Prolonged hypoglycaemia in an 84-year-old man with chronic kidney disease

Presentation

An 84-year-old man was brought to the emergency department by his daughter with confusion and a Glasgow Coma Scale (GCS) of 10. At home, she had found him unresponsive to voice and had measured a capillary blood glucose of 1.8 mmol/L. He had been given an immediate intravenous bolus of 10% glucose (100 mL), which improved his GCS to 14.

Medication history

He had type 2 diabetes mellitus diagnosed 12 years ago. His regular medications were:

• Glibenclamide 5 mg twice daily, started five years ago.
• Bisoprolol 2.5 mg once daily, started eight months ago for hypertension and rate control.
• Lisinopril 10 mg once daily, started one year ago for hypertension and renal protection.
• Atorvastatin 20 mg at night, started two years ago.

He had no known drug allergies.

Timeline

Two weeks before admission, he had a chest infection and was prescribed amoxicillin 500 mg three times daily by his general practitioner. His appetite had reduced significantly, and he ate very little for four days. He had no vomiting or diarrhoea. On the day before admission, he continued to eat poorly. On the day of admission, his daughter found him confused.

After initial stabilisation, his blood glucose continued to fall, requiring repeated intravenous dextrose infusions. The medical team noted that he had not received any insulin.

Examination and investigations

On admission, his temperature was 36.8°C, pulse 84 beats per minute, blood pressure 154/78 mmHg. After further assessment, there were no signs of infection; the chest infection had resolved. His weight was 70 kg.

Biochemistry:

• Blood glucose: 1.8 mmol/L (repeated).
• Serum creatinine: 200 µmol/L (estimated GFR 30 mL/min/1.73 m²). This was stable for the last six months.
• Urea: 14 mmol/L.
• Liver function tests: normal.
• Sepsis screen: negative.
• During a hypoglycaemic episode, serum C-peptide was elevated and insulin was high, consistent with a sulfonylurea effect.
• HbA1c was 7.0% (53 mmol/mol) three months ago.

Course in hospital

He was treated with repeated 5% dextrose infusion, and the hypoglycaemia persisted for 12 hours after admission. The sulfonylurea was withheld on the second day. His glucose stabilised within 24 hours and did not require further dextrose. His other medications were continued.

On day 3, a misplaced medication chart resulted in his usual glibenclamide dose being administered inadvertently. Two hours later, his blood glucose fell to 3.2 mmol/L, and he required oral glucose. This confirmed the association.

He recovered without neurological deficits and was switched to a more appropriate glycaemic control for renal impairment.