CARL Therapy is a new method of resuscitation following cardio-circulatory arrest (“sudden death”), which was developed in an interdisciplinary collaboration of physicians and perfusionists at the Department of Cardiovascular Surgery at Freiburg University Hospital. The innovative approach addresses the frequent occurrence of sudden death which is treatable to a very limited extent so far, even under optimal conditions.
When the heart stops beating.
The human organism depends on a continuous blood flow as blood supplies all cells, tissues and organs with essential nutrients and ensures the removal of metabolic products. If the heart stops, this circulation is interrupted (ischemia) and the energy balance of the cells and organs is impaired within seconds. Subsequently, ischemic damage triggers a series of metabolic adaptations in the cells.
Back on track.
In this situation the pre-damaged organism of an affected patient meets the efforts of first responders and later rescue personnel trying to restore circulation (reperfusion) and to provide oxygen as quickly as possible. This is part of routine cardio-pulmonary-resuscitation (CPR) which includes initially cardiac massage and lay respiratory support (mouth-to-mouth or mouth-to-nose).
Within the framework of an advanced CPR performed by medical staff, the patient is intubated, defibrillated and supplied with appropriate medication. By these means, cardiopulmonary circulation can ideally be restored, and the patient may be transferred to a hospital where the cause of the cardiac arrest can be treated.
Race against time.
However, the chances of successful resuscitation without neurological sequelae are low as the methods established to date are limited in regard to therapeutical possibilities. Only about ten per cent of all patients survive cardiovascular arrest outside a hospital, afterwards often suffering severe long-term neurological damage. Above all, the brain reacts extremely sensitive to interrupted circulation – but according to recent findings, this refers less to the consequences of ischemia than to the consequences of an uncontrolled resumption of blood flow.
The injurious impact in the phase of reperfusion is, among other things, due to the unspecific supply of oxygen, which cannot be adequately metabolized in the cells pre-damaged by ischemia. Thus, the highly reactive oxygen (free radicals) triggers severe damage to membranes, organelles, protein complexes and other cell components. We therefore refer to the overall damage after cardiac arrest as an ‘ischemia reperfusion injury’.
Within the framework of CARL Therapy, the above pathophysiological changes are taken into account and treated in a targeted manner. To this end, the body’s own circulatory system is first bridged with the aid of two blood pumps and a special tubing system (perfusion set), which is connected to the patient’s circulation via the groin vessels.
Then, important vital parameters – such as the oxygen content and pH value of the blood – are continuously measured and patient-individually modified so that the cells and therefore the whole organism can gradually recover from ischemia and re-establish physiological metabolic processes.
Physical reperfusion conditions, i.e., blood flow, blood pressure and body temperature, are also monitored and specifically adapted. The body core temperature is reduced to about 34 °C right at the beginning of the treatment as cooling supports the resuscitation process in the sense that at lower temperatures, metabolic processes run slower, thereby supporting the replenishment of cellular substrate deficiencies.
The research and development of the CARL Therapy have been and continues to be determined to save lives – and to give those lives a chance to re-establish a socially and cognitively fulfilling existence. Therefore, CARL is not only a therapy for treating patients in need of resuscitation. The new concept may moreover pave the way for a comprehensive targeted extracorporeal care of critically ill patients.