The correlation between creatine kinase and myoglobin in critical ill patients with rhabdomyolysis

Purpose

Following rhabdomyolysis there is a risk of acute renal failure (ARF). The nephrotoxic molecule is myoglobin (M). In clinical practice, creatine kinase (CK) is, however, measured to estimate the risk of ARF. It is often stated that the elimination of M is unpredictable [1]. The aim of the present study was therefore to investigate the correlation between CK and the effector molecule M.

Methods and materials

From 1 January 2003 until 30 June 2003 we prospectively measured CK and M in all patients in the ICU suspected of rhabdomyolysis. To investigate the observed trends further, we retrospectively studied all patients submitted to our ICU within the last 4.5 years with a plasma M > 5000 μg/l. Forty-two patients were included.

Results

Plasma M peaked on average 0.6 ± 0.4 days before CK. In the 76% of the patients M and CK increased in parallel and both decreased exponentially T 1/2 (M) 22 ± 10 hours and T 1/2 (CK) 26 ± 7 hours (Fig. 1.) In 17% of the patients an isolated increase in M was observed. In the majority of these patients abdominal complications was found. In 7% of the patients an isolated increase in CK was observed, typically in relation to mobilisation of the patients. ARF was treated with continuous venovenous haemofiltration.

Figure 1

Discussion

In the majority of patients with rhabdomyolysis, M and CK increase and decrease in parallel. Medium-sized molecules such as M are transported directly from the muscle to the blood, while large molecules such as CK are transported with the lymphatic system. Therefore an isolated increase in plasma CK might be observed following mobilisation. An isolated increase in plasma M ought to raise suspicion of abdominal complications.

Conclusion

In patients with rhabdomyolysis, measurement of the nephrotoxic molecule M can be used to predict the risk of ARF.