MRCP2-0841

A 28-year-old woman with a history of severe depression has been admitted to the medical admissions unit. She was found unconscious in a locked room at home after not being seen for six hours. There is a strong smell of alcohol. Upon examination, her Glasgow coma score is 7/15 and both pupils are dilated. Her pulse rate is 110 beats per minute and blood pressure is 110/70 mmHg. The patient experiences a grand mal seizure and is intubated and ventilated. An ECG shows sinus tachycardia with prolonged QRS complexes and a significantly prolonged QTc interval. Arterial blood gas analysis reveals metabolic acidosis.

What is the most appropriate initial treatment?