Severe Muscle Cramp due to Acute Hypomagnesaemia

Severe Muscle Cramp due to Acute
Hypomagnesaemia in Haemodialysis

British Medical Journal, 1969, 2, 804-805

Attention has recently been drawn to the complications of hypermagnesaemia induced by haemodialysis for chronic renal

failure (Govan et al., 1968).

We report here a case of severe muscle cramp due to acute hypomagnesaemia occurring in chronic intermittent haemodialysis. Wacker and Parisi (1968)

extensively reviewed abnormalities of magnesium metabolism in man; there is no reported evidence for acute hypomagnesaemia related to dialysis.

CASE REPORT

The patient, a 38-year-old white South African with advanced chronic glomerulonephritis, was started on regular twice-weekly

haemodialysis early in 1968, a Kolff kidney with twin coil 145 being used for nine hours per dialysis. After about four months

he began to develop severe muscle cramps in both legs and to a lesser degree in both arms. These involved the smaller muscles in

particular and usually came on about six to seven hours after the start of dialysis, gradually fading in the 12 hours after the end of

dialysis. The blood pressure and pulse remained normal throughout, and no excessive loss of weight was noted. Both oral quinine

and intravenous saline were given without any effect on the cramp.

Physical examination failed to show any abnormal signs beyond the muscle spasm. Both Chvostek and Trousseau signs were

negative. Plasma calcium and potassium were normal both at the beginning and at the end of dialysis. Predialysis magnesium, however,

was 2’5 mg/100 ml. (normal range 1-7-21 mg./100 ml.), and this fell to 1P3 mg./100 ml. at the end of dialysis (see Table).

Magnesium Concentrations (mg./100 ml.)

Predialysis Mg 2-5 2-5 1-3-2-2

Postdialysis Mg .. 1-3 1-8 1 0-1 9

Fall in plasma Mg concentration

during dialysis 1-2 0-7 0-10-7

Bath-water Mg. .. 0-8 1-8 0-8

No magnesium was added to the dialysing fluid, and the bath magnesium concentration was normally only 0-8 mg./100 ml.

During one of the acute cramps 4 mEq of magnesium in the form of 10% MgSO4 was administered intravenously, This brought

about a sudden and dramatic relief of the cramp, which did not recur during that dialysis. At the beginning of the next dialysis the

plasma magnesium was again 2’5 mg./100 ml. Severe cramp recurred during dialysis and was again relieved by a similar dose

of magnesium sulphate.

Magnesium sulphate was next added to the bath-water in order to bring the magnesium concentration up to 1-8 mg./100 ml. Since

then the patient has had no severe muscle cramp.

COMMENT

Although all of our patients on chronic intermittent haemodialysis are dialysed against a bath-water magnesium concentration

of 0.8 mg/100 ml., we have not seen these excruciating cramps in any others. The predialysis plasma magnesium

concentrations in six patients ranged from 1 3 to 2-2 mg/100 ml. (see Table).

Serial predialysis estimations over several months showed no tendency for hypomagnesaemia to develop.

Nevertheless, in none of these patients was the plasma magnesium level as high as 2-5 mg./100 ml. at the beginning

of dialysis, but the postdialysis magnesium levels (10 to 19 mg./100 ml.) are comparable with those found in the above patient.

At the time of the onset of severe cramps the patient’s plasma magnesium was 16 mg./100 ml., which is only just below the

normal range. This suggests that the clinical symptoms were not related to the absolute level of plasma magnesium but

rather to the rate and extent of fall in plasma magnesium level during dialysis. Symptoms occurred in the only patient with

a fall in plasma magnesium concentration exceeding 1 mg/100 ml. during the period of dialysis, and he became symptomfree

as soon as this rate of decline was reduced.

This situation may be related to the fact that this patient had a rather higher than normal plasma magnesium level. This

is an unusual feature in patients on long-term chronic intermittent dialysis, though hypermagnesaemia has been described

in acute renal failure with the use of flame photometry estimation (Wacker and Vallee, 1957).

We have not added magnesium sulphate to the bath-water of our other patients on chronic dialysis, since none of them

appear to have had any clinical evidence of magnesium deficiency.

Our plasma magnesium estimations were done by a colorimetric method (Bohuon, 1962). Although objections have been

raised to this method, and the atomic absorptiometer is superior, the findings in this case are probably valid because (1) the

estimations were repeatable, and (2) the important features in this case were the relative values before, during, and after

dialysis rather than the absolute values themselves.

D. R. TRIGER, M.A., B.M., B.CH.,

Resident Medical Officer.

A. M. JOEKES, M.A., B.M., F.R.C.P.,

Consultant Physician.

St. Peter’s, St. Paul’s, and St. Philip’s Hospitals, London W.C.2.

REFERENCES

Bohuon, G. (1962). Clinica Chimica Acta, 7, 811.

Govan, J. R., Porter, C. A., Cook, J. G. H., Dixon, B., and Trafford,

J. A. P. (1968). British Medical Yournal, 2, 278.

Wacker, W. E. C., and Panisi, A. F. (1968). New England 7ournal of

Medicine, 278, 658.

Wacker, W. E. C., and Vallee, B. L. (1957). New England Yournal of

Medicine, 257, 1254.