Preliminary clinical outcome study of mild resuscitative hypothermia after out-of-hospital cardiopulmonary arrest
Introduction
Cerebral protection and preservation via induced hypothermia prior to hypoperfusion has been shown to prevent postischemic brain damage following total circulatory arrest in the setting of cardiothoracic or neurologic surgery 1, 2, 3, 4, 5, 6. Therapeutic hypothermia is divided into four categories: mild (33–36°C) moderate (27–33°C), deep (16–27°C), and profound (4–16°C) 7, 8, 9. There are outcome studies in animals, which have shown that resuscitative (post arrest) mild hypothermia (MH) mitigates 7, 8, 9and even prevents [10]postischemic brain damage after normothermic cardiopulmonary arrest of 10–12 min. MH is thought to protect against secondary brain damage induced by cardiopulmonary arrest by inhibiting calcium loading, glutamate release, free–radical induced lipid peroxidation of membranes, and hypermetabolism 7, 11. Moderate hypothermia after cardiac arrest appears beneficial for cerebral, but risky for cardiac, recovery [12]. Mild hypothermia during cardiac arrest in dogs was found to be associated with better cerebral outcome [13]. In humans, there have been a few reports that suggest a beneficial effect of MH after CPA 1, 14, 15, 16.
Recently we developed a new protocol of MH for patients after out-of-hospital CPA and applied it in a pilot study comprised of 13 patients. The objective of this preliminary study was to determine the feasibility and usefulness of MH by evaluating background survival and neurological outcome of these patients compared to a historical group of normothermic controls.
Section snippets
Materials and methods
The National Defense Medical College is an 800-bed hospital in suburban Tokyo, with a catchment population of approximately 800 000. There are approximately 3000 CPA in this area every year, of which approximately 150 are treated in our center. In the Japanese emergency medical service (EMS) system, emergency medical technicians (EMTs) are allowed only to perform basic life support. In January 1995, the new Japanese EMS system enabled paramedics to perform certain advanced life support skills,
Results
In 11 subjects, core temperature was measured via bladder catheter; in these individuals the cooling blanket was automatically regulated by the bladder temperature. The remaining two used pulmonary artery temperature, with the cooling blanket regulated manually. In three cases both the bladder and the pulmonary artery temperatures were recorded. The differences between the two values were within 0.5°C (r2=0.861, p<0.01) and correlation was excellent.
Surface cooling was initiated within 78±28
Discussion
We have shown that fully recovered survivors tended to be more frequently observed in the MH group, as compared to the control group, patients. However, the results did not achieve statistical significant, thus limiting the conclusion we can draw. The reasons for our inability to achieve significance include the small number of patients in each group. Additionally, there were few witnessed collapses in the MH group as compared to controls. Usually the witnessed collapse leads to a more
Conclusion
The smaller number of the witnessed arrests in the MH group suggests more severe insults than in the control group. However, there was a trend toward better outcome in the MH group. MH might be potentially beneficial in patients after CPA. Accordingly, further human study is warranted. This study should address the safety of interventional hypothermia with definitive cooling protocol and overall outcome. A prospective randomized control trial has been instituted in our hospital and a
Acknowledgements
The authors thank Dr Peter Safar, Professor at the University of Pittsburgh, and Dr A. Joseph Layon, Professor of Anesthesiology, Surgery, and Medicine at the University of Florida College of Medicine for their helpful comments.
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