[Severe polyneuropathy after using nitrous oxide as an anesthetic. A preventable disease?].
BACKGROUND
Nitrous oxide is a commonly used anaesthetic agent. One complication of this is due to its capacity to inactivate cobalamin. Therefore, in patients with poor reserves of vitamin B12, neurological and hematological alterations may be induced after a short period of exposure to nitrous oxide.


METHODS
A 69 year old man was anesthetized for three hours with 50% nitrous oxide during a surgical operation. Two weeks later he complained of severe mixed, mainly sensory polyneuropathy and was unable to walk. On diagnostic studies, vitamin B12 levels were found to be 18 pg/ml. The Shilling test confirmed that there was lack of intrinsic factor. In the preoperative studies a striking increase in motor conduction velocity was observed. Neurophysiological studies showed that there was mixed polyneuropathy, predominantly axonal. After starting treatment with hydroxycobalamin there was marked improvement and the patient became able to walk unaided.


CONCLUSIONS
Since nitrous oxide may cause serious neurological alterations in patients with subclinical deficits of cobalamin, which may not always be accompanied by hematological changes, we consider the need for determination of plasma levels of vitamin B12 and if possible, of methylmalonic acid and homocysteine in elderly patients who are to have general anesthetics involving nitrous oxide.
Alarcia
R
R
Servicio de Neurología, Hospital Miguel Servet, Zaragoza, España.
Ara
J R
JR
Serrano
M
M
García
M
M
Latorre
A M
AM
Capablo
J L
JL
D000368:Aged; D018685:Anesthetics, Inhalation / Q000009:adverse effects*; D001369:Axons / Q000473:pathology; D019917:Blood Vessel Prosthesis Implantation; D003711:Demyelinating Diseases / Q000139:chemically induced*; D006801:Humans; D007437:Intrinsic Factor / Q000172:deficiency; D008297:Male; D009609:Nitrous Oxide / Q000009:adverse effects* / Q000494:pharmacology; D010264:Paraplegia / Q000139:chemically induced; D011183:Postoperative Complications / Q000139:chemically induced* / Q000517:prevention & control; D011300:Preoperative Care; D012678:Sensation Disorders / Q000139:chemically induced; D014805:Vitamin B 12 / Q000032:analysis / Q000037:antagonists & inhibitors*; D014806:Vitamin B 12 Deficiency / Q000139:chemically induced*
D018685:Anesthetics, Inhalation; D007437:Intrinsic Factor; D009609:Nitrous Oxide; D014805:Vitamin B 12