Anesthesiology
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During cardiopulmonary bypass, mixed venous oxygen saturation (Svo2) is frequently measured to assess circulatory adequacy. Fluctuations in Svo2 not related to patient movement or inadequate oxygen delivery have been attributed clinically to increased cerebral oxygen consumption due to "light" anesthesia. To evaluate the relationship between anesthetic depth and Svo2, we prospectively measured bispectral index (BIS) and Svo2 values in patients undergoing cardiac surgery with cardiopulmonary bypass. ⋯ In patients undergoing cardiopulmonary bypass, we found no overall association between BIS and Svo2. A weak but statistically significant association between BIS and Svo2 was observed in patients with temperatures less than 34.1 degrees C. These data suggest that low Svo2 values on bypass are unlikely to be due to light or inadequate anesthesia. The relationship among temperature, BIS and Svo2 deserves further study.
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Transfusion of erythrocytes is associated with increased morbidity in certain patient groups. Storage time of erythrocytes may contribute to respiratory complications. Using a syngeneic in vivo transfusion model, we investigated whether transfusion of stored rat erythrocytes causes lung injury in healthy and in lipopolysaccharide-primed rats in a "two-hit" model of lung injury. ⋯ Transfusion of aged erythrocytes induces lung injury in healthy rats. In a "two-hit" model, injury induced by aged erythrocytes was characterized by coagulopathy and was abrogated by washing. Washing of aged erythrocytes may decrease pulmonary complications in patients with an inflammatory condition who are exposed to a blood transfusion.
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Preclinical studies demonstrate increased neuroapoptosis after general anesthesia in early life. Neuraxial techniques may minimize potential risks, but there has been no systematic evaluation of spinal analgesic safety in developmental models. We aimed to validate a preclinical model for evaluating dose-dependent efficacy, spinal cord toxicity, and long-term function after intrathecal morphine in the neonatal rat. ⋯ The therapeutic ratio for intrathecal morphine (toxic dose/antinociceptive dose) was at least 300 at P3 and at least 20 at P21 (latter doses limited by side effects). These data provide relative efficacy and safety for comparison with other analgesic preparations and contribute supporting evidence for the validity of this preclinical neonatal safety model.
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Hypercapnic acidosis frequently occurs when patients with acute lung injury are initially ventilated with low tidal volume "protective" strategies. Hypercapnic acidosis per se, in the absence of any change in tidal volume or airway pressure, is protective when instituted before the onset of injury. However, the mechanisms by which hypercapnic acidosis confers this protection are incompletely understood, in particular, the effects on pulmonary oxidative reactions, which are potent mediators of tissue damage, have not been previously examined in vivo. ⋯ Hypercapnic acidosis reduced oxidative reactions in the acutely injured lung in vivo, within minutes of onset and was not reliant on nitric oxide-dependent peroxynitrite production. This rapid onset antioxidant action is a previously undescribed mechanism by which hypercapnic acidosis could act, even when acute lung injury is well established.