SUMMARY ON HD RELATED CRAMPS

Renal Pro Discussion Forum Summary on HD related cramps- Dr Elisabeth Linsay, Renalpro Moderator

How often do haemodialysis patients in your unit get cramps?

The RenalPro e-mail discussion on the management of HD related cramps recently came to a close. As part of the discussion a survey was carried out which brought 42 complete responses from 17 countries. This showed that in most units patients report cramps occasionally, but there are some where patients rarely or never report cramps and others where cramps are frequently reported. The survey didn’t show any obvious difference in practice between units where cramps are rare and those where they are frequent.

The most likely cause of cramps is poor blood flow to the affected area, which could be due to dehydration, inadequate refilling or cardiac output, or simply sitting still for four hours. Electrolyte imbalances can cause cramping, but low potassium can be ruled out by checking the post-dialysis levels and, with most dialysate compositions, other electrolytes should be normalised during treatment. With regards to poor blood flow, dehydration can easily be resolved by increasing the target weight and a review of target weight is the usual response to cramping. Units use a range of tactics to help the patient maintain sufficient blood volume by reducing the UF rate throughout the whole session (lower fluid gains, longer or more frequent sessions) or at when refilling is reduced (UF profiling and biofeedback).

Jean-Yves from Belgium said he doesn’t see dialysis-induced cramps as often as in the past and that the patients who do experience cramp are typically those who have a long history of high interdialytic fluid gains. He is convinced that ‘over time poor compliance to fluid restriction results in heart decompensation and, often in combination with vascular stiffness, leads to severe hypotension during dialysis sessions and finally cramps due to poor oxygenation of muscles’. J-Y added that one solution is to go to more frequent or longer sessions, but the patients often don’t want to.’

Traditional sodium profiling (or eating something salty pre-dialysis) seems unlikely to help prevent cramps as it promotes refilling early in the session, though it might work if you start with a low level and increase the dialysate sodium at the end.

Andre, from Belgium, warned that we can’t be sure what the sodium level in the dialysate really is. He measured the actual sodium level produced by machines with the same setting after Dr Eric Descombes from Fribourg (Switzerland), noticed that when patients changed from one brand dialysis machine to another, with the same dialysate prescription, they felt better or worse. The measured levels ranged from 138 to 143 mmol/L (https://www.ncbi.nlm.nih.gov/pubmed/29649799).
The usual response to cramps is to reduce or stop the ultrafiltration and to encourage the patients to move or stretch and/or massage or warm the affected area. Normal saline (or dialysate) boluses are usually only given if the initial intervention(s) fail. Patients in some units are given (or give themselves) salty food or drinks – including Swedish caviar! Hypertonic saline and dextrose are now used rarely.

18% of respondents said their units offer cycling or other intradialytic exercise. This may help prevent cramps caused by poor blood flow to the affected area. But the benefit of exercise is likely to be limited if poor flow is due to inadequate refilling or intradialytic hypotension related to heart failure. Inadequate refilling might be helped by profiling or by reducing the UF rate by decreasing interdialytic fluid gain or increasing treatment time or frequency. In patients with high fluid gains, a ‘sliding’ target weight may help if cramps are most often occurring after the long break. Where fluid gains are relatively low, higher dialysate sodium may be beneficial.

All the above preventative measures should only be employed after ensuring that the patient is not excessively fluid depleted post-dialysis. The techniques for managing fluid are mainly focussed on avoiding fluid overload but fluid depletion can also be harmful. Bioimpedance may help because it is sensitive to both over- and underhydration. 
Towards the end of the discussion, Pierre-Yves from France added an unexpected idea to the dialysis-related cramps. His research shows an association between cramps in HD patients using citrate dialysate and lower gut bacteria diversity and mitochondrial activity (https://www.ncbi.nlm.nih.gov/pubmed/30048977). They now need to find out if probiotics or faecal microbiota transplants can prevent cramps!

A big thank you goes to Wendi, John, Chava, Anna Diane, Peggy, Ulrich, Sabine, Jean-Yves, Andre, Pierre-Yves and to everyone who completed the survey. Although the problem of dialysis-induced cramps is not solved, it is hoped that this discussion has got people thinking!

Stop Press! The next topic for discussion will be ‘Ultrafiltration profiling and limitation of ultrafiltration rate’ with 56% of the vote. There was also a lot of support for setting up and maintaining exercise programmes for dialysis patients so that will be coming up soon. If you are not already a member please sign up at http://www.mailman.srv.ualberta.ca/mailman/listinfo/renalpro to join in. 


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