Midazolam 5mg IM beat haloperidol 5 mg, ziprasidone 20 mg, olanzapine 10 mg, and haloperidol 10 mg (all also given IM), with 71% sedated at 15 minutes. Olazapine came in second.
Delayed ROSC may occur after cessation of CPR - the so called Lazarus phenomenon. The incidence is around 6/1000 cases and usually occurred within 3-8 minutes after CPR cessation. All patients eventually died; 4 of 5 had PEA. It may be wise to allow 10 minutes before pronouncing death (or 4 days if the patient is actually named Lazarus).