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Open Access Retrospective Evaluation of Cardiopulmonary and Acid-Base Variables During Long-Term Balanced Anesthesia for Experimental Surgery in Dogs

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Cardiopulmonary and acid-base variables recorded during long-term balanced anesthesia lasting between 12.5 and 16.9 h were evaluated retrospectively in 15 healthy foxhounds that underwent experimental bulla osteotomy with implantation of hearing aids. After premedication with propionylpromazine (0.11 0.02 mg/kg of body weight) and L-methadone (0.71 0.06 mg/kg) intravenously (i.v.) and induction with pentobarbital sodium (6.02 0.83 mg/kg i.v.), anesthesia was maintained with halothane (end-tidal concentration; ETHAL: 0.4 to 1.5%) in nitrous oxide (2 L/min) and oxygen (1 L/min). Because of positional changes from sternal to right lateral recumbency after presurgical brain stem electric response audiometry and differences in duration of surgery, data obtained between 4 (baseline) and 14 h after induction of anesthesia were analyzed. Arterial (Pao2) and alveolar (PAo2) O2 tensions, arterial-to-alveolar O2 tension ratio (Pao2/PAo2), and arterial O2 content (Cao2) remained relatively stable throughout anesthesia. Arterial carbon dioxide tension (Paco2) was significantly increased above baseline (39, 33 to 46 mm Hg [median, range]) between 7 (39.8, 36.5 to 48.9 mm Hg) and 9 (42, 37.5 to 49.5 mm Hg) h after induction. Because changes in Paco2 were accompanied by significant increases in body temperature from baseline (36.3, 34.6 to 37.4°C) between 8 (37.1, 35 to 38°C) and 11 (37.6, 35.3 to 38.1°C) h after anesthesia induction as well as by slight increases in arterial blood pressure, the Paco2 increase may have been caused by increase in metabolic CO2 production and enhanced drainage of CO2 from the tissues into systemic circulation. Furthermore, mild metabolic acidosis (pHa: 7.31, 7.26 to 7.38; HCO3: 18.9, 16.7 to 21.8 mEq/L; base deficit [BD]: -6.3, -8.5 to -3.4 mEq/L) already existed at 4 h after induction and was related in part to tissue hypoperfusion. Small increases in pHa during the course of anesthesia were accompanied by significant increases in HCO3 concentration and significant decreases in BD between 5 and 10 h after induction. Minor circumscribed swelling of the dependent triceps or masseter muscle was noticed on the first postoperative day in two dogs, and marked tissue swelling with hematoma formation at the medial side of one hind limb was noticed in a third dog. All dogs recovered completely and were submitted to follow-up studies. The anesthetic protocol and extent of monitoring used were adequate to provide safe long-term anesthesia for an experimental surgical procedure with a 100% survival rate and uneventful recovery in most of the dogs.

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Document Type: Research Article

Affiliations: 1: Central Animal Research Facilities, Hannover Medical School, Hannover, Germany, Zentrales Tierlaboratorium, Medizinische Hochschule Hannover, Konstanty-Gutschow-Str. 8, 30625 Hannover, Germany 2: Department of Otolaryngology, Hannover Medical School, Hannover, Germany 3: Central Animal Research Facilities, Hannover Medical School, Hannover, Germany

Publication date: December 1, 1997

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  • Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.

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