Nitrous Oxide (N20)
Nitrous Oxide (N20), also known as laughing gas, is the only inorganic anesthetic gas in clinical use. Nitrous oxide was first prepared in 1773 by Joseph Priestley, an English clergyman and scientist, who ranks among the great pioneers of chemistry. Humphry Davy in 1798 performed brilliant investigations of several gases but focused much of his attention on nitrous oxide. Davy commented that nitrous oxide transiently relieved a severe headache, obliterated a minor headache, and briefly quenched an aggravating toothache. Davy's lasting nitrous oxide legacy was coining the phrase “laughing gas” to describe its unique property.
Essentially, N20 is colorless and odorless. N20 is as capable as oxygen of supporting combustion, although nonexplosive and nonflammable.
N20 has low tissue solubility, which results in quick removal and arousal of the patient. N20 should be used in combination of at least 30% Oxygen to avoid hypoxia and death if used alone. N20 should be used cautiously in pregnant patients because of potential teratogenic effects.
N20 effects on organs systems: (Cardiovascular)circulatory effects of N20 are explained by its tendency to stimulate the SNS. Even though N20 directly depresses myocardial contractility in vitro, arterial blood pressure, cardiac output, and heart rate are essentially unchanged or slightly elevated in vivo because of its stimulation of catecholamines. (Respiratory) N20 increases respiratory rate (tachypnea) and decreases tidal volume as a result of CNS stimulation and activation of pulmonary stretch receptors. The net effect is minimal change in minute ventilation and resting arterial CO2 levels. Hypoxic drive, the ventilatory response to arterial hypoxia that is mediated by peripheral chemoreceptors in the carotid bodies is depressed by even small amounts of N20. (Cerebral) by increasing CBF and cerebral blood blood volume, N20 produces a mild elevation of ICP. N20 also increases CMRO2....
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