MSFinals-0052

A 60-year-old man received a two unit blood transfusion 1 hour ago. He reports feeling a strange sensation in his chest, like his heart is skipping a beat. You conduct an ECG which reveals tall tented T waves in multiple leads.
An arterial blood gas (ABG) test shows:
Na+: 136 mmol/l (normal 135–145 mmol/l)
K+: 7.1 mmol/l (normal 3.5–5.0 mmol/l)
Cl–: 96 mmol/l (normal 95–105 mmol/l).
What immediate treatment should be administered based on these findings?