By Paul Kellerman, MD
As many of you have experienced, muscle cramps are a common complication during dialysis treatments. Cramps occur in 1/3 to 2/3 of all dialysis patients. Patients tend to experience cramps in the lower extremities, but they can occur in the hands, arms and abdominal muscles as well.
Although the exact cause is unknown, multiple causes have been proposed, including volume contraction (getting "too dry"), low blood sodium concentration, low body magnesium, and carnitine deficiency. Of these, the first two seem to be the most common. In terms of volume contraction, both getting below your "dry weight" (goal weight at the end of dialysis), as well as rapid removal of large volumes can result in cramps. Low concentrations of sodium in the dialysis bath can also cause cramps by lowering your blood sodium concentration.
Treatment has two components: prevention of cramps from occurring, as well as treatment of cramps when they occur. In terms of prevention, some of these measures are under your control, and some under your care team's control.
What works to prevent cramps?
- Minimize weight gains between dialysis: Simply put, restrict your fluids. The more you take in, the more we have to take off to get to your dry weight. The more taken off, the more likely you will get cramps.
- Assure your proper dry weight: If your blood pressure is low, you have no edema, and you are cramping, you may need to have your dry weight increased. Your nurse and doctor will work with you to get to the proper dry weight.
- Higher dialysate sodium concentration: Sometimes you will hear your nurse or doctor talk about being on a "sodium modeling program" with higher salt in the dialysate. If you are predisposed to cramps, this may help prevent them. Not everyone should be on a program, since the tradeoff of these programs is that you absorb more salt during the procedure, which makes you more thirsty between dialyses, so you tend to drink more fluid and gain more weight (see #1). Also, if your blood pressure tends to run high, the program will only make it that much harder to control your blood pressure to normal levels.
- Carnitine deficiency: If you have lots of cramps, your doctor may wish to measure a carnitine level in your blood. If your level is low, you can be given carnitine pills, which may help to prevent cramps.
- Quinine sulfate: Some of you already use quinine. One small study showed a benefit of quinine taken at the beginning of dialysis to prevent cramps. Because it is a pill that takes time to absorb, it is best if you take it 1-2 hours prior to dialysis. Like all medicines, it can on occasion have side effects, such as deafness, optic nerve problems, and gastrointestinal symptoms.
- Vitamin E: In one study of 29 patients, Vitamin E prevented cramps as well as quinine. There is some recent evidence, though, showing that Vitamin E may increase the chances of heart failure.
What can be done when you get cramps on dialysis?
- Hypertonic saline: In a study of 20 patients with 100 episodes of cramps, hypertonic saline effectively relieved cramps, as did 50% dextrose.
- Mannitol: This has also been shown to be effective for cramps, but we want to avoid giving it at the very end of the dialysis session.
- Massage and moist heat: Sometimes this can provide some comfort.
So in summary, if you have frequent cramps while on dialysis, what do you do? If you gain a lot of fluid, you need to decrease your fluid intake. If you don't have large fluid gains, talk with your doctor about reassessing your dry weight. If adjusting your dry weight does not solve the problem, you may be a candidate for dialysate sodium modeling, carnitine, quinine or Vitamin E.
Above all, we certainly don't want dialysis to "cramp" your lifestyle.