What is the optimal temperature range for total aortic arch surgery and why?

Optimal Temperature for Total Aortic Arch Surgery

For total aortic arch surgery, moderate hypothermia in the range of 20.1-28°C (specifically 24-28°C when combined with antegrade cerebral perfusion) should be used, as this approach reduces mortality and neurological complications compared to deep hypothermia while providing adequate organ protection. 1

Current Guideline Recommendations

The most recent 2024 EACTS/EACTAIC/EBCP guidelines provide a Class IIa recommendation (Level B evidence) for circulatory arrest under moderate hypothermia (20.1-28°C) in combination with antegrade cerebral perfusion for aortic arch reconstruction. 1 This represents an evolution from older practices that required deep hypothermia (18-22°C). 1

The 2014 ESC guidelines specifically note that innovative arch prostheses and antegrade cerebral perfusion techniques now allow moderate hypothermia (26-28°C) rather than deep hypothermia (20-22°C) for the majority of reconstructions, including total arch replacement with arrest times of 40-60 minutes. 1

Why This Temperature Range is Optimal

Mortality Benefits

• Moderate hypothermia (≥20°C) significantly reduces early mortality compared to deep hypothermia (<20°C), with in-hospital death rates of 0.7% vs 7.7% (OR 9.3, P=0.005) and 30-day mortality of 2.1% vs 9.0% (OR 4.7, P=0.02). 2
• Higher temperatures within the moderate range (24-28°C) are associated with lower 30-day mortality (HR 0.55, P=0.03), particularly when antegrade cerebral perfusion time is ≤40 minutes. 3

Neurological Protection

• The 2010 ACC/AHA guidelines emphasize that temperatures ranging from 12-30°C have been used successfully with extracorporeal circulation, but moderate hypothermia with adjunctive cerebral perfusion techniques provides superior outcomes. 1
• Stroke rates trend lower with moderate vs deep hypothermia (2.8% vs 7.6%, though not statistically significant in all studies). 2
• Brain hyperthermia must be avoided (Class III recommendation), making controlled rewarming essential. 1

Reduced Systemic Complications

• Shorter cardiopulmonary bypass times with moderate hypothermia (140±46 min vs 154±62 min, P=0.008). 2
• Less need for prolonged ventilatory support (>48 hours) and tracheostomy with higher temperatures within the moderate range. 4
• Reduced metabolic derangement with lactate levels averaging 2.3±1.2 mmol/L when using temperature-adapted circulatory arrest. 5

Practical Temperature Management Algorithm

For Standard Total Arch Replacement (arrest time 40-60 minutes):

• Target nasopharyngeal temperature: 24-28°C 1
• Core temperature (rectal/bladder) monitoring is mandatory 1
• Cerebral perfusion maintained at constant 28°C 5

For Complex/Extended Procedures (arrest time >60 minutes):

• Target nasopharyngeal temperature: 20-24°C 1
• Consider deeper hypothermia if antegrade cerebral perfusion time will exceed 40 minutes 3

For Shorter Procedures (arrest time <40 minutes):

• Higher temperatures (24-28°C) are particularly safe and beneficial 3
• Maximum protective effect seen with temperatures 24.1-28°C when UACP ≤40 minutes (HR 0.30, P=0.01) 3

Essential Adjunctive Strategies

Antegrade cerebral perfusion (ACP) is critical and should be considered in all complex aortic arch procedures (Class IIa recommendation). 1 The combination of moderate hypothermia with ACP is what enables the shift away from deep hypothermia. 1

Antegrade systemic perfusion using axillary cannulation should be considered (Class IIa) as the preferred arterial inflow method. 1

Bilateral near-infrared spectroscopy neuromonitoring is recommended (Class I) during aortic arch surgery to guide cerebral perfusion adequacy. 1

Common Pitfalls to Avoid

• Avoid deep hypothermia (<20°C) when antegrade cerebral perfusion is available, as it increases mortality without additional benefit. 2
• Do not allow brain hyperthermia during rewarming, as this causes neurological injury. 1
• Do not use excessively high temperatures (>28°C) for prolonged arrest times (>40 minutes), as the protective benefit disappears. 3
• Ensure adequate cooling time before initiating circulatory arrest—rushing to arrest increases risk regardless of target temperature. 5

Evolution of Practice

The shift from deep (18-22°C) to moderate (24-28°C) hypothermia represents a paradigm change enabled by improved cerebral perfusion techniques. 5 Research from 2012-2019 consistently demonstrates that temperature-adapted moderate hypothermia (adjusting depth to expected arrest duration) provides equivalent or superior organ protection with reduced systemic complications. 6, 4, 5 A 2019 study even reported successful total arch surgery at 34°C using modified techniques, though this remains investigational. 6