the following inhalation accumulates in air-filled cavities

Discussion in 'MRCS Forum' started by Lona., Nov 27, 2007.

  1. Lona.

    Lona. Guest

    Which of the following inhalation accumulates in air-filled cavities during general anesthesia?
    a- Diethyl ether
    b- Nitrous oxide
    c- Halothane
    d- Methoxyflurane
    e- Trichloroethylene
  2. Lona.

    Lona. Guest

    Answer: B. (Greenfield, 2/e, p 439) Nitrous oxide (N2O) has a low solubility compared with other inhalation anesthetics. Its blood-gas partition coefficient is 0.47 and it is 30 times more soluble in blood than is nitrogen (N2). N2O is also the only anesthetic gas less dense than air. As a result of these properties, N2O may cause progressive distension of air-filled spaces during prolonged anesthesia. This can lead to undesirable situations whenever there is a pneumothorax or intestinal obstruction or when procedures such as pneumoventriculography (in which the intracranial air space is not free to expand in response to the diffusion of gas into the ventricles) are performed. In each of these cases, N2O diffuses into the gas-filled compartment faster than N2 can diffuse out. Since the typical mixture of ingested air (or pneumothorax air) is 80% N2 and the usual mixture of nitrous oxide anesthetic gas is 80% N2O, rapid increase in the size of gas-filled chambers with potentially serious consequences may occur.

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