A 26-year-old female with type 1 diabetes mellitus (T1DM) suddenly developed coma after interrupting insulin therapy for 3 days. Blood glucose was 33.3 mmol/L, pH 7.2, with strongly positive urine glucose and ketones. After 2 hours of IV insulin and sodium bicarbonate, blood glucose dropped to 16.7 mmol/L, acidosis improved, and she briefly regained consciousness but then relapsed into coma. This phenomenon is most likely due to: