Heat-Related Muscle Cramps

To the Editor.  —We all owe a debt to Dr. J. P. Knochel for his masterful and comprehensive review of environmental heat illness.¹ We write now in relation to one relatively minor aspect, for Dr. Knochel commented that "... muscle necrosis and myoglobinuria could conceivably follow severe episodes of heat-related muscle cramps," but "this has not been reported."We described a construction worker who had diffuse cramps after working on a hot summer day, drinking freely without replacing salt.² Serum enzyme activity was increased and myoglobinuria was proven. There was transient azotemia and the urine contained casts, but this was attributed to the myoglobinuria; no other organs were overtly affected. Unless the renal injury is taken to mean (by definition) that, because an organ system other than the renal system was affected, this was a case of "heat exhaustion," it would seem to meet Dr. Knochel's definition of "heat