From: Influence of Methylenetetrahydrofolate Reductase Gene Polymorphisms on Homocysteine Concentrations after Nitrous Oxide Anesthesia Anesthes. 2008;109(1):36-43. doi:10.1097/ALN.0b013e318178820b Figure Legend: Fig. 3. Plasma homocysteine concentration in patients with very long nitrous oxide exposure (> 4 h) (n = 16). Postoperative homocysteine concentrations were significantly higher compared with preoperative: 8.1 (7.3–10.0) versus 14.60 (13.1–22.8) μm [median (lower–upper quartile)], P < 0.001, Wilcoxon signed rank test. A solid black box (▪) indicates the two patients who were double wild type, indicating that the effects of very long exposure to nitrous oxide are also operant in patients without MTHFR mutation. Date of download: 11/5/2017 Copyright © 2017 American Society of Anesthesiologists. All rights reserved.