Laughing Gas

LAUGHING GAS, a name denoting either nitrous oxide in pure form or a mixture of the latter with air, respectively with oxygen. Nitrous oxide, Nitrogenium oxydulatum-N₂O; molecular weight 44, specific gravity 1.524 (air=1); a colorless gas with a weak, pleasant odor and a sweetish taste; at a temperature of 0° and 30 atmospheres of pressure, it condenses into a liquid boiling at -89.8° and freezing at -102°. It is readily soluble in cold water. It supports combustion like oxygen, but does not support respiration. N₂O is produced by heating ammonium nitrate salt to no higher than 250° (caution is required to avoid explosion). It is commercially available in a compressed state (liquid in cylinders with a valve). When inhaled in pure form, N₂O causes, in approximately 1 minute, a state of anesthesia with loss of consciousness, sensitivity, and reflexes, and with muscle relaxation, and then, if inhalation is continued, asphyxia ensues. The convulsions usually observed in asphyxia do not occur here. If inhalation is stopped, the anesthesia continues for 1/3-1 minute, and then, due to the rapid elimination of laughing gas from the organism, the anesthetized person wakes up and quickly returns to normal. Anesthesia with laughing gas presents almost no danger and is used for short operations (1/2-1 minute). For more prolonged use, laughing gas is mixed with oxygen in a ratio of 4:1 (Paul Bert), i.e., in the ratios of nitrogen and oxygen in air. When inhaling such a mixture, some clouding of consciousness is observed, often with a cheerful mood (hence the term "laughing gas"), tinnitus, weakening of vision and pain sensations, but complete anesthesia does not occur. Laughing gas was used for attacks of angina pectoris, asthma, paroxysms of cough, as well as in childbirth and in dental practice; at present, much attention is once again being paid to laughing gas among anesthetic agents. To obtain complete anesthesia, Paul Bert proposed inhaling the specified mixture at a somewhat increased pressure so that the partial pressure of laughing gas is also increased to a full atmosphere, since inhaling gas at increased pressure with low external pressure would inevitably lead to emphysema. When applying Paul Bert's method, it is necessary that the pressure in the room where the anesthesia and operation are performed is also increased, and this, in turn, makes it necessary to construct special, hermetically sealed operating rooms with special ventilation devices. The anesthesia induced in this way develops very quickly, is almost entirely devoid of an excitation stage, is not accompanied by a drop in blood pressure, and can be maintained for a very long time: according to Martin's experiments on himself, up to 7 hours, and according to the same author's experiments on animals, up to 72 hours. When applying Paul Bert's mixture at normal pressure, mixed anesthesia is frequently resorted to with preliminary subcutaneous administration of morphine and scopolamine. In this case, prolonged anesthesia can also be achieved. When using laughing gas, the purity of the preparation is very essential; it must be tested for the presence of 1) carbon dioxide, 2) halogens, 3) acids and ammonia, 4) reducing gases. Literature: Vershinin N. V., Pharmacology as the Basis of Therapy, Tomsk, 1926; Hagers Handbuch der pharmazeutischen Praxis, B., 1927; Pouchet G., Lecons de pharmacodynamie et de matiere medicale, serie I, P., 1900.