Epsilon Archive for Student Projects

Abstract

Hypoxaemia is a common complication in equine general anaesthesia, primarily caused by ventilation-perfusion mismatch and atelectasis. While aerosolised salbutamol, a β₂-adrenergic agonist, is widely used to improve oxygenation, its efficacy and impact on haemodynamic variables remain debated. This retrospective study aimed to evaluate clinical use of salbutamol in horses under general anaesthesia, focusing on its effect on cardiovascular parameters, indications, administration and to explore if salbutamol was effective at different degrees of hypoxemia based on baseline values of saturation.

Medical records from 33 cases receiving salbutamol during general inhalation anaesthesia at the SLU University Animal Hospital (UDS) met the inclusion criteria. Data collected included anaesthetic protocols, administered doses, and monitored heart rate (HR), systolic (SYS), diastolic (DIA) and mean arterial blood pressure (MAP) and saturation (SpO2). Statistical analyses compared pre- and post-administration values using Friedman tests with Dunn’s post hoc comparisons.

Salbutamol dosing, duration of parameter monitoring after drug administration and individual alterations in collected parameters varied widely. A significant improvement in SpO₂ was observed in mildly hypoxaemic horses (baseline SpO₂ 90-94%) at 10 and 15 minutes (P < 0.0001) post-administration, but not in severely hypoxaemic (SpO₂ <90%) or non-hypoxaemic (SpO2 ≥95%) horses. No significant changes in HR or MAP were detected, contrasting with experimental studies in non-hypoxaemic horses.

In conclusion, salbutamol improved saturation in mildly hypoxaemic horses but showed inconsistent efficacy in severe hypoxaemia, with no significant cardiovascular effects observed in these cases. These results might indicate that the severity of hypoxaemia may influence salbutamol’s effect on oxygenation and cardiovascular parameters. The greater impact in less severe hypoxaemic horses raises questions regarding the drugs optimal indication, suggesting it as a preventive measure rather than a rescue intervention when aiming to promote oxygenation. Future research should aim to determine salbutamol’s mechanism of action, its effect in hypoxaemic clinical patients and haemodynamic variables and compare its efficacy with other oxygenation strategies. If the desired effect is achieved, salbutamol might be a cost-effective and practical technique promoting a safe general anaesthesia for the patient. However, clinicians should take careful consideration when electing salbutamol for treatment and be prepared to adjust the treatment strategy depending on individual patient response.