What are the considerations for anesthesia in a patient with respiratory or cardiovascular disease undergoing a procedure in the prone position?

Anesthetic Management for Prone Positioning in Patients with Respiratory or Cardiovascular Disease

Critical Pre-Positioning Assessment

Patients with cardiovascular disease or shock, and those with cardiac arrhythmias causing hemodynamic instability, should only undergo prone positioning after interdisciplinary risk-benefit assessment, as these conditions represent relative contraindications requiring careful consideration. 1

Absolute Hemodynamic Requirements

• Stabilize hemodynamics and optimize volume status before prone positioning. 1, 2, 3
• Ongoing vasopressor therapy is NOT a contraindication to prone positioning, as the intervention is generally well-tolerated hemodynamically. 1, 2, 3
• Patients may experience improved right ventricular loading in prone position, which can benefit those with right heart dysfunction. 2, 3

Cardiovascular Disease Considerations

For patients with coronary artery disease or valvular disease:

• Avoid rapid bolus induction with propofol, as this causes significant decreases in preload and afterload proportional to blood concentrations achieved. 4
• Use slow titration at approximately 20 mg every 10 seconds until induction onset (0.5-1.5 mg/kg for cardiac patients). 4
• Administer anticholinergic agents when increases in vagal tone are anticipated, as propofol reduces sympathetic activity and resets baroreceptor reflexes. 4
• Propofol reduces myocardial oxygen consumption, which may benefit ischemic heart disease patients. 4

Respiratory Disease Considerations

For patients with ARDS or severe respiratory compromise:

• Use prone positioning in invasively ventilated patients with ARDS and PaO2/FiO2 < 150 mmHg, as this improves oxygenation and may reduce mortality in severe cases. 1
• Apply protective ventilation with tidal volumes of 6-8 ml/kg predicted body weight. 2
• Set initial PEEP at 5 cm H2O and individualize to avoid increases in driving pressure while maintaining low tidal volume. 2
• Prone positioning and PEEP have additive effects on improving oxygenation. 2, 3
• Prone position causes significant decreases in dynamic lung compliance and increases in airway pressures during surgery. 5

Intraoperative Monitoring Requirements

Continuous hemodynamic monitoring must be performed during and after positioning, with particular attention to patients with cardiovascular disease. 2, 3

Specific Monitoring Parameters

• Maintain continuous waveform capnography throughout prone positioning. 2
• For patients at cardiovascular risk, invasive blood pressure monitoring may be useful to ascertain adequate perfusion. 1
• Verify and document tracheal tube depth before positioning, and confirm bilateral breath sounds and adequate chest rise after positioning. 2
• Check tracheal tube cuff pressure (20-30 cm H2O) before and after positioning. 2
• Regular inspection of pressure points throughout the procedure is mandatory. 1, 2, 3

Ventilatory Management Algorithm

Apply lung-protective ventilation principles including limitation of tidal volumes, prevention of derecruitment, and integration of spontaneous breathing components when appropriate. 1

Specific Parameters

• Tidal volume: 6-8 ml/kg predicted body weight 2
• Initial PEEP: 5 cm H2O, then individualized 2
• Monitor and minimize driving pressure (Pplat-PEEP) 2
• Anticipate increased peak airway pressures and decreased compliance in prone position 5

Emergence and Extubation Strategy

Elevate the head before emergence from anesthesia to prevent atelectasis and improve oxygenation, particularly critical in patients with respiratory disease. 6

Specific Technique

• Position patient with approximately 30-45° of head and upper torso elevation before emergence. 6
• Begin head elevation before the patient becomes responsive to optimize positioning. 6
• Administer supplemental oxygen continuously until the patient can maintain baseline saturation breathing room air. 2
• For obese patients or those with obstructive sleep apnea, consider continuing CPAP/BiPAP treatment in the head-elevated position. 6

Common Pitfalls to Avoid

• Never use rapid bolus induction in patients with cardiovascular disease or elderly/debilitated patients, as this dramatically increases the risk of hypotension, apnea, and oxygen desaturation. 4
• Do not assume vasopressor use is a contraindication to prone positioning—volume optimization is necessary but proceeding may be appropriate. 1, 3
• Avoid waiting until after extubation to elevate the head—positioning should be optimized before emergence begins. 6
• Do not rely on chest X-ray alone to confirm tracheal placement; use waveform capnography to confirm tracheal versus esophageal placement. 2
• Never proceed without securing all tubes and lines, as dislodgement during turning is a preventable catastrophe. 2, 3