Long-term effects of nitrous oxide anaesthesia on laboratory and clinical parameters in elderly Omani patients: A randomized double-blind study

Department of Clinical Pharmacology, Sultan Qaboos University, PO Box 35, Al-Khod, Muscat-123, Sultanate of Oman.
Journal of Clinical Pharmacy and Therapeutics (Impact Factor: 1.67). 09/2000; 25(4):271-7. DOI: 10.1046/j.1365-2710.2000.00287.x
Source: PubMed


This study examined the long-term effects of nitrous oxide anaesthesia on serum levels of cobalamin and folate, red cell folate levels and haematological parameters, and neurological status in elderly Omani patients.
Sixty-nine consecutive patients undergoing ophthalmic surgery were randomly and double-blind assigned to nitrous oxide or propofol anaesthesia. They met the following entry criteria: age 55 years or above, no major organ failure, no clinical signs or symptoms of cobalamin or folate deficiency, mean cell volume (MCV) </= 96 fl, haematocrit (Hct) higher than 0.3 and no cobalamin and/or folate substitution therapy during the preceding months. Serum levels of cobalamin and folate, red cell folate levels, and haematological parameters were measured prior to anaesthesia and 3-5 weeks later. At that time, the patients also underwent thorough neurological examination.
Data of 51 patients were complete and considered for analysis. In both nitrous oxide and propofol group, the range of exposure time was comparable (+/-1 h). In the nitrous oxide group, a slight but significant decrease in haemoglobin, Hct, and red blood cell count (RBC) (P < 0.001) was observed, whereas there was a mild increase in mean cell haemoglobin (MCH) and mean cell volume (P < 0.05). In addition, there was a significant decrease in serum folate levels (P < 0.05). Hct and RBC decreased slightly in the propofol group (P < 0. 05), whereas there was a small increase in MCH. There was no difference between the two anaesthetics with regard to serum cobalamin and red cell folate levels, but there was a significant decrease in serum folate levels in the nitrous oxide group compared to those in the propofol group. Three patients with pre-existing low red cell folate levels, who were randomized to nitrous oxide anaesthesia, developed clinical symptoms of folate deficiency.
This study showed that short-term (40-80 min) nitrous oxide anaesthesia did not affect cobalamin levels but reduced serum folate levels in this elderly population. Although this reduction was clinically irrelevant, some patients with pre-existing asymptomatic folate deficiency developed nitrous oxide-induced folate deficiency.

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Available from: Dirk Deleu, May 04, 2015
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    ABSTRACT: Nitrous oxide (N2O) has been used for about 150 years in clinical anaesthesia. Several recent reviews of the effect of nitrous oxide have concluded that there are certain contraindications to the use of this gas for general anaesthesia and its ecological effects, ozone depleting potential, immune depression and the proven factor of PONV have questioned the routine use of nitrous oxide in patients undergoing surgical procedures in general anaesthesia. This study comprised of 200 adult patients undergoing general anaesthesia with 40% O2 and Sevoflurane with and without N2O. All patients had standard anaesthetic care and monitoring with BIS monitoring in 120 patients. The effect of avoiding N2O was observed on anaesthetic perioperative management and haemodynamics, PONV and pain in PACU. Demographic and perioperative characteristics were similar to both groups. Nitrous oxide free group needed only 0.233% (mean) more Sevoflurane. There was a marked reduction in incidence of PONV (11% to 5%) in N2O free group. Duration of surgery (97.72 +/- 52.393 in N2O group, 103.75 +/- 48.671 in N2O free group) and induction dose of propofol (155.30 +/-38.572 in N2O group and 158.50 +/- 36.164 in N2O free group) did not differ significantly in the two groups. The omitting of N2O from anaesthetic regimen has a substantial impact on patient comfort after surgery by reducing incidence of PONV and it does not have any justifiable indication of its use in General anaesthesia.
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    ABSTRACT: Nitrous oxide interacts with vitamin B12 resulting in selective inhibition of methionine synthase, a key enzyme in methionine and folate metabolism. Thus, nitrous oxide may alter one-carbon and methyl-group transfer most important for DNA, purine and thymidylate synthesis. Long-term exposure to high concentrations of nitrous oxide may cause megaloblastic bone-marrow depression and neurological symptoms. Exposure to higher doses for less than 6 hours, as in clinical anaesthesia, are considered harmless. Recent studies seem to suggest a correlation between nitrous oxide anaesthesia and hyperhomocysteinaemia which is accepted to be an independent risk factor for coronary artery disease. As for today, available data do not support the notion that exposure to trace amounts of nitrous oxide is associated with impaired fertility or an increased risk of developing cancer. Emission of nitrous oxide from medical use is estimated to contribute less than 0·05% to total annual greenhouse gas emission.
    No preview · Article · Nov 2001 · ains · Anästhesiologie · Intensivmedizin
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