Prediction of the clinical course of rhabdomyolysis in patients with initial creatine kinase < 1000 U/l

We routinely screen patients with severe muscular exertion for the presence of rhabdomyolysis. We evaluated the significance of a low initial creatine kinase (CK), and factors associated with a rising CK in this group.

Methods

Consecutive patients with rhabdomyolysis were indentified over 44 months. A subgroup analysis of those with acute exertional rhabdomyolysis and initial CK < 1000 U/l identified two groups: patients whose CK values remained stable, and those whose CK values rose to greater than 2000 U/l. No one was excluded. Student's t test and the Fisher exact test were used to analyze continuous and categorical variables, respectively.

Results

See Table 1. Of 36 patients with CK < 1000 U/l, 15 (33%) had a rising CK. This was significantly associated with elevation of the anion gap and increased frequency of moderate to large urine test for heme. The stable CK group had a significantly higher blood urea nitrogen (BUN). In all cases the anion gap resolved with sedation and hydration, which is clinically consistent with acute lactic acidosis. Five of the 15 patients in the rising CK group had a rising creatinine, compared with 2/17 in the stable CK group. No one required hemodialysis.

Table 1

Conclusion

In patients with acute exertional rhabdomyolysis, a rising CK was significantly associated with initial elevation of the anion gap and large to moderate urine test for heme. We believe the anion gap reflected the intensity of anaerobic metabolism in injured muscle.