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BACKGROUND: Mechanical ventilation and administration of a high oxygen concentration are simultaneously used in the management of respiratory failure. We conducted this study to evaluate the effect of a high inspired oxygen concentration on ventilator-induced lung injury. METHODS: Forty sets of isolated/perfused rabbit lungs were randomized for 60 min of pressure-control ventilation at a plateau inspiratory pressure of 25 or 15 cm H(2)O and positive end-expiratory pressure of 3 cm H(2)O while receiving 100% or 21% O(2). The temperature, pH, and partial pressure of CO(2) in the perfusate were maintained the same in all groups (n = 10 for each group). The outcome measures used to assess lung injury included: the change in weight gain and ultrafiltration coefficient, the frequency of vascular failure, the histological lesions and the concentration of tumor necrosis factor-alpha and malondialdehyde in the bronchoalveolar lavage fluid. RESULTS: The two groups ventilated at the higher inspiratory pressure/tidal volume experienced greater weight gain and increases in the ultrafiltration coefficient, more frequently suffered vascular failure, and presented higher composite scores of histological damage than the two groups ventilated at the lower inspiratory pressure/tidal volume. Hyperoxia was not found to further increase any of the monitored markers of lung injury. No difference was noticed among the four experimental groups in the alveolar lavage fluid levels of tumor necrosis factor-alpha or malondialdehyde. CONCLUSIONS: These findings suggest that short-term administration of a high oxygen concentration is not a major determinant of ventilator-induced lung injury in this experimental model.

Background: There is mounting experimental evidence that hypercapnic acidosis protects against lung injury. However, it is unclear if acidosis per se rather than hypercapnia is responsible for this beneficial effect. Therefore, we sought to evaluate the effects of hypercapnic (respiratory) versus normocapnic (metabolic) acidosis in an ex vivo model of ventilator-induced lung injury (VILI).Methods: Sixty New Zealand white rabbit ventilated and perfused heart-lung preparations were used. Six study groups were evaluated. Respiratory acidosis (RA), metabolic acidosis (MA) and normocapnic-normoxic (Control - C) groups were randomized into high and low peak inspiratory pressures, respectively. Each preparation was ventilated for 1 hour according to a standardized ventilation protocol. Lung injury was evaluated by means of pulmonary edema formation (weight gain), changes in ultrafiltration coefficient, mean pulmonary artery pressure changes as well as histological alterations.Results: HPC group gained significantly greater weight than HPMA, HPRA and all three LP groups (P = 0.024), while no difference was observed between HPMA and HPRA groups regarding weight gain. Neither group differ on ultrafiltration coefficient. HPMA group experienced greater increase in the mean pulmonary artery pressure at 20 min (P = 0.0276) and 40 min (P = 0.0012) compared with all other groups. Histology scores were significantly greater in HP vs. LP groups (p < 0.001).Conclusions: In our experimental VILI model both metabolic acidosis and hypercapnic acidosis attenuated VILI-induced pulmonary edema implying a mechanism other than possible synergistic effects of acidosis with CO2 for VILI attenuation. © 2011 Kapetanakis et al; licensee BioMed Central Ltd.

Background General and spinal anesthesia are currently in widespread use during transurethral bladder tumor resection. However, local anesthetic methods are claimed to provide sufficient intra-operative analgesia and satisfactory post-operative pain management. We evaluated whether local levobupivacaine infiltration of the tumor would result in outcomes, in terms of intra-operative analgesia, similar to those for utilization of general anesthesia. Post-operative analgesia and patient satisfaction were also assessed. Patients and methods Twenty patients with recurrent solitary bladder tumors were randomly allocated in two groups. Group A, underwent tumor resection under general anesthesia and group B was treated with resection after local levobupivacaine infiltration. Post-operative analgesia was evaluated with utilization of a visual analogue scale, ranging from 0 to 10, with higher scores indicating more intense pain perception. Results Group A patients demonstrated significantly lower visual analogue scale scores at t = 0, which peaked at 4 h post-operatively. Group B scores were higher at t = 0, declined over a 2 h interval and reached zero after t = 4 h. Patients younger than 60 years and women benefitted more. Local anaesthesia was the method of pain control preferred by 90% of patients. Conclusion Local levobupivacaine infiltration for transurethral bladder tumor resection seems feasible, providing intra and post-operative pain control. In this preliminary setting, general anesthesia provided a higher level of pain control in the immediate post-operative period (< 4 h) while local levobupivacaine infiltration demonstrated excellent late post-operative analgesia (> 4 h). Also, patients seem to prefer local to general anesthesia in future surgery.