A comparison of respiratory function in pigs anaesthetised by propofol or alfaxalone in combination with dexmedetomidine and ketamine

Abstract

Background: General anaesthesia in pigs maintained with intravenous drugs such as propofol may cause respiratory depression. Alfaxalone gives less respiratory depression than propofol in some species. The aim of the investigation was to compare respiratory effects of propofol-ketamine-dexmedetomidine and alfaxalone-ketamine-dexmedetomidine in pigs. Sixteen pigs premedicated with ketamine 15 mg/kg and midazolam 1 mg/kg intramuscularly were anaesthetised with propofol or alfaxalone to allow endotracheal intubation, followed by propofol 8 mg/kg/h or alfaxalone 5 mg/kg/h in combination with ketamine 5 mg/kg/h and dexmedetomidine 4 µg/kg/h given as a continuous infusion for 60 min. The pigs breathed spontaneously with an FIO 2 of 0.21. Oxygen saturation (SpO 2), end-tidal CO 2 concentration (PE′CO 2), respiratory rate (f R) and inspired tidal volume (V T) were measured, and statistically compared between treatments. If the SpO 2 dropped below 80% or if PE′CO 2 increased above 10.0 kPa, the pigs were recorded as failing to complete the study, and time to failure was statistically compared between treatments. Results: Alfaxalone treated pigs had significantly higher respiratory rates and lower PE′CO 2 than propofol treated pigs, with a f R being 7.3 /min higher (P = 0.01) and PE′CO 2 0.8 kPa lower (P = 0.05). SpO 2 decreased by 0.6% and f R by 1.0 /min per kg increase in body weight in both treatment groups. Three of eight propofol treated and two of eight alfaxalone treated pigs failed to complete the study, and times to failure were not significantly different between treatments (P = 0.75). Conclusions: No major differences in respiratory variables were found when comparing treatments. Respiratory supportive measures must be available when using both protocols.

Long duration anaesthesia in pigs with an infusion of alfaxalone and dexmedetomidine

“…This is evidenced by most animals requiring additional alfaxalone or methadone when stimulated to position for radiographs. Interestingly, similar findings were reported during the previously described short duration alfaxalone and alfaxalone‐ketamine‐dexmedetomidine infusions with approximately 14%–35% of animals responding to epidural placement or dewclaw clamping, respectively (Bigby et al., 2017 ; Lervik et al., 2020 ). Alfaxalone is not an analgesic, and while information on dexmedetomidine in pigs is limited, it has been reported to provide significant analgesia when infused at 4 mcg/kg/h in combination with ketamine and propofol (Lervik et al., 2020 ).…”

“…The median alfaxalone infusion rate in our study was comparable to other studies in pigs in which alfaxalone was infused alone (4.8 mg/kg/h) (Bigby et al., 2017 ). Similar alfaxalone infusion rates (5 mg/kg/h) in combination with ketamine 5 mg/kg/h and dexmedetomidine 4 μg/kg/h were reported in another study following premedication with ketamine and midazolam (Lervik et al., 2020 ). Both studies maintained anaesthesia for only 60 min, and it is likely that the pre‐anaesthetic drugs influenced drug infusion rates during the short anaesthetic period.…”

“…(5 mg/kg/h) in combination with ketamine 5 mg/kg/h and dexmedetomidine 4 μg/kg/h were reported in another study following premedication with ketamine and midazolam (Lervik et al, 2020). Both studies maintained anaesthesia for only 60 min, and it is likely that the preanaesthetic drugs influenced drug infusion rates during the short anaesthetic period.…”

“…Alfaxalone is a neuroactive steroid that is commercially available in an unpreserved (Alfaxan®) and preserved (Alfaxan® Multidose) formulation that is registered for use in veterinary medicine as an intravenous induction and maintenance anaesthetic agent in dogs and cats. In pigs, alfaxalone has been used to induce and maintain anaesthesia and reported to have minimal cardiovascular effects at clinical does rates (Bigby et al., 2017 ; Lervik et al., 2020 ; Santos Gonzalez et al., 2013 ). As such, alfaxalone is an alternative choice as an intravenous maintenance anaesthetic agent in the pig, particularly if there is a potential shortage of commonly used human drugs (e.g., propofol) such as during the COVID‐19 pandemic.…”

Comparison of cardiorespiratory and anesthetic effects of ketamine-midazolam-xylazine-sufentanil and tiletamine-zolazepam-xylazine in miniature pigs

“…However, no single anesthetic agent is adequate for pigs during surgical operations. Thus, two or more drug combinations are needed [6][7][8][9]. The intramuscular drugs include dissociative agents (tiletamine and ketamine), benzodiazepines (zolazepam and midazolam), and α2-adrenergic receptor agonists (xylazine and dexmedetomidine) [6,9,10].…”