Rapid disappearance of protamine in adults undergoing cardiac operation with cardiopulmonary bypass.
BACKGROUND
Despite long use of protamine in cardiac operations, neither protamine concentrations nor pharmacokinetics have been reported in patients.


METHODS
Twenty-eight patients (age, 26 to 80 years) undergoing various cardiac surgical procedures gave their consent to receive 250 mg of protamine sulfate administered intravenously by an infusion pump during 5 minutes. Protamine was administered at the usual intraoperative time after separation from cardiopulmonary bypass for reversal of heparin. Timed arterial blood samples were obtained after protamine infusion. Blood plasma was subjected to solid-phase extraction and high-performance liquid chromatography. Total (free + heparin-bound) protamine concentration versus time data were subjected to pharmacokinetic modeling.


RESULTS
Twenty-six patients completed the study. Total plasma protamine concentrations declined rapidly. Model-independent pharmacokinetic analysis revealed median (range) values as follows: volume of distribution, 5.4 L (0.82 to 34 L); clearance, 1.4 L/min (0.61 to 3.8 L/min); and half-life, 4.5 min (1.9 to 18 min). Schwarz-Bayesian criterion identified a two-compartment exponential model with adjustment for weight in the central compartment volume of distribution as performing better than other compartmental or Michaelis-Menten models.


CONCLUSIONS
Protamine has a very short (approximately 5 minutes) half-life after a single 250-mg dose in adult patients. This short half-life could underlie recurrent anticoagulation after initial apparent reversal of heparin.
Butterworth
John
J
Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1009, USA. jbutter@wfubmc.edu
Lin
Yonggu A
YA
Prielipp
Richard C
RC
Bennett
Judy
J
Hammon
John W
JW
James
Robert L
RL
D000368:Aged; D002315:Cardiopulmonary Bypass; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006207:Half-Life; D006331:Heart Diseases / Q000097:blood / Q000601:surgery*; D006801:Humans; D007260:Infusion Pumps; D008297:Male; D008657:Metabolic Clearance Rate / Q000502:physiology; D008875:Middle Aged; D011479:Protamines / Q000008:administration & dosage / Q000493:pharmacokinetics*
D011479:Protamines