Impact of CRRT on Serum Carnitine and Micronutrient Levels

Background and Rationale:

Acute Kidney Injury (AKI) is characterized by a sudden loss of glomerular filtration rate and is a major factor increasing mortality and morbidity in hospitalized patients. In critically ill patients, Continuous Renal Replacement Therapy (CRRT) is frequently used to manage metabolic disturbances and fluid overload due to its advantages in hemodynamic stability. However, exposure to the extracorporeal circuit may lead to significant losses of micronutrients, including trace elements (e.g., selenium, zinc, copper) and water-soluble vitamins, which play crucial roles in cellular function and metabolism.

Study Objective:

The primary objective of this prospective study is to investigate the changes in serum and effluent (waste fluid) micronutrient levels in patients undergoing CRRT and to compare these levels with patients who have Stage 2-3 AKI but do not require CRRT.

Methodology and Procedures:

Study Setting and Design This prospective study was conducted in a 36-bed general Intensive Care Unit (ICU) at a tertiary education and research hospital. Patients diagnosed with Acute Kidney Injury (AKI) Stage 2 or 3 according to the KDIGO guidelines were included. Within the first hour of ICU admission, patients were evaluated for Continuous Renal Replacement Therapy (CRRT) requirement and divided into two groups: those receiving CRRT and those not receiving CRRT. The decision to initiate CRRT was made by the attending clinician independent of the study team.

Eligibility Criteria Inclusion criteria were:

Patients aged 18-90 years,Diagnosis of AKI Stage 2 or 3 according to KDIGO,Evaluation for CRRT requirement within the first hour of ICU admission.

Exclusion criteria

included:End-stage renal disease or history of chronic RRT., AKI due to dialyzable toxins,Child-Pugh C liver cirrhosis,Terminal malignancy,AKI secondary to cardiac arrest,High risk of mortality within the first 24 hours,Prior RRT for the current AKI episode,History of kidney transplantation,Prior inclusion in this study,Pregnancy or breastfeeding,Lack of informed consent from the patient or legal representative.

Clinical Data and Sample Collection Demographic data (age, sex), APACHE-II and SOFA scores, BMI, and admission diagnoses were recorded. Routine laboratory parameters including serum albumin, total protein, creatinine, urea, electrolytes, CRP, and blood gas values (pH, bicarbonate, lactate) were measured at the 1st and 24th hours.For micronutrient analysis, blood samples were collected at the 1st hour of ICU admission for all patients. Subsequent sampling was performed at the 24th hour of CRRT for the treatment group and at the 24th hour of ICU stay for the non-CRRT group. Samples were centrifuged at 4000 rpm for 5 minutes and stored at -80°C. Analyzed parameters included:Trace elements: Selenium, zinc, copper, iron.Vitamins: Vitamin B12, Vitamin C, folate.Amino acids: 22 subforms including leucine, isoleucine, valine, and others.Carnitine: Various subforms.CRRT Procedure and Effluent Analysis All CRRT procedures were performed in Continuous Veno-venous Hemodialysis (CVVHD) mode at a dose of 30 mL/kg/hour. An Ultraflux AV1000S polysulfone filter (1.8 m2) was used. Anticoagulation was achieved with unfractionated heparin, and no ultrafiltration was applied during the study period. Dialysate flow rate (Qd) was maintained at 30% of the blood flow rate (Qb) to ensure ideal dialysate saturation, with Qb fixed between 100-140 mL/min.To calculate extracorporeal losses, 20 mL samples were collected from each effluent bag during the 24-hour CRRT period and stored at -80°C. Total loss was calculated by multiplying the concentration in each bag by its total volume. Due to instability under light and room temperature, vitamins (C and B12) were excluded from effluent analysis to avoid confounding results.

Inclusion criteria

• Patients aged 18-90 years
• Diagnosis of AKI Stage 2 or 3 according to KDIGO
• Evaluation for CRRT requirement within the first hour of ICU admission.

Exclusion criteria

• End-stage renal disease or history of chronic RRT
• AKI due to dialyzable toxins,Child-Pugh C liver cirrhosis
• Terminal malignancy,AKI secondary to cardiac arrest
• High risk of mortality within the first 24 hours
• Prior RRT for the current AKI episode,History of kidney transplantation
• Prior inclusion in this study
• Pregnancy or breastfeeding
• Lack of informed consent from the patient or legal representative.