Anesthesiology
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To assess the change in venous admixture during breathing of 100 per cent oxygen (FIO2 1.0), shunt fraction (Qs/Qt) was calculated at a maintenance FIO2 (FIO2m:0.27--0.70) and at FIO2 1.0 in 40 studies of 34 patients with acute respiratory failure. At FIO2 1.0 Qs/Qt increased in 26 studies, but did not increase in 14 studies. ⋯ Respiratory failure was more severe in those in whom Qs/Qt decreased with oxygen, as indicated by high Qs/Qt values at FIO2m, evidence of diffuse pulmonary disease by roentgenography, and signs of adult respiratory distress syndrome. The authors conclude that changes in Qs/Qt in response to FIO2 1.0 in acute respiratory failure are related to the severity of respiratory insufficiency.
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Clinical Trial Controlled Clinical Trial
Antagonism of nitrous oxide analgesia by naloxone in man.
The possible reversal of nitrous oxide analgesia by naloxone was investigated. Two studies were conducted in 21 healthy male subjects, who responded to ischemic pain produced by tourniquet applied to the upper arm for 15 min, while breathing air or nitrous oxide, 33 per cent. Using a double-blind procedure, the subjects received intravenous injections of naloxone and saline solution on different days. ⋯ In 13 subjects, naloxone, 4 mg, also decreased significantly the effect of nitrous oxide analgesia in comparison with saline solution. Naloxone showed its reversal effect mainly on sensory response rating obtained during the painful stages of ischemia, between 11 and 15 min. The results suggest that analgesia induced by nitrous oxide may be partly related to the opiate receptor--endorphin system in man.