Abstract P139: A Paradoxical Increase in Brain Temperature Occurs Early During Cardiopulmonary Arrest.
Introduction: In patients with cardiac arrest, brain cooling is a powerful intervention to improve neurological outcome. However, brain temperature variation during the initial phase of untreated cardiac arrest has not been well characterized.
Objective: To describe passive changes in brain temperature in early untreated cardiac arrest.
Methods: Eleven domestic swine (35 kg) were anesthetized and routine respiratory and cardiovascular parameters were monitored and recorded. Temperature was recorded from various sites including the forebrain. External heat support was adjusted to maintain rectal temperature at 37±0.5 °C at baseline, but was discontinued thereafter. Ventricular fibrillation was then induced and cardiac arrest remained untreated for 15 minutes. During this phase, forebrain temperature was recorded every 60 seconds.
Results: The brain temperature increased in all animals after induction of cardiac arrest and remained above baseline for the duration of the study period. Peak mean (±SEM) increase above baseline was 0.26 (±0.03) °C and was reached after 9 minutes. Brain temperature slowly declined thereafter. The maximum and minimum temperature increase in individual animals was 0.42 °C and 0.13 °C, respectively.
Conclusions: Brain temperature consistently and rapidly increases in the early phase of untreated cardiac arrest in anesthetized swine. This may parallel ongoing, yet diminishing, heat production from cerebral metabolic activity in the face of cessation of convective heat removal via cerebral blood flow.