[Respiratory functional hypoxia in ruminants under general anesthesia]. / Die respiratorisch-funktionelle Hypoxie beim Wiederkäuer unter Allgemeinanästhesie.

General anesthesia causes a marked hypoxia in ruminants. We compared this phenomenon with anaesthesia related changes in the dog. Under alfentanil/etomidat anaesthesia some variables of the pulmonary circulation (TPR, PAP, PCWP) as well as arterial and venous blood gases and saturation (HbO2, pO2, ph) in dogs, sheep and calves were measured and calculated. The calculated pulmonary shunt fraction was compared between the three species. In ruminants there was an increase of total pulmonary resistance being associated with elevated PAP and decreased PCWP. The pulmonary shunt fraction was increased significantly and markedly during the surgical tolerance period, too. These parameters were not significantly changed in the dog. Ruminants seem to take an exceptional position concerning the anaesthesia related alterations of the pulmonary ventilation/perfusion system.