|
S
1)
Sevoflurane
a)
Classification
i)
Fluorinated hydrocarbon
ii)
Chemical isomer of isoflurane
b)
General Information
i)
A volatile liquid of low solubility that is
minimally metabolized by the liver
(1)
Liver metabolism exceeds that of isoflurane
ii)
Its extremely low solubility provided for the
quickest inductions, level adjustments, and recoveries of the currently
used inhalant anesthetics
(1)
With the exception of patients experiencing extreme
respiratory compromise sevoflurane is rarely of any advantage over
isoflurane
iii)
MAC
(1)
Dog – 2.1 to 2.4%
(2)
Cats – 2.6%
c)
Advantages/Recommended use
i)
This anesthetic agent is suitable for use with most
veterinary patients
ii)
As with isoflurane, sevoflurane does not sensitize
the heart to epinephrine induced arrhythmia
iii)
Along with isoflurane, an inhalant anesthetic of
choice for patients with:
(1)
Liver disease
(a)
More liver metabolism than isoflurane (~5%) but no
trifluoroacetic acid metabolites are produced
(2)
Intracranial disease
(a)
Less effect on CSF pressure compared to Halothane
d)
Cautionary Information
i)
As with any inhalant anesthetic, cardiac and
respiratory depression result as anesthetic concentrations are increased
(1)
Not all patients under sevoflurane will be able to
maintain adequate blood pressures
(2)
Switching to an alternative maintenance agent may be
necessary
ii)
Compound A (resulting from sevoflurane/sodasorb
interaction) appears to be of little concern
iii)
Although sevoflurane is considered a relatively safe
agent as pertains to staff exposure, we should all strive to minimize
our exposure to this or any other inhalant agent
e)
Dosage Information
i)
Routine use
(1)
Mask Induction
(a)
Start with 100% oxygen @ 3 liters/min for 3 - 5
minutes
(i)
Do not cover patients eyes
(b)
After 3 - 5 minutes of O2, start sevoflurane at 1 %
(c)
Increase by 1 % every 30 - 60 seconds until 3 % is
reached
(d)
Then increase to 5 % - 7 % to complete induction
(2)
Induction following injectable agent
(a)
Initiate flow rates of 1.0 to 1 liter per minute at
3.5 % - 5.0 %
(i)
Reduce percentage as indicated by patients response
(3)
Maintenance
(a)
Once stable, reduce oxygen flow to 500 ml to 1 liter
(i)
The reservoir bag must remain full
1.
If not, the flow rate must be increased and the
machine must be examined for leaks at the earliest possible convenience
(b)
Remember that prior to surgical stimulation, a
patient may appear adequately anesthetized only to show a dramatic
response to stimulation
(i)
An experienced anesthetist should be able to
anticipate and minimize this event
(c)
Effective analgesic & sedative premeds will
significantly reduce the level of inhalant agent necessary for
maintenance of a surgical plane of anesthesia
f)
Cost
i)
high
T
1)
TELAZOL
a)
Classification
i)
50/50 mixture of a benzodiazepine (Zolazepam) &
a dissociative agent (Tiletamine)
b)
General Information
i)
Similar to Ketamine and Diazepam
ii)
Can be used for induction in dogs and cats or as the
exclusive agent for short procedures in cats
iii)
Tiletamine is capable of providing the loading dose
for NMDA dorsal horn windup antagonism prior to ketamine CRI use
c)
Advantages/Recommended use
i)
Healthy animals in the Good to Excellent category
(1)
More ideal for cats vs. dogs
(2)
An acceptable induction agent for sighthounds
d)
Cautionary Information
i)
Avoid if:
(1)
Intracranial disease is suspected (can raise ICP)
(2)
Renal insufficiency is present (renal clearance)
ii)
Somewhat more stormy recoveries in dogs compared to
Ketamine/Diazepam
(1)
The ½ life of zolazepam is much longer than
the ½ life of the tiletamine in cats
(2)
The ½ life of zolazepam is shorter than the
½ life of the tiletamine in dogs increasing the risk that the patients
will be more agitated during the recovery
(a)
This is less of an issue if a longer procedure over
1.5 hours
e)
Dosage
i)
Routine induction
(1)
Dog & Cat – 2 mg/kg (1 mg/lb) IV bolus
(a)
Sedated or pre-existing CNS depression or
debilitation - draw up 2 mg/kg (1 mg/lb), give 25 - 50% as bolus then
additional increments to effect
ii)
Vicious, aggressive dogs
(1)
5 mg/kg (2.5 mg/lb) IM - usually reach lateral
recumbancy within 10 minutes
(2)
May be combined with acepromazine for more dramatic
effect
iii)
Routes of administration
(1)
IV – allows for lower telazol doses
(2)
IM more rapid in effect but more painful
(3)
SC - somewhat less painful and somewhat lower effect
but SQ administration is still a rapidly acting route
f)
Cost
i)
Moderately low
2)
THIOPENTAL
a)
Classification
i)
Ultra-short acting thiobarbiturate
b)
General Information
i)
Various concentration (2.5% and 5% solutions are the
most common)
c)
Advantages/Recommended use
i)
Healthy animals in the Good to Excellent category
d)
Cautionary Information
i)
It is safer to consistently use the same
concentration solution within a given facility rather than stocking
both 2.5% and 5% solutions
ii)
Not recommended for use with sight hounds
(1)
Lower volume of distribution and altered metabolism
make for a very narrow therapeutic index
iii)
Can cause significant decrease in PCV
(1)
Thiopental (and Acepromazine) cause splenic pooling
of RBCs leading to a rapid decrease in PCV of up to 30%
iv)
Can induce myocardial irritability
(1)
Usually bigeminal
(2)
Treatment not required if stable cardiac output
v)
There is an accumulative effect with this agent
vi)
Extravascular thiopental may produce tissue necrosis
(1)
Infiltrate area with saline, 0.5 to 1 mg of
dexamethasone and 1 mg/kg (0.5 mg/lb) of lidocaine
(2)
Additionally, a gauze soaked in DMSO can be wrapped
over the site
vii)
Unused thiopental should be discarded whenever any
precipitate is noted in solution or when 4 weeks has transpired since
mixing even if no precipitate is noted
e)
Dosage Information
i)
Dog & Cat
(1)
Begin with 12 mg/kg (6 mg/lb)
(a)
Administer 4 to 6 mg/kg (2 - 3 mg/lb) rapid bolus
initially followed by additional small boluses to effect
(i)
Excessively slow injection may precipitate unwanted
excitement
(b)
Reduce initial bolus in proportion to degree of
sedation produced by premeds
(2)
Maximum dose is 16 mg/kg (8 mg/lb)
(3)
If at any point the canine patient is
nearly, but not quite, able to be intubated, the addition of 2 mg/kg (1
mg/lb) lidocaine IV, may deepen the anesthetic effect and facilitate
successful intubation
(a)
This strategy is useful when minimizing the
induction agent for more critical patients
(b)
Cats are more sensitive to the toxic effects
of lidocaine (CNS stimulation, seizures). Lidocaine is not recommended
for use in cats at this time.
f)
Cost
i)
Moderate
3)
TILETAMINE
a)
Classification
i)
A dissociative agent
b)
General Information
i)
Combined with zolazepam to produce Telazol
ii)
For more information see Telazol
4)
TRAMADOL
a)
Classification
i)
An analgesic medication with a dual mode of action
(1)
Mu opioid receptor agonist
(2)
Monoamine reuptake inhibitor
b)
General Information
i)
An uncontrolled, oral
analgesic for use in dogs and cats
c)
Advantages/Recommended use
i) Acute or chronic mild to moderate pain management
ii)
May be combined with other classes of analgesics
including NSAIDs, NMDA antagonists, and gabapentin
d)
Cautionary Information
i)
May decrease seizure threshold
ii)
Do not
combine with TCAs, SSRIs, or MAO
inhibitors due to the risk of serotonin syndrome
iii)
Metabolism is principally via hepatic biotransformation, with a small
amount excreted unchanged by the kidneys. Reduce dose or discontinue if
significant hepatic or renal dysfunction exists
iv)
Side effects, though rare, may include GI upset and sedation
v)
This is a bitter medication that is not well accepted by cats even when
compounded in a cat friendly liquid base.
e)
Dosage Information
i)
Dog
(1)
3 to 5 mg/kg (0.5 to 2.5
mg/lb) TID to QID1
(b)
Anecdotal reports include 10 mg/kg QID for
more severe pain
iii)
Cats
(1)
1 to 2 mg/kg (0.5 to 1.0
mg/lb) BID to QID
ii)
Tramadol is available in 50 mg tablets
f)
Cost
i)
Moderately low
|
