The number of patients who undergo total knee arthroplasty (TKA) and total hip arthroplasty (THA) procedures has significantly increased over the past 2 to 3 decades. As life expectancy in the U.S. increases and medical advances allow patients with preexisting conditions to successfully undergo joint replacements, the demand for these procedures is expected to grow.1 In 2010, the CDC estimated that 719,000 patients underwent TKA procedures and 332,000 patients underwent THA procedures in the U.S.2 Kurtz and colleagues have projected that by 2030 the annual number of TKA procedures will increase to 3.5 million and the number of THA procedures will increase to 572,000.1
Although becoming more prevalent, these procedures are still associated with considerable intra- and postoperative blood loss that may lead to complications and blood transfusions.3 Previous studies have shown that perioperative anemia and red blood cell transfusions are associated with negative outcomes, including increased health care resource utilization; length of hospitalization; pulmonary, septic, wound, or thromboembolic complications; and mortality.4,5
In order to prevent excessive blood loss during TKA and THA procedures, antifibrinolytic agents, such as tranexamic acid, have been used. Tranexamic acid is a synthetic form of lysine that binds to the lysine-binding sites on plasminogen and slows the conversion of plasminogen to plasmin. This interaction inhibits fibrinolysis and theoretically decreases bleeding.6 Because tranexamic acid is an antifibrinolytic, its mechanism of action has raised concerns that it could increase the risk of clotting complications, such as venous thromboembolism and myocardial infarction.7
Several published meta-analyses and systematic reviews have shown that tranexamic acid reduces blood loss in patients undergoing orthopedic surgery. Despite positive results, many study authors have acknowledged limitations in their analyses, such as heterogeneity of study results, small trial size, and varied dosing strategies.3,7-12 There is no FDA-approved tranexamic acid dosing strategy for orthopedic procedures; therefore, its use in TKA and THA procedures is off label. This lack of guidance results in the medication being used at varied doses, timing of doses, and routes of administration with no clear dosing strategy showing the best outcomes.
Tranexamic acid was first used in TKA and THA surgical procedures at the Sioux Falls VA Health Care System (SFVAHCS) in South Dakota in October 2012. The dose used during these procedures was 1 g IV at first surgical incision and 1 g IV at incision closure. The objective of this study was to determine whether this tranexamic acid dosing strategy utilized at SFVAHCS safely improved outcomes related to blood loss.
Methods
A single-center retrospective chart review was performed on all patients who underwent TKA and THA procedures by 4 orthopedic surgeons between January 2010 and August 2015 at SFVAHCS. This study received approval by the local institutional review board and research and development committee in September 2015.
Patients were included in the study if they were aged ≥ 18 years and underwent primary unilateral TKA or THA procedures during the study time frame. Patients were excluded if they underwent bilateral or revision TKA or THA procedures, did not have recorded blood loss measurements during and/or after the procedure, or did not receive tranexamic acid between October 2012 and August 2015 at the standard dosing strategy utilized at SFVAHCS.
Patients who underwent surgery between January 2010 and October 2012 and did not receive tranexamic acid were included in the control groups. The treatment groups contained patients who underwent surgery between October 2012 and August 2015 and received tranexamic acid at the standard SFVAHCS dosing strategy. Patients in the control and treatment groups were divided and compared with patients who underwent the same type of surgery.
The primary endpoint of this study was total blood loss, which included intraoperative and postoperative blood loss. Intraoperative blood loss was measured by a suctioning device that the surgical physician’s assistant used to keep the surgical site clear of bodily fluids. The suctioning device collected blood as well as irrigation fluids used throughout the surgical procedure. The volume of irrigation fluids used during the procedure was subtracted from the total volume collected by the suctioning device to estimate the total blood volume lost during surgery. Sponges and other surgical materials that may have collected blood were not included in the intraoperative blood loss calculation. Postoperative blood loss was collected by a drain that was placed in the surgical site prior to incision closure. The drain collected postoperative blood loss until it was removed 1 day after surgery.
The secondary endpoints for the study were changes in hemoglobin (Hgb) and hematocrit (Hct) from before surgery to after surgery. These changes were calculated by subtracting the lowest measured postoperative Hgb or Hct level within 21 days postsurgery from the closest measured Hgb or Hct level obtained presurgery.
Follow-up appointments were routinely conducted 2 weeks after surgery, so the 21-day time frame would include any laboratory results drawn at these appointments. Other secondary endpoints included the number of patients receiving at least 1 blood transfusion during hospitalization and the number of patients experiencing clotting complications within 30 days of surgery. Postoperative and progress notes were reviewed by a single study investigator in order to record blood transfusions and clotting complications.
All patients who underwent TKA or THA procedures were instructed to stop taking antiplatelet agents 7 days prior to surgery and warfarin 5 days prior to surgery. If patients were determined to be at high risk for thromboembolic complications following warfarin discontinuation, therapeutic doses of low-molecular weight heparin or unfractionated heparin were used as a bridging therapy pre- and postsurgery. Enoxaparin 30 mg twice daily was started the day after surgery in all patients not previously on warfarin therapy prior to surgery to prevent clotting complications. If a patient was on warfarin therapy prior to the procedure but not considered to be at high risk of thromboembolic complications by the surgeon, warfarin was restarted after surgery, and enoxaparin 30 mg twice daily was used until therapeutic international normalized ratio values were obtained. If the patient had ongoing bleeding after the procedure or was determined to be at high risk for bleeding complications, the provider may have delayed anticoagulant use.
Some patients who underwent TKA or THA procedures during the study time frame received periarticular pain injections during surgery. These pain injections included a combination of ropivacaine 200 mg, ketorolac 30 mg, epinephrine 0.5 mg, and clonidine 0.08 mg and were compounded in a sterile mixture with normal saline. Several injections of this mixture were administered into the surgical site to reduce postoperative pain. These periarticular pain injections were first implemented into TKA and THA procedures in August 2012 and were used in patients at the surgeon’s discretion.
Baseline characteristics were analyzed using a chi-square test for categoric variables and an unpaired t test for continuous variables to determine whether any differences were present. Total blood loss, change in Hgb, and change in Hct were analyzed using an unpaired t test. Patients receiving at least 1 blood transfusion during hospitalization and patients experiencing a clotting complication were analyzed using a chi-square test. P values < .05 were considered to indicate statistical significance. Descriptive statistics were calculated using Microsoft Excel (Redmond, WA), and GraphPad Prism (La Jolla, CA) was used for all statistical analyses.
