Quality of restraint and the ease of intubation of intramuscular midazolam and medetomidine with ketamine or alfaxalone in swine.

  • Martina Cardinali
  • Luca Bellini
  • Francesca Zanusso
  • Giulia Maria De Benedictis


Swine often require sedation or general anaesthesia for various medical procedures. The aim of this study was to compare the effects of low doses of alfaxalone and ketamine on the quality of sedation and conditions for endotracheal intubation when midazolam and medetomidine are co-administered.

Sixteen female Large White swine, aged 6 months and weighing 28.4 ± 4.0 kg, were divided into two groups: all animals received medetomidine (7 µg/kg) and midazolam (0.4 mg/kg), with Group MMK receiving ketamine (7 mg/kg) and Group MMA receiving alfaxalone (2 mg/kg). All drugs were administered in the same syringe intramuscularly. The time from injection to recumbency was noted and defined as the onset time. A semiquantitative scale scored sedation quality at 5 and 10 minutes from injection. Intubation was then attempted, and if not feasible, additional alfaxalone was administered intravenously every 2 minutes until successful intubation was achieved. The total alfaxalone dose needed was noted, along with the assessment of the ease of endotracheal intubation.

Clinical variables evaluated at intubation time (Tpre), after 5 (T5) and 10 (T10) minutes included pulse rate, systemic arterial blood pressure, respiratory rate, arterial haemoglobin oxygen saturation (SpO2), end-tidal carbon dioxide (EtCO2), and body temperature. Both protocols induced effective restraint and smooth induction, with all animals reaching recumbency within four minutes, and no significant differences were observed between the groups. However, for successful intubation, both groups required additional boluses of alfaxalone. Muscle twitches were observed in seven swine in MMA group, but these were transient and did not adversely affect the induction period. No significant differences were found between groups in terms of sedation scores at 5 minutes or 10 minutes, induction scores, or the total dose of additional alfaxalone boluses. Respiratory rate, heart rate, and systemic arterial blood pressure and temperature also showed no significant differences between the two groups. However, EtCO2 was higher at T0, T5, and T10 compared to Tpre, and four swine experienced a decline in SpO2 below 90% after intubation.

In conclusion, low doses of alfaxalone and ketamine, in combination with medetomidine and midazolam, were effective in achieving predictable sedation in swine. The intramuscularly administered protocols allowed for the insertion of an intravenous catheter but proved insufficient for successful orotracheal intubation without additional boluses of alfaxalone. Both protocols demonstrated minimal and clinically non-relevant effects on cardiovascular and respiratory parameters. Some swine experienced hypoxaemia, emphasizing the potential need for supplemental oxygen in similar procedures.

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