Réponse ventilatoire à l'hypercapnie et à l'hypoxie hypocapnique du chien sous différents niveaux d'anesthésie à l'Alfatésine

Abstract

The authors have studied the response to hypercapnia and hypocapnic hypoxia in nine dogs anesthetised with Althesin, in correlation with three levels of anaesthesia defined by three different anaesthetic flow rates (A = 6.57 ± 2.00 μl . kg −1 . min −1; B = 13.88 ± 2.87 μl . kg −1 . min −1; C = 19.53 ± 5.34 μl . kg −1 . min −1). The animals were intubated. Ventilation was measured by means of a pneumotachograph. Arterial blood gases (pHa, PaCO 2, PaO 2) were measured before and at the end of each hypercapnia and hypocapnic hypoxia test. The results were compared with data in the literature concerning the dog awake. Increasing depth of anaesthesia leads to worsening hypoventilation and hypercapnia. As with other anaesthetic agents, the response to hypercapnia is more depressed the deeper the anaesthesia. On the other hand, unlike what has been described with other anaesthetic agents, hypoxia stimulates ventilation; the response to hypoxia is not abolished by the deeper states of anaesthesia. The possible mechanisms of this difference are discussed.