General Principals of Premedication
During the preparation of a patient for anesthesia, reducing the anxiety and stress of unfamiliar surroundings is essential. This can be provided by a combination of a quiet environment, calm and experienced patient restraint and administration of sedatives and analgesics. The administration of such agents dramatically improves the quality of the anesthetic induction, transition, maintenance and recovery periods.
The aims of premedication are to relieve stress of handling in the clinic environment, to smooth the stages of anesthesia (induction, maintenance and recovery), to contribute to muscle relaxation and to provide analgesia. Premedication may reduce the required amounts of induction and maintenance agents. Successful anesthesia and smooth recovery demands focus in the pre-anesthetic period.
- Phenothiazines (acepromazine)
- Benzodiazepines (diazepam, midazolam)
- Alpha-2 adrenoreceptor agonists (xylazine, medetomidine, dexmedetomidine)
- Opiates (methadone, morphine, butorphanol, buprenorphine, hydromorphone)
- NSAIDS (carprofen, meloxicam)
- Anti-cholinergic agents (atropine)
Please see the full prescribing information for guidance on the effects of different premedicate regimes on expected induction and maintenance dose requirements for Alfaxan.
The concomitant use of other CNS depressants will potentiate the effects of Alfaxan, often reducing the necessary dose and influencing the duration of anesthesia, particularly in sighthounds.27
Use of alpha-2 adrenoreceptor agonists such as xylazine, medetomidine and dexmedetomidine may decrease the required induction dose of Alfaxan and will markedly increase the duration of anesthesia in a dose-dependent fashion.
Benzodiazepines offer no analgesia and should not be used as the sole premedicant as anesthesia may be suboptimal. However, they can be used safely and effectively in combination with other premedicants and Alfaxan. When a benzodiazepine is used as the sole premedicant, excitation may occur in some cats and dogs during anesthesia and recovery.
Avoid standardized, blanket regimes of premedication – each patient should be assessed and the appropriate regime of medications administered at the appropriate time for that individual.
The optimal time between administration of premedicants and induction will depend on the drugs used, the route of administration and the individual patient’s physiological status and behavior. Premedicant drugs administered intravenously will have a more rapid onset of action than those given by other routes. The benefits of premedication on the anesthetic induction process are best achieved by allowing sufficient time for the premedicants to take effect.
Placement of an intravenous (IV) catheter is a best practice, offering immediate access for administration of medications and fluids. Consideration should be also be given to pre-oxygenation of patients, especially if there is a chance of airway obstruction (e.g. brachycephalic breeds of dogs or cats) or a potential delay between administration of the induction agent and successful connection to the anesthetic breathing system. Pre-oxygenation can delay the onset of hemoglobin oxygen desaturation.48