The current study investigates the effect of hypotensive anesthesia on patient hemoglobin levels during primary total knee arthroplasty. Considering that because of the tourniquet there is no blood loss during the first 60 minutes of the procedure changes in hemoglobin during the first 60 minutes should be primarily related to decrease in blood pressure and secondary to fluid loading during hypotensive anesthesia.

The specific aim of this prospective study is to collect serial hemoglobin levels intraoperatively during hypotensive anesthesia to evaluate if intraoperative intravenous fluid substitution will change hemoglobin levels during the time the tourniquet is inflated (no blood loss).

The combination of vasodilation during hypotensive anesthesia and fluid substitution will result in decrease of hemoglobin levels during the tourniquet time.

Tubes of 5cc to measure hemoglobin and hematocrit levels preoperatively, prior to inflation of the tourniquet, 15 minutes, 30 minutes, 45 minutes and 60 minutes after tourniquet inflation and in PACU as well as POD 1.

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.

All patients scheduled for primary total knee arthroplasty who meet the qualifications will be consented prior to the surgery.

Data

2 days following surgery