title: Preoperative folate and homocysteine status in patients undergoing major surgery.
abstract: OBJECTIVE
  Patients with folate deficiency and elevated homocysteine (Hcy) levels have increased risk of cerebrovascular and cardiovascular disease. They may also be at increased risk of complications after surgery because nitrous oxide interferes with folate metabolism. The aim of this study was to assess the incidence of folate deficiency and hyperhomocysteinemia in patients presenting for major surgery. We also tested the utility of a brief preoperative medical and dietary questionnaire to identify those with low folate or elevated Hcy levels.
  
  
  METHODS
  We enrolled 390 patients and obtained a preoperative fasting blood sample from each of the study participants (folate [n=386], homocysteine [n=387]).
  
  
  RESULTS
  Although only one patient had folate deficiency preoperatively (incidence +/-SD folate and Hcy concentrations were 23.7+/-5.2 nmol/l and 9.4+/-4.2 micromol/l, respectively. There was a negative correlation between folate and Hcy, r=-0.27, P<0.001. Multivariate analyses indicated that vegan status and folate supplementation prevented low folate status (P<0.05), while age of the patient, and history of heart failure and anaemia predicted elevated Hcy concentration.
  
  
  CONCLUSIONS
  Some factors identified by a brief medical and dietary questionnaire are associated with folate and homocysteine status. Hyperhomocysteinaemia occurs in about 7.5% of surgical patients; however, both low folate status and elevated Hcy concentration are less likely in those taking folate or vitamin B supplements. This has implications for patients undergoing nitrous oxide anaesthesia because of its inhibition of folate metabolism, and should prompt clinicians to consider folate and other nutritional supplementation before elective surgery.
authors.affiliation: Department of Anaesthesia and Perioperative Medicine, Alfred Hospital, Commercial Road, Academic Board of Anaesthesia and Perioperative Medicine, Monash University, Melbourne, Vic., 3004, Australia. p.myles@alfred.org.au
authors.forename: Paul S
authors.initials: PS
authors.lastname: Myles
authors.forename: Matthew T V
authors.initials: MT
authors.lastname: Chan
authors.forename: Andrew
authors.initials: A
authors.lastname: Forbes
authors.forename: Kate
authors.initials: K
authors.lastname: Leslie
authors.forename: Michael
authors.initials: M
authors.lastname: Paech
authors.forename: Philip
authors.initials: P
authors.lastname: Peyton
mesh_terms: D018685:Anesthetics, Inhalation / Q000009:adverse effects; D019587:Dietary Supplements; D005215:Fasting; D005260:Female; D005492:Folic Acid / Q000097:blood* / Q000378:metabolism; D005494:Folic Acid Deficiency / Q000453:epidemiology* / Q000378:metabolism; D006710:Homocysteine / Q000097:blood* / Q000378:metabolism; D006801:Humans; D020138:Hyperhomocysteinemia / Q000453:epidemiology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009609:Nitrous Oxide / Q000009:adverse effects; D015596:Nutrition Assessment; D009752:Nutritional Status; D011300:Preoperative Care; D011795:Surveys and Questionnaires
chemical_list: D018685:Anesthetics, Inhalation; D006710:Homocysteine; D005492:Folic Acid; D009609:Nitrous Oxide