Methods of spinal cord protection in aortic surgery. Experimental porcine studies

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Oulu University Hospital, auditorium 1

Topic of the dissertation

Methods of spinal cord protection in aortic surgery. Experimental porcine studies

Doctoral candidate

Doctor of medicine Hannu-Pekka Henrik Honkanen

Faculty and unit

University of Oulu Graduate School, Faculty of Medicine, Research unit of surgery, anesthesia and intensive care

Subject of study

Thorax surgery

Opponent

Docent Ilkka Mattila, Helsinki university hospital

Custos

Professor Tatu Juvonen, University of Oulu, Helsinki university hospital

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Methods of spinal cord protection in aortic surgery: Experimental porcine studies

Paraplegia is one of the most devastating complication after surgery for thoracic or thoracoabdominal aortic aneurysm. Despite the modern protection strategies utilized prior to, during and after the surgery, the risk of permanent paraplegia remains. In the repair of acute type A aortic dissection, selective cerebral perfusion (SCP) and lower body circulatory arrest (LBCA) are widely used operative methods to protect the central nervous system. The temperature used during SCP and LBCA has gradually been rising, which has not necessarily been beneficial for the spinal cord.
New methods to protect the spinal cord and eliminate the possibility of permanent paraplegia are needed. Ischaemic preconditioning was first introduced in the 1980s in myocardial protection, while remote ischaemic preconditioning (RIPC) was introduced in the 1990s. In experimental studies, RIPC has proven to be an effective method to protect the spinal cord from ischaemia. Nonetheless, to date, there is no evidence for its potential in aortic aneurysm surgery in a clinical setting. The complete mechanism by which RIPC exerts its protective action is also unknown. Ischaemic priming by occluding the segmental arteries in an elective setting before the surgical treatment of the aortic aneurysm is a promising new method in protection of the spinal cord from ischaemic insult. However, to our knowledge, ischaemic priming of the spinal cord has not yet been attempted in an acute setting.
The studies presented in this thesis were carried out as a chronic porcine study. The main objective of the studies was spinal cord protection during ischaemic insult. Study I demonstrated the protective effect of RIPC against spinal cord ischaemia. Pigs treated with RIPC exhibited a faster neurological recovery and preferable near-infrared spectroscopy values four hours after the spinal cord ischaemia compared to control pigs. In study II, acute ischaemic priming led to improved neurological recovery, lower lactate discharge and fewer histopathologic changes in the spinal cord compared to control pigs. In study III, LBCA and SCP in a simulated frozen elephant trunk operation with extent stent craft resulted in a disastrous outcome when the LBCA time was 65 minutes.
Last updated: 8.9.2022