Incidence of Severe Hypoxemia in Anesthetized Horses Undergoing Emergency Exploratory Laparotomy

Increased body condition score has a detrimental effect on arterial oxygen tension and increases the risk of hypoxaemia in anaesthetised horses

“…There is evidence that a positive association between bodyweight and alveolar dead space in halothane‐anaesthetised horses exists (Moens, 1989), but the specific effect of BCS or body shape was not investigated in that study. In a large retrospective study, an association between severe hypoxaemia and increased dead space ventilation in horses undergoing colic surgery was identified (Marchese et al., 2022). In the current study, calculation of estimated shunt fraction (F‐shunt), or P(A‐a)O 2 would have been desirable but due to the retrospective nature of the study, the data required for these calculations were not consistently available.…”

“…In a recent retrospective study, a shorter time between induction of general anaesthesia and arterial blood gas sampling was associated with a diagnosis of hypoxaemia in horses undergoing colic surgery (Marchese et al., 2022). Early blood gas analysis may have reduced the time for which horses were receiving 100% inspired oxygen and, furthermore, it is possible that samples were more urgently taken from the most compromised horses, therefore, causality cannot be implied.…”

“…Reported adverse effects of intra‐operative hypoxaemia in horses include an increased risk of incisional infection after colic surgery (Costa‐Farré et al., 2014), poor recovery quality (Rüegg et al., 2016) and increased blood lactate concentration and muscle deoxygenation (Portier et al., 2009). Two recent retrospective studies reported that increasing bodyweight, procedure type, high peak inspiratory pressure, increased dead space ventilation, aerosolised salbutamol administration, exploratory laparotomy and colon torsion in horses undergoing colic surgery were associated with hypoxaemia in anaesthetised horses (Hovda et al., 2022; Marchese et al., 2022). However, another study did not find a difference in PaO 2 or P(A‐a)O 2 between horses undergoing colic surgery compared to elective procedures (McCoy et al., 2011).…”

Persistent hypoxaemia and pulmonary oedema in a horse anaesthetised for emergency exploratory laparotomy

“…Development of hypoxaemia in horses anaesthetised for emergency exploratory laparotomy is a well‐recognised complication, primarily resulting from compression atelectasis, 1,2 with a variable reported incidence of 13%, 3 23% 4 and 15.3% 5 . Several risk factors have been identified, such as dorsal recumbency 6–8 ; distended intestines, with the likelihood of hypoxaemia being three times greater in horses suffering from lesions of the large intestine 4,5 ; peak inspiratory pressures (PIP) greater than 30 cmH 2 O 4 ; low pulse pressure and emergency procedures 9 ; and bodyweight more than 550 kg 4,5 …”

“…5 Several risk factors have been identified, such as dorsal recumbency [6][7][8] ; distended intestines, with the likelihood of hypoxaemia being three times greater in horses suffering from lesions of the large intestine 4,5 ; peak inspiratory pressures (PIP) greater than 30 cmH 2 O 4 ; low pulse pressure and emergency procedures 9 ; and bodyweight more than 550 kg. 4,5 Pulmonary oedema is a relatively infrequent but potentially serious event in the perianaesthetic period in horses. 10,11 It has been observed more commonly in the post-operative period in association with upper airway obstruction (UAO), [11][12][13] although the cause is often multifactorial.…”