What is the treatment for a patient with impaired renal function and vomiting?

Treatment of Vomiting with Elevated BUN (Prerenal Azotemia)

Aggressive intravenous fluid resuscitation with isotonic saline is the cornerstone of treatment, starting with 1 liter over the first hour, followed by continued IV fluids at a slower rate for 24-48 hours to correct the prerenal renal failure caused by volume depletion from vomiting. 1

Immediate Fluid Resuscitation

• Administer 0.9% normal saline 1 liter IV over the first hour to rapidly restore intravascular volume and reverse prerenal azotemia 1
• Continue isotonic saline infusion at a slower rate for the following 24-48 hours with frequent hemodynamic monitoring and measurement of serum electrolytes to avoid fluid overload 1
• Strict monitoring of fluid intake and output is necessary to assess response and prevent complications 1
• The elevated BUN (35 mg/dL) with vomiting indicates prerenal renal failure from dehydration, which is reversible with adequate fluid replacement 2, 3

Antiemetic Therapy

Ondansetron 8 mg IV is the first-line antiemetic for controlling vomiting in this setting, as it is approximately twice as effective as metoclopramide for uremia-associated nausea and vomiting 4

• Ondansetron can be administered intravenously over 2-5 minutes and repeated every 4-6 hours as needed 5, 6
• Alternative agents include metoclopramide 10 mg IV or prochlorperazine 5-10 mg IV every 6-8 hours if ondansetron is unavailable 5, 4
• Promethazine 12.5-25 mg IV/PO/PR every 4-6 hours is a second-line option, though caution is advised due to CNS depression and anticholinergic effects 5

Electrolyte Management

• Draw blood 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, 2
• Potassium chloride supplementation may be needed in IV fluids once urine output is established 2

Monitoring and Reassessment

• Monitor serum creatinine and BUN to confirm improvement in renal function with fluid resuscitation 2, 3
• If oliguria persists despite initial fluid resuscitation, consider a fluid challenge followed by furosemide to differentiate acute tubular necrosis from prerenal causes 1
• Reassess antiemetic efficacy after 24 hours and adjust therapy as needed 5

Critical Pitfalls to Avoid

• Do not delay fluid resuscitation while waiting for laboratory results—the clinical presentation of vomiting with elevated BUN mandates immediate IV fluid therapy 1
• Avoid using oral medications when vomiting is active, as the oral route is not feasible 5
• Do not overlook the underlying cause of vomiting (gastritis, bowel obstruction, metabolic causes) that may require specific treatment beyond supportive care 1, 2
• Recognize that latent renal insufficiency combined with dehydration from vomiting can cause rapid deterioration of renal function, making aggressive early treatment essential 2

Special Considerations

• If renal function does not improve with fluid resuscitation, consider other causes such as acute tubular necrosis or intrinsic renal disease 1, 7
• Patients with recurrent vomiting may develop chronic interstitial nephritis and may not fully recover baseline renal function even after resolution of the acute episode 2
• Consider gastric acid suppression with proton pump inhibitors or H2 blockers if gastric irritation is contributing to persistent nausea 8