Blood Volume Analysis of Total Hip Arthroplasty Patients Under Hypotensive Anesthesia

Blood Volume Analysis of Total Hip Arthroplasty Patients Under Hypotensive Anesthesia

Hypotensive Anesthesia is a type of regional anesthesia performed routinely at our hospital. This type of anesthesia reduces the average arterial pressure. Benefits include reduced bleeding and lower risk of blood clots.

The purpose of this study is to determine the effect of intravenous fluids administered with hypotensive anesthesia on your blood volume. With this parameter we will be able to understand how much of your blood is lost because of bleeding and how much of the drop is related to dilution.

Study hypothesis: Hemodilution associated with intravenous fluid substitution during hypotensive anesthesia results in decreased postoperative hemoglobin (Hb) levels

Recent technology allows the measurement of patients' total blood volume with 98% accuracy within 90 minutes or less. This is key to understanding the effect of hypotensive anesthesia on patients undergoing total hip arthroplasty. The drop in blood pressure enhances the dilutional effect of intravenous fluid given during the procedure. Increases in TBV could result in decreases of postoperative hemoglobin. Understanding the effect of hypotensive anesthesia on postoperative hemoglobin levels and TBV will enhance our understanding of postoperative blood management and transfusion triggers.

Inclusion Criteria:

• Non- inflammatory degenerative joint disease of the hip
• Patients scheduled for unilateral primary total hip arthroplasty
• Age between 50 and 75 years
• Hypotensive Spinal-epidural anesthesia with systolic BP < 95 and diastolic BP < 65.
• Adequate intraoperative fluid loading: a minimum of 3 L within 6 hours of surgery

Exclusion Criteria:

• Pregnant women or nursing mothers.
• Women of childbearing potential not using adequate birth control methods
• Known hypersensitivity to I-131 albumin or any other component of the Volumex injection kit
• 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 Hip Surgery
• Inadequate intravenous fluid substitution within the first 6 hrs (<3 liters)
• Inadequate hypotensive anesthesia (mean arterial pressure above 65 for more than 33% of the surgical time