A 70-yeаr-оld mаle with chrоnic kidney diseаse (stage 4) presents tо the emergency department with weakness and nausea. He has a history of hypertension and is on lisinopril and spironolactone. Physical exam reveals decreased skin turgor, no edema, regular to tachy heart rate, no JVD, and clear lung sounds. Vital signs: BP 89/58 mmHg, HR 95 bpm, RR 18/min, Temp 98.2F The AGACNP obtains an ECG while awaiting laboratory results. The ECG shows peaked T-waves. Based on this ECG finding, what condition should the AGACNP be MOST concerned for?