A 58-year-old man is admitted to the ICU following out-of-hospital cardiac arrest. After successful resuscitation, he remains comatose with bilateral pupillary changes and diffuse hyperreflexia. Continuous EEG monitoring shows the pattern marked **A** in the diagram — periodic sharp waves and spike-and-slow-wave complexes occurring independently over both hemispheres with different morphologies and out-of-phase timing, superimposed on a markedly attenuated, slow background. Which of the following is the MOST appropriate next step in management?