Arterial oxygen and carbon dioxide tensions in conscious laterally recumbent ponies

Abstract

Summary Six adult ponies were trained calmly to assume and maintain left lateral recumbency without the use of sedative or immobilising agents. During a 30 min recumbent period, pHa, arterial oxygen and carbon dioxide tensions (Pao2 and PacO2) and heart and respiratory rates were monitored at regular intervals to evaluate ventilatory response. Overall, there were no statistically significant differences found between mean control and recumbent or final standing values. When light‐weight ponies were compared to heavyweight ponies, only mean Pao2 at 10 mins recumbency was different. This information supports the hypothesis that ventilation impairment during the first 30 mins of equine general anaesthesia is primarily drug‐mediated, rather than initiated by recumbency per se.

Alfaxalone compared with ketamine for induction of anaesthesia in horses following xylazine and guaifenesin

“…These slightly elevated PaCO 2 values would not have contributed much to the reduction of alveolar oxygen concentration. Oxygen tensions during anaesthesia ranged from 5.1 to 8.8 kPa (38-63 mmHg) and 5.7-9.7 kPa (43-73 mmHg) for alfaxalone and ketamine respectively which were comparable to those measured during many protocols for field anaesthesia but below the expected values for awake horses breathing air (mean ± SD 94 ± 2 mmHg; Rugh et al 1984). Whatever the drug induced factor that causes hypoxia in equine anaesthesia, the two drugs appear to have had similar effects.…”

“…Rugh et al. (1984) measured arterial oxygen and carbon dioxide tensions in conscious ponies that were trained to lie in lateral recumbency for 30 minutes.…”

“…This may have contributed to longer recovery times. Rugh et al (1984) measured arterial oxygen and carbon dioxide tensions in conscious ponies that were trained to lie in lateral recumbency for 30 minutes. Although heavier ponies had significantly lower oxygen tensions than lighter ponies at 10 minutes, recumbency had no effect on oxygen tensions overall.…”

An evaluation of apnea or spontaneous ventilation in early recovery following mechanical ventilation in the anesthetized horse

“…In both groups, predictable changes in the respiratory function of an anesthetized horse were demonstrated. Anesthetized, recumbent horses are known to have reduced oxygen tensions during dorsal recumbency and greater A–a gradients than lateral recumbency (Rugh et al. 1984; Dobson et al.…”

Anaesthetic emergencies and complications: Part 1

“…Hypoxaemia and hypercarbia are common sequelae of general anaesthesia in horses, especially if positioned in dorsal recumbency or anaesthetised for prolonged durations (Hall 1971;McDonnell et aE. 1979;Rugh et al 1984;Stegman 1986;Nyman and Hedenstierna 1989). Hypoxaemia can be caused by the respiratory depressant effects of anaesthetic drugs (Hall 1979(Hall , 1984 in conjunction with absorptive and compressive atelectasis of the caudal lung lobes secondary to visceral compression (McDonnell et al 1979;Wagner et al 1990a;Nyman et al 1990).…”