Table 1.
Comparison of two recent trials of hypothermia in cardiac arrest
| Trial | ||||
| Study information and statistical significance | European [1] | Australian [2] | ||
| Type of study | Randomized: normothermia versus hypothermia | Randomized: normothermia versus hypothermia | ||
| Multicentered, with nine centers in five countries | Four accepting emergency departments | |||
| Blinded outcome | Not blinded for treatment or outcome | |||
| Number of patients | 275 Total | 77 Total | ||
| 138 Normothermia | 34 Normothermia | |||
| 137 Hypothermia | 43 Hypothermia | |||
| Criteria | Inclusion | Witnessed arrest | Initial rhythm VF | |
| Arrest secondary to VF | Continued coma after ROSC | |||
| Age 18–75 years | Age: women >50 years; men >18 years | |||
| <60 min to ROSC | ||||
| Exclusion | Temp <30°C | Cardiogenic shock (SBP <90 mmHg despite epinephrine) | ||
| Coagulopathy | ||||
| Pregnant | Pregnant | |||
| Awake before randomization | Other causes of coma | |||
| MAP <60 mmHg for >30 min | ICU bed unavailable | |||
| Hypoxemia for >15 min | ||||
| Terminal illness | ||||
| Unavailable for follow-up | ||||
| Enrolment in other study | ||||
| Comparability of hypothermia and normothermia groups | The normothermia group had higher rates of coronary artery disease and diabetes mellitus | The normothermia group had a higher percentage of bystander-performed cardiopulmonary resuscitation | ||
| Cooling | Temperature used | 32–34°C (bladder temperature) | 33°C | |
| Mechanism | Cool air circulating device and ice packs | Ice packs | ||
| Time to start | Mean 105 min | Cooling began prehospital at a rate of 0.9°C/hour | ||
| Duration | 24 hours | 12 hours | ||
| Rewarming | Passive over 8 hours | Passive | ||
| Side effects | No statistical difference between the two groups | No statistical difference between the two groups | ||
| End-points | Primary | Favorable neurologic outcome at 6 months after arrest | Discharge to home or rehabilitation | |
| Secondary | (1) Mortality within 6 months | Side effects of hemodynamic, biochemical, or hematological instability | ||
| (2) Complications within 7 days | ||||
| Outcomes | Hypothermia: favorable outcome in 75 patients (55%) | Hypothermia: favorable outcome in 21 patients (49%) | ||
| Normothermia: favorable outcome in 54 patients (39%) | Normothermia: favorable outcome in 9 patients (26%) | |||
| Statistical significance of the outcomes | P = 0.009 | P = 0.046 | ||
The table summarizes some of the features of the two recent studies that examined the neuroprotective advantage of hypothermia in treatment of cardiac arrest. ICU, intensive care unit; ROSC, restoration of spontaneous circulation; VF, ventricular fibrillation.