What is a suitable monitored anesthesia care regimen for shoulder surgery?

Monitored Anesthesia Care for Shoulder Surgery

For shoulder surgery, regional anesthesia with interscalene brachial plexus block combined with monitored anesthesia care is the most effective approach for optimal pain control and reduced morbidity compared to general anesthesia alone or MAC with local infiltration. 1, 2

Understanding Monitored Anesthesia Care (MAC)

Monitored anesthesia care is defined as a planned procedure during which the patient undergoes local anesthesia together with sedation and analgesia, while maintaining the ability to respond to commands and protect their airway 3. Key components of MAC include:

• Safe sedation with continuous monitoring of vital signs 4
• Control of patient anxiety through appropriate sedation 3
• Effective pain control through regional anesthesia techniques 4
• Maintenance of patient satisfaction and rapid discharge when appropriate 3

Recommended MAC Regimen for Shoulder Surgery

Regional Anesthesia Component

• Interscalene brachial plexus block (ISB) is the regional technique of choice for shoulder surgery 1, 2
  • Use the modified lateral approach for better safety profile and catheter placement 2
  • Employ a peripheral nerve stimulator or ultrasound guidance for accurate placement 1
  • Administer 30-40 ml of bupivacaine 0.375% after location of the brachial plexus 1
  • Consider continuous interscalene catheter for prolonged postoperative analgesia 5

Sedation Component

• Administer intravenous sedation with short-acting agents that allow for:
  • Titration based on surgical requirements 3
  • Rapid recovery profile 3
  • Options include propofol infusion or dexmedetomidine 4

Required Monitoring

During MAC for shoulder surgery, the following monitoring is essential:

• Pulse oximeter with plethysmograph 4
• Non-invasive blood pressure (NIBP) measured at least every 5 minutes 4
• ECG monitoring 4
• Temperature monitoring 4
• Waveform capnography (when there is loss of response to verbal contact) 4
• Processed EEG monitoring (when using total intravenous anesthesia with neuromuscular blockade) 4

Benefits of This Approach

• Reduced intraoperative opioid requirements (0.13 mg vs 0.29 mg fentanyl compared to GA alone) 1
• Extended postoperative analgesia (average 8.7 hours before first pain complaint) 1
• Decreased need for postoperative opioids (32% vs 86% with GA alone) 1
• Reduced recovery room stay (25% shorter duration) 1
• High patient satisfaction rates (84%) 1

Potential Complications and Management

• Phrenic nerve paralysis (10% incidence) - temporary during local anesthetic action 1
  • Use lower volumes of local anesthetic in patients with respiratory compromise 6
• Horner's syndrome (18% incidence) - temporary and self-limiting 1
• Recurrent laryngeal nerve block (1% incidence) - monitor for hoarseness 1
• Intravascular injection - perform careful aspiration before injection 7
  • Consider adding epinephrine (10-15 mcg) to the test dose to detect intravascular injection 7
  • Monitor for sudden increases in heart rate or blood pressure 7

Important Considerations

• MAC may be associated with higher mortality in some studies, likely due to selection bias in patients with significant comorbidities 4
• MAC provides poor blockade of stress response unless the regional block provides profound anesthesia 4
• If the regional block is inadequate, excessive sedation may be required, potentially negating the safety advantages 4
• Careful monitoring of cardiovascular and respiratory parameters is essential throughout the procedure 7

Special Populations

• For elderly or debilitated patients:
  • Use reduced doses of local anesthetics and sedatives 7
  • Consider processed EEG monitoring to avoid excessive anesthetic depth 4
  • Target lighter levels of sedation (BIS of 50 rather than 35) to reduce postoperative delirium 4

This approach combines the benefits of regional anesthesia with the safety of monitored anesthesia care, providing excellent pain control while minimizing complications associated with general anesthesia for shoulder surgery.