Differences in Kidney Function Estimates Based on Creatinine and/or Cystatin C in Non-Traumatic Amputation Patients and Their Impact on Drug Prescribing

Estimated glomerular filtration rate based on creatinine, cystatin C, β-trace protein and β2 microglobulin in patients undergoing nontraumatic lower extremity amputation

AIMS

The study's aim is to compare current and new equations for estimating glomerular filtration rate (GFR) based on creatinine, cystatin C, β-trace protein (BTP) and β2 microglobulin (B2M) among patients undergoing major amputation.

METHODS

This is a secondary analysis of data from a prospective cohort study investigating patients undergoing nontraumatic lower extremity amputation. Estimated GFR (eGFR) was calculated using equations based on creatinine (eGFRcre[2009] and eGFRcre[2021]), cystatin C (eGFRcys), the combination of creatinine and cystatin C (eGFRcomb[2012] and eGFRcomb[2021]) or a panel of all 4 filtration markers (eGFRpanel). Primary outcome was changed in eGFR across amputation according to each equation. Two case studies of prior amputation with GFR measured by 99mTc-DTPA clearance are described to illustrate the relative accuracies of each eGFR equation.

RESULTS

Analysis of the primary outcome included 29 patients (median age 75 years, 31% female). Amputation was associated with a significant decrease in creatinine concentration (-0.09 mg/dL, P = 0.004), corresponding to a significant increase in eGFRcre[2009] (+6.1 mL/min, P = 0.006) and eGFRcre[2021] (+6.3 mL/min, P = 0.006). Change across amputation was not significant for cystatin C, BTP, B2M or equations incorporating these markers (all P > 0.05). In both case studies, eGFRcre[2021] yielded the largest positive bias, eGFRcys yielded the largest negative bias and eGFRcomb[2012] and eGFRcomb[2021] yielded the smallest absolute bias.

CONCLUSION

Creatinine-based estimates were substantially higher than cystatin C-based estimates before amputation and significantly increased across amputation. Estimates combining creatinine and cystatin were stable across amputation, while the addition of BTP and B2M is unlikely to be clinically relevant.

Novel Damage Biomarkers of Sepsis-Related Acute Kidney Injury

Sepsis-related acute kidney injury (AKI) is one of the most common complications of sepsis at the intensive care unit (ICU) with more adverse mortality rates. The early diagnosis and reliable monitoring of sepsis-related AKI are essential in achieving a favorable outcome. Novel serum and urinary biomarkers could yield valuable information during this process. Regarding the widely used Kidney Disease Improving Global Outcomes (KDIGO) classifications, the diagnosis of AKI is still based on the increase of serum creatinine levels and the decrease of urine output; however, these parameters have limitations in reflecting the extent of kidney damage, therefore more sensitive and specific laboratory biomarkers are needed for the early diagnosis and prognosis of sepsis-related AKI. Regarding this, several serum parameters are discussed in this review including presepsin and the most important actin scavenger proteins (gelsolin, Gc-globulin) while other urinary markers are also examined including cell cycle arrest biomarkers, neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), Cystatin C and actin. Novel biomarkers of sepsis-related AKI could facilitate the early diagnosis and monitoring of sepsis-related AKI.

Polypharmacy, Dosing Trends and Drug-Drug Interaction Patterns Following High-Level Limb Amputation Surgery

OBJECTIVE

To examine peri-operative medication patterns, surrounding major amputation surgeries.

DESIGN

Retrospective chart review of 216 cases of major amputations (transfemoral, hip disarticulation, hemipelvectomy, forequarter) at an academic hospital, examining medications, dosing changes and drug-drug interaction warnings pre- and post-operatively.

RESULTS

Medications increased in 76.9% (166/216), remained the same in 10.6% (23/216), and decreased in 12.5% (27/216) of cases. Average number of medications was 7 pre-operatively and 10 post-operatively. In 189 cases with pre-operative medications present, post-operative dosing remained the same for 74.3%, increased for 9.2%, decreased for 7.6% and was unknown for 8.9% of medications. Increases in each of type C ("monitor therapy"), D ("consider therapy modification) and X ("avoid combination") drug-drug interaction warnings were seen respectively in 59.7%, 62.0% and 5.1% of cases.

CONCLUSION

Polypharmacy is involved pre-operatively and increased post-operatively in most cases of major limb amputation, with agent dosing remaining the same or increased in the majority of cases. Drug-drug interaction warnings also increase. These occur at a time of abrupt changes to the body's size, compartments, and physiologic responses. More research and clinical attention are warranted given anticipated changes in pharmacokinetics and pharmacodynamics.

[Symptom control in heart failure patients - how to handle GFR decrease and hyperkalaemia]

Bei Patienten mit Herzinsuffizienz und reduzierter Ejektionsfraktion wird durch eine optimierte medikamentöse Therapie sowohl die Symptomkontrolle verbessert als auch die Mortalität gesenkt. Eckpfeiler der Herzinsuffizienztherapie sind dabei Medikamente mit Einfluss auf das Renin-Angiotensin-Aldosteron-System, sogenannte RAAS-Inhibitoren. Dieser Artikel stellt einen kardiologisch-nephrologischen Konsens zur praxisorientierten Hilfestellung bei abnehmender glomerulärer Filtrationsrate oder Anstieg des Serum-Kaliumspiegels vor. Dies sind die 2 häufigsten Gründe für eine Dosisreduktion oder das Absetzen von prognoseverbessernden Medikamenten bei Herzinsuffizienzpatienten.

Pharmacokinetic Considerations in Amputees

PURPOSE

The purpose of this article is to review the currently available assessment tools for measuring renal function, body weight, and body surface area in the amputee population.

METHODS

PubMed and Web of Science were searched using the following key terms: amputation, dose adjustment, and estimation of body weight. Articles published in languages other than English were excluded from the search.

RESULTS

Despite the increasing prevalence of amputations, there is little literature available that discusses its impact on the patient and how these physiological changes can affect pharmacokinetics. Very little information is available to guide dose adjustment in this patient population. This article discusses several factors to consider when determining optimum dosing regimens in patients with different levels of amputations.

CONCLUSION

This article will evaluate the applicability of methods mentioned in existing literature for measuring changes in renal function, body weight, and body surface area in amputees.

Cystatin C: A Primer for Pharmacists

Pharmacists are at the forefront of dosing and monitoring medications eliminated by or toxic to the kidney. To evaluate the effectiveness and safety of these medications, accurate measurement of kidney function is paramount. The mainstay of kidney assessment for drug dosing and monitoring is serum creatinine (SCr)-based estimation equations. Yet, SCr has known limitations including its insensitivity to underlying changes in kidney function and the numerous non-kidney factors that are incompletely accounted for in equations to estimate glomerular filtration rate (eGFR). Serum cystatin C (cysC) is a biomarker that can serve as an adjunct or alternative to SCr to evaluate kidney function for drug dosing. Pharmacists must be educated about the strengths and limitations of cysC prior to applying it to medication management. Not all patient populations have been studied and some evaluations demonstrated large variations in the relationship between cysC and GFR. Use of eGFR equations incorporating cysC should be reserved for drug management in scenarios with demonstrated outcomes, including to improve pharmacodynamic target attainment for antibiotics or reduce drug toxicity. This article provides an overview of cysC, discusses evidence around its use in medication dosing and in special populations, and describes practical considerations for application and implementation.