Background: Patients who are going thorugh mechanical ventilation in the intensive care unit (ICU) often receive a high fraction of inspired oxygen (Fio2 ) and have a high arterial oxygen tension. The conservative use of oxygen may reduce oxygen exposure, diminish lung and systemic oxidative injury, and thereby increase the number of ventilator-free days (days alive and free from mechanical ventilation). Methods: We randomly assigned 1000 adult patients who were anticipated to require mechanical ventilation beyond the day after recruitment in the ICU to receive conservative or usual oxygen therapy. In the two groups, the default lower limit for oxygen saturation as measured by pulse oximetry (Spo2 ) was 90%. In the conservativeoxygen group, the upper limit of the Spo2 alarm was set to sound when the level reached 97%, and the Fio2 was decreased to 0.21 if the Spo2 was above the acceptable lower limit. In the usual-oxygen group, there were no specific measures limiting the Fio2 or the Spo2 . The primary outcome was the number of ventilatorfree days from randomization until day 28. Results: The number of ventilator-free days did not differ significantly between the conservative-oxygen group and the usualoxygen group, with a median duration of 21.3 days (interquartile range, 0 to 26.3) and 22.1 days (interquartile range, 0 to 26.2), respectively, for an absolute difference of −0.3 days (95% confidence interval [CI], −2.1 to 1.6; P=0.80). The conservativeoxygen group spent more time in the ICU with an Fio2 of 0.21 than the usual-oxygen group, with a median duration of 29 hours (interquartile range, 5 to 78) and 1 hour (interquartile range, 0 to 17), respectively (absolute difference, 28 hours; 95% CI, 22 to 34); the conservative-oxygen group spent less time with an Spo2 exceeding 96%, with a duration of 27 hours (interquartile range, 11 to 63.5) and 49 hours (interquartile range, 22 to 112), respectively (absolute difference, 22 hours; 95% CI, 14 to 30). At 180 days, mortality was 35.7% in the conservative-oxygen group and 34.5% in the usual-oxygen group, for an unadjusted odds ratio of 1.05 (95% CI, 0.81 to 1.37). Conclusions: In adults undergoing mechanical ventilation in the ICU, the use of conservative oxygen therapy, as compared with usual oxygen therapy, did not significantly affect the number of ventilator-free days.

Results with two different measurement technologies differed significantly for plasma sodium and chloride concentrations. These differences significantly affected the calculated AG and SID values and might lead clinicians to different assessments of acid-base and electrolyte status.

Summary: Purpose:We describe a sheep model of penicillininduced seizure activity using electroencephalography (EEG) and functional MRI (fMRI).Methods: Ten adult sheep were used. Spikes and seizures were generated by instillation of 8,000-10,000 IU of penicillin into the right prefrontal cortex via a specially designed port. Bilateral intracranial EEG was acquired by using carbon fiber electrodes. Animals had behavioral characterization of their seizures and were then anesthetized for fMRI studies. Functional MRI was performed at 1.5 and 3 Tesla by measuring blood oxygen level-dependent (BOLD) weighted signal intensity at different times during the evolution of seizures.Results: Behavioral seizures were associated with electrographic seizures. Intracranial EEG obtained in the MR scanner was of high quality. Focal spiking and seizures were seen in all animals and developed 11.3 ± 11.2 s and 17.3 ± 12.1 min after penicillin administration, respectively. An average of 13 ± 4.8 seizures were seen per animal, each lasting 27.3 ± 12.3 s. Functional MR images with little parenchymal artefact were obtained. Regional BOLD signal-intensity changes were observed during seizures at the seizure focus and ipsilateral amygdala.Conclusions: We have developed an animal model of partial epilepsy in which seizures can be reliably elicited with concurrent fMRI and intracranial EEG. During unilateral electrographic seizures, focal BOLD signal changes occurred at the seizure focus and ipsilateral amygdala, suggesting the presence of a cortico-subcortical loop. This observation illustrates the potential of the model for understanding seizure generation, spread, and possibly the consequences of repeated seizures on the brain. Key Words: EEG-Epilepsy-Functional MRIMagnetic resonance-Seizure models-Sheep.Seizures are associated with electrical discharges measured on the electroencephalogram (EEG) together with increased blood flow and oxygenation at the site of the epileptic focus (1-3). Functional magnetic resonance imaging (fMRI) shows increased signal intensity in areas of high blood flow due to a decrease in deoxyhemoglobin concentration, as detected by blood oxygen leveldependent (BOLD) contrast techniques (4). Sequential images can be rapidly obtained, giving fMRI the unique ability to provide good temporal and excellent spatial information. The response predictably follows neuronal activation, typically beginning after 3 s and peaking after ∼6 s (5-8). During seizures, however, the temporal relation between blood-flow changes, electrical discharges, and behavioral seizures is not understood. Indeed, BOLD signals may even precede the onset of electrographic seizures (9,10).Some attempts have been made to study seizures in humans with fMRI, but these reports are few and anecdotal, and none correlates EEG with the BOLD response (10,11). As seizures are not predictable and difficult to study in the MR system, imaging of interictal activity by EEG spike-triggered fMRI techniques has been developed (12-16). None of these studies, however...

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