Nitrous oxide respiratory effects

Nitrous oxide produces respiratory depression (38,39). It has been shown to produce a direct myocardial depressant effect in dogs (40) and in humans breathing a 40% N2O/60% oxygen mixture (41) however, this may be offset by the activation of the sympathetic nervous system (42). The combination of nitrous oxide and opioids can produce decreases in myocardial contractiHty, heart rate, and blood pressure (43). 

Jin T, Ishihara H, Ohshiro Y, Murakawa T, Kogure M, Ookura I, Tsukamoto A, Sakaki T, Oyama T. [Effect of nitrous oxide on the circulatory and respiratory functions.] Masui 1980 29(5) 458-61. 

Respiratory System Nitrous oxide causes modest increases in respiratory rate and decreases in tidal volume in spontaneously breathing patients. The net effect is that minute ventilation is not significantly changed and remains normal. Even modest concentrations of N O markedly depress the ventilatory response to hypoxia. Thus, it is prudent to monitor arterial saturation directly in patients receiving or recovering from nitrous oxide. 

Respiratory effects Rate of respiration may be increased by inhaled anesthetics, but tidal volume and minute ventilation are decreased, leading to an increase in arterial CO tension. Inhaled anesthetics decrease ventilatory response to hypoxia even at subanesthetic concentrations (eg, during recovery). Nitrous oxide has the smallest effect on respiration. 

The oxides of nitrogen are somewhat sol in w, reacting with it in the presence of oxygen to form nitric and nitrous acids. This is the action that takes place deep in the respiratory system. The acids formed are irritants, causing congestion of the throat and bronchi, and edema of the lungs. The acids are neutralized by the alkalies present in the tissues, with the formation of nitrates and nitrites. The latter may cause some arterial dilation, fall in blood press, headache and dizziness, and there may be some formation of methemoglobin. However, the nitrite effect is of secondary importance... 

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