Summary
Lower rates of deep vein thrombosis have been noted following total hip replacement
under epidural anesthesia in patients receiving exogenous epinephrine throughout surgery.
To determine whether this is due to enhanced fibrinolysis or to circulatory effects
of epinephrine, 30 patients scheduled for primary total hip replacement under epidural
anesthesia were randomly assigned to receive intravenous infusions of either low dose
epinephrine or phenylephrine intraoperatively. All patients received lumbar epidural
anesthesia with induced hypotension and were monitored with radial artery and pulmonary
artery catheters.
Patients receiving low dose epinephrine infusion had maintenance of heart rate and
cardiac index whereas both heart rate and cardiac index declined significantly throughout
surgery in patients receiving phenylephrine (p = 0.0001 and p = 0.0001, respectively). Tissue plasminogen activator (t-PA) activity increased significantly
during surgery (p <0.0005) and declined below baseline postoperatively (p <0.005) in both groups. Low dose epinephrine was not associated with any additional
augmentation of fibrinolytic activity perioperatively. There were no significant differences
in changes in D-Dimer, t-PA antigen, α2-plasmin inhibitor-plasmin complexes or thrombin-antithrombin III complexes perioperatively
between groups receiving low dose epinephrine or phenylephrine. The reduction in deep
vein thrombosis rate with low dose epinephrine is more likely mediated by a circulatory
mechanism than by augmentation of fibrinolysis.
