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BACKGROUND: Carbon monoxide (CO) can be produced in the anesthesia circuit when inhaled anesthetics are degraded by dried carbon dioxide absorbent and exhaled CO can potentially be rebreathed during low-flow anesthesia. Exposure to low concentrations of CO (12.5 ppm) can cause neurotoxicity in the developing brain and may lead to neurodevelopmental impairment. In this study, we aimed to quantify the amount of CO present within a circle system breathing circuit during general endotracheal anesthesia in infants and children with fresh strong metal alkali carbon dioxide absorbent and define the variables associated with the levels detected. METHODS: Fifteen infants and children (aged 4 months to 8 years) undergoing mask induction followed by general endotracheal anesthesia were evaluated in this observational study. CO was measured in real time from the inspiratory limb of the anesthesia circuit every 5 minutes for 1 hour during general anesthesia. Carboxyhemoglobin (COHb) levels were measured at the 1-hour time point and compared with baseline. RESULTS: CO was detected in all patients older than 2 years (0-18 ppm, mean 3.7 +/- 4.8 ppm) and rarely detected in patients younger than 2 years (0-2 ppm, mean 0.2 +/- 0.6 ppm). Only the relationship between CO concentration and fresh gas flow to minute ventilation ratio (FGF:(.)VE) remained significant after adjustment in longitudinal regression analysis (P < 0.001). Although not powered to determine such a relationship, CO levels were weakly associated with the use of desflurane and female sex. There was no significant association between CO concentration and anesthetic concentration. Baseline COHb levels were higher in children younger than 2 years and decreased significantly at the 1-hour time point compared with baseline and children older than 2 years. However, COHb levels increased significantly from baseline in a predictable manner consistent with CO exposure in children older than 2 years. FGF:(.)VE correlated significantly with change in COHb using simple linear regression (r = 0.62; P < 0.02). CONCLUSIONS: CO was detected routinely during general anesthesia in infants and children when FGF:(.)VE was

A 44-year-old man underwent aortic valve replacement with a porcine bioprosthesis 21 years ago for infective endocarditis complicated by a cerebral mycotic aneurysm and intracranial bleeding. Nine years ago, he had a second aortic valve replacement with a mechanical bileaflet tilting-disk prosthesis because of porcine prosthesis degeneration. No pseudoaneurysm was noted on the operative report. Six months ago, he developed angina and had a positive stress test for ischemia. Angiography showed severe left main coronary artery (LM) stenosis, which was treated with intravascular ultrasound–guided percutaneous coronary intervention with a zotarolimus-eluting stent. Two months ago, he again developed angina. Follow-up angiography and intravascular ultrasound revealed severe in-stent restenosis in the proximal third of the LM and systolic narrowing of the distal third, suggestive of extrinsic compression (Figure 1 and online-only Data Supplement Movie 1). In-stent restenosis was treated at that time with a sirolimus-eluting stent. A transesophageal echocardiogram revealed a large pseudoaneurysm lateral to the aortic root; color …