Hypothermia for neuroprotection in adults after cardiopulmonary resuscitation
Abstract
Background
Good neurologic outcome after cardiac arrest is hard to achieve. Interventions during the resuscitation phase and treatment within the first hours after the event are critical. Experimental evidence suggests that therapeutic hypothermia is beneficial, and a number of clinical studies on this subject have been published.
Objectives
We performed a systematic review and meta‐analysis to assess the effectiveness of therapeutic hypothermia in patients after cardiac arrest. Neurologic outcome, survival and adverse events were our main outcome parameters. We aimed to perform individual patient data analysis if data were available, and to from subgroups according to the cardiac arrest situation.
Search methods
We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2007 Issue 1); MEDLINE (1971 to January 2007); EMBASE (1987 to January 2007); CINAHL (1988 to January 2007); PASCAL (2000 to January 2007); and BIOSIS (1989 to January 2007).
Selection criteria
We included all randomized controlled trials assessing the effectiveness of the therapeutic hypothermia in patients after cardiac arrest without language restrictions. Studies were restricted to adult populations cooled with any cooling method applied within six hours of cardiac arrest.
Data collection and analysis
Validity measures, the intervention, outcome parameters and additional baseline variables were entered into the database. Meta‐analysis was only done for a subset of comparable studies with negligible heterogeneity. For these studies individual patient data were available.
Main results
Four trials and one abstract reporting on 481 patients were included in the systematic review. Quality of the included studies was good in three out of five included studies. For the three comparable studies on conventional cooling methods all authors provided individual patient data. With conventional cooling methods patients in the hypothermia group were more likely to reach a best cerebral performance categories score of one or two (CPC, five point scale; 1= good cerebral performance, to 5 = brain death) during hospital stay (individual patient data; RR, 1.55; 95% CI 1.22 to 1.96) and were more likely to survive to hospital discharge (individual patient data; RR, 1.35; 95% CI 1.10 to 1.65) compared to standard post‐resuscitation care. Across all studies there was no significant difference in reported adverse events between hypothermia and control.
Authors' conclusions
Conventional cooling methods to induce mild therapeutic hypothermia seem to improve survival and neurologic outcome after cardiac arrest. Our review supports the current best medical practice as recommended by the International Resuscitation Guidelines.
PICOs
Plain language summary
Cooling the body after cardiac arrest
To date about one tenth to a third of successfully resuscitated patients leave hospital to live an independent life again. Clinical studies have shown that this outcome can be improved by cooling the body to about 33°C for several hours after cardiac arrest. We found five randomized trials with data on a total of 481 cardiac arrest survivors. With conventional cooling methods patients were more likely to leave hospital without major brain damage and they were more likely to survive to hospital discharge. No cooling specific adverse events were reported. In summary there is currently evidence supporting the use of conventional cooling to induce mild hypothermia in cardiac arrest survivors within the first hours of restoration of spontaneous circulation.
