Management of Elderly Patient with Hyperglycemia, Abdominal Pain, and Prerenal Azotemia
This elderly patient requires immediate aggressive fluid resuscitation with isotonic saline at 15-20 mL/kg/h (1-1.5 liters in the first hour) to correct the prerenal azotemia indicated by the elevated BUN/Creatinine ratio of 36, followed by insulin therapy once adequate hydration is established. 1
Immediate Concerns and Initial Management
Prerenal Azotemia from Hyperglycemia-Induced Osmotic Diuresis
The BUN/Creatinine ratio of 36 (normal 12-28) with BUN 31 mg/dL strongly indicates prerenal azotemia from volume depletion, likely secondary to glucose-induced osmotic diuresis given the glucose of 192 mg/dL. 1
The eGFR of 69 mL/min/1.73m² represents mild renal impairment common in elderly patients, where renal function declines by approximately 1% per year after age 40, potentially resulting in 40% decline by age 70. 1
Hyperglycemia causes osmotic diuresis leading to hypovolemia, decreased glomerular filtration rate, and prerenal azotemia—this patient's presentation with "hot cold" (likely fever/chills) and abdominal pain suggests an underlying infection precipitating hyperglycemic crisis. 1
Fluid Resuscitation Protocol
Begin with isotonic saline (0.9% NaCl) at 15-20 mL/kg/h for the first hour in the absence of cardiac compromise, which typically amounts to 1-1.5 liters in an average adult. 1
After the initial hour, switch to 0.45% NaCl at 4-14 mL/kg/h if corrected serum sodium is normal or elevated (current sodium 136 mmol/L is at lower limit of normal). 1
Once urine output is established, add 20-30 mEq/L potassium (2/3 KCl and 1/3 KPO4) to IV fluids, as the current potassium of 5.0 mmol/L will drop with insulin therapy and correction of acidosis. 1
Fluid replacement should correct estimated deficits within 24 hours, with successful progress judged by hemodynamic monitoring (blood pressure improvement), fluid input/output measurement, and clinical examination. 1
Hyperglycemia Management
While this glucose level of 192 mg/dL does not meet criteria for diabetic ketoacidosis (DKA requires glucose ≥250 mg/dL) or hyperosmolar hyperglycemic state (HHS requires glucose ≥600 mg/dL), the patient requires treatment given symptoms and prerenal azotemia. 1, 2
In elderly patients, hyperglycemia management must be approached cautiously as they are less likely to experience typical symptoms like polyuria and polydipsia due to increased renal threshold for glycosuria and impaired thirst mechanisms. 1
If insulin therapy is initiated after adequate hydration, use regular insulin 0.1 units/kg/h continuous IV infusion only after excluding hypokalemia (K+ <3.3 mEq/L). 1
For elderly patients with type 2 diabetes, target HbA1c should be 8.0-8.5% to minimize hypoglycemia risk, which carries a 2-fold increased mortality risk in this population. 3
Infection Workup
The combination of fever/chills ("hot cold"), abdominal pain, elevated WBC 10.8 x10³/uL (upper limit of normal), absolute neutrophils 7.1 x10³/uL (elevated), and absolute monocytes 1.8 x10³/uL (elevated) strongly suggests underlying infection as the precipitating cause. 1
Obtain urinalysis with culture, blood cultures, chest X-ray, and consider abdominal imaging (CT scan) given the abdominal pain to rule out intra-abdominal infection, cholecystitis, or other surgical emergencies. 1
Underlying infections are the most common precipitating cause of hyperglycemic crises in elderly patients. 1, 2
Additional Laboratory Monitoring
Obtain arterial or venous blood gas to assess for metabolic acidosis (venous pH is usually 0.03 units lower than arterial pH and is adequate for monitoring). 1
Check serum osmolality to calculate osmolar gap and assess severity of hyperosmolarity. 1, 2
Monitor electrolytes, glucose, BUN, and creatinine every 2-4 hours initially to assess response to fluid resuscitation and guide potassium replacement. 1
The corrected sodium should be calculated by adding 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL: corrected Na = 136 + (1.6 × 0.92) = 137.5 mEq/L, which is low-normal. 1
Medication Considerations
If the patient is on metformin, it must be discontinued immediately given the elevated BUN/Creatinine ratio and eGFR of 69 mL/min/1.73m², as metformin is contraindicated with eGFR <30 and initiation is not recommended with eGFR 30-45. 4
Metformin increases risk of lactic acidosis in elderly patients, particularly those with renal impairment, dehydration, infection, or acute illness—all potentially present in this patient. 4
Review all medications for nephrotoxic agents (NSAIDs, ACE inhibitors, ARBs) that should be temporarily held during acute illness with prerenal azotemia. 4
Common Pitfalls to Avoid
Do not give insulin before adequate fluid resuscitation, as this can worsen hypotension and renal perfusion. Fluid therapy takes priority. 1
Do not add potassium to IV fluids until urine output is established and serum potassium is known to be <5.3 mEq/L, as the current K+ of 5.0 may reflect pseudohyperkalemia from dehydration. 1
Avoid overly aggressive glucose lowering in elderly patients—target glucose decline of 50-75 mg/dL per hour, not faster. 1
Do not overlook the "yellow urine" complaint—while concentrated urine from dehydration is most likely, ensure urinalysis rules out bilirubinuria, infection, or hematuria given the abdominal pain. 1
Monitor for cerebral edema risk if osmolality changes exceed 3 mOsm/kg/h during treatment, though this is more common in pediatric DKA. 1
Expected Clinical Course
With appropriate fluid resuscitation, BUN and creatinine should normalize within 24-48 hours as prerenal azotemia resolves. 1
The glucose should decline to <250 mg/dL within 4-6 hours with fluid therapy alone or combined with insulin if needed. 1
If BUN/Creatinine ratio does not improve with fluids, consider alternative diagnoses such as intrinsic renal disease, though the current presentation strongly favors prerenal etiology. 1