Carnitine deficiency in chronic critical illness.
OBJECTIVE
New insight in mitochondrial physiology has highlighted the importance of mitochondrial dysfunction in the metabolic and neuroendocrine changes observed in patients presenting with chronic critical illness. This review highlights specifically the importance of carnitine status in this particular patient population and its impact on beta-oxidation and mitochondrial function.


RESULTS
The main function of carnitine is long chain fatty acid esterification and transport through the mitochondrial membrane. Carnitine depletion should be suspected in critically ill patients with risk factors such as prolonged continuous renal replacement therapy or chronic parenteral nutrition, and evidence of beta-oxidation impairments such as inappropriate hypertriglyceridemia or hyperlactatemia. When fatty acid oxidation is impaired, acyl-CoAs accumulate and deplete the CoA intramitochondrial pool, hence causing a generalized mitochondrial dysfunction and multiorgan failure, with clinical consequences such as muscle weakness, rhabdomyolysis, cardiomyopathy, arrhythmia or sudden death. In such situations, carnitine plasma levels should be measured along with a complete assessment of plasma amino acid, plasma acylcarnitines and urinary organic acid analysis. Supplementation should be initiated if below normal levels (20 μmol/l) of carnitine are observed. In the absence of current guidelines, we recommend an initial supplementation of 0.5-1 g/day.


CONCLUSIONS
Metabolic modifications associated with chronic critical illness are just being explored. Carnitine deficiency in critically ill patients is one aspect of these profound and complex changes associated with prolonged stay in ICU. It is readily measurable in the plasma and can easily be substituted if needed, although guidelines are currently missing.
aCenter for Molecular Diseases, Lausanne University Hospital bAdult Intensive Care & Burns, Lausanne University Hospital, Lausanne, Switzerland cDivision of Endocrinology, Diabetes, and Bone Disease, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Luisa
L
Bonafé
Mette M
MM
Berger
Yok Ai
YA
Que
Jeffrey I
JI
Mechanick
D009202:Cardiomyopathies / Q000097:blood / Q000517:prevention & control; D002331:Carnitine / Q000097:blood / Q000172:deficiency*; D002908:Chronic Disease; D016638:Critical Illness / Q000628:therapy; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D022124:Hyperammonemia / Q000097:blood / Q000517:prevention & control; D008928:Mitochondria / Q000378:metabolism*; D009135:Muscular Diseases / Q000097:blood / Q000517:prevention & control
D005227:Fatty Acids; D002331:Carnitine