Treatment of Vomiting with Elevated BUN (Prerenal Azotemia)

Immediate Fluid Resuscitation

Administer 0.9% normal saline 1 liter IV over the first hour to rapidly restore intravascular volume and reverse prerenal azotemia, as recommended by the Journal of Internal Medicine and MMWR Recommendations and Reports 1, 2
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, according to the Journal of Internal Medicine 1
Strict monitoring of fluid intake and output is necessary to assess response and prevent complications, as stated by MMWR Recommendations and Reports 2

Ondansetron can be administered intravenously over 2-5 minutes and repeated every 4-6 hours as needed, with alternative agents including metoclopramide 10 mg IV or prochlorperazine 5-10 mg IV every 6-8 hours if ondansetron is unavailable, as suggested by Praxis Medical Insights 3

Draw blood for serum electrolytes (Na, K), creatinine, BUN, and glucose before initiating therapy, as recommended by the Journal of Internal Medicine 1
Check and correct electrolyte abnormalities, particularly hypokalemia and metabolic alkalosis that commonly develop with protracted vomiting, according to the Journal of Internal Medicine 1

If oliguria persists despite initial fluid resuscitation, consider a fluid challenge followed by furosemide to differentiate acute tubular necrosis from prerenal causes, as stated by MMWR Recommendations and Reports 2
Reassess antiemetic efficacy after 24 hours and adjust therapy as needed, as suggested by Praxis Medical Insights 3

Do not delay fluid resuscitation while waiting for laboratory results—the clinical presentation of vomiting with elevated BUN mandates immediate IV fluid therapy, as recommended by the Journal of Internal Medicine and MMWR Recommendations and Reports 1, 2
Avoid using oral medications when vomiting is active, as the oral route is not feasible, as suggested by Praxis Medical Insights 3
Do not overlook the underlying cause of vomiting that may require specific treatment beyond supportive care, as stated by the World Journal of Emergency Surgery 4

If renal function does not improve with fluid resuscitation, consider other causes such as acute tubular necrosis or intrinsic renal disease, as stated by MMWR Recommendations and Reports 2
Consider gastric acid suppression with proton pump inhibitors or H2 blockers if gastric irritation is contributing to persistent nausea, as suggested by Praxis Medical Insights 5