Hypoglycaemia After Insulin in a Patient with Diabetic Foot Infection and Renal Impairment
Mr. S., 54, has had type 2 diabetes for 12 years and is admitted with a Wagner grade 3 infected ulcer on the right foot. His eGFR is 36 mL/min/1.73 m². He is prescribed glibenclamide 5 mg twice daily, insulin glargine 18 units at 22:00, and a correction-dose regular insulin sliding scale. At 02:30 he is sweaty and confused; capillary blood glucose is 44 mg/dL. His blood pressure is 150/90 mmHg and pulse 96/min. The IV cannula inserted at 23:00 has tissued and there is no patent line. He ate about half of his dinner and his temperature is 38.2°C. The ward has 50% dextrose, glucagon 1 mg, oral glucose gel, and a new cannula. The ward protocol defines hypoglycaemia as below 70 mg/dL and requires treatment and recheck in 15 minutes. His wife is not with him; he lives alone and has no refrigerator at home. He has poor vision and needs daily dressing for the foot ulcer.
1. State the immediate management sequence for this hypoglycaemic episode, giving the reason for each action and explaining why oral glucose gel is not the first choice.
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Because he is confused, I would not give oral glucose gel first: swallowing is unsafe and aspiration is a real risk. I would check airway, breathing, and ability to swallow, call for help, and protect him from injury. If he cannot swallow safely, I would give glucagon 1 mg intramuscularly and simultaneously prepare a new IV cannula. Once IV access is patent, I would give 50% dextrose 25–50 mL slowly per protocol, then start a 10% dextrose infusion to prevent recurrence. I would recheck capillary blood glucose in 15 minutes and repeat dextrose if it remains below 70 mg/dL. When he is alert and swallowing safely, I would give a complex carbohydrate snack. The reasoning is that glucagon depends on liver glycogen and may be less effective in a patient who has eaten poorly, whereas IV dextrose acts immediately. I would document the time, glucose value, treatment, and response.
2. Explain why glibenclamide makes this hypoglycaemia more dangerous than insulin alone, and what you would request from the doctor before the next dose.
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Glibenclamide is a long-acting sulfonylurea that continues to stimulate insulin secretion for many hours, so hypoglycaemia can recur after a single dose of dextrose. In renal impairment with an eGFR of 36, glibenclamide and its active metabolites accumulate, prolonging the effect. Insulin glargine also has a long duration, so the combination is high-risk. Therefore I would monitor capillary blood glucose hourly for at least four to six hours and consider a continued dextrose infusion rather than assuming one correction is enough. I would request that the doctor review and stop glibenclamide, and reassess the insulin regimen; a shorter-acting agent or dose adjustment may be safer, but that is a medical decision. I would not give the next scheduled dose simply because the glucose has returned to normal. I would also report the temperature of 38.2°C, because infection can destabilise glucose control. I would document the episode and the request made.
3. Identify two discharge safety problems for this patient and give one realistic solution for each, considering that he lives alone, has poor vision, and has no refrigerator.
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First, insulin storage without a refrigerator. The solution is not to tell him to 'keep it cool' vaguely; I would check which insulin product he is prescribed and teach the safe room-temperature storage limit for that product, usually up to 28 days for an in-use pen or cartridge, with instructions never to freeze it. I would arrange a small cool box with conditioned ice packs or ask a trusted neighbour to store the reserve supply, and give written large-print instructions. Second, poor vision plus a foot ulcer and living alone creates a high risk of missed hypoglycaemia and inability to inspect the foot. I would arrange a family member or ASHA worker to visit for dressing and foot checks, provide a talking glucose meter if available, keep glucose gel at the bedside, and give a large-print sick-day and hypoglycaemia plan. I would not discharge him until glucose is stable and a responsible person has been identified.