What is the recommended anesthetic approach for a patient undergoing retrograde intrarenal surgery with an infrarenal (below the renal arteries) aneurysm of 3.5 centimeters?

Anesthetic Management for Retrograde Intrarenal Surgery with 3.5cm Infrarenal Aneurysm

Primary Recommendation

For a patient undergoing retrograde intrarenal surgery (RIRS) with a 3.5cm infrarenal abdominal aortic aneurysm, either general anesthesia or combined spinal-epidural anesthesia can be safely used, as the aneurysm does not require intervention and poses minimal perioperative risk at this size. 1, 2

Aneurysm Management Context

The Aneurysm Does Not Require Intervention

• Intervention is contraindicated for asymptomatic infrarenal AAAs measuring less than 5.0 cm in men (Class III recommendation). 1
• At 3.5cm diameter, this aneurysm requires surveillance only, with imaging every 12 months to monitor for expansion. 2
• The annual rupture risk for aneurysms of this size is <1%, far lower than any operative mortality risk. 3
• The aneurysm should not influence the decision to proceed with RIRS, as it is not a contraindication to surgery. 1, 2

Perioperative Cardiac Risk Management

• Perioperative beta-adrenergic blocking agents should be administered (in the absence of contraindications) to reduce the risk of adverse cardiac events in patients with known AAA undergoing any surgical procedure. 1
• Blood pressure control is essential perioperatively to minimize hemodynamic stress on the aneurysm. 1
• The presence of an AAA indicates underlying atherosclerotic disease, warranting standard cardiac risk stratification. 1

Anesthetic Technique Selection

Combined Spinal-Epidural Anesthesia (CSEA) as Preferred Option

• CSEA can be completed successfully for RIRS with no anesthetic conversions required, demonstrating equivalent efficacy and safety compared to general anesthesia. 4
• CSEA offers significant cost savings (approximately 50% reduction in anesthetic costs) compared to general anesthesia. 4
• Patients undergoing RIRS with CSEA experience less hemoglobin drop (6.5±3.2 g/L vs 8.6±2.7 g/L with GA), suggesting better hemodynamic stability. 4
• Postoperative pain scores at 6 and 24 hours are equivalent between CSEA and general anesthesia. 4

General Anesthesia as Alternative

• General anesthesia remains a safe and effective option for RIRS, with no difference in operative time, stone fragmentation time, complication rates, or stone-free rates compared to CSEA. 4
• GA may be preferred if the patient has contraindications to neuraxial anesthesia or if prolonged operative time is anticipated. 4
• The slightly higher hemoglobin drop with GA suggests potentially greater hemodynamic fluctuations, though this difference is clinically modest. 4

Specific Anesthetic Considerations

Hemodynamic Management

• Maintain strict blood pressure control throughout the procedure to minimize wall stress on the aneurysm. 1
• Avoid hypertensive episodes during intubation, surgical stimulation, and emergence if using general anesthesia. 1
• With CSEA, the sympathetic blockade may provide more stable hemodynamics and reduce cardiac workload. 4

Positioning and Duration

• RIRS is typically performed in lithotomy position with the patient supine or slightly Trendelenburg. 4
• Mean operative times range from 60-90 minutes, making both CSEA and GA feasible options. 4
• The aneurysm location (infrarenal) means it is not directly affected by renal manipulation during RIRS. 2

Monitoring Requirements

• Standard ASA monitoring is sufficient for both anesthetic techniques. 4
• Invasive arterial monitoring is not routinely required for a 3.5cm infrarenal AAA during RIRS, unless other comorbidities dictate. 1
• Consider arterial line placement if significant hemodynamic instability is anticipated or if the patient has severe cardiovascular disease. 1

Common Pitfalls to Avoid

• Do not delay or cancel RIRS based solely on the presence of a 3.5cm infrarenal AAA, as this size does not meet criteria for intervention and poses minimal perioperative risk. 1, 2
• Do not assume general anesthesia is mandatory for RIRS—CSEA is equally safe and effective with potential advantages in hemodynamic stability and cost. 4
• Do not omit perioperative beta-blockade in patients with known AAA and coronary artery disease, as this significantly reduces cardiac morbidity and mortality. 1
• Do not confuse the presence of an aneurysm with the need for aneurysm repair—at 3.5cm, surveillance is the appropriate management strategy. 1, 2, 3

Postoperative Management

• Continue beta-blocker therapy postoperatively if initiated preoperatively. 1
• Maintain adequate blood pressure control during recovery. 1
• Schedule surveillance imaging for the AAA at 12-month intervals as per standard protocols. 2
• Hospital stay duration is equivalent between CSEA and GA for RIRS, typically 1-2 days. 4