NKF K/DOQI GUIDELINES 2000
The use of L-carnitine in MD patients is attractive on the theoretical level, because it is well known that patients undergoing MD usually have low serum free L-carnitine concentrations and that skeletal muscle carnitine is sometimes decreased. Because L-carnitine is known to be an essential co-factor in fatty acid and energy metabolism, and patients on dialysis tend to be malnourished, it might follow that repletion of L-carnitine by the intravenous or oral route could improve nutritional status, particularly among patients with low dietary L-carnitine intakes. L-carnitine has been proposed as a treatment for a variety of metabolic abnormalities in ESRD, including hypertriglyceridemia, hypercholesterolemia, and anemia. It has also been proposed as a treatment for several symptoms or complications of dialysis, including intradialytic arrhythmias and hypotension, low cardiac output, interdialytic and post-dialytic symptoms of malaise or asthenia, general weakness or fatigue, skeletal muscle cramps, and decreased exercise capacity or low peak oxygen consumption. Studies using L-carnitine for each of these potential indications were reviewed. Randomized clinical trials were given particular consideration, although the evidence was not restricted to these studies, many of which are summarized in Appendix X.
There was complete agreement that there is insufficient evidence to support the routine use of L-carnitine for MD patients. In selected individuals who manifest the above symptoms or disorders and who have not responded adequately to standard therapies, a trial of L-carnitine may be considered. In reaching these conclusions, we considered the strength of available evidence as well as the alternative therapies available for each potential indication.
1. Additional clinical trials in the area of erythropoietin-resistant anemia, carefully accounting for anticipated differences in response based on factors such as iron stores and the level of inflammatory mediators.
2. Further definition of the L-carnitine response by taking an "outcomes" approach to patients treated with L-carnitine. Can patient subgroups be identified who are likely to respond to L-carnitine for one or more of its proposed indications? Are certain individuals uniform "responders" across indications (a "carnitine-deficient" phenotype) or do certain patient characteristics predict specific responses?
3. A randomized clinical trial of L-carnitine in MD patients with cardiomyopathy and reduced ejection fraction.
4. A randomized clinical trial of L-carnitine for the treatment of hyperlipidemia, restricted to patients with preexisting hyperlipidemia.
The constant used in this last equation (0.029 kg/mg/24 h) was derived from individuals without renal disease234 and should be reevaluated for ESRD patients; at least one study suggests that this constant is also applicable for MD patients.232 Skeletal or cardiac muscle protein intake as well as total protein intake can affect the creatinine index,235,236 and marked variations in these nutrients may therefore have major effects on the creatinine index. Thus, until the relationships between total protein intake and muscle intake and the creatinine index are well defined for ESRD patients, some caution must be exercised in interpreting the creatinine index, particularly if the diet of the individual in question is particularly high or low in these nutrients.