Background: Postoperative stroke is a rare but major complication after surgery. The most often proposed mechanism is an embolus originating from the heart or great vessels. The role of intraoperative hypotension in the occurrence and evolution of postoperative stroke is largely unknown. Methods: A case-control study was conducted among 48,241 patients who underwent noncardiac and nonneurosurgical procedures in the period from January 2002 to June 2009. A total of 42 stroke cases (0.09%) were matched on age and type of surgery to 252 control patients. Conditional logistic regression analysis was used to estimate the effect of the duration of intraoperative hypotension (defined according to a range of blood pressure thresholds) on the occurrence of an ischemic stroke within 10 days after surgery, adjusted for potential confounding factors. Results: After correction for potential confounders and multiple testing, the duration that the mean blood pressure was decreased more than 30% from baseline remained statistically significantly associated with the occurrence of a postoperative stroke.
PurposeWe assessed test–retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2), and oxygen extraction fraction (OEF) measurements derived from dynamic 15O positron emission tomography (PET) scans.ProceduresIn seven healthy volunteers, complete test–retest 15O PET studies were obtained; test–retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO2 in arterial flow territories were calculated.ResultsWhole-brain test–retest coefficients of variation for CBF, CBV, CMRO2, and OEF were 8.8%, 13.8%, 5.3%, and 9.3%, respectively. Test–retest variability of CBV left-to-right ratios was <7.4% across all territories. Corresponding values for CBF, CMRO2, and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively.ConclusionsThe test–retest variability of CMRO2 measurements derived from dynamic 15O PET scans is comparable to within-session test–retest variability derived from steady-state 15O PET scans. Excellent regional test–retest variability was observed for CBF, CMRO2, and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF.
A qualitative MRI scoring system helps assess hypoxic-ischemic brain injury severity following cardiac arrest and may provide useful prognostic information in comatose cardiac arrest patients.
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