No abstract

High fractional concentrations of inspired oxygen (FiO 2 ) delivered over prolonged periods produce characteristic histological changes in the lungs and airway of exposed animals. Modern medical anaesthetic machines are adapted to deliver medical air (FiO 2 =0.21) for the purpose of reducing FiO 2 ; anaesthetic machines designed for the veterinary market have not been so adapted. Two inexpensive modifications that allow medical air to be added to the gas flow from veterinary anaesthetic machines are described. The advantages and disadvantages of each modification are discussed.HIGH oxygen (O 2 ) concentrations are toxic to dogs (Cimons and others 1966, Clarke and others 1973), cats (Lambertsen and others 1953) and laboratory animal species (Frank and others 1978), including pigs (Yam and Roberts 1980), when delivered over prolonged periods (Smith 1899) or under hyperbaric conditions. They also increase the risk of combustion or explosion during surgery involving high-energy devices (Wolf and others 2004). Oxygen toxicity, which may be fatal, is characterised by adverse neurological signs, for example, seizures and pulmonary signs (atalectasis, pulmonary capillary congestion, interstitial oedema, haemorrhage) that appears to be dependent on age and species. Younger animals have a variable response to high inspired fractional O 2 concentrations (FiO 2 ): precocial neonates such as guinea pigs respond in a similar fashion to adults, but rat, mouse and rabbit neonates appear to be resistant (Frank and others 1978); the same is true for piglets (Yam and Roberts 1980). However, although they survive hyperoxic environments, altricial neonates show abnormal alveolarisation and pulmonary vascular development (Frank 1991). These factors may be important in prolonged administration of high O 2 concentrations to companion animals in the intensive care setting; laboratory animal studies of lung structure or function; prolonged surgical or experimental procedures involving anaesthesia, where O 2 -induced lung damage may increase morbidity, and extendedCorrespondence: e.clutton@ed.ac.uk. Provenance not commissioned; externally peer reviewed Europe PMC Funders Group

A 16‐year‐old, 550 kg Connemara gelding was anaesthetised for resection of multiple small intestine strangulating lipomas via ventral midline celiotomy. Severe hypoxaemia, detected throughout the anaesthetic period (lowest PaO2 58 mmHg [7.6 kPa]), was unresponsive to the ventilatory strategies implemented. Flared nostrils and increased respiratory rate were present at recovery from anaesthesia. When the horse was returned to the yard, bilateral foamy nasal discharge and increased respiratory effort and rate were noticed, consistent with pulmonary oedema. The horse received oxygen supplementation and furosemide, which led to complete resolution within 24 hours.

Torsade de pointes is an unusual complication seen in dogs during pacemaker implantation, although ventricular fibrillation has been previously reported. This case report describes torsade de pointes in a dog during pacemaker implantation that degenerated into ventricular fibrillation, and discusses the possible contributory factors. It also illustrates the relevance of a pre-emptive resuscitation plan and how this might have affected the outcome in the patient.