Critical illness polyneuropathy: incidence and risk factors

Critical illness polyneuropathy (CIP) is an axional peripheral neuropathy. CIP is increasingly diagnosed in ICU patients. The prevalence of CIP, however, is essentially unknown, as are the risk factors of CIP. The aim of this study was to assess the incidence of CIP and to define potential risk factors for CIP.

A database analysis was performed on 1450 patients admitted to the ICU of a tertiary care hospital between March 1998 and December 2003. Diagnosis of CIP was based on clinical judgement confirmed by electrophysiologic evaluation. Clinical, laboratory and haemodynamic variables were analysed for risk prediction of CIP.

The overall CIP incidence was 3.3% (48 out of 1450 patients) with a continuous increase in the annual CIP rate (1.4% in 1998 to 5.5% in 2003). CIP patients had higher APACHE II (17 ± 9 vs 21 ± 8; P = 0.002) and SAPS II scores (44 ± 22 vs 53 ± 16; P = 0.01), a higher incidence of mechanical ventilation (1000/1402 vs 48/48; P = 0.0001) and renal support (266/1402 vs 22/48; P = 0.0001), as well as a longer duration of mechanical ventilation (median 4 vs 30 days; P = 0.0001), renal support (median 4 vs 11 days; P = 0.0001) and ICU stay (median 5 vs 36 days; P = 0.0001). Furthermore a higher bicarbonate on admission was noted. In the multivariate analysis, only high bicarbonate on admission (P = 0.0002) and renal support (P = 0.0001) were independent risk factors for the development of CIP. Evaluating factors associated with CIP (as a cause or as a consequence), high bicarbonate (P = 0.0016), duration of ICU stay (P = 0.0001) and duration of renal support (P = 0.043) were independently associated with CIP.

CIP is diagnosed in approximately 5% of ICU patients. The incidence of CIP is rising, as are the ICU stay and severity of disease. Development of CIP was associated with severity of disease and ICU length of stay.