Reply to: Neurological outcome after cardiac arrest: cold and dark issues [editorial] - Critical Care Science (CCS)
We are thankful for the interest in our editorial.() We agree that the study population in Kim et al.() is different from that of Leão et al.(), insofar as the first consisted of patients who had pre-hospital cardiorespiratory arrest, and the second consisted of patients with out-of-hospital and in-hospital cardiorespiratory arrest. However, neither study showed benefits to achieving the target hypothermia more quickly. In addition, the study by Leão et al. suggested a worse prognosis in patients who reached hypothermia more quickly.() As mentioned in the editorial, although the study had several limitations, there is a pathophysiological rationale for this finding.(,)
Obviously, we agree that the study of Leão et al.() did not aim to assess the impact of temperature control. However, by showing that reaching hypothermia early was associated with worse neurological outcomes, the study adds to other recent evidence questioning the use of this therapeutic strategy.(,) It is important to highlight that the two major studies in which the recommendation to apply hypothermia after spontaneous circulation is restored compared hypothermia with no intervention on the patients’ temperature.(,) In both studies, the control group had a core temperature above 37.5°C in the first 24 hours after recovery of spontaneous circulation. An important issue associated with these studies is that it is known that early hyperthermia after restoration of spontaneous circulation is associated with worse prognosis.() Thus, the better outcomes associated with hypothermia may merely be a consequence of temperature control and not of the hypothermia itself in the intervention groups. The study by Nielsen et al. shows that this assumption may be true, as normothermia (36°C) led to results similar to hypothermia (33°C) in regards to mortality, neurological deficits(), and quality of life.() Moreover, one of the studies mentioned above should be considered “quasi-randomized” considering the methodology employed.()
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We are thankful for the interest in our editorial.() We agree that the study population in Kim et al.() is different from that of Leão et al.(), insofar as the first consisted of patients who had pre-hospital cardiorespiratory arrest, and the second consisted of patients with out-of-hospital and in-hospital cardiorespiratory arrest. However, neither study showed benefits to achieving the target hypothermia more quickly. In addition, the study by Leão et al. suggested a worse prognosis in patients who reached hypothermia more quickly.() As mentioned in the editorial, although the study had several limitations, there is a pathophysiological rationale for this finding.(,)
Obviously, we agree that the study of Leão et al.() did not aim to assess the impact of temperature control. However, by showing that reaching hypothermia early was associated with worse neurological outcomes, the study adds to other recent evidence questioning the use of this therapeutic strategy.(,) It is important to highlight that the two major studies in which the recommendation to apply hypothermia after spontaneous circulation is restored compared hypothermia with no intervention on the patients' temperature.(,) In both studies, the control group had a core temperature above 37.5°C in the first 24 hours after recovery of spontaneous circulation. An important issue associated with these studies is that it is known that early hyperthermia after restoration of spontaneous circulation is associated with worse prognosis.() Thus, the better outcomes associated with hypothermia may merely be a consequence of temperature control and not of the hypothermia itself in the intervention groups. The study by Nielsen et al. shows that this assumption may be true, as normothermia (36°C) led to results similar to hypothermia (33°C) in regards to mortality, neurological deficits(), and quality of life.() Moreover, one of the studies mentioned above should be considered "quasi-randomized" considering the methodology employed.()
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