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Intervertebral Disc Degeneration

2013-04-16T00:42:24Z

Caramolly: /* Hansen Type I */

{{OpenPagesTop}}
Also Known As: '''''IVDD''''' — '''''Hansen Type I IVDD''''' — '''''Hansen Type II IVDD''''' — '''''Fibrocartilagenous Embolic Myelopathy''''' — '''''FCE''''' — '''''Explosive Disc'''''

==Introduction==
[[File:Intervertebral disc degeneration.jpg|200px|right|thumb|Intervertebral disc degeneration (Courtesy of Bristol Biomed Image Archive)]]
The term ''''Intervertebral Disc Disease'''' ('''IVDD''') refers to several pathological processes involving the intervertebral discs. It is common in the '''dog''', and certain breeds of dog have a genetic predisposition to early-onset IVDD. Any disc in the [[Spinal Column - Anatomy & Physiology|spinal column]] may be affected with the most prevalent clinical signs resulting from lesions in the '''cervical, thoracic or lumbar discs'''.

==Hansen Type I==

In '''[[Chondrodysplasia|chondrodystrophic breeds]]''' such as the '''dachshund''' and the '''bassett hound''', the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]] undergoes '''chondroid degeneration'''. These breeds are genetically predisposed to such pathology and changes such as '''[[Mineralisation - Pathology|mineralisation]]''' are normally apparent in more than one disc by the time the dog is one year old. The abnormal disc may bulge, chronically impinging on the ventral cord and producing slow onset of clinical signs. However dorsal '''extrusion''' of the degenerate nucleus pulposus - which ruptures through the annulus fibrosis into the spinal canal - can occur at any point, causing '''acute''' [[Spinal Cord - Anatomy & Physiology|spinal cord]] '''trauma'''. The initial impact of the nucleus causes '''contusion''' of the spinal cord, and the extruded nucleus continues to '''compress''' the cord. This is known as '''Type I (Hansen) IVDD'''.

Type I IVDD most commonly occurs in '''small and [[Chondrodysplasia|chondrodystrophic breeds]]''', but it can occur in any dog. It is most likely to occur in '''young to middle-aged''' dogs. Clinical signs are '''acute''' in onset. Neurolocalisation will depend on which disc is affected but the classic signs are a T3-L3 myelopathy (the most common localisation) are '''a non-ambulatory pelvic limb para-paresis and poor paw placement (proprioception)'''. Withdrawal reflexes may be absent or abnormal, deep pain perception may be absent, and patellar reflexes may be absent or abnormal (e.g. crossed extensor reflex) dependent on the location and severity of the lesion.

* '''Cervical discs''' - neck pain is the most common clinical sign, paresis is less common as there is more space in the vertebral canal at this point, so compression is less severe.

* '''Thoracolumbar discs''' - pelvic limb paresis and ataxia are the most common clinical signs.

* '''Lumbosacral discs''' - pelvic limb lameness, spinal pain and urinary incontinence are the most common clinical signs.

==Hansen Type II ==
'''Type II IVDD''' is more common in '''older, large breed dogs''' such as the German Shepard Dog. IVDD type II involves '''fibroid degeneration of the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]]''' and '''protrusion of the [[Spinal Column - Anatomy & Physiology|annulus fibrosis]]'''. Over time the fibroid tissue in the disc is replaced by '''collagenous tissue'''. At the same time, '''hypertrophy''' of the surrounding '''annulus''' occurs, causing '''progressive compression of the spinal cord'''. Mineralisation of the discs is rare.

Clinical signs are normally '''insidious''' but the dog may present acutely. It is common for the dog to only show signs of '''dynamic compression''' of the spinal cord, for example when jumping. As the onset of disease is normally '''gradual''' and '''progressive''', so clinical signs are normally less severe on presentation. These include:

* Yelping (unprovoked or when handled)
* Reluctance to jump or climb
* Low head carriage and arched back
* Reluctance to move head and neck
* Restlessness and panting

==Fibrocartilagenous Embolic Myelopathy (FCE)==
This '''vascular''' disease is typically seen in '''young medium to large breed dogs''' but it can occur in any dog or cat. It occurs when a '''[[Embolism|fibrocartilagenous embolus]]''' causes an '''[[Infarction|infarction]] of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] parenchyma'''.

It is typically '''peracute''' in onset and clinical signs are '''non-progressive''', with a classic history of a dog jumping for a toy, yelping, and collapsing with paresis. The disease is '''non-painful''' as no pain receptors are present in the spinal cord '''parenchyma'''.

=='Explosive Disc'==
Explosive disc is the '''low volume, high velocity traumatic extrusion of the normal nucleus pulposus'''. This causes a '''non-compressive contusion injury to the spinal cord'''. The signalment, clinical signs and history are normally similar to FCE, with the dog presenting with a non-progressive paresis of peracute onset.

==Diagnosis==

A thorough '''history, clinical exam and neurological exam''' should be performed on presentation. The [[Neurological Examination - Dog & Cat|neurological exam]] should reveal the '''severity and neuro-localisation''' of the disease. Motor function, proprioception, spinal reflex arcs, the location of spinal pain and most importantly the presence or absence of conscious pain perception can provide an overall picture of location and severity.

Once this has been achieved imaging modalities can be used to further localise and classify the lesion.

===Radiography===
Survey radiographs should be taken to identify any signs of intervertebral disc disease. These signs include:
* '''A narrowing of the intervertebral disc space'''
* '''Small or opaque intervertebral foramen'''
* '''The presence of gas in the intervertebral foramen'''
* '''Calcificiation of disc material overlying the vertebral canal'''
* '''Presence of disc material in the spinal canal'''

Radiographs are normally taken when the animal in '''anaesthetised''' to allow appropriate positioning. '''Lateral and ventrodorsal views''' should be taken. Should these radiographs fail to demonstrate the full extent of the lesion, a '''[[Cerebral Spinal Fluid - Anatomy & Physiology|CSF]] sample''' should be taken to provide more information.

===Myelography===
Myelography involves injection of '''non-ionic contrast medium''' into the '''subarachnoid space''', which '''outlines the spinal cord'''. It should be performed in all cases which showed no clear signs on survey radiographs, cases where the survey radiographs do not match the clinical signs, cases where the extent of the lesion is unknown and any potentially surgical cases. The procedure should be performed under general anaesthesia - often the animal will be moved directly to theatre following myelography. Myelography can identify the lesion and confirm IVDD:

'''1) Extradural''' - The contrast medium bulges towards the cord - this is the sign you would expect to see in Type I and II IVDD.

'''2) Intramedullary''' - The contrast lines are further pushed apart by an intramedullary lesion. This pattern is seen with FCE. Common differentials are neoplasia and spinal cord oedema.

'''3) Intradural-extramedullary''' - The contrast medium surrounds the lesion in these cases, producing a fork-shape in the contrast line. This is most commonly caused by a nerve root tumour.

===MRI===
MRI is the '''gold-standard''' for identifying IVDD, however it is generally only available in '''referral hospitals''' and is very expensive.

==Treatment==
With '''Type I IVDD''' you may consider '''immediate referral'''. Providing there are no cost constraints, performing '''prompt surgery''' to relieve the pressure on the spinal cord results in an '''improved prognosis''' and specialist referral units are equipped to do this. '''Conservative treatment''' may be considered if signs are '''mild''' (presence of mild pain) and '''non-progressive''', if performing surgery is against the owners wishes or there are significant '''cost constraints'''. '''Type II IVDD''' is treated in the same way as type I but as clinical signs are less acute, a rapid decision about the choice of treatment is rarely necessary.

===Surgery===
The surgical procedure performed depends on the location of the lesion. The procedure performed on a '''thoracolumbar lesion''' is a '''hemilaminectomy'''. A '''ventral slot''' is performed on '''cervical lesions'''. Generally a fenestration is made in the vertebral canal and the extruded disc material is cooped out to relieve pressure on the spinal cord. Prophylactic laminectomies may be performed on unaffected discs to prevent recurrence.

Post-operatively, it is essential that the dog is placed on a program of '''strict cage rest and physiotherapy''' for a minimum of '''6 weeks'''. [[NSAIDs]] may also be given.

===Conservative Treatment===
The aims of conservative treatment are to:
:allow the '''extruded disc material time to dissipate''', relieving pressure on the spinal cord
:allow the '''dorsal annulus to heal''', preventing further extrusion of disc material.
This involves '''strict cage rest for a minimum of 6 weeks''', very short '''lead walk''' and '''physiotherapy'''. NSAIDs may also be given.

FCE and 'explosive disc' are non-progressive and the appropriate treatment is '''supportive care''' (management of the recumbent animal), '''time''' and '''physiotherapy'''.

Steroid treatment is now contraindicated in acute spinal trauma.

==Prognosis==
Prognosis for IVDD type I depends on the '''severity and duration of clinical signs and the treatment options'''. If '''[[Sensory Pathways - Anatomy & Physiology|deep pain''' sensation]] is present and surgery is performed immediately then prognosis is good. Prognosis worsens the longer deep pain is absent - prognosis is grave with a loss of deep pain longer than 48 hours.

Type II IVDD prognosis depends on the '''severity of the presenting signs''', but as there is a more chronic loss of function recovery is '''slower''' and some functional deficits may never be regained.

Prognosis for FCE and explosive disc can be judged on the level of '''deep pain sensation and [[Peripheral Nervous System Pathology Overview|LMN function]]'''. Although clinical signs may look bad (especially to the owners), dogs with appropriate deep pain sensation have the ability to make an impressive recovery.

{{Learning
|flashcards = [[Small Animal Emergency and Critical Care Medicine Q&A 16]]
}}

==References==
Kirby, R (1998) '''Self-Assessment Colour Review - Small Animal Emergency & Critical Care Medicine''' ''Manson''

McKee, M (2000) '''Intervertebral disc disease in the dog 1. Pathophysiology and diagnosis''' ''In Practice 2000 22: 355-36''

McKee, M (2000) '''Intervertebral disc disease in the dog 2. Management options''' ''In Practice 2000 22: 458-47''

RVC staff (2009) '''Nervous System and Special Senses''' RVC Integrated BVetMed Course, ''Royal Veterinary College''

{{review}}

{{OpenPages}}

[[Category:Joints - Degenerative Pathology]]
[[Category:Neurological Diseases - Dog]]
[[Category:Expert Review - Small Animal]]

Intervertebral Disc Degeneration

2013-04-16T00:23:55Z

Caramolly: /* Introduction */

{{OpenPagesTop}}
Also Known As: '''''IVDD''''' — '''''Hansen Type I IVDD''''' — '''''Hansen Type II IVDD''''' — '''''Fibrocartilagenous Embolic Myelopathy''''' — '''''FCE''''' — '''''Explosive Disc'''''

==Introduction==
[[File:Intervertebral disc degeneration.jpg|200px|right|thumb|Intervertebral disc degeneration (Courtesy of Bristol Biomed Image Archive)]]
The term ''''Intervertebral Disc Disease'''' ('''IVDD''') refers to several pathological processes involving the intervertebral discs. It is common in the '''dog''', and certain breeds of dog have a genetic predisposition to early-onset IVDD. Any disc in the [[Spinal Column - Anatomy & Physiology|spinal column]] may be affected with the most prevalent clinical signs resulting from lesions in the '''cervical, thoracic or lumbar discs'''.

==Hansen Type I==

In '''[[Chondrodysplasia|chondrodystrophic breeds]]''' such as the '''dachshund''' and the '''bassett hound''', the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]] undergoes '''chondroid degeneration'''. This is normal in these breeds and changes such as '''[[Mineralisation - Pathology|mineralisation]]''' are normally apparent in more than one disc by the time the dog is one year old. However '''extrusion''' of the degenerate nuclei can occur at any point, causing '''acute''' [[Spinal Cord - Anatomy & Physiology|spinal cord]] '''trauma'''. The initial impact of the nucleus causes '''contusion''' of the spinal cord, and the extruded nucleus continues to '''compress''' the cord. This is known as '''Type I (Hansen) IVDD'''.

Type I IVDD most commonly occurs in '''small and [[Chondrodysplasia|chondrodystrophic breeds]]''', but it can occur in any dog. It is most likely to occur in '''young to middle-aged''' dogs. Clinical signs are '''acute''' in onset. Neurolocalisation will depend on which disc is affected but the classic signs are a T3-L3 myelopathy (the most common localisation) are '''a non-ambulatory pelvic limb para-paresis, poor paw placement and the presence of withdrawal and patellar reflexes'''.

* '''Cervical discs''' - neck pain is the most common clinical sign, paresis is less common as there is more space in the vertebral canal at this point, so compression is less severe.

* '''Thoracolumbar discs''' - paresis and ataxia are the most common clinical signs.

* '''Lumbosacral discs''' - pelvic limb lameness and pain and incontinence are the most common clinical signs.

==Hansen Type II ==
'''Type II IVDD''' is more common in '''older, large breed dogs''' such as the German Shepard Dog. IVDD type II involves '''fibroid degeneration of the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]]''' and '''protrusion of the [[Spinal Column - Anatomy & Physiology|annulus fibrosis]]'''. Over time the fibroid tissue in the disc is replaced by '''collagenous tissue'''. At the same time, '''hypertrophy''' of the surrounding '''annulus''' occurs, causing '''progressive compression of the spinal cord'''. Mineralisation of the discs is rare.

Clinical signs are normally '''insidious''' but the dog may present acutely. It is common for the dog to only show signs of '''dynamic compression''' of the spinal cord, for example when jumping. As the onset of disease is normally '''gradual''' and '''progressive''', so clinical signs are normally less severe on presentation. These include:

* Yelping (unprovoked or when handled)
* Reluctance to jump or climb
* Low head carriage and arched back
* Reluctance to move head and neck
* Restlessness and panting

==Fibrocartilagenous Embolic Myelopathy (FCE)==
This '''vascular''' disease is typically seen in '''young medium to large breed dogs''' but it can occur in any dog or cat. It occurs when a '''[[Embolism|fibrocartilagenous embolus]]''' causes an '''[[Infarction|infarction]] of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] parenchyma'''.

It is typically '''peracute''' in onset and clinical signs are '''non-progressive''', with a classic history of a dog jumping for a toy, yelping, and collapsing with paresis. The disease is '''non-painful''' as no pain receptors are present in the spinal cord '''parenchyma'''.

=='Explosive Disc'==
Explosive disc is the '''low volume, high velocity traumatic extrusion of the normal nucleus pulposus'''. This causes a '''non-compressive contusion injury to the spinal cord'''. The signalment, clinical signs and history are normally similar to FCE, with the dog presenting with a non-progressive paresis of peracute onset.

==Diagnosis==

A thorough '''history, clinical exam and neurological exam''' should be performed on presentation. The [[Neurological Examination - Dog & Cat|neurological exam]] should reveal the '''severity and neuro-localisation''' of the disease. Motor function, proprioception, spinal reflex arcs, the location of spinal pain and most importantly the presence or absence of conscious pain perception can provide an overall picture of location and severity.

Once this has been achieved imaging modalities can be used to further localise and classify the lesion.

===Radiography===
Survey radiographs should be taken to identify any signs of intervertebral disc disease. These signs include:
* '''A narrowing of the intervertebral disc space'''
* '''Small or opaque intervertebral foramen'''
* '''The presence of gas in the intervertebral foramen'''
* '''Calcificiation of disc material overlying the vertebral canal'''
* '''Presence of disc material in the spinal canal'''

Radiographs are normally taken when the animal in '''anaesthetised''' to allow appropriate positioning. '''Lateral and ventrodorsal views''' should be taken. Should these radiographs fail to demonstrate the full extent of the lesion, a '''[[Cerebral Spinal Fluid - Anatomy & Physiology|CSF]] sample''' should be taken to provide more information.

===Myelography===
Myelography involves injection of '''non-ionic contrast medium''' into the '''subarachnoid space''', which '''outlines the spinal cord'''. It should be performed in all cases which showed no clear signs on survey radiographs, cases where the survey radiographs do not match the clinical signs, cases where the extent of the lesion is unknown and any potentially surgical cases. The procedure should be performed under general anaesthesia - often the animal will be moved directly to theatre following myelography. Myelography can identify the lesion and confirm IVDD:

'''1) Extradural''' - The contrast medium bulges towards the cord - this is the sign you would expect to see in Type I and II IVDD.

'''2) Intramedullary''' - The contrast lines are further pushed apart by an intramedullary lesion. This pattern is seen with FCE. Common differentials are neoplasia and spinal cord oedema.

'''3) Intradural-extramedullary''' - The contrast medium surrounds the lesion in these cases, producing a fork-shape in the contrast line. This is most commonly caused by a nerve root tumour.

===MRI===
MRI is the '''gold-standard''' for identifying IVDD, however it is generally only available in '''referral hospitals''' and is very expensive.

==Treatment==
With '''Type I IVDD''' you may consider '''immediate referral'''. Providing there are no cost constraints, performing '''prompt surgery''' to relieve the pressure on the spinal cord results in an '''improved prognosis''' and specialist referral units are equipped to do this. '''Conservative treatment''' may be considered if signs are '''mild''' (presence of mild pain) and '''non-progressive''', if performing surgery is against the owners wishes or there are significant '''cost constraints'''. '''Type II IVDD''' is treated in the same way as type I but as clinical signs are less acute, a rapid decision about the choice of treatment is rarely necessary.

===Surgery===
The surgical procedure performed depends on the location of the lesion. The procedure performed on a '''thoracolumbar lesion''' is a '''hemilaminectomy'''. A '''ventral slot''' is performed on '''cervical lesions'''. Generally a fenestration is made in the vertebral canal and the extruded disc material is cooped out to relieve pressure on the spinal cord. Prophylactic laminectomies may be performed on unaffected discs to prevent recurrence.

Post-operatively, it is essential that the dog is placed on a program of '''strict cage rest and physiotherapy''' for a minimum of '''6 weeks'''. [[NSAIDs]] may also be given.

===Conservative Treatment===
The aims of conservative treatment are to:
:allow the '''extruded disc material time to dissipate''', relieving pressure on the spinal cord
:allow the '''dorsal annulus to heal''', preventing further extrusion of disc material.
This involves '''strict cage rest for a minimum of 6 weeks''', very short '''lead walk''' and '''physiotherapy'''. NSAIDs may also be given.

FCE and 'explosive disc' are non-progressive and the appropriate treatment is '''supportive care''' (management of the recumbent animal), '''time''' and '''physiotherapy'''.

Steroid treatment is now contraindicated in acute spinal trauma.

==Prognosis==
Prognosis for IVDD type I depends on the '''severity and duration of clinical signs and the treatment options'''. If '''[[Sensory Pathways - Anatomy & Physiology|deep pain''' sensation]] is present and surgery is performed immediately then prognosis is good. Prognosis worsens the longer deep pain is absent - prognosis is grave with a loss of deep pain longer than 48 hours.

Type II IVDD prognosis depends on the '''severity of the presenting signs''', but as there is a more chronic loss of function recovery is '''slower''' and some functional deficits may never be regained.

Prognosis for FCE and explosive disc can be judged on the level of '''deep pain sensation and [[Peripheral Nervous System Pathology Overview|LMN function]]'''. Although clinical signs may look bad (especially to the owners), dogs with appropriate deep pain sensation have the ability to make an impressive recovery.

{{Learning
|flashcards = [[Small Animal Emergency and Critical Care Medicine Q&A 16]]
}}

==References==
Kirby, R (1998) '''Self-Assessment Colour Review - Small Animal Emergency & Critical Care Medicine''' ''Manson''

McKee, M (2000) '''Intervertebral disc disease in the dog 1. Pathophysiology and diagnosis''' ''In Practice 2000 22: 355-36''

McKee, M (2000) '''Intervertebral disc disease in the dog 2. Management options''' ''In Practice 2000 22: 458-47''

RVC staff (2009) '''Nervous System and Special Senses''' RVC Integrated BVetMed Course, ''Royal Veterinary College''

{{review}}

{{OpenPages}}

[[Category:Joints - Degenerative Pathology]]
[[Category:Neurological Diseases - Dog]]
[[Category:Expert Review - Small Animal]]

Propofol

2013-04-15T23:39:29Z

Caramolly: /* Mechanism of Action */

'''Propofol''' is one of the most commonly used injectable anaesthetic agents in small animal practice. It is a ''very short acting'' alkylphenol. It is generally used as a induction agent but can be used for maintenance of anaesthesia via a total intravenous anaesthesia (TIVA) protocol.

==Mechanism of Action==
Propofol binds to and activates GABA-A receptors, similarly to [[#barbituates|thiopental]], benzodiazepines and alcohol, although it binds at a different site on this complex multi-subunit receptor. GABA is a major inhibitory neurotransmitter in the CNS. Activation of the GABA-A receptor causes increased chloride conductance leading to hyperpolarisation of the postsynaptic neuronal cell membrane, thus inhibiting conductance producing depression of the CNS.

==Pharmacological Considerations==
Propofol is highly lipid soluble and insoluble in aqueous solution so is formulated as a 1% oil-in-water emulsion. Once a vial has been opened it should be refrigerated and then discarded after 24 hours. Administration of the agent is via an intravenous route and should be given slowly to effect (over 2 minutes usually), with onset of action between 60-90 seconds. Administration of premedications such as [[Alpha-2 Agonists|alpha-2 agonists]] or [[opioids|opioids]] can significantly reduce the amount of propofol required to anaesthetise a patient.

Propofol is ''highly distributed'' meaning that blood levels significantly fall rapidly. It is metabolised by the liver and conjugates are excreted in urine. It is this hepatic metabolism that allows for repeated dosing as this rapid metabolism that means there is little accumulation of the drug, making it a suitable agent for TIVAs in some species.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*Decreased myocardial contractility without reflex tachycardia.
*Greatest hypotension compared to any other injectable agents. However, it is of short duration.
*Occassionally profound bradycardia may be seen.

===Respiratory Effects===
*Most common side effect seen is apnoea upon induction. This is thought to be related to dose and rate of administration.

===Propofol in Cats===
In cats, glucuronide conjugation is reduced, which is require for phenolic compound metabolism. This means that recovery from propofol TIVAs is prolonged in cats and has been known to reduce the packed cell volume (PCV) in some patients. Repeated dosing in cats is also not advisable as it causes significant Heinz body formation as well as anorexia, diarrhoea, facial oedema, and depression.

==Uses==
As previously mentioned, propofol can be used as '''both''' induction and maintenance agents. It is useful in patients undergoing caesarean section as it has mininal foetal depression. It also has anticonvulsant properties and so can be used to anaesthetise a seizuring animal when other treatments, such as [[phenothiazines|diazepam]] , have been ineffective. Similarly to [[#barbitutates|thiopental]], propofol reduces intracranial pressure (ICP), so it can also be used in patients with increased ICP. It may be beneficial to use propofol in patients with upper airway obstructive disease due to rapid recovery meaning that airway reflexes are more rapidly recovered.

[[Category:Injectable Anaesthetic Agents]]

Steroid Agents

2013-04-15T23:23:08Z

Caramolly: /* Pharmacological Considerations */

==Introduction==
The only available steroid anaesthetic for use in veterinary patients is '''alfaxalone''' (3-α-hydroxy-5-α-pregnane-11,20-dione). It is a progesterone derived ''neurosteroid''.

==Mechanism of Action==
Neurosteroids act similarly to other anaesthetic agents by acting at the GABAa receptor chloride channels to enhance the inhibitory effect of GABA. This produces hypnosis and muscle relaxation.

==Pharmacological Considerations==
Alfaxalone is water-insoluble, and was first available in combination with the similar molecule alfadolone solubilised in polyoxyethylated castor oil (Cremophor EL) for use in humans, cats and dogs. A newer formulation of alfaxalone (without alfadolone) solubilised in cyclodextrin is available for dogs and cats.

Alfaxalone can be administered intravenously in cats and dogs and intramuscularly in cats, though the efficacy of intramuscular injection is species dependent - '''do not''' rely on intramuscular injection of alfaxalone to sedate or induce anaesthesia in dogs. It has a rapid onset of action, inducing anaesthesia with 30-60 seconds when given intravenously. Its duration of action is dose dependent. If given intramuscularly, onset of anaesthesia is within 7-10 minutes. Recovery occurs due to a combination of metabolism via and redistribution.

The formulation of alfaxalone in cyclodextrin has a volume of distribution after a single injection of a clinical dose in dogs and cats of 2.4 L/kg and 1.8 L/kg, respectively. In cats, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 45 minutes for a 5 mg/kg dose. Mean plasma clearance for a 5 mg/kg dose is 25.1 ± 7.6 mL/kg/min. In dogs, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 25 minutes for a 2 mg/kg dose. Plasma clearance for a 2 mg/kg dose is 59.4 ± 12.9 mL/kg/min. (Product literature)

===Drug Interactions===
Alfaxalone in cyclodextrin has been used safely after administration of an extremely wide range of premedication and peri-operative drugs. Dose dependent CNS depression can be accentuated by administration of sedatives and analgesics. Alfaxalone should not be administered concurrently with other intravenous anaesthetic induction drugs, but has been used safely as an induction agent prior to maintenance with halothane, isoflurane, sevoflurane and desflurane. It should not be mixed in the same syringe as other medications, as the cyclodextrin has a propensity to bind other molecules. If a need exists to dilute the alfaxalone in cyclodextrin solution, it has been shown to be stable in 0.9% Saline for up to 7 days. Slight adsorption to plastic of giving sets has been recognised, though this appears to be of no clinical significance.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*At clinical doses, and employing the concepts of balanced anaesthesia, alfaxalone in cyclodextrin causes little cardiovascular effect, however a dose dependent decrease in arterial blood pressure thought to be due to decreased myocardial contractility and stroke volume can be recognised at supra-clinical doses.

===Respiratory Effects===
*Minimal respiratory effects. Rapid intravenous administration can produce a short period of apnoea, therefore when using the IV route alfaxalone should be administered steadily over a period of 60 seconds (e.g. 1/4 dose every 15 seconds) while assessing the depth of anaesthesia achieved.

===Other Effects===
*Administration of the combination product (alfaxalone/aldalone) solubilised in Cremophor EL is associated with adverse effects. In cats hyperaemia or oedema of the ears and forepaws is observed in over half of animals; and in dogs it can induce an anaphylactoid reaction with histamine release leading to a fall in arterial blood pressure, urticaria and skin erythema. Its association with histamine release means it is contraindicated in animals with conditions such as asthma or mast cell tumours.

These adverse effects are '''not''' experienced in cats or dogs following administration of the aqueous cyclodextrin formulation of alfaxalone, which is Cremophor-free.

==Uses==
Alfaxalone can be used for induction and maintenance of anaesthesia in dogs and cats.

{{unfinished}}
[[Category:To Do - Drugs]][[Category:To Do - Anaesthesia]]
[[Category:Injectable Anaesthetic Agents]]

Steroid Agents

2013-04-15T23:12:21Z

Caramolly: /* Introduction */

==Introduction==
The only available steroid anaesthetic for use in veterinary patients is '''alfaxalone''' (3-α-hydroxy-5-α-pregnane-11,20-dione). It is a progesterone derived ''neurosteroid''.

==Mechanism of Action==
Neurosteroids act similarly to other anaesthetic agents by acting at the GABAa receptor chloride channels to enhance the inhibitory effect of GABA. This produces hypnosis and muscle relaxation.

==Pharmacological Considerations==
Alfaxalone is available as either a single agent solution at 10mg/ml, or in combination with alfadolone with polyoxyethylated castor oil as a solvent. Alfaxalone can be administered intravenously and intramuscularly, though the efficacy of intramuscular injection is species dependant - '''do not''' rely on intramuscular injection of alfaxalone to sedate or induce anaesthesia in dogs. It has a rapid onset of action, inducing anaesthesia with 30-60 seconds when given intravenously. Its duration of action is dose dependent. If given intramuscularly, onset of anaesthesia is within 7-10 minutes. Recovery occurs due to a combination of metabolism via and redistribution.

The formulation of alfaxalone in cyclodextrin has a volume of distribution after a single injection of a clinical dose in dogs and cats of 2.4 L/kg and 1.8 L/kg, respectively. In cats, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 45 minutes for a 5 mg/kg dose. Mean plasma clearance for a 5 mg/kg dose is 25.1 ± 7.6 mL/kg/min. In dogs, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 25 minutes for a 2 mg/kg dose. Plasma clearance for a 2 mg/kg dose is 59.4 ± 12.9 mL/kg/min. (Product literature)

===Drug Interactions===
Alfaxalone in cyclodextrin has been used safely after administration of an extremely wide range of premedication and peri-operative drugs. Dose dependant CNS depression can be accentuated by administration of sedatives and analgesics. Alfaxalone should not be administered concurrently with other intravenous anaesthetic induction drugs, but has been used safely as an induction agent prior to maintenance with halothane, isoflurane, sevoflurane and desflurane. It should not be mixed in the same syringe as other medications, as the cyclodextrin has a propensity to bind other chemicals. If a need exists to dilute the alfaxalone in cyclodextrin solution, it has been shown to be stable in 0.9% Saline for up to 7 days. Slight absorbtion to plastic of giving sets has been recognised, though this appears to be of no clinical significance.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*At clinical doses, and employing the concepts of balanced anaesthesia, alfaxalone in cyclodextrin causes little cardiovascular effect, however a dose dependent decrease in arterial blood pressure thought to be due to decreased myocardial contractility and stroke volume can be recognised at supra-clinical doses.

===Respiratory Effects===
*Minimal respiratory effects. Rapid intravenous administration can produce a short period of apnoea, therefore when using the IV route alfaxalone should be administered steadily over a period of 60 seconds (e.g. 1/4 dose every 15 seconds) while assessing the depth of anaesthesia achieved.

===Other Effects===
*Administration of the combination product (alfaxalone/aldalone) solubilised in Cremophor EL is associated with adverse effects. In cats hyperaemia or oedema of the ears and forepaws is observed in over half of animals; and in dogs it can induce an anaphylactoid reaction with histamine release leading to a fall in arterial blood pressure, urticaria and skin erythema. Its association with histamine release means it is contraindicated in animals with conditions such as asthma or mast cell tumours.

These adverse effects are '''not''' experienced in cats or dogs following administration of the aqueous cyclodextrin formulation of alfaxalone, which is Cremophor-free.

==Uses==
Alfaxalone can be used for induction and maintenance of anaesthesia in dogs and cats.

{{unfinished}}
[[Category:To Do - Drugs]][[Category:To Do - Anaesthesia]]
[[Category:Injectable Anaesthetic Agents]]

Steroid Agents

2013-04-15T23:10:11Z

Caramolly: /* Cardiovascular Effects */

==Introduction==
The only available steroid anaesthetic for use in veterinary patients is '''alfaxalone'''. It is a progesterone derived ''neurosteroid''.

==Mechanism of Action==
Neurosteroids act similarly to other anaesthetic agents by acting at the GABAa receptor chloride channels to enhance the inhibitory effect of GABA. This produces hypnosis and muscle relaxation.

==Pharmacological Considerations==
Alfaxalone is available as either a single agent solution at 10mg/ml, or in combination with alfadolone with polyoxyethylated castor oil as a solvent. Alfaxalone can be administered intravenously and intramuscularly, though the efficacy of intramuscular injection is species dependant - '''do not''' rely on intramuscular injection of alfaxalone to sedate or induce anaesthesia in dogs. It has a rapid onset of action, inducing anaesthesia with 30-60 seconds when given intravenously. Its duration of action is dose dependent. If given intramuscularly, onset of anaesthesia is within 7-10 minutes. Recovery occurs due to a combination of metabolism via and redistribution.

The formulation of alfaxalone in cyclodextrin has a volume of distribution after a single injection of a clinical dose in dogs and cats of 2.4 L/kg and 1.8 L/kg, respectively. In cats, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 45 minutes for a 5 mg/kg dose. Mean plasma clearance for a 5 mg/kg dose is 25.1 ± 7.6 mL/kg/min. In dogs, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 25 minutes for a 2 mg/kg dose. Plasma clearance for a 2 mg/kg dose is 59.4 ± 12.9 mL/kg/min. (Product literature)

===Drug Interactions===
Alfaxalone in cyclodextrin has been used safely after administration of an extremely wide range of premedication and peri-operative drugs. Dose dependant CNS depression can be accentuated by administration of sedatives and analgesics. Alfaxalone should not be administered concurrently with other intravenous anaesthetic induction drugs, but has been used safely as an induction agent prior to maintenance with halothane, isoflurane, sevoflurane and desflurane. It should not be mixed in the same syringe as other medications, as the cyclodextrin has a propensity to bind other chemicals. If a need exists to dilute the alfaxalone in cyclodextrin solution, it has been shown to be stable in 0.9% Saline for up to 7 days. Slight absorbtion to plastic of giving sets has been recognised, though this appears to be of no clinical significance.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*At clinical doses, and employing the concepts of balanced anaesthesia, alfaxalone in cyclodextrin causes little cardiovascular effect, however a dose dependent decrease in arterial blood pressure thought to be due to decreased myocardial contractility and stroke volume can be recognised at supra-clinical doses.

===Respiratory Effects===
*Minimal respiratory effects. Rapid intravenous administration can produce a short period of apnoea, therefore when using the IV route alfaxalone should be administered steadily over a period of 60 seconds (e.g. 1/4 dose every 15 seconds) while assessing the depth of anaesthesia achieved.

===Other Effects===
*Administration of the combination product (alfaxalone/aldalone) solubilised in Cremophor EL is associated with adverse effects. In cats hyperaemia or oedema of the ears and forepaws is observed in over half of animals; and in dogs it can induce an anaphylactoid reaction with histamine release leading to a fall in arterial blood pressure, urticaria and skin erythema. Its association with histamine release means it is contraindicated in animals with conditions such as asthma or mast cell tumours.

These adverse effects are '''not''' experienced in cats or dogs following administration of the aqueous cyclodextrin formulation of alfaxalone, which is Cremophor-free.

==Uses==
Alfaxalone can be used for induction and maintenance of anaesthesia in dogs and cats.

{{unfinished}}
[[Category:To Do - Drugs]][[Category:To Do - Anaesthesia]]
[[Category:Injectable Anaesthetic Agents]]

Steroid Agents

2013-04-15T23:08:16Z

Caramolly: /* Respiratory Effects */

==Introduction==
The only available steroid anaesthetic for use in veterinary patients is '''alfaxalone'''. It is a progesterone derived ''neurosteroid''.

==Mechanism of Action==
Neurosteroids act similarly to other anaesthetic agents by acting at the GABAa receptor chloride channels to enhance the inhibitory effect of GABA. This produces hypnosis and muscle relaxation.

==Pharmacological Considerations==
Alfaxalone is available as either a single agent solution at 10mg/ml, or in combination with alfadolone with polyoxyethylated castor oil as a solvent. Alfaxalone can be administered intravenously and intramuscularly, though the efficacy of intramuscular injection is species dependant - '''do not''' rely on intramuscular injection of alfaxalone to sedate or induce anaesthesia in dogs. It has a rapid onset of action, inducing anaesthesia with 30-60 seconds when given intravenously. Its duration of action is dose dependent. If given intramuscularly, onset of anaesthesia is within 7-10 minutes. Recovery occurs due to a combination of metabolism via and redistribution.

The formulation of alfaxalone in cyclodextrin has a volume of distribution after a single injection of a clinical dose in dogs and cats of 2.4 L/kg and 1.8 L/kg, respectively. In cats, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 45 minutes for a 5 mg/kg dose. Mean plasma clearance for a 5 mg/kg dose is 25.1 ± 7.6 mL/kg/min. In dogs, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 25 minutes for a 2 mg/kg dose. Plasma clearance for a 2 mg/kg dose is 59.4 ± 12.9 mL/kg/min. (Product literature)

===Drug Interactions===
Alfaxalone in cyclodextrin has been used safely after administration of an extremely wide range of premedication and peri-operative drugs. Dose dependant CNS depression can be accentuated by administration of sedatives and analgesics. Alfaxalone should not be administered concurrently with other intravenous anaesthetic induction drugs, but has been used safely as an induction agent prior to maintenance with halothane, isoflurane, sevoflurane and desflurane. It should not be mixed in the same syringe as other medications, as the cyclodextrin has a propensity to bind other chemicals. If a need exists to dilute the alfaxalone in cyclodextrin solution, it has been shown to be stable in 0.9% Saline for up to 7 days. Slight absorbtion to plastic of giving sets has been recognised, though this appears to be of no clinical significance.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*At clinical doses, and employing the concepts of balanced anaesthesia, alfaxalone in cyclodextrin causes little cardiovascular effect, however a dose dependent decrease in arterial blood pressure thought to be due to myocardial contractility and stroke volume can be recognised at supra-clinical doses.

===Respiratory Effects===
*Minimal respiratory effects. Rapid intravenous administration can produce a short period of apnoea, therefore when using the IV route alfaxalone should be administered steadily over a period of 60 seconds (e.g. 1/4 dose every 15 seconds) while assessing the depth of anaesthesia achieved.

===Other Effects===
*Administration of the combination product (alfaxalone/aldalone) solubilised in Cremophor EL is associated with adverse effects. In cats hyperaemia or oedema of the ears and forepaws is observed in over half of animals; and in dogs it can induce an anaphylactoid reaction with histamine release leading to a fall in arterial blood pressure, urticaria and skin erythema. Its association with histamine release means it is contraindicated in animals with conditions such as asthma or mast cell tumours.

These adverse effects are '''not''' experienced in cats or dogs following administration of the aqueous cyclodextrin formulation of alfaxalone, which is Cremophor-free.

==Uses==
Alfaxalone can be used for induction and maintenance of anaesthesia in dogs and cats.

{{unfinished}}
[[Category:To Do - Drugs]][[Category:To Do - Anaesthesia]]
[[Category:Injectable Anaesthetic Agents]]

Steroid Agents

2013-04-15T23:05:17Z

Caramolly: /* Other Effects */

==Introduction==
The only available steroid anaesthetic for use in veterinary patients is '''alfaxalone'''. It is a progesterone derived ''neurosteroid''.

==Mechanism of Action==
Neurosteroids act similarly to other anaesthetic agents by acting at the GABAa receptor chloride channels to enhance the inhibitory effect of GABA. This produces hypnosis and muscle relaxation.

==Pharmacological Considerations==
Alfaxalone is available as either a single agent solution at 10mg/ml, or in combination with alfadolone with polyoxyethylated castor oil as a solvent. Alfaxalone can be administered intravenously and intramuscularly, though the efficacy of intramuscular injection is species dependant - '''do not''' rely on intramuscular injection of alfaxalone to sedate or induce anaesthesia in dogs. It has a rapid onset of action, inducing anaesthesia with 30-60 seconds when given intravenously. Its duration of action is dose dependent. If given intramuscularly, onset of anaesthesia is within 7-10 minutes. Recovery occurs due to a combination of metabolism via and redistribution.

The formulation of alfaxalone in cyclodextrin has a volume of distribution after a single injection of a clinical dose in dogs and cats of 2.4 L/kg and 1.8 L/kg, respectively. In cats, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 45 minutes for a 5 mg/kg dose. Mean plasma clearance for a 5 mg/kg dose is 25.1 ± 7.6 mL/kg/min. In dogs, the mean terminal plasma elimination half-life (t1/2) for alfaxalone is approximately 25 minutes for a 2 mg/kg dose. Plasma clearance for a 2 mg/kg dose is 59.4 ± 12.9 mL/kg/min. (Product literature)

===Drug Interactions===
Alfaxalone in cyclodextrin has been used safely after administration of an extremely wide range of premedication and peri-operative drugs. Dose dependant CNS depression can be accentuated by administration of sedatives and analgesics. Alfaxalone should not be administered concurrently with other intravenous anaesthetic induction drugs, but has been used safely as an induction agent prior to maintenance with halothane, isoflurane, sevoflurane and desflurane. It should not be mixed in the same syringe as other medications, as the cyclodextrin has a propensity to bind other chemicals. If a need exists to dilute the alfaxalone in cyclodextrin solution, it has been shown to be stable in 0.9% Saline for up to 7 days. Slight absorbtion to plastic of giving sets has been recognised, though this appears to be of no clinical significance.

==Contraindications and Side Effects==
===Cardiovascular Effects===
*At clinical doses, and employing the concepts of balanced anaesthesia, alfaxalone in cyclodextrin causes little cardiovascular effect, however a dose dependent decrease in arterial blood pressure thought to be due to myocardial contractility and stroke volume can be recognised at supra-clinical doses.

===Respiratory Effects===
*Minimal respiratory effects.

===Other Effects===
*Administration of the combination product (alfaxalone/aldalone) solubilised in Cremophor EL is associated with adverse effects. In cats hyperaemia or oedema of the ears and forepaws is observed in over half of animals; and in dogs it can induce an anaphylactoid reaction with histamine release leading to a fall in arterial blood pressure, urticaria and skin erythema. Its association with histamine release means it is contraindicated in animals with conditions such as asthma or mast cell tumours.

These adverse effects are '''not''' experienced in cats or dogs following administration of the aqueous cyclodextrin formulation of alfaxalone, which is Cremophor-free.

==Uses==
Alfaxalone can be used for induction and maintenance of anaesthesia in dogs and cats.

{{unfinished}}
[[Category:To Do - Drugs]][[Category:To Do - Anaesthesia]]
[[Category:Injectable Anaesthetic Agents]]