Patient selection: < 16 years of age with acute GI bleeding
Exclusion criteria:
(1) blood transfusion within 24 hours of admission
(2) dehydration
(3) renal disease
(4) hematemesis without hematochezia
(5) melena for >= 3 days prior to hospitalization AND admission hemoglobin < 7.0 g/dL
Theories for rise in BUN with upper GI bleeding:
(1) increased absorption of protein from blood in the small bowel
(2) decreased urinary excretion of BUN into the urine because of hypovolemia
Parameters:
(1) BUN in mg/dL
(2) serum creatinine in mg/dL
BUN to creatinine ratio =
= (serum BUN) / (serum creatinine)
A ratio => 30 was 69% for upper GI bleeding and 98% specific.
A ratio < 30 is seen more often for lower GI bleeding but is not specific.
If the bleeding is from the upper GI tract, then the ratio can help predict the blood loss mass.
predicted change in hemoglobin in g/dL =
= (0.08 * (ratio)) +/- 0.8 g/dL
