During the bleed, there will be sympathetic mediated vasoconstriction and also hemostasis (platelet plug).

It has been demonstrated in an acidic environment (6.0 compared physiological pH 7.4), there is a 2-4 fold prolongation of prothrombin time, aPTT, and thrombin time.

Thus, in an acidic environment, the coagulation cascade and platelet aggregation are inhibited and disaggregation of stable platelet plugs occurs.

In addition, pepsinogen is converted to pepsin under acidic conditions. Pepsin can lyse the blood clots that plug vessels in the ulcer base and induce re-bleeding thereafter.


  1. Green F., Kaplan M., Curtis L., Levine P.. Effect of acid and pepsin on blood coagulation and platelet aggregation. A possible contributor prolonged gastroduodenal mucosal hemorrhage. Gastroenterology. 1978;74:38–43.
  2. Low J., Dodds A., Biggs J. Fibrinolytic activity of gastroduodenal secretions–a possible role in upper gastrointestinal haemorrhage. Thromb Res. 1980;17:819–830
  3. Leontiadis GI, Sharma VK, Howden CW. Proton pump inhibitor treatment for acute peptic ulcer bleeding. Cochrane Database Syst Rev. 2006:CD002094.
  4. Lin HJ. Role of proton pump inhibitors in the management of peptic ulcer bleeding. World Journal of Gastrointestinal Pharmacology and Therapeutics. 2010;1(2):51-53. doi:10.4292/wjgpt.v1.i2.51.
  5. Lau JY, Sung JJ, Lee KK, Yung MY, Wong SK, Wu JC, Chan FK, Ng EK, You JH, Lee CW, et al. Effect of intravenous omeprazole on recurrent bleeding after endoscopic treatment of bleeding peptic ulcers. N Engl J Med. 2000;B:310–316.


Extensive bleeding from the upper gastrointestinal (GI) tract will cause an increase in Urea (BUN).

HOW? Blood is full of proteins (i.e Hemeglobin, Immunoglobins) which are absorbed in the GI tract. Since it is an upper GI bleed (above the ligament of treitz) there is time for adequate absorption.

  • Blood Urea Nitrogen (BUN) reflects the end product of the metabolic breakdown of protein
  • Hence when there is bleeding => protein breakdown & absorption => increase in Urea

*It is often debated that a GI bleed (if severe enough) can also result in hypovolemia -> causing prerenal azotemia and raise the BUN

NOTE: Cannot be utilized in the setting of diuretics or CKD


  1. Witting MD, Magder L, Heins AE, Mattu A, Granja CA, Baumgarten M (May 2006). “ED predictors of upper gastrointestinal tract bleeding in patients without hematemesis”. Am J Emerg Med 24 (3): 280–5. doi:10.1016/j.ajem.2005.11.005. .