Micronutrient deficiencies in critically ill patients receiving continuous renal replacement therapy.

Background & Aims: Continuous renal replacement therapy (CRRT) is essential to the management of acute kidney injury (AKI) in critical illness. Unfortunately, large quantities of micronutrients are shown to be lost in CRRT effluent. Current literature describes serum micronutrient values in CRRT patients to be below-reference range, yet seldom compares such values to other critically ill populations unexposed to CRRT. The aim of this study was to describe and compare the prevalence of micronutrient and carnitine deficiencies in critically ill patients at high malnutrition risk exposed to CRRT to a group of patient unexposed to CRRT.

Methods: A retrospective chart review was conducted at Duke University Hospital using the electronic medical record. The study group consisted of patients at high malnutrition risk requiring intensive care unit (ICU) admission from 01/01/2017-12/31/2018 with one or more of the following serum micronutrient levels checked: carnitine, copper, zinc, selenium, and vitamins B1, B6, B9, and C. Micronutrient deficiencies were defined as below the reference range and carnitine deficiencies were interpreted as an acyl to free carnitine ratio (ACFR) of >0.4.

Results: 106 ICU patients met inclusion criteria and 46% were exposed to CRRT. At least one micronutrient deficiency was reported in 90% of CRRT patients compared to 61% patients unexposed to CRRT (p = 0.002). A greater percentage of copper (p < 0.001) and carnitine (p < 0.001) deficiencies were found among patients exposed to CRRT, while more zinc deficiencies were noted among non-CRRT patients (p = 0.001).

Conclusions: The vast majority of CRRT patients presented with micronutrient deficiencies. Clinicians should have a heightened awareness of the risk for serum copper, carnitine, and vitamin B6 deficiencies among CRRT patients. Further prospective and randomized-controlled trials are needed to better define this new category of malnutrition and test supplementation strategies to address and prevent these clinically-relevant deficiencies.