Close this window to return to IVIS wwwivisorg
Proceedings of the 36th World Small Animal Veterinary Congress
WSAVA
Oct 14 - 17 2011 Jeju Korea
Next Congress
Reprinted in IVIS with the permission of WSAVA httpwwwivisorg
592011 WSAVAmiddotFASAVA World Congress Proceedings
14(Fri) ~ 17(Mon) October 2011
ICC Jeju Korea
2011 WSAVAFASAVA World Congress
wwwwsava2011org
AFTER THIOPENTALOPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
KW Clarke MA VetMb DVetMed DVA Dip ECVA MRCA FRCVS
Hon Prof of Veterinary Anaesthesia Royal Veterinary College
Hatfield Hertfordshire AL9 7TA UK
IntroductionThiopental and other barbiturates have been the mainstay for induction of anaesthesia since the 1940s
Over the past 30 years they have been replaced gradually mainly by propofol and ketamine and now can be
difficult to obtain This presentation will consider what is currently and easily available for induction of
anaesthesia the advantages and disadvantages for use in both dogs and cats in the practice situation and will
concentrate then on what is (relatively) new or controversial
This presentation will consider
(a) Some general principles of use of injectable anaesthetic agents in small animals
(b) Brief revision of most relevant clinical pharmacology in particular re unwanted side effects
(c) Whatrsquos new or controversial
(d) In the verbal presentation some suggested protocols for induction of or very short-term anaesthesia
General Principles1 A cat is not a small dog The catrsquos lack of glucuronyl transferes enzymes mean that metabolism of some
drugs (in particular propofol) is delayed and that some of the solvents or preservatives may be cumulative
andor toxic
2 Once a drug is injected it can only be removed by metabolism- this may vary with species or breed and
may be influenced by disease states
3 The dose of anaesthetic required will vary with the premedication used (combinations may have
synergistic effects) and with the clinical state of the patient
4 Some agents used in anaesthetic combinations (alpha 2 adrenoceptor agonists benzodiazepines opioids)
CAN be antagonised-it is important to match duration of antagonist and agonist
5 Route of administration - Intravenous (IV) best as easiest to judge depth BUT not all agents work in a
circulation time (thiopental does so but pentobarbitone not) so effect is delayed IV administration is
AP-C21
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
60 2011 WSAVAmiddotFASAVA World Congress Proceedings
usually best given slowly Intramuscular (IM) or similar is always second best - depth of anaesthesia
achieved is much less controllable and depend is on speed of uptake 6 ALL anaesthetics are respiratory
depressant even if the animal breaths fast so using injectable agents still needs OXYGEN a clear
AIRWAY the ability to VENTILATE if necessary and excellent MONITORING
Anaesthetic agentscombinations A (very) brief resume of the major clinically important pharmacology [1]
Thiopental Barbiturate presented as solid to dissolve in water Irritant extravascularly IV route only Rapid
onset of anaesthesia (one circulation time) initital recovery by re-distribution slow metabolism and cumulative
Poor analgesia Very respiratory depressant Vasodilates Increases heart rate
Propofol Presentation usually in lipid but see below Non-irritant but sometimes pain on injection IV route
only Rapid onset anaesthesia non-cumulative and recovery fast-and complete except in cats [2 Poor
analgesia Very respiratory depressant Cardiovascular effects as thiopental but less tachycardia
Ketamine Presentation in solution with preservatives Many routes of administration Non-irritant but pain on
IM injection Onset of anaesthesia after IV injection not immediate Excellent analgesia Respiratory depressant
but animal may breath rapidly and shallowly Technically myocardial depression but sympathetic stimulation
result in CV system being well maintained Hallucinogenic and muscle rigidity so usually used in combination
with alpha 2 agonists or benzodiazepines
Etomidate Rapidly acting IV induction agent with rapid recovery from induction dose Pain on injection
Venous phlebitis Poor analgesia Myoclonic activity Minimal cardiovascular effects (so popular for the
compromised dog) See below for concern re cortisol suppression
Alphaxalone - see detail below
Benzodiazepineopioids may also be used to induce anaesthesia [3] Neither of these agents work in a circulation
time
Whatrsquos new or currently controversial(a) Propofol in catsThe major route (there are others) of metabolism of propofol is through glucuronidation of the parent drug
followed by glucuro‐conjugation of hydroxylated metabolite via cytochrome P450 to produce other conjugates Cats lack the enzymes necessary for this and also are slow to metabolise the lipids in the
carrier As a result propofol is not as short acting in the cat as in the dog Its safe use as an induction agent
and use for short duration infusion appears satisfactory but there is continual controversy as to whether it is
suitable for longer infusions or for use several days in succession (when under experimental conditions
toxicity has occurred [2])
(b) Propofol formulationsThe original lecithin based formulation of propofol had to be used within a very short time of opening-
making it expensive Since becoming lsquoout of patent a number of new versions have included preservatives
of varying efficacy These versions state on their marketing authorisation the time after opening the vial
when the product is considered safe The most recent on the veterinary market includes benzyl alcholol
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
612011 WSAVAmiddotFASAVA World Congress Proceedings
AFTER THIOPENTAL OPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
and in the USA has authorisation to be open for 28 days (some other countries give a shorter time) There
are some questions as to the toxicity of the Benzyl alcohol particularly in cats but again this is only likely
to be a problem with prolonged infusions
An emulsion formulation of propofol that does not include oils and again has a long lsquoshelf lifersquo after
opening has been available but in the UK has been (possibly temporarily) withdrawn for commercial
reasons
Etomidate Etomidate has not been used as a CRI in intensive care for many years since it was realised that the
adrenocortical suppression in such patients increased the overall death rate most usually from infections In the
last few years there has been considerable controversy over whether the short-term (a few hours) adrenocortical
suppression it induces means that it should not be used for IV induction of anaesthesia in particular in patients
with sepsis There is no evidence as to whether this is a potential problem in veterinary anaesthesia
Alfaxalone (3-alpha-hydroxy-5-alpha-pregnane-1120-dione) solubalized in 2 alpha-hydroxypropyl beta
cyclodextrin (HPBCD) Licenced product - Alfaxanreg
Steroid anaesthesia is not new- over the last 50 years a number of agents have been used - the problem has been
solubility Alphaxalone alphadalone combination solublised in cremaphor was used in humans and in cats
(Saffanreg) - but the cremaphor caused histamine release
Facts about Alfaxalone as Alfaxanreg
(a) Originally licenced in Australia and used there now for some years Now licenced in many countries for
cats and dogs Licensed dose rates without sedative premedication are 3mg kg-1 dogs and 5 mg kg-1 cats
Administer IV over 60 seconds Recommended to premedicate healthy animals
(b) Effective anaesthesia on IV use in (close to) a circulation time Induction quality usually good but
improved by sedation Advise from practice use is to ensure anaesthesia is adequate before endotracheal
intubation otherwise if the animal is stimulated it wakes up
(c) Non irritant IV or if accidental extra-vascular It could be given IM but volume too large for use
without deep sedation
(d) Short half-life non-cumulative Metabolised by the liver
(e) Very good safety margin especially if ventilate (massive overdose may causes apnoea)
(f) No evidence of histamine release
(g) Can be used together (not in same syringe) with most commonly used sedatives analgesics or
subsequent inhalation agents
(h) Cardiovascular effects - minimal at clinical or even heavy clinical doses [345]- after this (supra-
clinical doses for licensing procedures) dose dependant fall in blood pressure and systemic vascular
resistance
(i) Transient apnoea if injected fast - more prolonged at massive overdose
(j) Can get some disturbed recoveries These are much less likely to happen if extubation is whilst
anaesthesia is still deep and the animal allowed to recover somewhere quiet
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
62 2011 WSAVAmiddotFASAVA World Congress Proceedings
References1 Hall LW Clarke KW and Trim CM 2001 Chapter 5 In Veterinary Anaesthesia WB Saunders London Pgs
113-131
2 Andress JL Day TK Day D 1995 The effects of consecutive day propofol anesthesia on feline red blood
cells Vet Surg 24 277-82
3Psatha E Alibhai HI Jimenez-Lozano A et al2011 Clinical efficacy and cardiorespiratory effects of
alfaxalone or diazepamfentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk Vet
Anaesth Analg 38 24-36
4Muir W Lerche P Wiese A et al 2008 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in dogs Vet Anaesth Analg 35 1-12
5 Muir W Lerche P Wiese A et al 2009 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in cats Vet Anaesth Analg 36 42-54
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
592011 WSAVAmiddotFASAVA World Congress Proceedings
14(Fri) ~ 17(Mon) October 2011
ICC Jeju Korea
2011 WSAVAFASAVA World Congress
wwwwsava2011org
AFTER THIOPENTALOPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
KW Clarke MA VetMb DVetMed DVA Dip ECVA MRCA FRCVS
Hon Prof of Veterinary Anaesthesia Royal Veterinary College
Hatfield Hertfordshire AL9 7TA UK
IntroductionThiopental and other barbiturates have been the mainstay for induction of anaesthesia since the 1940s
Over the past 30 years they have been replaced gradually mainly by propofol and ketamine and now can be
difficult to obtain This presentation will consider what is currently and easily available for induction of
anaesthesia the advantages and disadvantages for use in both dogs and cats in the practice situation and will
concentrate then on what is (relatively) new or controversial
This presentation will consider
(a) Some general principles of use of injectable anaesthetic agents in small animals
(b) Brief revision of most relevant clinical pharmacology in particular re unwanted side effects
(c) Whatrsquos new or controversial
(d) In the verbal presentation some suggested protocols for induction of or very short-term anaesthesia
General Principles1 A cat is not a small dog The catrsquos lack of glucuronyl transferes enzymes mean that metabolism of some
drugs (in particular propofol) is delayed and that some of the solvents or preservatives may be cumulative
andor toxic
2 Once a drug is injected it can only be removed by metabolism- this may vary with species or breed and
may be influenced by disease states
3 The dose of anaesthetic required will vary with the premedication used (combinations may have
synergistic effects) and with the clinical state of the patient
4 Some agents used in anaesthetic combinations (alpha 2 adrenoceptor agonists benzodiazepines opioids)
CAN be antagonised-it is important to match duration of antagonist and agonist
5 Route of administration - Intravenous (IV) best as easiest to judge depth BUT not all agents work in a
circulation time (thiopental does so but pentobarbitone not) so effect is delayed IV administration is
AP-C21
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
60 2011 WSAVAmiddotFASAVA World Congress Proceedings
usually best given slowly Intramuscular (IM) or similar is always second best - depth of anaesthesia
achieved is much less controllable and depend is on speed of uptake 6 ALL anaesthetics are respiratory
depressant even if the animal breaths fast so using injectable agents still needs OXYGEN a clear
AIRWAY the ability to VENTILATE if necessary and excellent MONITORING
Anaesthetic agentscombinations A (very) brief resume of the major clinically important pharmacology [1]
Thiopental Barbiturate presented as solid to dissolve in water Irritant extravascularly IV route only Rapid
onset of anaesthesia (one circulation time) initital recovery by re-distribution slow metabolism and cumulative
Poor analgesia Very respiratory depressant Vasodilates Increases heart rate
Propofol Presentation usually in lipid but see below Non-irritant but sometimes pain on injection IV route
only Rapid onset anaesthesia non-cumulative and recovery fast-and complete except in cats [2 Poor
analgesia Very respiratory depressant Cardiovascular effects as thiopental but less tachycardia
Ketamine Presentation in solution with preservatives Many routes of administration Non-irritant but pain on
IM injection Onset of anaesthesia after IV injection not immediate Excellent analgesia Respiratory depressant
but animal may breath rapidly and shallowly Technically myocardial depression but sympathetic stimulation
result in CV system being well maintained Hallucinogenic and muscle rigidity so usually used in combination
with alpha 2 agonists or benzodiazepines
Etomidate Rapidly acting IV induction agent with rapid recovery from induction dose Pain on injection
Venous phlebitis Poor analgesia Myoclonic activity Minimal cardiovascular effects (so popular for the
compromised dog) See below for concern re cortisol suppression
Alphaxalone - see detail below
Benzodiazepineopioids may also be used to induce anaesthesia [3] Neither of these agents work in a circulation
time
Whatrsquos new or currently controversial(a) Propofol in catsThe major route (there are others) of metabolism of propofol is through glucuronidation of the parent drug
followed by glucuro‐conjugation of hydroxylated metabolite via cytochrome P450 to produce other conjugates Cats lack the enzymes necessary for this and also are slow to metabolise the lipids in the
carrier As a result propofol is not as short acting in the cat as in the dog Its safe use as an induction agent
and use for short duration infusion appears satisfactory but there is continual controversy as to whether it is
suitable for longer infusions or for use several days in succession (when under experimental conditions
toxicity has occurred [2])
(b) Propofol formulationsThe original lecithin based formulation of propofol had to be used within a very short time of opening-
making it expensive Since becoming lsquoout of patent a number of new versions have included preservatives
of varying efficacy These versions state on their marketing authorisation the time after opening the vial
when the product is considered safe The most recent on the veterinary market includes benzyl alcholol
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
612011 WSAVAmiddotFASAVA World Congress Proceedings
AFTER THIOPENTAL OPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
and in the USA has authorisation to be open for 28 days (some other countries give a shorter time) There
are some questions as to the toxicity of the Benzyl alcohol particularly in cats but again this is only likely
to be a problem with prolonged infusions
An emulsion formulation of propofol that does not include oils and again has a long lsquoshelf lifersquo after
opening has been available but in the UK has been (possibly temporarily) withdrawn for commercial
reasons
Etomidate Etomidate has not been used as a CRI in intensive care for many years since it was realised that the
adrenocortical suppression in such patients increased the overall death rate most usually from infections In the
last few years there has been considerable controversy over whether the short-term (a few hours) adrenocortical
suppression it induces means that it should not be used for IV induction of anaesthesia in particular in patients
with sepsis There is no evidence as to whether this is a potential problem in veterinary anaesthesia
Alfaxalone (3-alpha-hydroxy-5-alpha-pregnane-1120-dione) solubalized in 2 alpha-hydroxypropyl beta
cyclodextrin (HPBCD) Licenced product - Alfaxanreg
Steroid anaesthesia is not new- over the last 50 years a number of agents have been used - the problem has been
solubility Alphaxalone alphadalone combination solublised in cremaphor was used in humans and in cats
(Saffanreg) - but the cremaphor caused histamine release
Facts about Alfaxalone as Alfaxanreg
(a) Originally licenced in Australia and used there now for some years Now licenced in many countries for
cats and dogs Licensed dose rates without sedative premedication are 3mg kg-1 dogs and 5 mg kg-1 cats
Administer IV over 60 seconds Recommended to premedicate healthy animals
(b) Effective anaesthesia on IV use in (close to) a circulation time Induction quality usually good but
improved by sedation Advise from practice use is to ensure anaesthesia is adequate before endotracheal
intubation otherwise if the animal is stimulated it wakes up
(c) Non irritant IV or if accidental extra-vascular It could be given IM but volume too large for use
without deep sedation
(d) Short half-life non-cumulative Metabolised by the liver
(e) Very good safety margin especially if ventilate (massive overdose may causes apnoea)
(f) No evidence of histamine release
(g) Can be used together (not in same syringe) with most commonly used sedatives analgesics or
subsequent inhalation agents
(h) Cardiovascular effects - minimal at clinical or even heavy clinical doses [345]- after this (supra-
clinical doses for licensing procedures) dose dependant fall in blood pressure and systemic vascular
resistance
(i) Transient apnoea if injected fast - more prolonged at massive overdose
(j) Can get some disturbed recoveries These are much less likely to happen if extubation is whilst
anaesthesia is still deep and the animal allowed to recover somewhere quiet
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
62 2011 WSAVAmiddotFASAVA World Congress Proceedings
References1 Hall LW Clarke KW and Trim CM 2001 Chapter 5 In Veterinary Anaesthesia WB Saunders London Pgs
113-131
2 Andress JL Day TK Day D 1995 The effects of consecutive day propofol anesthesia on feline red blood
cells Vet Surg 24 277-82
3Psatha E Alibhai HI Jimenez-Lozano A et al2011 Clinical efficacy and cardiorespiratory effects of
alfaxalone or diazepamfentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk Vet
Anaesth Analg 38 24-36
4Muir W Lerche P Wiese A et al 2008 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in dogs Vet Anaesth Analg 35 1-12
5 Muir W Lerche P Wiese A et al 2009 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in cats Vet Anaesth Analg 36 42-54
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
60 2011 WSAVAmiddotFASAVA World Congress Proceedings
usually best given slowly Intramuscular (IM) or similar is always second best - depth of anaesthesia
achieved is much less controllable and depend is on speed of uptake 6 ALL anaesthetics are respiratory
depressant even if the animal breaths fast so using injectable agents still needs OXYGEN a clear
AIRWAY the ability to VENTILATE if necessary and excellent MONITORING
Anaesthetic agentscombinations A (very) brief resume of the major clinically important pharmacology [1]
Thiopental Barbiturate presented as solid to dissolve in water Irritant extravascularly IV route only Rapid
onset of anaesthesia (one circulation time) initital recovery by re-distribution slow metabolism and cumulative
Poor analgesia Very respiratory depressant Vasodilates Increases heart rate
Propofol Presentation usually in lipid but see below Non-irritant but sometimes pain on injection IV route
only Rapid onset anaesthesia non-cumulative and recovery fast-and complete except in cats [2 Poor
analgesia Very respiratory depressant Cardiovascular effects as thiopental but less tachycardia
Ketamine Presentation in solution with preservatives Many routes of administration Non-irritant but pain on
IM injection Onset of anaesthesia after IV injection not immediate Excellent analgesia Respiratory depressant
but animal may breath rapidly and shallowly Technically myocardial depression but sympathetic stimulation
result in CV system being well maintained Hallucinogenic and muscle rigidity so usually used in combination
with alpha 2 agonists or benzodiazepines
Etomidate Rapidly acting IV induction agent with rapid recovery from induction dose Pain on injection
Venous phlebitis Poor analgesia Myoclonic activity Minimal cardiovascular effects (so popular for the
compromised dog) See below for concern re cortisol suppression
Alphaxalone - see detail below
Benzodiazepineopioids may also be used to induce anaesthesia [3] Neither of these agents work in a circulation
time
Whatrsquos new or currently controversial(a) Propofol in catsThe major route (there are others) of metabolism of propofol is through glucuronidation of the parent drug
followed by glucuro‐conjugation of hydroxylated metabolite via cytochrome P450 to produce other conjugates Cats lack the enzymes necessary for this and also are slow to metabolise the lipids in the
carrier As a result propofol is not as short acting in the cat as in the dog Its safe use as an induction agent
and use for short duration infusion appears satisfactory but there is continual controversy as to whether it is
suitable for longer infusions or for use several days in succession (when under experimental conditions
toxicity has occurred [2])
(b) Propofol formulationsThe original lecithin based formulation of propofol had to be used within a very short time of opening-
making it expensive Since becoming lsquoout of patent a number of new versions have included preservatives
of varying efficacy These versions state on their marketing authorisation the time after opening the vial
when the product is considered safe The most recent on the veterinary market includes benzyl alcholol
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
612011 WSAVAmiddotFASAVA World Congress Proceedings
AFTER THIOPENTAL OPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
and in the USA has authorisation to be open for 28 days (some other countries give a shorter time) There
are some questions as to the toxicity of the Benzyl alcohol particularly in cats but again this is only likely
to be a problem with prolonged infusions
An emulsion formulation of propofol that does not include oils and again has a long lsquoshelf lifersquo after
opening has been available but in the UK has been (possibly temporarily) withdrawn for commercial
reasons
Etomidate Etomidate has not been used as a CRI in intensive care for many years since it was realised that the
adrenocortical suppression in such patients increased the overall death rate most usually from infections In the
last few years there has been considerable controversy over whether the short-term (a few hours) adrenocortical
suppression it induces means that it should not be used for IV induction of anaesthesia in particular in patients
with sepsis There is no evidence as to whether this is a potential problem in veterinary anaesthesia
Alfaxalone (3-alpha-hydroxy-5-alpha-pregnane-1120-dione) solubalized in 2 alpha-hydroxypropyl beta
cyclodextrin (HPBCD) Licenced product - Alfaxanreg
Steroid anaesthesia is not new- over the last 50 years a number of agents have been used - the problem has been
solubility Alphaxalone alphadalone combination solublised in cremaphor was used in humans and in cats
(Saffanreg) - but the cremaphor caused histamine release
Facts about Alfaxalone as Alfaxanreg
(a) Originally licenced in Australia and used there now for some years Now licenced in many countries for
cats and dogs Licensed dose rates without sedative premedication are 3mg kg-1 dogs and 5 mg kg-1 cats
Administer IV over 60 seconds Recommended to premedicate healthy animals
(b) Effective anaesthesia on IV use in (close to) a circulation time Induction quality usually good but
improved by sedation Advise from practice use is to ensure anaesthesia is adequate before endotracheal
intubation otherwise if the animal is stimulated it wakes up
(c) Non irritant IV or if accidental extra-vascular It could be given IM but volume too large for use
without deep sedation
(d) Short half-life non-cumulative Metabolised by the liver
(e) Very good safety margin especially if ventilate (massive overdose may causes apnoea)
(f) No evidence of histamine release
(g) Can be used together (not in same syringe) with most commonly used sedatives analgesics or
subsequent inhalation agents
(h) Cardiovascular effects - minimal at clinical or even heavy clinical doses [345]- after this (supra-
clinical doses for licensing procedures) dose dependant fall in blood pressure and systemic vascular
resistance
(i) Transient apnoea if injected fast - more prolonged at massive overdose
(j) Can get some disturbed recoveries These are much less likely to happen if extubation is whilst
anaesthesia is still deep and the animal allowed to recover somewhere quiet
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
62 2011 WSAVAmiddotFASAVA World Congress Proceedings
References1 Hall LW Clarke KW and Trim CM 2001 Chapter 5 In Veterinary Anaesthesia WB Saunders London Pgs
113-131
2 Andress JL Day TK Day D 1995 The effects of consecutive day propofol anesthesia on feline red blood
cells Vet Surg 24 277-82
3Psatha E Alibhai HI Jimenez-Lozano A et al2011 Clinical efficacy and cardiorespiratory effects of
alfaxalone or diazepamfentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk Vet
Anaesth Analg 38 24-36
4Muir W Lerche P Wiese A et al 2008 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in dogs Vet Anaesth Analg 35 1-12
5 Muir W Lerche P Wiese A et al 2009 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in cats Vet Anaesth Analg 36 42-54
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
612011 WSAVAmiddotFASAVA World Congress Proceedings
AFTER THIOPENTAL OPTIONS FOR SHORT TERM INJECTAbLE ANAESTHESIA
and in the USA has authorisation to be open for 28 days (some other countries give a shorter time) There
are some questions as to the toxicity of the Benzyl alcohol particularly in cats but again this is only likely
to be a problem with prolonged infusions
An emulsion formulation of propofol that does not include oils and again has a long lsquoshelf lifersquo after
opening has been available but in the UK has been (possibly temporarily) withdrawn for commercial
reasons
Etomidate Etomidate has not been used as a CRI in intensive care for many years since it was realised that the
adrenocortical suppression in such patients increased the overall death rate most usually from infections In the
last few years there has been considerable controversy over whether the short-term (a few hours) adrenocortical
suppression it induces means that it should not be used for IV induction of anaesthesia in particular in patients
with sepsis There is no evidence as to whether this is a potential problem in veterinary anaesthesia
Alfaxalone (3-alpha-hydroxy-5-alpha-pregnane-1120-dione) solubalized in 2 alpha-hydroxypropyl beta
cyclodextrin (HPBCD) Licenced product - Alfaxanreg
Steroid anaesthesia is not new- over the last 50 years a number of agents have been used - the problem has been
solubility Alphaxalone alphadalone combination solublised in cremaphor was used in humans and in cats
(Saffanreg) - but the cremaphor caused histamine release
Facts about Alfaxalone as Alfaxanreg
(a) Originally licenced in Australia and used there now for some years Now licenced in many countries for
cats and dogs Licensed dose rates without sedative premedication are 3mg kg-1 dogs and 5 mg kg-1 cats
Administer IV over 60 seconds Recommended to premedicate healthy animals
(b) Effective anaesthesia on IV use in (close to) a circulation time Induction quality usually good but
improved by sedation Advise from practice use is to ensure anaesthesia is adequate before endotracheal
intubation otherwise if the animal is stimulated it wakes up
(c) Non irritant IV or if accidental extra-vascular It could be given IM but volume too large for use
without deep sedation
(d) Short half-life non-cumulative Metabolised by the liver
(e) Very good safety margin especially if ventilate (massive overdose may causes apnoea)
(f) No evidence of histamine release
(g) Can be used together (not in same syringe) with most commonly used sedatives analgesics or
subsequent inhalation agents
(h) Cardiovascular effects - minimal at clinical or even heavy clinical doses [345]- after this (supra-
clinical doses for licensing procedures) dose dependant fall in blood pressure and systemic vascular
resistance
(i) Transient apnoea if injected fast - more prolonged at massive overdose
(j) Can get some disturbed recoveries These are much less likely to happen if extubation is whilst
anaesthesia is still deep and the animal allowed to recover somewhere quiet
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
62 2011 WSAVAmiddotFASAVA World Congress Proceedings
References1 Hall LW Clarke KW and Trim CM 2001 Chapter 5 In Veterinary Anaesthesia WB Saunders London Pgs
113-131
2 Andress JL Day TK Day D 1995 The effects of consecutive day propofol anesthesia on feline red blood
cells Vet Surg 24 277-82
3Psatha E Alibhai HI Jimenez-Lozano A et al2011 Clinical efficacy and cardiorespiratory effects of
alfaxalone or diazepamfentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk Vet
Anaesth Analg 38 24-36
4Muir W Lerche P Wiese A et al 2008 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in dogs Vet Anaesth Analg 35 1-12
5 Muir W Lerche P Wiese A et al 2009 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in cats Vet Anaesth Analg 36 42-54
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea
62 2011 WSAVAmiddotFASAVA World Congress Proceedings
References1 Hall LW Clarke KW and Trim CM 2001 Chapter 5 In Veterinary Anaesthesia WB Saunders London Pgs
113-131
2 Andress JL Day TK Day D 1995 The effects of consecutive day propofol anesthesia on feline red blood
cells Vet Surg 24 277-82
3Psatha E Alibhai HI Jimenez-Lozano A et al2011 Clinical efficacy and cardiorespiratory effects of
alfaxalone or diazepamfentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk Vet
Anaesth Analg 38 24-36
4Muir W Lerche P Wiese A et al 2008 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in dogs Vet Anaesth Analg 35 1-12
5 Muir W Lerche P Wiese A et al 2009 Cardiorespiratory and anesthetic effects of clinical and supraclinical
doses of alphaxalone in cats Vet Anaesth Analg 36 42-54
Reprinted in IVIS with the permission of WSAVA Close this window to return to IVIS
36th World Small Animal Veterinary Congress 2011 - Jeju Korea