Cerebral protection in aortic arch surgery with a special reference to Acute Type A Aortic Dissection

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Oulu University Hospital, auditorium 1. Remote access: https://oulu.zoom.us/j/64117586249?pwd=ckVGT1gwNUE4NlV1aWFJR0V1bDRydz09

Topic of the dissertation

Cerebral protection in aortic arch surgery with a special reference to Acute Type A Aortic Dissection

Doctoral candidate

Doctor of Medicine Caius Mustonen

Faculty and unit

University of Oulu Graduate School, Faculty of Medicine, Research Unit of Surgery, Anesthesia and Intensive Care

Subject of study

Cardiothoracic surgery

Opponent

Docent Pekka Jaakkola, Univeristy of Eastern Finland

Custos

Professor Tatu Juvonen, University of Oulu

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The effects of remote ischemic preconditioning and emergency ascending aortic cannulation on neurological outcome in experimental models

Acute Stanford Type A Aortic Dissection (ATAAD) is one of the most life-threatening acute pathologies in the human body; without treatment mortality nears 100%. One third of ATAAD patients suffer from cerebral malperfusion, and permanent ischaemic brain injury occurs in approximately 10% of patients. ATAAD is treated with open aortic arch surgery that involves cardiopulmonary bypass (CPB) and deep or profound (18–24 °C) hypothermic circulatory arrest (HCA); they can provide sufficient cerebral protection for up to 20–30 minutes by lowering the glucose and oxygen consumption of the brain. However, additional strategies on cerebral protection are still needed.

ATAAD patients often present with shock, cardiac tamponade, malperfusion, or they could be still resuscitated while they are brought to the operation room. The rapid institution of antegrade cerebral blood flow through the CPB circuit is particularly vital for these patients and a new aortic cannulation strategy of direct true lumen cannulation after venous exsanguination (DTLC) was developed accordingly. However, associated normothermic circulatory arrest carries an inherent risk for neurologic sequalae.

Our research group has studied the field of cerebral protection in aortic arch surgery extensively for the last 20 years through the use of a porcine model that closely simulates the clinical situation. One of the most promising neuroprotective strategies that has emerged from this research has been remote ischaemic preconditioning (RIPC), which is based on the notion that applying short ischaemia-reperfusion periods to a skeletal muscle increases ischaemic tolerance in other organs including the brain. Therefore, the present thesis studied whether DTLC with a 5- minute normothermic circulatory arrest was safe in terms of cerebral ischaemia (I), if RIPC would prolong the permissible period of HCA (II), and if it would improve the neurologic outcome combined with moderate hypothermia (III).

The first study suggested that DTLC would not impair the neurologic outcome, even with a prolonged cannulation process. The second study proposed that RIPC would prolong the permissible period of HCA to up to nine minutes at 18 °C. The third study suggested that RIPC at 24 °C would provide five additional minutes of permissible HCA as compared to HCA alone at 18 °C. It also proposed that moderate HCA at 24 °C combined with RIPC would provide a superior neurologic outcome as compared to deep HCA alone at 18 °C.
Last updated: 8.9.2021