Sedatives during circulatory arrest are not necessary for aortic arch repair in acute type A aortic dissection

The standard protocol for maximizing cerebral protection during open aortic arch surgery in acute type A aortic dissection (ATAAD) typically involves a combination of perioperative strategies, including hypothermic circulatory arrest (HCA) and cerebral perfusion, often supplemented with pharmacologic agents such as barbiturates. These agents are routinely used intraoperatively in most cases, despite limited evidence supporting their incremental neurological benefits. This study aimed to evaluate the cerebral protection provided by intraoperative administration of adjunctive sedatives during aortic arch surgery with HCA and antegrade cerebral perfusion (ACP) in ATAAD patients. The hypothesis was that adjunctive sedatives would not offer additional cerebral protection but would prolong patients’ wake-up and intubation times due to their sedative effects.

The study was conducted at the University of Michigan, Michigan Medicine, and included 120 ATAAD patients who underwent aortic arch surgery with HCA and ACP between September 2011 and January 2018. The patients were divided into two groups based on whether additional intraoperative sedatives were used during HCA. Phenobarbital was used as the sedative from September 2011 to January 2015, while no adjunctive sedatives were used from February 2015 to January 2018. To ensure consistency, all surgeries were performed by a single surgeon using the same cerebral protection strategy. No patients were excluded from the study.

Data were collected from the University of Michigan Cardiac Surgery Data Warehouse, supplemented by medical record reviews and the National Death Index database for long-term survival tracking. The primary outcomes measured were immediate stroke, in-hospital stroke, and operative mortality. Secondary outcomes included wake-up and intubation times. Immediate stroke was defined as a stroke identified immediately upon waking from anesthesia in the ICU or confirmed by imaging if the patient never woke up. In-hospital stroke included any stroke occurring post-operation and before discharge. Wake-up time was measured from sedation cessation to signs of waking in the ICU, while intubation time was measured from ICU arrival to extubation.

The aortic arch was replaced either as a hemiarch replacement or a zone 1/2/3 arch replacement. Indications for zone 1–3 arch replacement included an arch aneurysm larger than 4 cm, an intimal tear located in the arch, or dissection of arch branch vessels with malperfusion. Arch branch vessels were resected and replaced if significantly thrombosed due to dissection. A frozen elephant trunk was placed into the true lumen of the descending thoracic aorta if the intimal tear was found in the proximal descending aorta or if a narrow true lumen was identified in the distal thoracic or abdominal aorta on CT angiogram.

ACP was used in all cases, either unilaterally (78%) or bilaterally (22%). Unilateral ACP was achieved through an 8 mm Dacron graft sewn to the innominate, intrathoracic right subclavian, right axillary, or right common carotid arteries. The left common carotid artery was clamped during unilateral ACP to prevent cerebral perfusion steal. If significant back bleeding or a drop in left cerebral saturation occurred, bilateral ACP was initiated. Moderate hypothermia (bladder temperature 24–28°C) was maintained during HCA, with ACP blood temperatures between 18–24°C. Topical cooling was achieved using ice packs around the head. Mannitol and solumedrol were administered prior to HCA, with or without phenobarbital.

The median age of the cohort was 59 years, with no significant differences in demographics or preoperative conditions between the phenobarbital and no-sedatives groups. Intraoperative differences included shorter HCA time, higher bladder temperature during HCA, and fewer blood transfusions in the no-sedatives group. Postoperative outcomes showed no significant differences in immediate, in-hospital, or permanent stroke rates between the groups. In-hospital and operative mortality rates were also similar. However, wake-up and intubation times were significantly shorter in the no-sedatives group.

Multivariable logistic regression analysis found that age, gender, HCA time, and the absence of intraoperative sedatives were not significant risk factors for postoperative in-hospital stroke. One-year survival rates were similar between the groups. Immediate stroke occurred in two patients in the no-sedatives group, both of which were attributed to factors unrelated to the lack of sedatives. Delayed in-hospital ischemic strokes in two additional patients were also unrelated to intraoperative management.

The study concluded that adjunctive sedatives during HCA and ACP for aortic arch repair in ATAAD patients did not provide additional cerebral protection but prolonged wake-up and intubation times. Prolonged intubation increases the risk of complications such as ventilator-associated pneumonia and extends ICU and hospital stays. Phenobarbital, with its long half-life, was particularly associated with these adverse effects. The study supports avoiding adjunctive sedatives during aortic arch surgery with HCA and ACP, as excellent neurological outcomes were achieved without them.

The study’s limitations include its retrospective, non-randomized, single-center design and small sample size. The incidence of stroke was low, and the diagnosis was clinical rather than radiographic, potentially underestimating subclinical stroke rates. However, the consistency in surgical management by a single surgeon strengthens the study’s findings. The results provide preliminary evidence that adjunctive sedatives are unnecessary for aortic arch repair with HCA and ACP in ATAAD patients.

In summary, this study demonstrates that adjunctive sedatives are not necessary for cerebral protection during aortic arch repair with HCA and ACP in ATAAD patients. The use of such sedatives prolongs wake-up and intubation times without providing additional neurological benefits. The findings suggest that avoiding adjunctive sedatives can reduce intubation times and associated risks, improving overall patient outcomes.

doi.org/10.1097/CM9.0000000000001248

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