tracking under the soft tissues, which may result in airway compromise once the endotracheal tube is removed.

c. Postoperative management

Subacromial decompression is usually performed as an ambulatory procedure but can be associated with a moderate amount of pain, especially when combined with a rotator cuff repair. This necessitates the aggressive management of pain.

Many practitioners offer a single-shot interscalene block for postoperative analgesia. This provides excellent pain control but is limited by the duration of the block.

Although some authors have advocated for the routine use of interscalene catheters for even minor arthroscopic procedures, the evidence supporting this is scant. Instead, all patients at our institution receive single-shot blocks for these procedures, as well as multimodal PO analgesic regimens that include acetaminophen, an NSAID such as ibuprofen, and a prescription for a mild opioid such as oxycodone. Patients are counseled to begin taking the PO meds at the first hint of discomfort or of the block wearing off. In situations where the patient has gone to bed and the block is still working well, we recommend that the PO acetaminophen and NSAID be taken so that when the block does eventually wear off, some baseline level of analgesia is on board.

Patients are also counseled regarding the care of their anesthetized limb. Although the patient's arm is in a sling, improper positioning or resting of the arm against a hard surface can cause permanent injury since the normal warning signals are not being processed. Patients are advised to keep their arms well padded, to sleep on their backs with several pillows supporting their elbow, and to be aware of their anesthetized arm at all times until the block has resolved.

Another option for postoperative pain control is a suprascapular nerve block. This is an attractive option for subacromial decompression, as this nerve supplies sensory fibers to the subacromial bursa, the acromioclavicular joint, and 70% of the glenohumeral joint capsule. An interscalene block will anesthetize this nerve (a branch of the superior trunk), but if performed alone for postoperative pain, the suprascapular block spares the patient much of the motor blockade of the arm and the diaphragm, as well as sensation in the hand, which may improve patient satisfaction in the early part of the recovery. However, its use is not widespread as it is not sufficient for surgical anesthesia alone, and training in this technique is not universal.

A third option is injection of local anesthetic (either single shot or via an indwelling continuous catheter) in the subacromial space. Evidence for the former is disappointing, and even when local anesthetic was delivered continuously, studies have shown conflicting results. Of note, the infusion of bupivacaine into the glenohumeral joint via a catheter system is no longer recommended due to concerns regarding the association with glenohumeral chondrolysis.

If for some reason a block is not performed, patients can still be discharged with the same medication regimen. However, they are more likely to need the oxycodone in addition to the other multimodal oral analgesics and in some cases where postoperative pain is predicted to be more intense, the addition of twice-daily sustained released oxycodone is useful as a background.

What's the Evidence?

Pohl, A, Cullen, DJ. "Cerebral ischemia during shoulder surgery in the upright position: a case series". J Clin Anesth. vol. 17. 2005. pp. 463-9.

(This series draws attention to the potential problem of hypoperfusion of the brain during the beach chair position for shoulder surgery.)

Liguori, GA, Kahn, RL, Gordon, J, Gordon, MA, Urban, MK. "The use of metoprolol and glycopyrrolate to prevent hypotensive/bradycardic events during shoulder arthroscopy in the sitting position under interscalene block". Anesth Analg. vol. 87. 1998. pp. 1320-5.

(This randomized controlled study investigates the effect of prophylactic beta-blockade and glycopyrrolate in the incidence of hypotensive-bradycardic events [the Bezold-Jarisch reflex].)

Urmey, WF, McDonald, M. "Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics". Anesth Analg. vol. 74. 1992. pp. 352-7.

(This descriptive study demonstrates the effect of interscalene block and phrenic nerve palsy on spirometry.)

Brull, R, McCartney, CJL, Chan, VWS, El-Beheiry, H. "Neurological complications after regional anesthesia: contemporary estimates of risk". Anesth Analg. vol. 104. 2007. pp. 965-74.

(This review of current rates of injury after regional anesthetic procedures reinforces the notion that while temporary neuropathy after interscalene block can be up to 14%, complete resolution is the rule rather than the exception and permanent injury is exceedingly rare.)

Fredrickson, MJ, Krishnan, S, Chen, CY. "Postoperative analgesia for shoulder surgery: a critical appraisal and review of current techniques". Anaesthesia. vol. 65. 2010. pp. 608-24.

(This critical appraisal evaluates the evidence base for postoperative analgesic options following shoulder surgery.)

Mariano, EM, Afra, R, Loland, VJ, Sandhu, NS, Bellars, RH, Bishop, ML, Cheng, GS, Choy, LP, Maldonado, RC, Ilfeld, BM. "Continuous interscalene brachial plexus block via an ultrasound-guided posterior approach: a randomized, triple-masked, placebo-controlled study". Anesth Analg. vol. 108. 2009. pp. 1688-94.

(This randomized controlled study demonstrates that for shoulder surgery of moderately painful intensity [including subacromial decompression], a continuous interscalene block for 2 days reduces opioid consumption and results in improved analgesia, sleep, and patient satisfaction compared with single shot blockade.)

Provencher, MT, McIntire, S, Gaston, TM, Frank, RM, Solomon, DJ. "Avoiding complications in shoulder arthroscopy: pearls for lateral decubitus and beach chair positioning". Tech Should Surg. vol. 11. 2010. pp. 1-3.

(This review paper outlines the advantages and disadvantages of the two common positions for shoulder arthroscopy, citing evidence.)

Singelyn, FJ, Lhotel, L, Fabre, B. "Pain relief after arthroscopic shoulder surgery: a comparison of intra-articular analgesia, suprascapular nerve block, and interscalene brachial plexus block". Anesth Analg. vol. 99. 2004. pp. 589-92.

(This randomized controlled trial concluded that interscalene block provides better dynamic pain relief, decreased morphine utilization, and greater patient satisfaction than suprascapular or intra-articular blocks.)
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