Half of the nurses in this study un

Half of the nurses in this study underestimated
the occurrence of delirium. The incidence of delirium
in ICU patients varies between 40·2% (Luetz et al.,
2010; Svenningsen and Tønnesen, 2011) and 81·7%
(Ely et al., 2004). Failure to identify delirium is serious
because morbidity, mortality and length of stay in the
ICU increase with delirium (Ely et al., 2004; Girard
et al., 2010). A study of the subtypes of delirium,
including hyperactive, hypoactive andmixed delirium,
showed that the mixed and hypoactive types were
most common (Peterson et al., 2006). Flagg et al. (2010)
found that nurses recognized hyperactive delirium
far more often than hypoactive delirium. These
findings underline the importance of not ignoring calm
behaviour in ICU patients if escalation of delirium is
to be avoided and targeted care be implemented.