Wednesday June 27, 2007
Heparin rebound phenomenon
Heparin rebound phenomenon, is considered to be a contributive factor in excessive postoperative bleeding after cardiac surgery. It is due to the reappearance of anticoagulant activity despite adequate neutralization with protamine.This phenomenon is well known since atleast last 45 years 1.
The underlying etiology is due to the fact that a significant amount of heparin remains bound to plasma proteins and escape neutralization by protamine. Later this heparin get released and may contribute to excessive postoperative bleeding after cardiac surgery. Though logically, the treatment is more administration of prtoamine but caution should be taken as high and inappropriate protamine dose may lead to 'acute' pulmonary hypertension 2 and interestingly failed to show decrease in blood product adminstration 3 or any difference in the thrombelastographic profiles or coagulation screen (PT, PTT, ACT and platelets) 2. Also life threatening protamine reactions is another risk need to be considered 5.
Note: This Heparin rebound phenomenon is different from Rebound increase in Thrombin Generation and Activity after cessation of intravenous heparin in patients with acute coronary syndromes which is also often referred as heparin rebound phenomenon 4.
References: click to get abstract/article
1. Heparin rebound phenomenon in extracorporeal circulation - Surg Gynecol Obstet.1962 Aug;115:191-8.
2. Heparin rebound phenomenon--much ado about nothing? - Blood Coagul Fibrinolysis. 1992 Apr;3(2):187-91.
3. Can extra protamine eliminate heparin rebound following cardiopulmonary bypass surgery? - J Thorac Cardiovasc Surg 2004;128:211-219
4. Rebound Increase in Thrombin Generation and Activity After Cessation of Intravenous Heparin in Patients With Acute Coronary Syndromes - Circulation. 1995;91:1929-1935.
5. Life Threatening Protamine Reactions In Cardiac Surgery: Literature Review With A Case Report - The Internet Journal of Thoracic and Cardiovascular Surgery. 2005. Volume 7 Number 1
