This study will be conducted at pre-hospital emergency care (PHEC) facilities. The PHECs are medical units that are fully equipped and staffed to provide adequate emergency medical care to patients with PDIT. The study is designed to evaluate the safety and efficacy of Ryanodex in an on0site pre-hospital emergency setting where subjects are anticipated to be treated over a short period of time and then transferred to another medical facility or released. After screening and diagnosis of PDIT, SOC treatment will be initiated. Subjects eligible for the study will be randomized to either receive SOC + Ryanodex or to receive SOC only. Study subjects are expected to remain at the study site for a maximum of 6 hours post-baseline.