High incidence of elevated serum creatine kinase in the ICU: an underestimated problem

Introduction

An elevation in the serum creatine kinase (CPK) level (without a simultaneous rise in the MB fraction or massive ischaemic cerebral infarction) correlates with the extent of muscular damage. Although usually asymptomatic, it could evolve into a life-threatening condition of rhabdomyolysis complicated by acute renal failure and/or disseminated intravascular coagulation. Critically ill patients may present with an elevated CPK for a number of different reasons. We performed an observational prospective pilot study during 31 days in a mixed ICU in a tertiary referral teaching hospital in order to study the incidence of elevated CPK levels and its possible influence on outcome.

Subjects and methods

With the exception of cardiac surgery patients and children below the age of 16, all patients admitted to the ICU were included. Patients were excluded when either an elevated troponin I >0.50 ng/ml, an elevated CPK–MB fraction (>6% of total CPK) or a cerebral infarction was present. A CPK level >170 IU/l was arbitrarily defined as elevated. The number of patients with CPK levels >2000 IU/l were also identified. We sought to compare differences in 28-day mortality and length of stay (LOS) in the ICU (max 28 days) and LOS in the hospital (max 28 days).

Results

See Table 1. Most patients with an elevated CPK level were surgical patients (including trauma). A cause could be identified in 86% of all cases. Of the unidentified causes, 80% were in medical patients. No statistical significance was observed for mortality or LOS.

Table 1

Conclusion

Elevated CPK is frequently observed in a mixed ICU population. Surgical patients are more prone to elevated CPK levels than medical patients. Unexplained CPK elevation is more observed in medical patients. LOS, mortality and the number of patients with a LOS >28 days rise in parallel with the level of elevation of CPK independent of the APACHE II score, although no statistical significance could be observed. Further investigation of the true incidence, complication rate and independent risk factors for elevated CPK seems to be indicated.