A Study of the Appropriate Day and Frequency of Hemoglobin Level Monitoring after Total Knee Arthroplasty
Authors: payapanon payap , Narkbunnam Rapeepat , Pornrattanamaneewong Chaturong , Chareancholvanich Keerati 
Published: September 2024

Background Total knee arthroplasty (TKA) is a commonly performed and successful orthopedic procedure that is increasing in frequency annually. Despite its success, TKA is associated with significant estimated blood loss ranging from 700-1,500 ml as reported in many studies. Postoperative changes in hemoglobin (Hb) and hematocrit (Hct) concentrations can evoke a stress response in patients and may increase morbidity, particularly when Hb levels drop below 8.0 mg/dL even in healthy individuals. While monitoring Hb levels and clinical parameters is standard postoperative care, existing literature lacks a standardized guideline for postoperative blood concentration monitoring. This leading to the question of whether routine postoperative blood concentration monitoring is necessary and what the appropriate timing and frequency for blood collection should be to minimize the frequency of blood collections. Achieving this could reduce the cost of investigations and alleviate the discomfort associated with frequent blood collections. we would like to study whether routine postoperative blood concentration monitoring is necessary and determine the appropriate timing and frequency for blood collection postoperatively to minimize the frequency of blood collection in patients and reduce the cost of investigations and the pain associated with blood collection.Methods A total of 203 patients (167 females and 36 males) undergoing unilateral TKA, and 130 patients (110 females and 20 males) undergoing simultaneous bilateral TKA were enrolled in a prospective observational study. All patients received tranexamic acid and underwent tourniquet use during the procedures. Preoperative Hb levels were obtained from each patient, and subsequent measurements were taken at 24 and 48 hours postoperatively with the aim of establishing a correlation between preoperative and postoperative Hb levels and blood transfusion rates. Patient was collected Hb pre-operatively and 24 hour and 48 hour post-operatively to find a correlation between pre- and post-operative of hemoglobin level and blood transfusion rate. In additional to find a correlation between patient characteristics and blood transfusion. According to blood transfusion protocol, blood was transfused when Hb level < 8.0 or patient had anemic symptoms.Results The mean difference in Hb levels between preoperative and 24 hours postoperative was 2.1 (± 1.0) g/dL in unilateral TKA and 2.78 (± 1.16) g/dL in bilateral TKA. The most significant decrease in Hb levels was observed at 24 hours postoperative compared to the previous day. The overall blood transfusion rate was 6.4% (13/203 patients) in unilateral TKA and 37.6% (49/130) in bilateral TKA. From the results, in unilateral TKA patients with hemoglobin levels of 13.1 (± 1.3) g/dL and 12.99 (± 1.13) g/dL in bilateral TKA, no blood transfusions were administered. The first-day blood transfusion rate was 46% in unilateral TKA and 48.9% in bilateral TKA groups.Conclusion Our study indicates that routine postoperative Hb level monitoring should be conducted at 24 hours postoperative for most cases, except for patients undergoing unilateral TKA with a preoperative Hb level exceeding 14 g/dL. For simultaneous bilateral TKA, monitoring should be extended to 48 hours postoperative if Hb levels at 24 hours postoperative fall below 10.58 (± 1.07) g/dL. This tailored monitoring approach aims to mitigate anemia symptoms that could impact the recovery process of the patients undergoing these procedures.