Background and Purpose-Abnormal physiological parameters after acute stroke
may induce early neurological deterioration. Studies of the effect of dehy
dration on stroke outcome are limited. We examined the association of raise
d plasma osmolality on stroke outcome at 3 months and the change of plasma
osmolality with hydration during the first week after stroke.
Methods-Acute stroke patients had their plasma osmolality measured at admis
sion and at days 1, 3, and 7. Maximum plasma osmolality and the area under
curve (AUC) were also calculated during the first week. Patients were strat
ified according to how they were hydrated: orally, intravenously, or both.
Outcome included survival at 3 months after stroke. Logistic regression was
performed to examine the association between raised plasma osmolality (>29
6 mOsm/kg) and survival, adjusting for stroke severity. Linear regression w
as performed to examine the pattern of plasma osmolality across hydration g
roups.
Results-One hundred sixty-seven patients were included. Mean admission (300
mOsm/kg, SD 11.4), maximum (308.1 mOsm/kg, SD 17.1), and AUC (298.3 mOsm/k
g, SD 11.7) plasma osmolality were significantly higher in those who died c
ompared with survivors (293.1 mOsm/kg [SD 8.2], 297.7 mOsm/kg [SD 8.7], and
291.7 mOsm/kg [SD 8.1], respectively; P<0.0001). Admission plasma osmolali
ty >296 mOsm/kg was significantly associated with mortality (OR 2.4, 95% CI
1.0 to 5.9). In patients hydrated intravenously, there was no significant
fall in plasma osmolality compared with patients hydrated orally (P=0.68).
Conclusions-Raised plasma osmolality on admission is associated with stroke
mortality, after correcting for case mix. Correction of dehydration after
stroke requires a more systematic approach. Trials are required to determin
e whether correcting dehydration after stroke improves outcome.