With Focus on Cost Cutting, Post-Op Labs Not Needed After Knee Replacement

Routine postoperative laboratory testing is not necessary for low-risk patients having elective total knee arthroplasty (TKA), according to a study published Jan. 18 in the Journal of Clinical Orthopaedics and Trauma. The authors say targeted postoperative testing should be guided by patient risk factors.

"With joint replacement procedures already making up the largest proportion of inpatient surgical procedures for Medicare beneficiaries and with the demand expected to increase several folds by 2030, it is of vital importance to look for opportunities to curb unnecessary costs and resource utilization," write the authors led by Mohamad Halawi, from University of Connecticut Health Center in Farmington. "With expansion of the bundled payment models, there may exist an opportunity to cut overall costs while maintaining quality of care by eliminating unnecessary interventions."

The researchers retrospectively reviewed charts for 319 patients who underwent TKAs at a single institution (Jan. 1, 2015, through and July 15, 2017). Pre- and post-operative laboratory values for hemoglobin, hematocrit, sodium, potassium, and creatinine were available for all patients and outcomes were assessed for rates of acute blood loss anemia requiring transfusion, acute kidney injury (AKI), electrolyte abnormalities, and 90-day emergency department visits and readmissions. Additionally, the researchers sought to identify risk factors among patients with abnormal postoperative laboratory values.

Analysis showed that just over one-fourth of patients (27.9 percent) had abnormal postoperative laboratory results. However, the vast majority of patients with abnormal results (78 percent) were due to electrolyte (sodium or potassium) abnormalities. The rate of AKI was 3.8 percent and 1 percent for blood transfusion.

Abnormal baseline electrolyte levels and preoperative anemia were significantly associated with postoperative electrolyte abnormalities. Need for blood transfusion was associated with were American Society of Anesthesiologist Physical Status Classification (ASA) score, preoperative anemia, and no tranexamic acid use during surgery, while AKI was associated with chronic kidney disease, as well as a combination of older age, higher body mass index, ASA score, diabetes, heart disease and/or anemia.

There was no increased risk for 90-days emergency department visits or readmissions associated with abnormal laboratory values and for most patients (95.6 percent) laboratory results did not change the course of care.

"With increasing pressure for cost containment in an era of bundled payment models, the very low rate of laboratory associated interventions suggest that routine postoperative laboratory tests is not justified," write the authors. "A strategy aimed at preventing complications combined with good patient history and clinical examination cannot be overemphasized and it should be used to guide laboratory testing."

Takeaway: In an era of cost containment, routine postoperative laboratory testing provides little clinical value for low-risk patients undergoing TKA.