| Abstract: | Lung-mechanics during cardio-pulmonary bypass were studied in 20 patients operated upon for heart disease. Pulmonary resistance to gas flow, pressures and compliance were continuously measured with the aid of a respiratory analogue computer. Measurements were made at constant blood gas tensions in the oxygenator with various combinations of inspired carbon dioxide fractions with oxygen, halothane and methoxyflurane. Oxygen with carbon dioxide proved to be a strong broncho-dilatator as well as oxygen + halothane with decreases in resistance of 15–8% of control values, respectively. This was combined with an increase in compliance of 6–5%. In contrast to halothane and carbon dioxide, the mixture of oxygen + methoxyflurane resulted in an increase of resistance with 6%. Methoxyflurane and carbon dioxide resulted in a decrease of the resistance with 16%. It is concluded that halothans and carbon dioxide have a direct action on bronchial smooth muscles, but that such an effect is lacking for methoxyflurane. If diethyl-ether, which was not tested due to explosive risks, has similar pharmacological properties as methoxyflurane then the beneficial effect of diethyl-ether in bronchoconstrictive conditions ought to be elicited through adrenergic stimulation with the liberation of cathecholamines into the pulmonary circulation. Such an action of diethyl-ether is known to support the myocardial function during anaesthesia. The study of anaesthetic agents on smooth muscles of the bronchial system during conditions of lung bypass is of interest, as conclusions can be drawn as to the most suitable anaesthetics to be given to patients with bronchoconstrictive disease. The results indicate that halothane is such an agent in contrast to methoxyflurane. |
