Influence of the Neuroleptanalgesic Combination of Etorphine and Acepromazine on the Horse: Blood Gases and Acid‐base Balance

Abstract

SUMMARY Respiratory function and acid‐base variables were studied in Welsh Mountain ponies before and at predetermined times after the intravenous injection of Immobilon and Revivon. A marked depression of respiratory rate was accompanied by large reductions in arterial blood oxygen tension and saturation and the development of a mild respiratory acidosis following the injection of Immobilon. It was concluded that at least three factors contributed to the hypoxic hypoxia produced by Immobilon; the posture of lateral recumbency, the decrease in respiratory rate and the laboured character of the respiration. Arterial oxygen and carbon dioxide tensions returned towards control levels soon after administering Revivon. Mixed venous oxygen tensions were little affected by either Immobilon or Revivon, and mixed venous carbon dioxide tensions were increased to smaller degrees than those of arterial blood. Haemoglobin concentration was increased initially by Immobilon, had returned to the control level by 30 min and fell below the control following the administration of Revivon. RÉSUMÉ La fonction respiratoire et les variations acide‐base furent étudiées sur des poneys Welsh Mountain, avant, puis à des moments pré‐déterminés suivant l'administration d'Immobilon et de Revivon. Une dépression marquée du rythme respiratoire accompagnée par une chute importante de la pression d'oxygène dans le sang artériel et par une acidose respiratoire modèrée furent constatés, après injection d'Immobilon. On en a conclu que trois facteurs au moins contribuent à l'hypoxie engendrée par l'Immobilon: le decubitus latéral, le ralentissement du rythme respiratoire, et le caractère pénible de la respiration. Après l'injection de Revivon le taux de l'oxygène artériel et de CO2 revinrent rapidement à la normale. La tension veineuse d'oxygène fut peu modifiée par l'Immobilon ou par le Revivon, la tension de CO2 veineuse étant accrue à un moindre degré que dans le sang artériel. L'Immobilon éleva la concentration en hémoglobine à la phase initiale, concentration revenant à la normale après 30 minutes puis diminuant après injection de Revivon. ZUSAMMENFASSUNG Die Atemfunktionen und Säure‐Basenwerte von Welshponies wurde vor und zu bestimmten Zeiten nach der intravenösen Injektion von Immobilon und Revivon untersucht. Eine deutliche Depression der Atemfrequenz wurde begleitet von einer starken Reduktion der arteriellen Sauerstoffspannung und –sättigung und von der Entwicklung einer milden respiratorischen Acidose nach der Injektion von Immobilon. Es wurde geschlossen, dass zum mindesten drei Faktoren für die Hypoxie nach Immobilongabe verantwortlich gewesen sind: die Seitenlage, der Abfall der Atemfrequenz und die angestrengte Atmung. Arterielle Sauerstoff‐ und Kohlensäurespannungen kehrten kurz nach der Verabreichung von Revivon zur Norm zurück. Gemischte venöse Sauerstoffspannungen wurden von Immobilon und Revivon wenig beeinflusst und die venöse Kohlensäurespannung erhöhte sich weniger deutlich als in arteriellem Blut. Die Haemoglobinkonzentration...

Rectal prolapse associated with a healed pelvic fracture in a pregnant free-ranging African black rhinoceros (Diceros bicornis). Part 1 : anaesthesia : case report

“…The increase in the CO2 tension (37 %) indicated an increase in ventilatory depression in time that was confirmed by subjective observation of the reservoir bag. However, the CO2 tension was higher compared to partial pressures reported for etorphine-acepromazine-immobilised horses breathing air (7.3 kPa) 3 . The decrease in the PO 2 from 26.5 to 15.5 kPa as was observed in the rhinoceros may have been an indication of deterioration in pulmonary function.…”

“…A mixed respiratory-and metabolic acidosis resulted in a decrease in the pH to 7.16 and the standard base excess to 4.2 mmol/ . In comparison, the pH for mixed venous blood only decreased from 7.35 to 7.32 units in etorphine-acepromazine anaesthetised horses 3 . Acidosis may adversely affect cardiac contractility 16 if the arterial pH decreases below 7.2.…”

“…It is suggested that the ventilatory depression imposed by etorphine is partially countered by the hypoxic ventilatory drive, thus increasing minute ventilation. Hypoxia is a common finding during etorphine immobilisation in large mammals 3 . Inhalation of high oxygen concentrations results in increased partial pressure of oxygen in comparison to the pressures when breathing air, resulting in a decrease in the hypoxic ventilatory drive and decreased minute ventilation.…”

Metabolic and hormonal responses to neuroleptanalgesia (etorphine and acepromazine) in the horse

“…The cardiovascular and respiratory effects of the agent have been well documented (Hillidge andLees 1971, 1975a;Daniel and Ling 1972;Jenkins et al 1972;Schlarmann, Gorlitz, Wintzer and Frey 1973). There are some reports on the influence of this drug combination on serum enzyme activity in the horse (Hillidge, Lees, Mullen and Serrano 1974;Hillidge 1978) but few on its metabolic (Hillidge and Lees 1971) and hormonal effects (Mackenzie 1977). In this paper, the effects of Immobilon and of its antagonist diprenorphine (Large Animal Revivon; Reckitt and Coleman) on the haematocrit, venous pH and blood gases, blood glucose and lactate, plasma non-esterified fatty acids (NEFA), insulin and cortisol are described and the significance of these changes discussed.…”

The Analgesic Effect of Buprenorphine, Etorphine and Pethidine in the Pig: A Randomized Double Blind Cross‐over Study

“…Etorphine is an extremely potent morphine-like analgesic which is used for restraining wild animals (Harthoorn 1966) and as a component of neuroleptanalgesic combinations in different species (Hermansen & Larsen 1974;Hillidge & Lees 1975). In the pig etorphine has mainly been used for immobilization (Cox et a/.…”