Assessment of isoflurane-induced anesthesia in ferrets and rats.

OBJECTIVE: To characterize isoflurane (ISO)-induced anesthesia in ferrets and rats. ANIMALS: 8 ferrets (Mustela putorius furo) and 8 Sprague-Dawley rats. PROCEDURE: Ferrets and rats were anesthetized in a similar manner, using ISO in oxygen. Minimum alveolar concentration (MAC) was determined, using the tail-clamp method. Immediately thereafter, assessments were recorded for 0.8, 1.0, 1.5, and 2.0 MAC (order randomized) of ISO. RESULTS: MAC of ISO was (mean +/- SEM) 1.74 +/- 0.03 and 1.58 +/- 0.05% for ferrets and rats, respectively. Mean arterial blood pressure (MAP) was 75.0 +/- 4.3 and 107.9 +/- 2.7 mm Hg at 0.8 MAC for ferrets and rats, respectively, and decreased in a parallel dose-dependent manner. Respiratory frequency decreased in rats as ISO dose increased; however, respiratory frequency increased in ferrets as ISO dose increased from 0.8 to 1.5 MAC but then decreased at 2.0 MAC. At 0.8 MAC, hypoventilation was much greater in ferrets (PaCO2 = 71.4 +/- 3.5 mm Hg), compared with rats (PaCO2 = 57.7 +/- 1.9 mm Hg). In both species, PaCO2 progressively increased as anesthetic dose increased. Eyelid aperture of ferrets increased in a dose-dependent manner. Pupil diameter in ferrets and rats increased as ISO dose increased. CONCLUSIONS AND CLINICAL RELEVANCE: The MAP and PaCO2 in ferrets and rats and eyelid aperture in ferrets consistently and predictably changed in response to changes in anesthetic dose of ISO. Magnitude of respiratory depression was greater in ferrets than rats. Changes in MAP and PaCO2 in ferrets and rats and eyelid aperture in ferrets are consistent guides to changes in depth of ISO-induced anesthesia.

A comparison of simultaneously collected arterial, mixed venous, jugular venous and cephalic venous blood samples in the assessment of blood-gas and acid-base status in the dog.

Blood samples were collected simultaneously from the pulmonary artery, jugular vein, cephalic vein, and carotid artery in awake dogs. Blood-gas and acid-base values were measured from these blood samples in normal dogs and in dogs after production of metabolic acidosis and metabolic alkalosis. The values obtained from each of the venous sites were compared with those obtained from arterial blood to determine if venous blood from various sites accurately reflected acid-base balance and could therefore be used in the clinical patient. The results of this study demonstrated significant differences between the blood from various venous sites and the arterial site for PCO2 and pH in all acid-base states. Significant differences for standard bicarbonate (SHCO3) were found only when jugular and cephalic venous blood were compared with arterial blood in dogs with a metabolic acidosis. No significant differences were found for BE when blood from the venous sites was compared with arterial blood. The values for pH, HCO3, TCO2, BE, and SHCO3 measured on blood collected at the various venous sites were found to correlate well with those obtained from arterial blood, with a correlation coefficient of 0.99 for HCO3, TCO2, BE, and SHCO3. These correlation coefficients, together with similar values in BE at all collection sites, indicate that, in the dog with normal circulatory status, blood from any venous site will accurately reflect the acid-base status of the patient.