Research from JAMA — Surgical Site Infection and the Routine Use of Perioperative Hyperoxia in a General Surgical Population — A Randomized Controlled Trial — ContextSurgical site infection (SSI) in the general surgical population is a significant public health issue. The use of a high fractional inspired concentration of oxygen (FIO2) during the perioperative period has been reported to be of benefit in selected patients, but its role as a routine intervention has not been investigated.ObjectiveTo determine whether the routine use of high FIO2 during the perioperative period alters the incidence of SSI in a general surgical population.Design, Setting, and PatientsDouble-blind, randomized controlled trial conducted between September 2001 and May 2003 at a large university hospital in metropolitan New York City of 165 patients undergoing major intra-abdominal surgical procedures under general anesthesia.InterventionsPatients were randomly assigned to receive either 80% oxygen (FIO2 of 0.80) or 35% oxygen (FIO2 of 0.35) during surgery and for the first 2 hours after surgery.Main Outcome MeasuresPresence of clinically significant SSI in the first 14 days after surgery, as determined by clinical assessment, a management change, and at least 3 prospectively defined objective criteria.ResultsThe study groups were closely matched in a large number of clinical variables. The overall incidence of SSI was 18.1%. In an intention-to-treat analysis, the incidence of infection was significantly higher in the group receiving FIO2 of 0.80 than in the group with FIO2 of 0.35 (25.0% vs 11.3%; P = .02). FIO2 remained a significant predictor of SSI (P = .03) in multivariate regression analysis. Patients who developed SSI had a significantly longer length of hospitalization after surgery (mean [SD], 13.3 [9.9] vs 6.0 [4.2] days; P<.001).ConclusionsThe routine use of high perioperative FIO2 in a general surgical population does not reduce the overall incidence of SSI and may have predominantly deleterious effects. General surgical patients should continue to receive oxygen with cardiorespiratory physiology as the principal determinant.

OBJECTIVE: The objective of this study was to evaluate the utility of diffusion tensor imaging (DTI) tractography–based targeting of the dentatorubrothalamic tract (DRT) for magnetic resonance–guided focused ultrasound (MRgFUS) thalamotomy in patients with essential tremor (ET) and correlate postprocedural tract disruption with clinical outcomes.METHODS: Four patients received preprocedural and immediate postprocedural DTI in addition to traditional anatomical MRI sequences for MRgFUS thalamotomy. Optimal ablation sites were selected based on the patient-specific location of the DRT as demonstrated by DTI (direct targeting) and correlated with traditional atlas-based measurements for thalamic ventral intermediate nucleus (Vim) lesioning (indirect targeting). Fiber tracts were displayed three-dimensionally during the procedure and used in conjunction with clinical signs of tremor control for fine correction of the ablation site. Immediately following the conclusion of the procedure, the MRgFUS head frame was removed and patients were placed in a 32-channel MRI head coil for follow-up DTI and anatomical MRI sequences.RESULTS: All patients had excellent postoperative tremor control and successful pre- and postprocedural DTI fiber tracking of the corticospinal tract, medial lemniscus, and DRT. Immediate postprocedure DTI failed to track the DRT ipsilateral to the lesion site with a preserved contralateral DRT, coincident with substantial resolution of contralateral tremor.CONCLUSIONS: DTI can reliably identify the optimal ablation target and demonstrates tract disruption on immediate postprocedural imaging. A clinical improvement of ET was observed immediately following the procedure, correlating with DRT disruption and suggesting that interruption of the DRT is a consequence of clinically successful MRgFUS thalamotomy. These findings may have utility for both MRgFUS procedure planning in surgically naive patients and retreatment of patients who have previously undergone unsuccessful thalamic Vim lesioning.

In this work we analyze electro-corticography (ECoG) recordings in human sub- jects as they are anesthetized. We hypothesize that the decrease in responsiveness that defines anesthesia induction is concomitant with the stabilization of neuronal dynamics. To test this hypothesis, we performed a moving vector autoregressive analysis and quantified stability of neuronal dynamics using eigenmode decompo- sition of the autoregressive matrices, independently fitted to short sliding temporal windows. Consistent with the hypothesis we show that while the subject is awake, many modes of oscillations of neuronal activity are found at the edge of instabil- ity, but as the subject becomes anesthetized the fitted dynamics becomes more damped. Analysis of eigenmode distributions in the awake and anesthetized brain revealed statistically significant stabilization not present in surrogate data. Sta- bility analysis thus offer a novel way of quantifying changes in neuronal activity that characterize loss of consciousness induced by general anesthetics. Specifically, our analysis suggests that the effect of the anesthetic procedure is to damp out high frequency activity while still allowing for low frequency modes to perform a function.