Management of Volume Depletion with Acute Kidney Injury in an Elderly Patient
This 78-year-old woman with diarrhea, vomiting, and acute kidney injury (urea 62, creatinine 3.2) requires immediate intravenous fluid resuscitation with isotonic saline (0.9% normal saline) at 1 liter over the first hour, followed by continued IV fluids at a slower rate with close monitoring, alongside antiemetic therapy and withdrawal of any nephrotoxic medications. 1
Immediate Assessment and Diagnosis
Assess for moderate to severe volume depletion by checking for at least four of the following seven signs: confusion, non-fluent speech, extremity weakness, dry mucous membranes, dry tongue, furrowed tongue, or sunken eyes 2. This patient's elevated urea and creatinine strongly suggest prerenal azotemia from volume depletion secondary to gastrointestinal losses.
The BUN:creatinine ratio is markedly elevated (approximately 19:1 when converted to mg/dL), which is characteristic of prerenal azotemia rather than intrinsic renal disease 1, 3.
Fluid Resuscitation Protocol
Administer 0.9% normal saline 1 liter IV over the first hour to rapidly restore intravascular volume and reverse prerenal azotemia 1. This aggressive initial approach is critical in elderly patients with volume depletion.
- Continue isotonic saline infusion at a slower rate for the following 24-48 hours with frequent hemodynamic monitoring 1
- Older adults with volume depletion should receive isotonic fluids via the oral, nasogastric, subcutaneous, or intravenous route 2
- Strict monitoring of fluid intake and output is necessary to assess response and prevent fluid overload 1
Critical pitfall to avoid: Do not delay fluid resuscitation while waiting for laboratory results—the clinical presentation of vomiting and diarrhea with elevated BUN mandates immediate IV fluid therapy 1.
Antiemetic Management
Administer ondansetron intravenously over 2-5 minutes, which can be repeated every 4-6 hours as needed 1, 4. Alternative agents include metoclopramide 10 mg IV or prochlorperazine 5-10 mg IV every 6-8 hours if ondansetron is unavailable 1.
Avoid oral medications when vomiting is active, as the oral route is not feasible 1.
Laboratory Monitoring
Draw blood immediately for serum electrolytes (Na, K), creatinine, BUN, and glucose before initiating therapy 1. Check and correct electrolyte abnormalities, particularly hypokalemia and metabolic alkalosis that commonly develop with protracted vomiting 1.
Monitor renal function closely during fluid resuscitation. If oliguria persists despite initial fluid resuscitation, consider a fluid challenge followed by furosemide to differentiate acute tubular necrosis from prerenal causes 1.
Medication Review and Nephrotoxin Avoidance
Immediately review and discontinue nephrotoxic medications, particularly ACE inhibitors, ARBs, NSAIDs, and diuretics 2, 3. Volume depletion causing acute renal failure in patients taking ACE inhibitors is not uncommon, and reversible renal impairment may occur during intercurrent illnesses characterized by diarrhea and vomiting 3.
The "triple whammy" combination of NSAIDs, diuretics, and ACE inhibitors/ARBs more than doubles the risk of developing AKI 2. These medications should remain discontinued until volume status is restored and renal function normalizes.
Expected Clinical Course
With appropriate fluid resuscitation, renal function should begin to improve within 24-48 hours 1, 3. Peak creatinine typically occurs early, and complete recovery of renal function is expected with adequate volume replacement 3.
If renal function does not improve with fluid resuscitation, consider other causes such as acute tubular necrosis or intrinsic renal disease 1. However, in the context of clear volume depletion from gastrointestinal losses, prerenal azotemia is the most likely diagnosis and should respond to fluid therapy.
Special Considerations for Elderly Patients
Elderly patients are at particular risk for volume depletion due to age-related changes in thirst perception and renal concentrating ability 2. However, they are also at increased risk for fluid overload, necessitating careful monitoring during resuscitation 1, 5.
Consider gastric acid suppression with proton pump inhibitors or H2 blockers if gastric irritation is contributing to persistent nausea 1.
Monitoring Parameters
- Hourly urine output (target >100-150 mL during first 6 hours) 6
- Serial creatinine and BUN measurements every 12-24 hours 1
- Electrolytes (particularly potassium) every 12-24 hours 1
- Clinical signs of volume status (mucous membranes, skin turgor, mental status) 2
- Hemodynamic parameters (blood pressure, heart rate, orthostatic changes) 2