1. Future of Thoracic Trauma Management: Bringing Back the ‘Dead’
Mr Syed Mohiyaddin1, Dr Nathan Tyson1, Adnan Yousaf2 Prof S Ashraf 1
1Department of Cardiothoracic Surgery, Morriston Hospital
2Dept of Cardiology, Morriston Hospital
Background
The Evidence
Human Studies
Major Trauma is the worlds leading cause of death or disability. In the UK alone In 2004, the World Health Organization (WHO) ranked road traffic accidents as the ninth leading cause of DALYs. By 2030, such accidents are projected by the WHO to rank third. Recently there have been advances in Trauma management which is now approved by the FDA in The sad part is there is no active participation of the Cardiothoracic Surgeons in this area of trauma management.
Suspended Animation has now neen used as a tool to bring back the victims of major trauma including cardiothoracic trauma from being declared dead on the spot. Susppended animation is defined as “immediate preservation of heart and brain (by dropping the entire body temperature) for subsequent surgery during exsanguination induced cardiac arrest with delayed resuscitation”1. He demonstrated that hypothermia protected vital organs from ischemic injury. Hossman previously showed improved EEG of cats who suffered cardiac arrest during accidental mild hypothermia2. William and Spencer in 1958 presented the first case report about the effect of mild hypothermia after cardiac arrest3. Bernard observed that inducing hypothermia after resuscitation of cardiac arrest victims was associated with 49% survival4. The European hypothermia after cardiac arrest study on 275 cardiac arrest patients showed that those who received hypothermia after resuscitation had 55% survival to better neurological recovery compared to 39% survival for those who were resuscitated without hypothermia5. A meta-analysis including the European trial also showed a favorable outcome in the hypothermic group. The current guidelines recommend that extended hypothermia at 32-34°C should be applied for resuscitated victims of cardiac arrest for hours.
The role of hypothermia in cardiac surgery has evolved since Euqene in 1960 performed open heart surgery without cardiopulmonary bypass after cooling the patient down to 28°C. Randall in 1970 validated the use of hypothermia in cerebral protection.
Despite all this, hypothermia is the only known factor that improves neurological outcomes after cardiac arrest. We have to differentiate between two types of hypothermia, induced hypothermia which requires sedation and muscle relaxation to prevent shivering, and spontaneous hypothermia which occurs due to depletion of energy stores and failure of the body homeostatic mechanisms22,23.
Even with prompt patient transfer to the hospital, time taken to identify & repair the source of bleeding and restore normal circulation in normothermic patient results in significant cerebral and other organs dysfunction. Induced hypothermia, however, gives more time for preservation of the organs. At mild hypothermia (34-36°C) the brain tolerates 15 minutes of cardiac arrest, and at profound hypothermia (6-10°C) the brain can tolerate up to 60 minutes of cardiac arrest24,25. The idea of ‘suspended animation’ is to induce rapid hypothermia by cold fluid flushes into the aorta at the scene of the accident within 5 minutes of the cardiac arrest to make the victim hypothermic. After identifying & repairing the source of bleeding, the patient can be actively rewarmed on cardiopulmonary bypass and spontaneous circulation can be restored.
There are no human studies of profound hypothermia in cardiac arrests but the EPR-CAT trial is currently in phase 2. It aims to use profound hypothermia in year-olds who suffered cardiac arrest due to penetrating trauma. The primary outcome will be hospital discharge free of disability
Key Animal Model Trials in Profound Hypothermic Cardiac Arrest
Study
Model
Experimental
Groups
Outcome:
Survival (%)
Neurological Deficit
Capone et al.
Canine model: Hypothermic Circulatory arrest
Group 1: Normothermic, MAP of 30mmHg
Group 2: Normothermic, MAP of 40mmHg;
Group 3: Hypothermic, MAP of 30mmHg
Group 4: Hypothermic, MAP of 40mmHg
Group 1, 40% Group 2, 40% Group 3, 100% Group 4, 100%
All surviving animals had good neurological outcome
Rhee et al.
Porcine model: exsanguination induced, profound hypothermia and cardiopulmonary bypass
Group 1: Low Flow
Group 2: No Flow
Group 1, 71.4% Group 2, 66.7%
80% had good neurological outcomes in group 1 and 66.7% in group 2.
Behringer et al.
Canine model: exsanguination induced, profound hypothermia and cardiopulmonary bypass for varying time
Group 1: Cardiac arrest of 60 minutes
Group 2: Cardiac Arrest of 90 minutes
Group 3: Cardiac Arrest of 120 minutes
All subjects survived
Good neurological outcome in groups 1 and 2;
Mixed neurological and performance outcomes in Group 3.
Wu et al.
Canine model:
Haemorrhagic shock induced,
60 minutes of resuscitation before 2 hours on cardiopulmonary bypass
Group 1: Normothermic CPR
Group 2: Profound hypothermia during CPR, mild hypothermia for 12 hours
Group 3: Profound hypothermia during CPR, mild hypothermia for 36 hours
Group 1, 0%
Groups 2 and 3, 85.7%
Better neurological outcomes observed in group 3.
Sailhamer et al.
Porcine Model:
Arrest induced followed by profound hypothermia
Group 1: Vascular injury only,
Group 2: Bowel and vascular injury;
Group 3: Vascular, bowel and splenic injury
Group 1, 90% Group 2, 87.5% Group 3, 75%
Summary
Thoracic trauma victims who suffer from massive hemorrhage usually die at the scene of the accident, the source of this massive hemorrhage is mostly from injury to the thoracic aorta, the heart or the pulmonary artery. With this new technique, patients are exsanguinated on scene with infusion of a cytopreservative solution at 4°C. The patient is then transferred straight to the operating theatre. Teams participate in dealing with all life threatening injuries. The patient is then reperfused with blood and rewarmed on a cardio pulmonary bypass machine. In normal circumstances attempts to resuscitate them fail because of the ongoing bleeding. Application of this technique of emergency preservation and resuscitation to these victims, who otherwise will die, will provide a hope of life for them with a better neurological outcome in 70-80% of cases from initial trails.