Abnormal carnitine concentrations in critical illness associated with compromised outcome

Area of Science:

• Biochemistry
• Critical Care Medicine
• Nutritional Science

Background:

• Carnitine plays a vital role in mitochondrial function and muscle energy metabolism.
• The impact of carnitine levels on outcomes in critically ill patients is not well understood.
• Investigating plasma free carnitine concentrations in prolonged critical illness is crucial.

Purpose of the Study:

• To examine the association between plasma free carnitine concentrations and patient outcomes during prolonged critical illness.
• To determine if abnormal carnitine levels predict recovery and survival in the ICU.

Main Methods:

• Secondary analysis of the EPaNIC randomized controlled trial involving 1600 patients.
• Plasma free carnitine concentrations measured on ICU-day-6.
• Cox proportional hazards models and logistic regression used to analyze associations with ICU discharge, morbidity, and mortality.

Main Results:

• Higher plasma free carnitine concentrations were surprisingly associated with a lower likelihood of earlier ICU discharge.
• Both very low (<24 µmol/L) and very high (>50 µmol/L) carnitine levels were linked to delayed ICU/hospital recovery, prolonged need for life support, and increased 90-day mortality.
• High carnitine levels (>50 µmol/L) also correlated with muscle weakness and increased long-term mortality.

Conclusions:

• On ICU-day-6, both low and high plasma free carnitine concentrations are associated with delayed recovery and increased morbidity and mortality.
• A U-shaped relationship exists between plasma free carnitine levels and outcomes in critically ill patients.
• Carnitine homeostasis is critical for optimal recovery during critical illness.