Prognosis after cardiac arrest and hypothermia: a new paradigm

Abstract

Before the use of hypothermia as a treatment for comatose post-cardiac arrest patients, several prognostic variables were widely accepted as reliable and valid for the prediction of poor outcome. Recent studies using hypothermia have reported on patients with recovery of consciousness in spite of absent or extensor motor responses after 3 days, absent bilateral cortical N20 responses after 24 h, serum neuron-specific enolase levels greater than 33 μg/L, and early myoclonus status epilepticus. Hypothermia and its associated use of sedative and paralytic agents may delay neurologic recovery and affect the optimal timing of prognostic variables. Recent developments in brain imaging may provide additional objective prognostic information and deserve further study. Pending the results of future validation studies in patients treated with hypothermia, we recommend that irreversible management decisions not be made based on a single prognostic parameter, and, if there is uncertainty, these decisions be delayed for several days to allow for repeated testing.

Figure 1

Brain MRI showing the diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC), and fluid-attenuated inversion recovery (FLAIR) sequences of a 50 year-old woman who had been resuscitated for 18 minutes for a ventricular fibrillation cardiac arrest. At 72 hours after the event she had no motor response to pain, intact brainstem reflexes, a peak NSE value greater than 130 μg/L, and bilaterally absent N20 responses by somatosensory evoked potential. The MRI was obtained 81 hours after the arrest and shows widespread areas of reduced diffusion and increased T2 signal involving the entire cortex, the basal ganglia, and the thalamus. Five days after the arrest she died after supportive care was withdrawn.

Figure 2

Algorithm for prognostication of outcome for comatose post-cardiac arrest patients treated with hypothermia. cEEG—continuous electroencephalography; EEG—electroencephalography; NSE—neuron-specific enolase; ROSC—return of spontaneous circulation; SSEP—somatosensory evoked potentials.