ResultsA total of 372 223 (5.3%) patients admitted with AIS had ARF. Dialysis was required in 2364 (0.6%) of 372 223 patients. Patients with ARF were older (mean age, 74±28 versus 72±31 years; P<0.0001) and predominantly men (52%; P<0.0001). Comorbid conditions, such as hypertension, diabetes mellitus, atrial fibrillation, and congestive heart failure, were significantly higher in patients with ARF (Table I in the online-only Background and Purpose-Acute renal failure (ARF) in setting of acute ischemic stroke (AIS) is associated with worse outcome. We sought to determine the prevalence of ARF and effect on outcomes of patients with AIS. Methods-Data from all patients admitted to US hospitals between 2002 and 2010 with a primary discharge diagnosis of ischemic stroke and secondary diagnosis of ARF were included. The effect of ARF on rates of intracerebral hemorrhage and discharge outcomes was analyzed after adjusting for potential confounders using logistic regression analysis. Results-Of 7 068 334 patients with AIS, 372 223 (5.3%) had ARF during hospitalization. Dialysis was required in 2364 (0.6%) of 372 223 patients. Patients with AIS with ARF had higher rates of moderate to severe disability (41.3% versus 30%; P<0.0001), intracerebral hemorrhage (1.0% versus 0.5%; P<0.0001), and in-hospital mortality (8.4% versus 2.9%; P<0.0001) compared with those without ARF. After adjusting for confounding factors, patients with AIS with ARF had higher odds of moderate to severe disability (odds ratio, 1.3; 95% confidence interval, 1.3-1.4; P<0.0001), intracerebral hemorrhage (odds ratio, 1.4; 95% confidence interval, 1.3-1.6; P<0.0001), and death (odds ratio, 2.2; 95% confidence interval, 2.0-2.2; P<0.0001). Conclusions-ARF in patients with AIS is associated with significantly higher rates of moderate to severe disability at discharge and in-hospital mortality.

Electrocorticography (ECoG) and functional MRI (BOLD-fMRI) have been used previously to measure brain activity during working memory delay periods. These studies have separately reported oscillation changes in the theta (4-8 Hz) band and BOLD-fMRI increases during delay periods when information is maintained in memory. However, it is not known how intracranial cortical field potential (CFP) changes relate to BOLD-fMRI responses during delay periods. To answer this question, fMRI was obtained from six epilepsy patients during a visual working memory task. Then, following subdural macroelectrode implant, continuous ECoG was used to record CFPs during the same task. Time-frequency analyses showed delay period gamma band oscillation amplitude increases on electrodes located near fMRI activity, while in the theta band changes were higher for electrodes located away from fMRI activation. The amplitude of the ECoG gamma band response was significantly positively correlated with the fMRI response, while a negative correlation was found for the theta band. The findings are consistent with previous reports of local field potential (LFP) coupling in the gamma band with BOLD-fMRI responses during visual stimulation in monkeys, but are novel in that the relationship reported here persists after the disappearance of visual stimuli while information is being maintained in memory. We conclude that there is a relationship between BOLD-fMRI increases and human working memory delay period gamma oscillation increases and theta decreases. The spectral profile change provides a basis for comparison of working memory delay period BOLD-fMRI with field potential recordings in animals and other human intracranial EEG studies.