The Utility of Obtaining a Complete Blood Count After Total Knee Arthroplasty in the Era of Tranexamic Acid

J-shaped association of operation duration and blood transfusion risk in patients undergoing primary total knee arthroplasty

PURPOSE

Blood transfusion is a common perioperative complication of primary total knee arthroplasty (TKA) that can lead to adverse outcomes, prolonged hospital stays, and increased medical costs. The purpose of our study was to explore the risk factors for blood transfusion and to establish whether operation duration is independently related to blood transfusion risk in patients undergoing primary TKA after adjusting for other covariates.

METHODS

This was a secondary analysis of data from a retrospective cohort study involving patients who underwent primary TKA in Singapore. The patients' baseline data, comorbidity, and surgical characteristics were collected. The independent variable was operation duration and the dependent variable was blood transfusion events. Patients were divided into three groups according to operation durations (90 and 120 min). Univariate logistic regression was used to explore the risk factors associated with blood transfusion after primary TKA. Multivariate analysis was used to assess the independent effect of operation duration on blood transfusion risk after adjusting for other covariates. Additionally, we performed subgroup analyses to identify specific groups, test the robustness of the relationships, and explore whether there were interactions between the different variables. Furthermore, restricted cubic splines (RCS) were used to identify the relationship between the two variables.

RESULTS

A total of 2,562 patients were included in the study, of whom 136 (5.61%) had a transfusion event. Operation durations were 95.55 ± 36.93 and 83.86 ± 26.29 min for blood transfused and non-transfused patients, respectively. Univariate logistic regression analysis showed that age, BMI, ASA status, Hb level, OSA, CHF, creatinine level > 2 mg/dL, and anaesthesia type were risk factors for blood transfusion. After adjusting for all covariates, multivariate logistic regression models showed that operation duration was positively associated with blood transfusion risk (odds ratio [OR] = 1.87, 95% CI = 1.174-2.933, P = 0.007). Compared to patients with an operation duration of less than 90 min, those with an operation duration of more than 120 min had a 2.141-fold increased risk of blood transfusion (OR = 2.141, 95% CI = 1.035-4.265, P = 0.035). Stratified analysis results showed that the association persisted in patients aged > 50 years, Chinese, BMI > 30 kg/m 2, Hb level > 11 g/dL, ASA status levels 2 and 3, general anaesthesia, and unilateral primary TKA. A non-linear (P-non-linear = 0.30) and J-shaped relationship was identified. The risk of transfusion increased as the operation duration decreased or exceeded the inflection point (73.2 min).

CONCLUSION

Our study demonstrated a non-linear and J-shaped relationship between operation duration and blood transfusion events in patients undergoing primary TKA. Blood transfusion risk was the lowest when the operation duration was 73.2 min. A shorter operation duration implies irregular surgical procedures and incomplete intraoperative haemostasis, leading to increased perioperative blood loss and blood transfusion. These results will be useful for clinical decision-making.

Risk factors for blood transfusion and postoperative anaemia following total knee arthroplasty

Aims

Blood transfusion and postoperative anaemia are complications of total knee arthroplasty (TKA) that are associated with substantial healthcare costs, morbidity, and mortality. There are few data from large datasets on the risk factors for these complications.

Methods

We retrospectively reviewed the records of TKA patients from a single tertiary care institution from February 2016 to December 2020. There were a total of 14,901 patients in this cohort with a mean age of 67.9 years (SD 9.2), and 5,575 patients (37.4%) were male. Outcomes included perioperative blood transfusion and postoperative anaemia, defined a priori as haemoglobin level < 10 g/dl measured on the first day postoperatively. In order to establish a preoperative haemoglobin cutoff, we investigated a preoperative haemoglobin level that would limit transfusion likelihood to ≤ 1% (13 g/dl) and postoperative anaemia likelihood to 4.1%. Risk factors were assessed through multivariable Poisson regression modelling with robust error variance.

Results

In multivariable analyses, each gram of tranexamic acid reduced transfusion likelihood by 39% (adjusted risk ratio (ARR) 0.61 (95% confidence interval (CI) 0.47 to 0.78)). Risk factors associated with an increased risk of transfusion included operating time (ARR 2.07 (95% CI 1.54 to 2.77)) and drain use (ARR 1.73 (95% CI 1.34 to 2.24)).

Conclusion

In this study, we found that increased tranexamic acid dosing, decreased operating time, and decreased drain use may reduce transfusions following TKA. We also established a single preoperative haemoglobin cutoff of 13 g/dl that could help minimize transfusions and reduce postoperative complete blood counts.

Choosing which in-hospital laboratory tests to target for intervention: a scoping review

INTRODUCTION

Some laboratory testing practices may be of low value, leading to wasted resources and potential patient harm. Our scoping review investigated factors and processes that developers report using to inform decisions about what tests to target for practice improvement.

METHODS

We searched Medline on May 30th, 2019 and June 28th, 2021 and included guidelines, recommendation statements, or empirical studies related to test ordering practices. Studies were included if they were conducted in a tertiary care setting, reported making a choice about a specific test requiring intervention, and reported at least one factor informing that choice. We extracted descriptive details, tests chosen, processes used to make the choice, and factors guiding test choice.

RESULTS

From 114 eligible studies, we identified 30 factors related to test choice including clinical value, cost, prevalence of test, quality of test, and actionability of test results. We identified nine different processes used to inform decisions regarding where to spend intervention resources.

CONCLUSIONS

Intervention developers face difficult choices when deciding where to put scarce resources intended to improve test utilization. Factors and processes identified here can be used to inform a framework to help intervention developers make choices relevant to improving testing practices.

Predicting Postoperative Anemia and Blood Transfusion Following Total Knee Arthroplasty

BACKGROUND

While transfusion and clinically relevant anemia after elective primary total knee arthroplasty (TKA) are uncommon, there remains a question of who needs postoperative hemoglobin monitoring, especially in the setting of increasing incidence of outpatient TKA. The purpose of this study was to create predictive models for postoperative anemia and blood transfusion to guide clinical decision-making.

METHODS

The records of consecutive TKA patients were reviewed from February 2016 to December 2020 at a single institution. Two multivariable logistic regression models, for postoperative anemia (hemoglobin < 10 g/dL) and allogeneic blood transfusion included 8 variables: age, sex, body mass index, preoperative hemoglobin level, tranexamic acid total dose, American Society of Anesthesiologists level, operative time, and drain use. Model performance was assessed using accuracy, area under the curve (AUC), sensitivity, and specificity.

RESULTS

The records of 14,901 patients were included in this study. Patients had a mean (± standard deviation) age of 67.9 ± 9.2 years and mean body mass index of 31.3 ± 6.5 kg/m². The postoperative anemia model had an accuracy of 88% (95% confidence interval [CI], 87%-89%) and AUC of 0.88 (95% CI, 0.87-0.89). The blood transfusion model had an accuracy of 97% (95% CI, 96%-97%) and AUC of 0.90 (95% CI, 0.87-0.93).

CONCLUSION

The postoperative anemia and blood transfusion model accurately predicted each outcome. Patients with less than a 5% probability of postoperative anemia may not benefit from a complete blood count at postoperative day 1. Application of these criteria may save the healthcare system hundreds of millions of dollars.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.