Shoulder Arthroscopy with Interscalene Block
Patient phenotype
Rotator cuff repair, labral repair, acromioplasty. Age 40-70 typical, sometimes athletes younger. Often outpatient. Beach-chair OR lateral decubitus.
Procedure
Arthroscopic ports through deltoid + posterior shoulder. Beach-chair (semi-sitting) most common. Surgical time 60-180 min depending on complexity.
Anesthetic plan
Interscalene block (single-shot or catheter for prolonged) + GA + LMA for airway. Beach-chair = monitor cerebral perfusion (zero a-line at brain level). PNB virtually eliminates postop opioid need.
Setup
- ·Standard ASA + cerebral oximetry (NIRS) for beach-chair
- ·PIV
- ·Interscalene block kit + ultrasound
- ·LMA size 3-4 (or ETT if obese / GERD)
- ·Beach-chair attachment / armrest
- ·A-line if cardiac concern (zero at tragus for beach-chair)
Biggest concerns by phase
Interscalene block risks + benefits
Risks: phrenic nerve block (100% incidence — diaphragm paralysis on that side; AVOID in severe COPD/baseline pulmonary disease), Horner syndrome (transient, expected), recurrent laryngeal nerve block (hoarseness — usually unilateral OK), pneumothorax (rare with US), LAST. Benefits: 8-24h analgesia, motor block of arm, opioid-sparing.
Block before or after sedation?
Interscalene under heavy sedation OR GA controversial: paresthesia warning lost, intraneural injection risk. Best: lightly sedated + cooperative patient, ultrasound guidance, see local spread. Some institutions accept under GA with US.
Beach-chair position — cerebral perfusion drop
Sitting → 30-50% drop in venous return + cerebral perfusion. Brain ~25 cm above heart in beach-chair → MAP at brain is BP-cuff-MAP minus 25 mmHg (1 mmHg per 1.36 cm). Zero a-line at tragus. Maintain MAP-at-brain > 60. NIRS helpful.
Phrenic nerve block + ventilation
Diaphragm paralyzed on operative side → 25-30% reduction in FVC. Healthy patients tolerate, COPD/asthma may not. Plan: avoid in severe pulm disease, lighter sedation, sit up post-op early.
Hypotensive bradycardic event (Bezold-Jarisch reflex)
Beach-chair + interscalene + epinephrine in injection → reflex bradycardia + hypotension via cardiac stretch receptors. Treatment: atropine + vasopressor + flat the chair temporarily. Some prophylactically use glycopyrrolate.
Discharge with motor block — arm sling + counseling
Arm completely paralyzed for 8-24h post-block. Sling REQUIRED to prevent injury (arm dangles). Patient counseled: don't drive, don't try to use arm, watch for nerve symptoms persisting > 24-48h.
Mock-defense scenarios
Practice answering these out loud. The probes show what an examiner is listening for.
Beach-chair shoulder arthroscopy under interscalene + LMA. Patient is asleep on volatile, MAP from arm cuff is 90/55, cuff at heart level. Cerebral oximetry just dropped from 65% to 50% on the operative side. What's happening and what do you do?
What an examiner probes for
- ▹Recognize cerebral hypoperfusion in beach-chair
- ▹Calculate MAP-at-brain: arm MAP minus ~25 mmHg
- ▹Action: raise BP (vasopressor + lighten anesthetic), lay back slightly
- ▹Verify NIRS sensor placement
- ▹Communicate surgeon: may need to flatten temporarily
Sources
- ASRA Guidelines
- Miller's Ch 60
- Pohl 'cerebral oxygenation in beach-chair'
Anatomy reference
Sourced reference images. 4 matches for "shoulder humerus brachial plexus".
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