Interactive diabetes case 15: A 74-year-old patient with type 2 diabetes and recurrent hyperkalemia

CASE — A 74-year-old woman returns to your care after an interval of 10 months. Fasting laboratory values obtained five days ago in anticipation of this office visit are as follows: glucose 389 mg/dL (21.6 mmol/L), blood urea nitrogen (BUN) 48 mg/dL, and creatinine 1.6 mg/dL; sodium 142 mEq/L, potassium 6.0 mEq/L, chloride 107 mg/dL, and bicarbonate 30 mEq/L; glycated hemoglobin (A1C) 8.8 percent; hematocrit 34.4 percent. The sample is not hemolyzed. The urinalysis reveals 2+ protein, as in the past, when a 24-hour urine collection contained 771 mg of protein. A repeat serum potassium level was 5.9 mEq/L yesterday. A blood glucose value in the office by fingerstick is 401 mg/dL (22.3 mmol/L).

The patient lives in Italy and travels to the United States every year to see her family. In Italy she sees a local clinician. Although you send a copy of your office notes with the patient when she returns to Italy each year, the patient's medications are usually different when she returns.

The patient's glucose diary contains only occasional entries. The fasting blood glucose values in Italy were usually 140 to 170 mg/dL (7.77 to 9.44 mmol/L). Since her arrival in the United States three weeks ago, the fasting blood glucose values have been in the 251 to 411 mg/dL (13.9 to 22.8 mmol/L) range. Values before supper in Italy were usually in the low 200s; since her return to the United States, they have been in the mid to high 300s. She complains of a dry mouth and nocturia two to three times a night. An electrocardiogram shows nonspecific ST and T wave changes. The T waves are not peaked, and the QRS interval is not prolonged.

She has a 23-year history of type 2 diabetes with persistently elevated A1C values in the 8.8 to 10.4 percent range complicated by retinopathy, nephropathy with proteinuria, and distal sensory neuropathy. She has enteropathy with episodes of recurrent severe constipation and abdominal pain over the last eight years treated with enemas, lactulose, intermittent oral phosphosoda (in the past), and intermittent Miralax (polyethylene glycol) more recently. The patient has a three-year history of anemia, previously treated with transfusions of packed red blood cells, but now treated with Aranesp (darbepoetin alpha). She has hypertension and mixed hyperlipidemia. Her lipid disorder is treated with medical nutrition therapy, efforts to achieve metabolic control of the diabetes, and atorvastatin. One year ago, a kidney duplex ultrasound revealed no evidence of renal artery stenosis or hydronephrosis.

On examination, the patient is in no acute distress. Blood pressure is 150/70 mmHg supine, 160/80 mmHg upright, heart rate 78 bpm regular, weight 161 lbs, height 5' 1", body mass index (BMI) 30.4 kg/m². Her fundi are obscured by central cataracts. The chest examination is clear to percussion and auscultation. The cardiovascular examination reveals no increase in jugular venous pressure, a normal S1, and a single S2. There is no murmur, rub, gallop, or heave. The abdominal examination reveals a well-healed, right upper quadrant cholecystectomy scar and no palpable liver, spleen, kidney, or mass. There is no distension or tenderness. Neurologic examination shows reduced sensation to light touch to the knees, absent vibratory sensation at the great toes and medial malleoli, and absent knee and ankle jerks. Peripheral pulses are intact.

Her medications are as follows: NPH insulin 32 units before breakfast and 32 units before supper, hydrochlorothiazide 25 mg daily, atorvastatin 40 mg every evening, aspirin 81 mg daily, Aranesp 25 micrograms subcutaneously every two weeks, senna tablets 2 every evening, and sorbitol syrup 1 to 2 teaspoons at night periodically. The patient had previously been on lisinopril, which had been stopped because of mild hyperkalemia, in the 5.2 to 5.4 range.

What is your assessment and plan?

●You conclude that the patient has hyperglycemia-induced hyperkalemia in the setting of impaired kidney function. You attribute the kidney dysfunction to diabetic nephropathy in a patient with proteinuria and retinopathy and note that the patient also has erythropoietin deficiency, probably on the same basis. You decide that hypertension may also contribute.

You review the patient's diet, with emphasis on the intake of potassium and provide a printout of a low potassium diet. She notes a high intake of tomatoes but says she cannot live without tomatoes in her diet. You advise her to reduce the quantity of tomatoes by at least half. You refer the patient to a registered dietitian for further discussion of a low potassium diet. (See "Interactive diabetes case 15: A 74-year-old patient with type 2 diabetes and recurrent hyperkalemia – A1".)

●You conclude that the patient has hyperglycemia-induced hyperkalemia in the setting of impaired kidney function. You attribute the kidney dysfunction to diabetic nephropathy in a patient with proteinuria and retinopathy and note that the patient also has erythropoietin deficiency, probably on the same basis. You decide that hypertension may also contribute.

You review the patient's diet. She acknowledges that she has been eating much larger portions of carbohydrates such as pasta and bread since her return to the United States. She notes a high intake of tomatoes but says she cannot live without tomatoes in her diet. You advise her to reduce the quantity of tomatoes by at least half. You also instruct her to reduce portions of the pasta and bread to the quantities she consumed in Italy but not to eliminate these items from her diet. You emphasize the need to reduce the intake of potassium and provide a printout of a low potassium diet. You refer the patient to a registered dietitian for medical nutrition therapy of diabetes and for further discussion of a low potassium diet. You ask your nurse to give the patient 8 units of regular insulin. You increase the morning dose of NPH insulin to 40 units and the pre-supper dose of NPH insulin to 35 units. (See "Interactive diabetes case 15: A 74-year-old patient with type 2 diabetes and recurrent hyperkalemia – A2".)

●You conclude that the patient has hyperkalemia due to impaired kidney function. You attribute the kidney dysfunction to diabetic nephropathy in a patient with proteinuria and retinopathy and note that the patient also has erythropoietin deficiency, probably on the same basis. You decide that hypertension may also contribute.

You advise the patient to eliminate orange juice, bananas, and dried fruits to reduce dietary potassium intake. You refer her to a nephrologist. (See "Interactive diabetes case 15: A 74-year-old patient with type 2 diabetes and recurrent hyperkalemia – A3".)

●You conclude that the patient has hyperkalemia due to hyporeninemic hypoaldosteronism (type 4 renal tubular acidosis [RTA]). You attribute this disorder to diabetic nephropathy in a patient with proteinuria and note that the patient also has erythropoietin deficiency, probably on the same basis.

You advise the patient to eliminate orange juice, bananas, and dried fruits to reduce dietary potassium intake. You prescribe fludrocortisone 0.1 mg by mouth daily as a mineralocorticoid replacement therapy for the aldosterone deficiency. (See "Interactive diabetes case 15: A 74-year-old patient with type 2 diabetes and recurrent hyperkalemia – A4".)