Homocysteine After Nitrous Oxide Anesthesia

Medical University of Vienna

Status and phase: Completed; Phase 4

Conditions: Adverse Effects; Anesthesia, General; Nitrous Oxide

Treatments: Drug: Nitrous oxide

Study type: Interventional

Funder types: Other

Identifiers

NCT00482456

EK 286/2004

Details and patient eligibility

About

Our study looks at the interaction of a common mutation in the MTHFR gene and the risk of developing higher homocysteine levels after nitrous oxide (N2O) anesthesia.

Specifically, we want to test the hypothesis that healthy patients carrying the MTHFR 677C>T haplotype develop abnormal homocysteine levels after nitrous oxide anesthesia.

Full description

Nitrous oxide - laughing gas - is a widely used anaesthetic gas with many favourable but also some dangerous properties. Among the latter is the increase in homocysteine levels after nitrous oxide (N2O) exposure by inhibition of enzymes in the vitamin B12 pathway. Elevated homocysteine levels have been found to be an independent risk factor for ischemic events and are associated with an increased risk for perioperative myocardial ischemia. If a patient carries one or more loss-of-function mutations in enzymes of the methionine/homocysteine/folate pathway he is at an increased risk for hyperhomocysteinemia and if exposed to N2O might suffer severe, sometimes disastrous neurological damage. Recently, a case report in the New England Journal of Medicine reported the death of a child with an enzyme defect in the MTHFR gene after anaesthesia with nitrous oxide (NEJM 2003;349:45-50).

Thus, we are convinced that if we can determine the risk of patients who carry mutations in the MTHFR gene and undergo anaesthesia with N2O for developing pathological levels of homocysteine, we can add an important piece of information to the safety profile of N2O.

Our study tests the hypothesis that patients who carry the 677C<T mutation in the MTHFR gene (the most common mutation) have a higher risk of developing hyperhomocysteinemia after N2O anaesthesia.

Enrollment: 140 patients

Sex: All

Ages: 18+ years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Patient scheduled for general anaesthesia (> 2 hours)
• Age > 18 years
• ASA status I-II

Exclusion criteria

• Pregnancy
• Age < 18 years
• contraindication against N2O: pneumothorax, mechanical bowel obstruction, middle ear occlusion, laparoscopic surgery
• recent use of vitamin preps (B12, B6, folate)

Trial design

Primary purpose: Basic Science

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)