52/f ,weighing 80kg, with h/o of alleged deliberate self harm after taking few tabs of paracetamol plus etodolac combination {history not clear and provided by daughter}12 hours prior to the presentation. She was not speaking and looked depressed. Her vitals were stable and was admitted for NAC infusion. Her systemic exam was normal labs and ABG, ECG were normal. After 3 hours she developed acute dyspnea and went into cardiac arrest.

She was immediately resuscitated after CPR and adrenaline. She was intubated and pt was revived. After 2 days she was extubated and was doing well. Can anyone explain the possibility of her arrest which is confusing?