What are the anesthetic concerns for a patient in the beach chair position?

Anesthetic Concerns for Patients in Beach Chair Position

The beach chair position during anesthesia poses significant risks including cerebral hypoperfusion, hemodynamic instability, and potential neurocognitive effects, requiring careful monitoring of blood pressure at the level of the brain and maintenance of cerebral perfusion pressure. 1, 2

Hemodynamic Concerns

• The beach chair position causes significant reductions in mean arterial pressure (MAP), with studies showing decreases of up to 35% from baseline when anesthesia is induced in the sitting position 3
• Induction of anesthesia should be performed in a reclining beach chair position rather than sitting position to minimize hemodynamic instability and reduce the need for vasopressors 3
• Blood pressure should be measured at the level of the external acoustic meatus (ear level) to accurately reflect cerebral perfusion pressure, as standard arm measurements may overestimate the actual pressure at brain level 2
• Patients with cerebral desaturation events show greater blood pressure drops when positioned in beach chair compared to those without desaturation events 2

Cerebral Perfusion and Oxygenation

• Cerebral desaturation events occur in approximately 25% of patients undergoing surgery in beach chair position, even in ASA I-II patients 2
• Continuous monitoring of cerebral oxygenation using near-infrared spectroscopy (NIRS) is recommended to detect cerebral desaturation events early 2
• Cerebral blood flow velocity in the middle cerebral artery decreases significantly in patients experiencing cerebral desaturation events 2
• Controlled hypotension techniques commonly used during shoulder surgery may further compromise cerebral perfusion and should be used cautiously 2

Ventilation Strategy

• Before induction of anesthesia, position the patient with head of bed elevated 30° (beach chair) to optimize respiratory mechanics 1
• Use non-invasive positive pressure ventilation (NIPPV) or continuous positive airway pressure (CPAP) before loss of spontaneous ventilation to attenuate anesthesia-induced respiratory changes 1
• Initial ventilator settings should deliver tidal volumes of 6-8 ml/kg predicted body weight with PEEP of 5 cm H₂O; zero end-expiratory pressure (ZEEP) is not recommended 1
• Higher PEEP levels may be required during beach chair positioning to maintain adequate lung compliance and prevent atelectasis 1

Positioning Considerations

• Modern mechanical operating tables should be used to achieve the beach chair position, which protects operating theater staff from musculoskeletal injury but requires proper training to ensure patient safety 1
• The beach chair position offers advantages including ease of setup, reduced brachial plexus stress, improved glenohumeral and subacromial visualization, and the ability to easily convert to an open procedure if needed 4
• Proper patient positioning requires a minimum of three staff members plus the anesthetist for patients weighing >50 kg 1
• Attention to pressure areas is essential to prevent nerve injuries and pressure ulcers during prolonged procedures 1, 5

Neurological Complications

• While major neurological complications are rare, minor transient anesthetic and position-related complications may occur in 10-30% of patients 6
• Patients experiencing cerebral desaturation events show greater negative impact on neurobehavioral tests 24 hours after surgery compared to patients without such events 2
• Potential neurological complications include cervical neurapraxia and end-organ hypoperfusion injuries, particularly when deliberate hypotension is used 6
• Hypotensive bradycardic events may occur more frequently in beach chair-positioned patients receiving epinephrine-containing interscalene anesthetics 6

Practical Management Recommendations

• Maintain MAP above 70 mmHg at the level of the brain to ensure adequate cerebral blood flow 7
• Consider using invasive arterial blood pressure monitoring with the transducer placed at the level of the external acoustic meatus 2
• Avoid excessive head and neck manipulation during positioning to prevent carotid compression or cervical nerve injuries 6
• Monitor end-tidal CO₂ closely, as changes in PaCO₂ can significantly affect cerebral blood flow in the beach chair position 7, 2
• Use vasopressors proactively rather than reactively to maintain cerebral perfusion pressure 3, 2

Special Considerations

• Patients with pre-existing cerebrovascular disease, hypertension, or diabetes may have impaired cerebral autoregulation and require higher perfusion pressures 2
• Elderly patients may be more susceptible to cerebral hypoperfusion due to age-related changes in cerebral autoregulation 2
• Consider using total intravenous anesthesia (TIVA) rather than volatile anesthetics in high-risk patients, as some studies suggest better maintenance of cerebral autoregulation 2
• Interscalene blocks may cause phrenic nerve paralysis and respiratory compromise, which can be exacerbated in the beach chair position 6