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Nitrous oxide is a commonly used inhaled anesthetic for medical procedures, as well as a drug of abuse throughout the world. Excessive nitrous oxide inhalation has been shown to cause a functional vitamin B12 deficiency and hyperhomocysteinemia, which can lead to peripheral neuropathy and hypercoagulability, respectively. While the development of neurologic toxicity from chronic nitrous oxide abuse (i.e., encephalopathy, myelopathy, and neuropathy) has been previously described, the thrombotic potential of chronic nitrous oxide abuse is less known. The authors report two cases of nitrous oxide abuse leading to both neurologic and thrombotic complications.
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Citation Peltier MR, Gurzenda EM, Murthy A, Chawala K, Lerner V, Kharode I, Arita Y, Rhodes A, Maari N, Moawad A, Hanna N. Can oxygen tension contribute to an abnormal placental cytokine milieu? Am J Reprod Immunol 2011; 66: 279-285 Objective The aim of this study was to determine whether culturing human placental explants under different oxygen tensions will alter expression of pro- and anti-inflammatory mediators. Methods Placental explant cultures from second-trimester, elective, terminations-of-pregnancy were incubated under 21, 5, or 1% O(2) concentrations for 24 hr in the presence or absence of IL-10. Cytokine concentrations in the conditioned medium were quantified by immunoassay. Results Culture of placental explants under 21, 5, or 1% O(2) concentrations produced hyperoxic (143 +/- 1.6 mmHg), normoxic (37 +/- 1.6 mmHg), and hypoxic (18.2 +/- 1.6 mmHg) pO(2) levels for the maternal-fetal interface in the medium. Oxygen tension had profound effects on basal placental cytokine levels as well as on IL-10-stimulated cytokine production. IL-1beta and TNF-alpha, but not IFN-gamma production, was reduced by 21% O(2) . Moreover, 21% O(2) levels increased the anti-inflammatory cytokines IL-10 and IL-13 while 1% O(2) tended to decrease the production of these cytokines. Conclusions Five percent- O(2) incubation more accurately represents in vivo pO(2) conditions at the maternal-fetal interface. Routine culture of placental explants in room air produces a superphysiologic oxygen tension that tended to increase the production of anti-inflammatory and decrease the production of pro-inflammatory cytokines. In addition, low pO(2) may reduce responsiveness of the placenta to the anti-inflammatory actions of IL-10