The Effect of Hypotensive Anesthesia on Hemoglobin Levels During Total Knee Arthroplasty

Inclusion Criteria: * Non- inflammatory degenerative joint disease of the knee * Patients scheduled for unilateral primary total Knee arthroplasty * Age between 40 and 80 years * Hypotensive spinal-epidural anesthesia with systolic BP \< 95 and diastolic BP \< 65. * Adequate intraoperative fluid loading: a minimum of 1500 ml IV fluids should be infused during procedure: at least 300 cc/15 minutes. Exclusion Criteria: * Blood coagulopathies resulting in a hypocoagulable state (hemophilia, von Willebrand disease, etc.) * Blood coagulopathies resulting in a hypercoagulable state (factor V leiden, antithrombin III deficiency, protein C deficiency, protein S deficiency) * Patients on anti-coagulants (coumadin, plavix, pradaxa, heparin) * Congestive Heart Failure (at least one medication to treat congestive heart failure) * Coronary artery disease (s/p bypass, stent or AMI) * Kidney insufficiency (creatinine \> 1.5) * Aortic or mitral valve disease * Pulmonary hypertension * Revision Knee Surgery * Inadequate intravenous fluid substitution during the procedure 1.5L during 60 minutes.