Defence: Harald Arne Bergan

ECMO has similarities to the cardiopulmonary bypass apparatus and is used to treat patients with severe cardiac and/or pulmonary failure. ECMO may also be used as a tool for cardiopulmonary resuscitation (E-CPR) and is increasingly used in this way in the management of refractory cardiac arrest. The treatment modality is not fully established.

In the present thesis, cand.med. Harald A. Bergan has investigated E-CPR in animal experiments. A successful E-CPR strategy was demonstrated, resuscitating long-lasting (15-min) cardiac-arrest cases.

Resuscitated patients frequently develop an early post-arrest cardiac dysfunction with circulatory failure that increases the risk of adverse neurological function and a poor outcome.

In the present thesis, the post-arrest cardiac function was assessed by cardiac MRI (imaging technique), used for the first time in this context. A severe global left ventricle (LV) dysfunction was demonstrated early post-arrest, characterised by almost similar reductions (50–70%) of systolic LV motions in all three deformation directions. LV ejection fraction and stroke volume were decreased by approximately 50% post-arrest.

Therapeutic hypothermia is an established treatment in resuscitated patients, hypothesized to improve cardiac and neurological outcome. In the present thesis, E-CPR had the ability to rapidly induce therapeutic hypothermia (32-33ºC). Two-hour hypothermic E-CPR offered an equal resuscitation success rate but did not preserve the post-arrest LV function nor reduce the magnitude of myocardial injury compared with normothermic E-CPR.

Although hypothermia is usually well-tolerated circulatory, it negatively affects the velocities of myocardial motions. Long-acting beta₁-adrenergic receptor blocking agents are frequently used pre-arrest by the cardiac-arrest population, but the combined effects of hypothermia and beta-blockade on LV function have not been previously investigated. The present work demonstrates the distinct and additive effects of hypothermia and beta-blockade (esmolol-infusion) on active myocardial motions. The combination induced both systolic and diastolic LV function impairment even in non-arrested healthy pig hearts.