Table 3. Summary of case studies on nitrous oxide toxicity.

Study	Patient's age	Concentration and duration of exposure to N2O	Time of onset of symptoms	History or undiagnosed disease	Treatment	Consequences
Lassen et al. (1956) [42]	10 years	14 days	14th day	-	-	-
	11 years	12 days	6–10th day	-	-	-
	15 years	17–18 days	17–18th day	-	-	Mortality (on 29th day)
	53 years	16 days	16th day	-	-	Mortality (on 16th day)
Koblin and Biebuyck (1986) [43]	25 years	1st: 90 min, 1980, Mar.	2 months later	Ileal resection for Crohn's disease	Cyanocobalamin injection	Reversible
		2nd: 1982, Apr.
	58 years	90 min	6 weeks later	Pernicious anemia	Cyanocobalamin injection	Reversible
Hadzic et al. (1995) [44]	47 years	70% for 8 hours	6 weeks later	Pernicious anemia	Cobalamin injection	Reversible
Rosener and Dichgans (1996) [45]	50 years	66% for 2 hours	4 weeks later	Vegetarian diet	Cyanocobalamin injection	Reversible
McNeely et al. (2000) [37]	6 months	-	2 weeks later	Breast feeding vegetarian mother	Vitamin B12 supplementation	Developmental delay
Ilniczky et al. (2002) [32]	52 years	-	1 week later	Macrocytic, hyperchromic anemia with decreased serum levels of vitamin B12	IM injection of vitamin B12	Reversible
	57 years	-	2 months later	Borderline anemia with decreased serum levels of vitamin B12	IM injection of vitamin B12	Reversible
Selzer et al. (2003) [40]	3 months	1st: 60% for 45 min	25 days after 2nd anesthesia	MTHFR deficiency	-	Mortality (46 days after 2nd anesthesia)
		2nd: 60% for 270 min (4 days after 1st anesthesia)
Lacassie et al. (2006) [46]	52 years	1st: 50% for 200 min for	2 weeks after 1st anesthesia	Polymorphism of MTHFR	Vitamin B12 and folic acid supplementation	Reversible
		2nd: 50%, 105 min (8 weeks after 1st anesthesia)
Singer et al. (2008) [47]	27 years	-	2 months later	Pernicious anemia	IM injection of vitamin B12	Reversible
Renard et al. (2009) [48]	46 years	-	2 days later	Borderline anemia	IM injection of vitamin B12	Reversible

Min: minutes, IM: Intramuscular, MTHFR: 5,10-Methylenetetrahydrofolate Reductase.