Carotid Perfusion During Circulatory Arrest Cardiac Surgery
For aortic arch surgery requiring circulatory arrest, selective antegrade cerebral perfusion (SACP) via direct cannulation of the brachiocephalic arteries or axillary artery is the preferred neuroprotective strategy, performed at 50-80 mmHg perfusion pressure with moderate hypothermia (28-30°C), allowing safe circulatory arrest periods beyond the 30-minute limit of deep hypothermic circulatory arrest alone. 1, 2
Understanding the Clinical Problem
During aortic arch surgery, the surgeon must interrupt normal circulation to work on the vessel. This creates a critical challenge: the brain cannot tolerate prolonged periods without blood flow. 2 The goal is to maintain adequate cerebral perfusion while providing a bloodless surgical field.
Primary Neuroprotective Strategy: Selective Antegrade Cerebral Perfusion
Technical Approach
SACP is typically instituted through one of three cannulation methods: 1
- Direct cannulation of the brachiocephalic arteries - allows immediate perfusion when the arch vessels are anastomosed to the graft
- Side-graft anastomosis to the axillary artery (usually right) - permits extracorporeal circulation and cooling without manipulating the diseased aorta, then serves as the conduit for antegrade brain perfusion 1
- Direct cannulation of the aortic replacement graft - used after a brief period of circulatory arrest 1
Perfusion Parameters
Target perfusion pressure: 50-80 mmHg 1, 2
Temperature management: Moderate hypothermia (28-30°C) is sufficient when combined with SACP, avoiding the complications of profound hypothermia 2, 3. The combination of moderate hypothermia with SACP provides superior neuroprotection compared to deep hypothermic circulatory arrest (DHCA) alone, as demonstrated by better EEG recovery, lower inflammatory markers (caspase-3, PARP), and higher neuroprotective proteins (VEGF, RBM3) 3.
Alternative: Deep Hypothermic Circulatory Arrest Alone
If SACP is not used, DHCA must be limited to a maximum of 30 minutes to prevent neurological complications 2. DHCA involves cooling to 12-30°C (typically 15-18°C for profound hypothermia), which reduces cerebral metabolic rate by approximately 6% for every 1°C reduction 2, 4.
The critical limitation: adverse neurodevelopmental effects become significant when DHCA duration exceeds 41 minutes 2. In older patients, periods exceeding 45 minutes are associated with marginal cerebral protection and increased neurologic morbidity 5.
Retrograde Cerebral Perfusion: A Controversial Alternative
Retrograde cerebral perfusion (RCP) via superior vena cava cannulation at 20-40 mmHg can extend safe arrest time but remains controversial 1, 2. While RCP can maintain brain hypothermia 2, there is significant debate about its ability to support brain metabolic function and improve neurological outcomes 1, 2. Some centers report reduced neurologic morbidity with RCP during prolonged arrest periods (>45 minutes), with mean perfusion times of 63 minutes showing acceptable outcomes 5.
Monitoring During Cerebral Perfusion
Essential monitoring includes: 1, 2
- Electroencephalography (EEG) - guides timing of circulatory arrest and confirms adequate metabolic suppression 1, 3
- Cerebral oximetry (near-infrared spectroscopy) - non-invasive monitoring of brain oxygenation 1, 5
- Jugular bulb oxyhemoglobin saturation - direct measurement of cerebral oxygen extraction 1
- Bispectral index - depth of cerebral metabolic suppression 1
Critical Pitfalls to Avoid
Do not exceed 30 minutes of circulatory arrest without cerebral perfusion, even with profound hypothermia 2. The nonlinear relationship between arrest time and neurologic injury means outcomes deteriorate rapidly beyond this threshold.
Avoid unilateral SACP without confirming circle of Willis patency, as incomplete perfusion can result in regional ischemia 1. Bilateral brachiocephalic cannulation may be considered when anatomy is uncertain 1.
Do not use ties that pass circumferentially around the neck post-operatively, as this can obstruct venous return from the brain 1.
Adjunctive Neuroprotective Measures
While institutional experience varies, some centers use barbiturates, calcium channel blockers, or steroids for added protection, though no prospective randomized trials have confirmed their efficacy 1, 2.
Topical cooling of the head may enhance cerebral hypothermia during HCA 6.
Post-Operative Cerebral Protection
Following return of circulation, maintain cerebral perfusion pressure and avoid hyperthermia 1. Target mean arterial pressure ≥65 mmHg and avoid both hyperoxia (PaO2 >300 mmHg) and hypoxia 1. Maintain normocapnia with PaCO2 35-45 mmHg, as both hypocapnia (causing cerebral vasoconstriction) and severe hypercapnia (causing elevated intracranial pressure) are harmful 1.
Evidence Quality and Institutional Factors
The experience and outcomes of the operating surgeon and institution are critical considerations in selecting a brain protection strategy 1, 2. Most contemporary data suggests that SACP provides outcomes comparable to or better than DHCA alone or RCP, particularly for prolonged arrest periods 1. The ability to use moderate rather than profound hypothermia with SACP reduces systemic complications while maintaining excellent cerebral protection 3.