A Proposal to Examine the Effects of Two Interventions in Reducing Perioperative Blood Loss among Older Adults Undergoing Total Hip Arthroplasty

Introduction/Background

Total hip arthroplasty (THA) is associated with a substantial amount of intraoperative and postoperative blood loss. It is among the top ten surgeries with the highest incidence of blood product transfusion. As the elderly population continues to rapidly expand, the projected growth in frequency of THA is expected to increase dramatically over the next two decades, thus unveiling innovative ways to reduce morbidity and mortality associated with this target population becomes increasingly important. There are variety of ways used to reduce perioperative blood loss including administration of erythropoetin or tranexamic acid (TXA), using blood salvage, and hemodilution.  Controlled hypotension (CH) with remifentanil infusion is one modality proven in the literature that is effective in controlling intraoperative bleeding in surgeries that are associated with losing large volumes of blood.  Another method used in reducing surgical blood losses is administration of tranexamic acid (TXA), a newer, widely used antifibrinolytic. While these techniques were extensively researched separately, there are limited studies addressing the effects of their combined use.

 Purpose/Hypothesis

We seek to determine if using CH in older adults undergoing THA who are receiving TXA will lead to further reductions in surgical blood loss and transfusion requirements compared to a group receiving normotensive anesthesia (NT) and TXA. To the researchers’ knowledge, no such study has been conducted comparing outcomes using these two techniques (CH + TXA) together against a group only receiving TXA. We hypothesize that the CH + TXA group will have an additive effect at reducing blood losses and frequency of blood transfusion during and after surgery.

Conceptual Framework

The Roy Adaptation Model (RAM) will be used to guide the present study, which highlights the physiologic-physical mode of the model (Fig.1).  In applying the RAM, THA (the external stimuli) causes intraoperative blood loss thus stimulating the regulator to respond physiologically.  By utilizing methods such as controlled hypotension with remifentanil and the use of TXA in an attempt to reduce blood loss created THA, the anesthesia provider could manipulate or control the person’s hemodynamic responses. 

Methods

A randomized controlled study design of 60 males and females between 50-80 years of age, with an American Society of Anesthesiologist physical status I and II, and undergoing unilateral THA.  All subjects with receive total intravenous anesthesia (TIVA) and TXA bolus (15 mg/kg) before incision and continuous infusion (1.0 mg/kg/hr.) during the procedure.  Subjects will be randomly assigned into two groups: the CH group and the normotensive (NT) group. The CH group will received TIVA with remifentanil infusion (0.5 to 3mcg/kg/min) titrated to maintain a mean arterial pressure (MAP) between 50-60mmHg. The NT group will only receive TIVA and their MAP will be maintained above 60mmHg by titration of anesthetic as well as vasopressors. Intraoperative blood loss will be measured in suction canisters, by quantity weight of saturated lap pads and estimation of blood around the surgical area. Postoperative blood loss is will be measured from blood accumulated in any surgical drains. MAP will be continuously monitored and recorded via radial artery catheter transducer. Power analysis was calculated based on number projections from previous studies, a two-tailed t-test of difference between means and between two-study arms with significance level of 0.05 will yield 90% power for N=30 in each group.   

Implications/Summary

Reducing blood loss during surgery is important to improve the hemodynamic stability of the patient, create a better operative field, and decrease the need for transfusions, which is associated with various complications. Hypotensive anesthesia has been widely used to decrease surgical blood loss. Results from this study can be used to promote further research in the use of CH and TXA in older adults undergoing THA, as well as combining methods of decreasing perioperative blood loss. If results reveal better outcomes in the CH+TXA group, the use of both these techniques together may provide nurse anesthesia providers with the best method when faced with the need to reduce blood losses during surgery, thus improving outocme of this target population.