['To ascertain whether initial depression of conscious level in children with diabetic ketoacidosis (DKA) is related to hyperosmolality, acidosis or other factors.', 'In 225 episodes of DKA without evidence of cerebral edema, we examined the relationship between conscious level and initial biochemical variables. We contrasted these findings with those in 42 children who later developed cerebral oedema.', 'On admission, 42/225 (19%) had mild (pH 7.26-7.35); 96 (44%) moderate (pH 7.11-7.25); and 80 (37%) severe DKA (pH <or= 7.10). Conscious level: alert and oriented (group 1, n=123), drowsy but oriented when woken (group 2, n=62), semi-conscious or confused/agitated (group 3, n=9), comatose (group 4, n=4). Glasgow Coma Score (GCS) was available in 65. pH varied significantly with conscious level; group 1, 7.20+/- 0.11(mean+/- SD); group 2, 7.10+/- 0.16; group 3, 6.96+/- 0.11; group 4, 6.88+/- 0.09 (anova, p<0.001). Blood glucose (BG) was not different between the groups. GCS was related to pH (r(s) = 0.49, p < 0.001), but not to BG or electrolyte levels. Age, sex, plasma sodium, corrected sodium and osmolality also varied with conscious level in a univariate model. Using multivariate analysis comparing groups 1 with groups 2-4, lower pH and younger age were the only independent determinants of impaired conscious level (p<0.001, p=0.036). Conscious level in the children with cerebral edema was also closely related to pH and not to other biochemical variables. pH was lower at each conscious level in the children with later cerebral edema.'] Is conscious level in children with diabetic ketoacidosis related to severity of acidosis and not to blood glucose concentration?