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Anaesthesia is not routine

Anaesthesia is not routine

General anaesthesia is never routine. Although the processes of anaesthesia may be consistent, each patient varies according to their own functional anatomy, physiologic status, and individual response to medications. For success, each anaesthetic must be tailored to suit the specific needs of each patient. A focus on peri-operative stress reduction, pain management, muscle relaxation and unconsciousness using the principles of ‘considered polypharmacy’ results in repeatable, reliable, balanced anaesthesia.

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Pre-operative assessment and equipment check

Practices should have a system of checks that are performed prior to every patient being anaesthetised.

Patient Checks

  • History
  • Physical Examination
  • Pain assessment
  • Other Suggested Diagnostic Procedures – (blood tests, cardiac investigation etc)
  • Concurrent Disease and Medication Assessment
  • ASA Classification ASA Physical Status Classification System,Amer Soc Anesth. (prior to premedication)
  • Effect of Premedications (prior to induction)

Equipment Checks

  • Oxygen and Inhalation Agent Levels
  • Gas Line Connections and Valve Function
  • Emergency oxygen button function
  • Patient Breathing System Selection (including a range of endotracheal tubes)
  • Soda-lime and Scavenger System
  • Patient Monitoring and Warming Devices
  • Required Drugs
  • Emergency Drugs

Patient risk assessment

It is advisable to allocate a risk assessment for each patient being anaesthetised. The American Society of Anesthesiologists (ASA) has determined a classification for the clinical status of human patients when assessed pre-operatively. This is readily adoptable by veterinary practices and can be used to help tailor anaesthetic protocols to individual patients and can be accessed at this link.

Premedication

Use of premedication can decrease patient stress and anxiety, improve the ease of patient handling,improve muscle relaxation and decrease the requirements for the more potent anaesthetic drugs. As a result of these effects, a smoother anaesthetic induction, transition, maintenance and recovery can be acheived. A range of medications are commonly used in the premedication period including;

  • Phenothiazines (acepromazine)
  • Benzodiazepines (diazepam, midazolam)
  • Alpha-2-adrenoreceptor agonists (xylazine, medetomidine, dexmedetomidine)
  • Opiates (methadone, morphine, butorphanol, buprenorphine, hydromorphone)
  • NSAIDS (carprofen, meloxicam)
  • Anticholinergic agents (atropine)

Gentle and considered handling of patients in a quiet and calm environment will help maximise the effects of premedication. Alfaxan® has been proven safe with drugs from all of these classes. Zaki, S., K. Ticehurst, and Y. Miyaki, Clinical evaluation of Alfaxan®-CD(R) as an intravenous anaesthetic in young cats.Aust Vet J, 2009. 87(3): p. 82-7 Mathis, A., et al., Comparison of quality of recovery from anaesthesia in cats induced with propofol or alfaxalone.Veterinary Anaesthesia and Analgesia, 2012. 39(3): p. 282-290 Maddern, K., et al., Alfaxalone induction dose following administration of medetomidine and butorphanol in the dog. Veterinary Anaesthesia and Analgesia, 2010. 37(1): p. 7-13. O’Hagan, B., et al., Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.Australian Veterinary Journal, 2012. 90(9): p. 346-50 O’Hagan, B., et al., Clinical evaluation of alfaxalone as an anaesthetic induction agent in cats less than 12 weeks of age.Australian Veterinary Journal, 2012. 90(10): p. 395-401 Pasloske, K., et al., Plasma pharmacokinetics of alfaxalone in both premedicated and unpremedicated Greyhound dogs after single, intravenous administration of Alfaxan® at a clinical dose.Journal of Veterinary Pharmacology and Therapeutics, 2009. 32: p. 510-513. Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8. Pasloske, K.,et al. A multicentre clinical trial evaluating the efficacy and safety of Alfaxan® administered to cats for induction and maintenance of anaesthesia.in British Small Animal Veterinary Association Congress. 2007. Birmingham, UK. Pasloske, K., et al. A multicentre clinical trial evaluating the efficacy and safety of Alfaxan ® -CD RTU administered to dogs for induction and maintenance of anaesthesia.in British Small Animal Veterinary Association Congress. 2005. Birmingham, UK Some premedicants have greater or lesser effect on the anaesthetic. For example, Alpha-2 agonists (xylazine, medetomidine etc) may decrease the required dose of Alfaxan® and markedly increase the duration of anaesthesia. Benzodiazepines can be used safely and effectively in combination with other premedicants and Alfaxan®, however, given a more variable effect on patients, should not be used as the sole premedicant. In addition, allowing sufficient time for premedicants to take effect is essential to ensuring a smooth anaesthetic induction. As a component of best practice, Jurox encourages veterinarians to make placement of an intravenous catheter prior to anaesthetic induction a standard practice.

Premedication Agents

Drug Time to peak
sedation or effect		 Duration of action Reversible? Analgesia?
Acepromazine 35-40 minutes i.m.
15-20 minutes i.v.		 4-6 hours No No
Medetomidine 15-20 minutes i.m.
2-3 minutes i.v.		 Sedation: 2-3 hours
Analgesia: 1 hour		 Yes – with atipamezole Yes
Midazolam 10-15 minutes i.m.
5 minutes i.v.		 1-1.5 hours Yes – with flumazenil No
Diazepam 10-15 minutes i.m.
5 minutes i.v.		 2 hours Yes – with flumazenil No
Atropine 20-30 minutes i.m.
1-2 minutes i.v.		 Vagal inhibition: 2-3 hours No No
Glycopyrronium 20-30 minutes i.m.
2-3 minutes i.v.		 Vagal inhibition:2-3 hours No No
Methadone,
hydromorphone		 20-30 minutes i.m.
2-5 minutes i.v.		 2-4 hours Yes – with naloxone Yes
Morphine 20-30 minutes i.m.
Not recommended i.v.		 2-4 hours Yes – with naloxone Yes
Pethidine
(merperidine)		 20-30 minutes i.m.
Contraindicated i.v.		 1-1.5 hours Yes – with naloxone Yes
Buprenorphine 30-45 minutes i.m.
12-15 minutes i.v.		 6 hours Yes – with naloxone Yes
Butorphanol 20-30 minutes i.m.
2-5 minutes i.v.		 1-1.5 hours Yes – with naloxone Yes

*Note that the duration of action of many of these drugs will vary between species and will depend on the dose administered. The times given are approximate guidelines only. Please refer to the Alfaxan® package insert for the dose sparing effects recognized with individual premedication regimes.
Reproduced with permission from the BSAVA Manual of Canine and Feline Anaesthesia and Analgesia, 2nd edition, © BSAVA

Induction

Alfaxan® possesses many properties that have been associated with the ideal anaesthetic induction agent.

Performing successful anaesthesia requires more than simply using a high quality agent. Attention to administration rate and technique, and familiarity with the agent allow for titration of the correct dose, enhancing the benefits of Alfaxan®, and achieving optimal anaesthesia.

After a single full induction dose of Alfaxan®, the duration of anaesthesia will vary dependent on patient, concurrent medications and disease processes.  However, 2 mg/kg administered to a healthy unpremedicated dog will result in approximately 10 minutes of anaesthesia and 5 mg/kg administered to a healthy unpremedicated cat will result in approximately 25 minutes of anaesthesia. Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.

Induce

The Ideal Induction Agent

There are many lists that outline properties of an ideal anaesthetic induction agent. The ideal induction agent does not exist... However, Alfaxan® exhibits many attributes on the list

Optimum results are obtained if the agent is injected slowly. This effectively allows the patient to choose the dose that they require to produce unconsciousness.

  1. Rapid onset of action Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36. Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  2. Smooth induction Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36. Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  3. Smooth recovery Martinez Taboada, F. and P.J. Murison, Induction of anaesthesia with alfaxalone or propofol before isoflurane maintenance in cats.Veterinary Record, 2010. 167(3): p. 85-89 Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8.
  4. Non-irritant Heit, M.C., et al. Safety and efficacy of Alfaxan® CD RTU Administered once to cats subcutaneously at 10 mg/kg.in ACVIM. 2004
  5. Short duration of action Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  6. Non-cumulative Whittem, T., et al., The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan®at clinical and supraclinical doses. J Vet Pharmacol Ther, 2008. 31(6): p. 571-9 Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8.
  7. Rapid metabolism Whittem, T., et al., The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan®at clinical and supraclinical doses. J Vet Pharmacol Ther, 2008. 31(6): p. 571-9 Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36.
  8. Non-toxic or no metabolites Whittem, T. and K. Pasloske, JX9604.03-E013 The in-vitro metabolism and clearance of the neurosteroid, alfaxalone, by cat and dog hepatocytes at concentrations of 1, 5, 10 and 100 mg/L. 2005, Jurox In House Report
  9. Does not cause histamine release Patten, B., et al., RD9604.03/06 The Safety of Jurox Alfaxan®-CD Anaesthetic Injection in dogs. 2000, Jurox in house Patten, B., et al., RD9604.03/01 The Safety of Alfaxalone-Cyclodextrin Complex in cats.1998, Jurox in House
  10. Minimal cardiorespiratory side effects Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  11. Produces a degree of muscle relaxation Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  12. Stable in storage Jurox, NADA 141-342 Alfaxan® Intravenous injectable anesthetic for use in cats and dogs. Product Insert.2012, USFDA
  13. Stable in solution Jurox, NADA 141-342 Alfaxan® Intravenous injectable anesthetic for use in cats and dogs. Product Insert.2012, USFDA
  14. High therapeutic index Sear, J.W., C. Prys-Roberts, and K.C. Phillips, Age influences the minimum infusion rate (ED50) for continuous infusions of Althesin and methohexitone.Eur J Anaesthesiol, 1984. 1(4): p. 319-25 Child KJ, C.J., Dis B, Dodds MG, Pearce DR, Twissell DJ., The pharmacological properties in animals of CT1341--a new steroid anaesthetic agent.Br J Anaesth, 1971. 43(1): p. 2-13

Optimal Results with Alfaxan

To optimize results with Alfaxan®, remember the following points:

  • Administer over 60 seconds

    The rate of intravenous injection should result in the total dose, if required, being administered over a period of 60 seconds.

  • Slow is best

    Administer one quarter of the calculated dose slowly every fifteen seconds.

  • Intubate when anaesthetised

    Administration should proceed until the patient is fully anaesthetised or the total dose has been administered. Intubate when anaesthetised, rather than deeply sedated.

  • Wait

    If, 60 seconds after complete delivery of this first induction dose, intubation is still not possible, one further similar dose may be administered to effect.

  • Oxygenate

    Once the endotracheal tube is placed begin supplying oxygen and maintenance agents.

  • Transition

    Patients administered Alfaxan® in accordance with the above recommendations generally ventilate spontaneously and will transition to maintenance with gaseous agents quite smoothly. Should apnoea of more than 60 seconds occur, positive pressure ventilation (PPV) should be delivered to the patient.

IV Dose Recommendations

Alfaxan® induction – intravenous dosage recommendation

Dogs

Dog Unpremedicated Dog Premedicated
3 mg/kg 2 mg/kg
0.3 mL/kg 0.2 mL/kg

Cats

Cats Unpremedicated Cats Premedicated
5 mg/kg 5 mg/kg
0.5 mL/kg 0.5 mL/kg

 

The dosing syringe should be prepared to contain the calculated dose. Plan administration over 60 seconds, and continue until satisfied that the depth of anaesthesia is sufficient for endotracheal intubation, or the entire dose has been administered. Premedication can result in significant dose requirement reductions, so dose titration is very important.

Maintenance with Alfaxan®

After induction, anaesthesia may be maintained with an inhalation agent or with Alfaxan®. Maintenance doses of Alfaxan® can be given as supplemental boluses or by constant rate infusion.

Alfaxan® is registered for use as a maintenance agent, and has been used safely and effectively in dogs and cats for procedures of considerable duration. Vettorato E. Prolonged intravenous infusion of alfaxalone in a cat. Vet Anaesth Analg 09/13;40:551–2. Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8.   Maintenance with intravenous alfaxalone is particularly useful where inhalational agents and their side effects are contraindicated.

When maintaining anaesthesia with Alfaxan® the anaesthetist should monitor the patient’s anaesthetic depth and adjust the infusion rate, bolus volume or interval appropriately.

Note that other medications used concurrently such as premedicant analgesics, sedatives, and anxiolytics, as well as some disease processes, can reduce the amount of maintenance Alfaxan® required.

Suggested intravenous dosages for maintenance with Alfaxan® APVMA, Alfaxan ® Anaesthetic Injection Australian Product Insert Leaflet.2010

Cats

  Un-premedicated Premedicated
Dose for constant rate infusion
mg/kg/hour 10-11 7-8
mg/kg/minute 0.16-0.18 0.11-0.13
mL/kg/minute 0.016-0.018 0.011-0.013
Bolus dose for each 10 minutes maintenance
mg/kg 1.6-1.8 1.1-1.3
mg/kg 0.16-0.18 0.11-0.13

 

Dogs

  Un-premedicated Premedicated
Dose for constant rate infusion
mg/kg/hour 8-9 6-7
mg/kg/minute 0.13-0.15 0.10-0.12
mL/kg/minute 0.013-0.015 0.010-0.012
Bolus dose for each 10 minutes maintenance
mg/kg 1.3-1.5 1.0-1.2
mg/kg 0.13-0.15 0.10-0.12

Peri-operative Analgesia

Peri-operative analgesia should be considered standard practice in the 21st century, and pain should not be considered a natural immobilisation agent. Reduction of pain greatly assists recovery from surgery. The first step to improving pain management is to have a repeatable process for assessment. One good tool is the Glasgow Composite Pain Scale. Glasgow University short form composite measure pain score (CMPS-SF). 2012

Jurox recommends that peri-operative pain relief is administered in all procedures requiring anaesthesia where pain either already exists or the procedure could potentially induce noxious stimuli. Provision of analgesia throughout the process contributes to smooth induction, transition, maintenance and recovery phases of anaesthesia.

  • Anxiolytic agents

    Acepromazine and benzodiazepines can augment the effect of opiate medications by decreasing sympathetic drive in the patient.

  • Recovery

    Giving analgesics until the patient is no longer painful is extremely important, especially as modern induction and maintenance agents are rapidly eliminated. A rapidly recovering painful patient is very likely to have a poor recovery.

  • Intra-operative

    Maintain analgesia through the surgery period

  • Opioids

    Multiple beneficial effects including analgesia and reduced requirement for anaesthetic agents.

  • Alpha-2 agonist

    (Medetomidine, dexmedetomidine) Decrease anaesthetic drug requirements and can augment the effects of other analgesics

  • Pre-emptive

    Instigate analgesic actions prior to noxious stimuli wherever possible

  • Multimodal

    Plan to administer analgesic agents with different modes of action to synergistically improve the efficacy of pain control and reduce the required dose of each agent.

  • Assessment

    Whilst there is difficulty assessing the degree of pain in patients that can not speak, techniques such as Glasgow Composite Pain Scale can become a rapid pain assessment tool in clinical practice.

Recovery

A sobering fact

In a study of deaths associated with veterinary anaesthesia in the United Kingdom, covering 117 practices, 98,036 dogs and 79,178 cats, almost 50 per cent of canine fatalities and over 60 per cent of feline fatalities occurred in the recovery period or up to 24 hours post-surgery. Brodbelt, D.C.,et al., The risk of death: the confidential enquiry into perioperative small animal fatalities.Vet Anaesth Analg, 2008. 35(5): p. 365-73

A safe and comfortable recovery is the final objective of anaesthesia. 
Recovery remains the most overlooked phase of anaesthesia and rushing a recovery may not be best for the patient.

While the actual numbers of fatalities were low the study authors noted: 
“That nearly 50% of the postoperative deaths in this study occurred within three hours of the end of anaesthesia suggested that if closer monitoring and management of patients in this early postoperative period were instituted, then mortality might be reduced.” Brodbelt, D.C.,et al., The risk of death: the confidential enquiry into perioperative small animal fatalities.Vet Anaesth Analg, 2008. 35(5): p. 365-73

Optimal recovery requires consideration of the patient’s changing neurologic status. Consider the following

  • effects of all medications administered;
  • minimise sound, movement and touch stimulus
  • address pain
  • anxiety can result from recovering rapidly from unconsciousness in an unfamiliar environment

As Alfaxan® is rapidly eliminated from the body, extra attention to the recovery period is warranted, as animals can arouse very rapidly. Whittem, T., et al., The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan®at clinical and supraclinical doses. J Vet Pharmacol Ther, 2008. 31(6): p. 571-9 Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36.

Studies have demonstrated that use of Alfaxan® as an induction and/or maintenance anaesthetic in combination with effective premedication resulted in uneventful induction, maintenance and recovery. Zaki, S., K. Ticehurst, and Y. Miyaki, Clinical evaluation of Alfaxan®-CD(R) as an intravenous anaesthetic in young cats.Aust Vet J, 2009. 87(3): p. 82-7 Mathis, A., et al., Comparison of quality of recovery from anaesthesia in cats induced with propofol or alfaxalone.Veterinary Anaesthesia and Analgesia, 2012. 39(3): p. 282-290 Maddern, K., et al., Alfaxalone induction dose following administration of medetomidine and butorphanol in the dog. Veterinary Anaesthesia and Analgesia, 2010. 37(1): p. 7-13. O’Hagan, B., et al., Clinical evaluation of alfaxalone as an anaesthetic induction agent in dogs less than 12 weeks of age.Australian Veterinary Journal, 2012. 90(9): p. 346-50 O’Hagan, B., et al., Clinical evaluation of alfaxalone as an anaesthetic induction agent in cats less than 12 weeks of age.Australian Veterinary Journal, 2012. 90(10): p. 395-401 Pasloske, K., et al., Plasma pharmacokinetics of alfaxalone in both premedicated and unpremedicated Greyhound dogs after single, intravenous administration of Alfaxan® at a clinical dose.Journal of Veterinary Pharmacology and Therapeutics, 2009. 32: p. 510-513. Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8. Pasloske, K.,et al. A multicentre clinical trial evaluating the efficacy and safety of Alfaxan® administered to cats for induction and maintenance of anaesthesia.in British Small Animal Veterinary Association Congress. 2007. Birmingham, UK. Pasloske, K., et al. A multicentre clinical trial evaluating the efficacy and safety of Alfaxan ® -CD RTU administered to dogs for induction and maintenance of anaesthesia.in British Small Animal Veterinary Association Congress. 2005. Birmingham, UK

The Ideal Induction Agent

There are many lists that outline properties of an ideal anaesthetic induction agent. The ideal induction agent does not exist... However, Alfaxan® exhibits many attributes on the list

Optimum results are obtained if the agent is injected slowly. This effectively allows the patient to choose the dose that they require to produce unconsciousness.

  1. Rapid onset of action Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36. Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  2. Smooth induction Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36. Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  3. Smooth recovery Martinez Taboada, F. and P.J. Murison, Induction of anaesthesia with alfaxalone or propofol before isoflurane maintenance in cats.Veterinary Record, 2010. 167(3): p. 85-89 Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8.
  4. Non-irritant Heit, M.C., et al. Safety and efficacy of Alfaxan® CD RTU Administered once to cats subcutaneously at 10 mg/kg.in ACVIM. 2004
  5. Short duration of action Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  6. Non-cumulative Whittem, T., et al., The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan®at clinical and supraclinical doses. J Vet Pharmacol Ther, 2008. 31(6): p. 571-9 Ambros B, Duke-Novakovski T, Pasloske KS. Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs. Am J Vet Res 2008;69:1391–8.
  7. Rapid metabolism Whittem, T., et al., The pharmacokinetics and pharmacodynamics of alfaxalone in cats after single and multiple intravenous administration of Alfaxan®at clinical and supraclinical doses. J Vet Pharmacol Ther, 2008. 31(6): p. 571-9 Ferre, P.J.,et al., Plasma pharmacokinetics of alfaxalone in dogs after an intravenous bolus of Alfaxan®-CD RTU. Vet Anaesth Analg, 2006. 33(4): p. 229-36.
  8. Non-toxic or no metabolites Whittem, T. and K. Pasloske, JX9604.03-E013 The in-vitro metabolism and clearance of the neurosteroid, alfaxalone, by cat and dog hepatocytes at concentrations of 1, 5, 10 and 100 mg/L. 2005, Jurox In House Report
  9. Does not cause histamine release Patten, B., et al., RD9604.03/06 The Safety of Jurox Alfaxan®-CD Anaesthetic Injection in dogs. 2000, Jurox in house Patten, B., et al., RD9604.03/01 The Safety of Alfaxalone-Cyclodextrin Complex in cats.1998, Jurox in House
  10. Minimal cardiorespiratory side effects Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  11. Produces a degree of muscle relaxation Muir, W., et al., Cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in dogs.Vet Anaesth Analg, 2008. 35(6): p. 451-462. Muir, W.,et al., The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats.Veterinary Anaesthesia and Analgesia, 2009. 36(1): p. 42-54.
  12. Stable in storage Jurox, NADA 141-342 Alfaxan® Intravenous injectable anesthetic for use in cats and dogs. Product Insert.2012, USFDA
  13. Stable in solution Jurox, NADA 141-342 Alfaxan® Intravenous injectable anesthetic for use in cats and dogs. Product Insert.2012, USFDA
  14. High therapeutic index Sear, J.W., C. Prys-Roberts, and K.C. Phillips, Age influences the minimum infusion rate (ED50) for continuous infusions of Althesin and methohexitone.Eur J Anaesthesiol, 1984. 1(4): p. 319-25 Child KJ, C.J., Dis B, Dodds MG, Pearce DR, Twissell DJ., The pharmacological properties in animals of CT1341--a new steroid anaesthetic agent.Br J Anaesth, 1971. 43(1): p. 2-13

Optimal Results with Alfaxan

To optimize results with Alfaxan®, remember the following points:

  • Administer over 60 seconds

    The rate of intravenous injection should result in the total dose, if required, being administered over a period of 60 seconds.

  • Slow is best

    Administer one quarter of the calculated dose slowly every fifteen seconds.

  • Intubate when anaesthetised

    Administration should proceed until the patient is fully anaesthetised or the total dose has been administered. Intubate when anaesthetised, rather than deeply sedated.

  • Wait

    If, 60 seconds after complete delivery of this first induction dose, intubation is still not possible, one further similar dose may be administered to effect.

  • Oxygenate

    Once the endotracheal tube is placed begin supplying oxygen and maintenance agents.

  • Transition

    Patients administered Alfaxan® in accordance with the above recommendations generally ventilate spontaneously and will transition to maintenance with gaseous agents quite smoothly. Should apnoea of more than 60 seconds occur, positive pressure ventilation (PPV) should be delivered to the patient.

IV Dose Recommendations

Alfaxan® induction – intravenous dosage recommendation

Dogs

Dog Unpremedicated Dog Premedicated
3 mg/kg 2 mg/kg
0.3 mL/kg 0.2 mL/kg

Cats

Cats Unpremedicated Cats Premedicated
5 mg/kg 5 mg/kg
0.5 mL/kg 0.5 mL/kg

 

The dosing syringe should be prepared to contain the calculated dose. Plan administration over 60 seconds, and continue until satisfied that the depth of anaesthesia is sufficient for endotracheal intubation, or the entire dose has been administered. Premedication can result in significant dose requirement reductions, so dose titration is very important.