Elevation of creatine kinase is associated with worse outcomes in 2009 pH1N1 influenza A infection

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Current medical knowledge lacks specific information regarding creatine kinase (CK) elevation in influenza A pH1N1 (2009) infection. Primary endpoints were correlation between CK at intensive care unit (ICU) admission and ICU mortality. Secondary endpoints were ICU length of stay (LOS), mechanical ventilation (MV), and requirement of renal replacement techniques (RRT). A prospective multicenter register included all adults admitted for severe acute respiratory insufficiency (SARI) with confirmed pH1N1 in 148 ICUs. Clinical data including demographics, comorbidities, laboratory information, organ involvement, and prognostic data were registered. Post hoc classification of subjects was determined according to CK level. Data are expressed as median (interquartile range). Five hundred and five (505) patients were evaluable. Global ICU mortality was 17.8 % without documented differences between breakpoints. CK ≥500 UI/L was documented in 23.8 % of ICU admissions, being associated with greater renal dysfunction: acute kidney injury (AKI) was more frequent (26.1 versus 17.1 %, p < 0.05) and twofold requirement of RRT [11 versus 5.6 %, p < 0.05; odds ratio (OR) = 2.09 (95 % confidence interval [CI] 1.01-4.32)]. Increase of CK ≥1,000 UI/L was associated with two or more quadrant involvement on chest X-ray (63.2 versus 40.2 %, p < 0.01) and increased intubation risk (73.9 versus 56.7 %, p = 0.07) and duration of mechanical ventilation (median 15 days versus 11 days, p < 0.01). As a result, CK ≥1,000 UI/L was associated with 5 extra days of ICU and hospital LOS. CK is a biomarker of severity in pH1N1 infection. Elevation of CK was associated with more complications and increased ICU LOS and healthcare resources.