Inhalation Anesthesia or Balanced Anesthesia in Swine

Abstract

Swine have been used as animal models in experimental surgeries. In order to determine possible alterations in the physiological parameters caused by inhalation anesthesia and balanced anesthesia in swine undergoing lateral thoracoscopy, 14 animals weighing 15 to 20 kg were used.  The animals were divided into two groups, group I (inhalation anesthesia) and group II (balanced anesthesia). Both groups received preanesthetic medication (atropine sulphate and midazolam). In group I, anesthesia was induced by the administration of thiopental sodium. Anesthesia was maintained by administering oxygen and isoflurane. In group II, anesthesia was induced by an association between fentanyl and midazolam, followed by thiopental sodium and pancuronium. Then the animals were mechanically ventilated. Anesthesia was maintained with isoflurane and continuous administration of fentanyl and pancuronium every 20 minutes. Cardiocirculatory variables, respiratory and body temperature were measured every 15 minutes during 60 minutes of anesthesia. PaO₂ (in mmHg) of group II at T₀ presented a significant reduction from 415.43 ± 47.35 to 332.06 ± 55.81, which may be explained by the occurrence of apnea caused by the use of pancuronium. PaCO₂ of group II presented a significant reduction at all times measured. Mean values (in mmHg) of the four times in group I and group II were 35.33 ± 8.67 and 24.20 ± 10.98, respectively, which may be explained by reduced muscle metabolism and decreased CO₂ production due to the use of pancuronium associated with the effect of artificial ventilation. We concluded that the use of neuromuscular blockers associated with artificial ventilation may reduce the concentrations of PaCO₂ in thoracic surgeries in swine.