Smalltest nr 3 part 2 Flashcards
Definitions:
General Anaesthesia
- Injectable or inhalation
- Injectable has 1 exception, in which it has a painkiller effect and can be used as a premed: ketamine
- But remember! Ketamine causes muscle rigidity!!! Mustn’t be given on its own!
(BDZ and ⍺-2 agonist combined with ketamine)
- Also, remember that its analgesic effect isn’t strong as e.g. fentanyl
Definitions:
Balanced anaesthesia
There is no one substance that can provide all 3 requirements of surgery
- Total unconsciousness
- Total muscle relaxation
- Total analgesia
Balanced = a combination of drugs
Definitions:
TIVA
- Total intravenous anaesthesia
- Must maintain pressure because ↓ BP during anesthesia, which can lead to:
- acute renal failure (must keep BP above a certain level, 90mmHg. This can be done via catheter)
- Can also inject certain injectable anaesthetics via IM,
- however, it will give you a less safe anaesthesia
Definitions:
Neuroleptanalgesia
- Tranquilisers + opioids
- Muscle relaxation and analgesia
- Ø total unconsciousness!
- Used in minor procedures
Definitions:
Ataranalgesia
- Benzodiazepine + opioid
- Less deep than neuroleptanalgesia
Anesthesia during surgery
Premedication
AIMS
- Sedation
- Potentiation (Lowers needed dose for anesthesia and painkillers used later on)
- Avoidance of pre-excitmentation
- Avoidance of histamine (HA) release
Anesthesia during surgery
Induction
AIMS
- Get rid of reflex so that you can put an endotracheal tube down the trachea to provide oxygen during surgery as well as
- maintain trachea diameter (some breeds are more prone to trachea collapse during surgery)
Anesthesia during surgery
Maintenance
AIMS
Fulfill the 3 requirements
- Total unconsciousness
- Total muscle relaxation
- Analgesia
Once fulfilled → can begin the procedure
Anesthesia during surgery
Premedications
SUBSTANCES
- Tranquilizers → potentiate analgesics and anti-HA (acepromazine)
- ⍺-2 agonists → analgesia potentiation, some analgesic effect
- BDZ → pre/post narcotic effect
- Opioids → analgesia
- Ketamine → premed (subhypnotic dose) and maintenance, potentiates anaesthesia and has analgesic effect (desensitization of pain)
Anesthesia during surgery
Induction
SUBSTANCES
- Injectables
- Propofol
(use lower dose because of premed potentiators)
- Thiopental (eq)
- Inhalations
- Sevoflurane → doesn’t cause irritation
Anesthesia during surgery
Maintenance
SUBSTANCES
- Inhalation (isoflurane, sevoflurane, etc)
- Injectables (IV)
Use combinations, e.g.
Ketamine + BDZ
Ketamine + ⍺-2 agonists
Anesthesia during surgery
Premedication
IMPLEMENTATION COMMENTS
- ⍺-2 agonists have painkilling effect, but not enough for maintenance (potentiate analgesic effect)
- Morphine → must wait ~30 min before beginning the procedure
-
Buprenorphine and butorphanol are not enough for painful surgeries. They’re also partial agonists!!
- Mustn’t be used if you’re planning to use full agonists (morphine/fentanyl) later on!!
- Fentanyl → not used as premed
Anesthesia during surgery
Induction
IMPLEMENTATION COMMENTS
- Isoflurane → nephrotoxic and causes irritation
(due to irritation, it’s not used for this step since animals, especially rabbits, will be too irritated to inhale)
Injectable anaesthetics and opioids can be given as bolus dose
→ repeat bolus when required to maintain depth of anaesthesia (otherwise the animal will wake up on the surgery table).
Injectable anaesthetics
More safe
More safe would be to use the continuous rate infusion
( dose per hour/BWkg), however, keep in mind that if it’s stopped suddenly, it’ll be eliminated much faster
Anticonvulsants
Definitions:
- Sudden
- Transient
- Repetitive brain malfunction
- Convulsions or tic
- Depends on severity and area of brain affected
Anticonvulsants
Epilepsy
- Malfunction of motor neuron
- Can be due to several different causes
- - Toxicosis
- - Liver failure
- - Metabolism disease
- - Trauma (lesions)
Anticonvulsants
Idiopathic epilepsy
Idiopathic epilepsy → seen in dogs <6 years
Anticonvulsants
Aim of treatment
→ to eliminate or decrease frequency/gravity of epileptic episodes
Anticonvulsants
When to start treatment:
- Convulsions last longer than 5 minutes
- 3+ generalised convulsions in 24 hrs
- 2+ convulsions within 6 months
- When postictal symptoms can still be seen for more than 1 day after an epileptic episode
= (vocalization and/or other strange behaviours)
Active agents for status epilepticus treatment
- Diazepam
- Phenobarbital
- Pentobarbital
- Levetiracetam
- Propofol
- Isoflurane, (sevoflurane)
- Ketamin
Diazepam
Administration
- *IV or rectal**
- *Diazepam** solution → vehicle’s absorption via IM is bad
Diazepam
Comment
Midazolam, lorazepam
→ can be given IM (better absorption, but onset = longer)
Phenobarbital
Administration
IV (onset = 20-30 min)
Pentobarbital
Administration
- IV
- Trace amount used (micrograms!)
Levetiracetam
Administration
- IV
- Rectal
Propofol
Administration
- IV
- Bolus, or
- continuous infusion
Isoflurane, (sevoflurane)
Administration
Inhalation
Ketamin
Comment
In certain cases
Causes muscle rigidity, use after diazepam, phenobarbital
What is If seizures proceed even afterwards
- Then give continuous rate infusion of diazepam or propofol, (ketamine?)
- keep the animal sedated as long as needed.
- Withdrawal drugs from time to time to see if the animal can manage,
- if seizure comes back,
- sedate the animal again.
Active agents to prevent epilepsy, epilepsy control:
Test type I
Phenobarbital (A)
Imepitoin (A)
Potassium bromide (B)
I= controlled trials;
II= case-control or cohort study;
III= case reports or series;
IV= expert opinion
Recommendation levels
A= high;
B= moderate;
C= low;
D= not recommended
Active agents to prevent epilepsy, epilepsy control:
Test type II
Primidone (D)
I= controlled trials;
II= case-control or cohort study;
III= case reports or series;
IV= expert opinion
Recommendation levels
A= high;
B= moderate;
C= low;
D= not recommended
Active agents to prevent epilepsy, epilepsy control:
Test type III
Zonisamide (C)
I= controlled trials;
II= case-control or cohort study;
III= case reports or series;
IV= expert opinion
Recommendation levels
A= high;
B= moderate;
C= low;
D= not recommended
Active agents to prevent epilepsy, epilepsy control:
Test type IV
Levetiracetam (C)
I= controlled trials;
II= case-control or cohort study;
III= case reports or series;
IV= expert opinion
Recommendation levels
A= high;
B= moderate;
C= low;
D= not recommended
What if you want to change drug
- To change drugs, you must do it gradually!
- New drug, begin with a low dose and increase until therapeutic range, and at the same time,
- You decrease the dose of the current drug.
Phenobarbital
in general
administration
- *First line!**
- *Success: ~80%**
- *Administration:**
- IV or
- Orally (Po absorption is good with slow onset of reaction)
Phenobarbital
On set of action
Measure of blood levels
Half life
- Onset = slow (20-30 min); takes 2-3 weeks to reach steady plasma state, thus have to wait 2-3 weeks to evaluate its effectiveness (must warn the owner about this)
- Measure blood levels:
- If phenobarbital blood level is below range → ↑dose
- If above the range and the patient is still experiencing seizures, then phenobarbital ≠ effective. Either combine or change drug
- It there’s no epileptic episode for 6-12 months and phenobarbital blood level is above range, then you can ↓ dose
- Half-life = 2-3 days (admin. 2x daily)
Phenobarbital
General
- Anticonvulsant at subhypnotic doses
- Enzyme inducer of CYP450!
(responsible for the metabolism of other drugs!! Thus, have to increase their doses) → autoinduction (induces its own metabolism via activating liver enzymes → increases the rate of metabolism)
- Does not exert its effects immediately → so if the dog has a seizure the following day of 1st administration, do not change the drug immediately (2-3 weeks)
Phenobarbital
Side effects
Side effects:
- Sedation & ataxia → last only a few days after admin.
- Polyphagia → increase appetite ⇒ weight gain
- Polyurea → increase drinking ⇒ increase urine volume
- Ca → sensitivity (liver damage) → idiosyncratic reaction
Potassium Bromide
General
Potassium bromide
- Ø fe! (lethal lung oedema)
- Success: 50-70%
- Can be a first line drug
- Failure → combination (phenobarbital as a combination partner)
- It’s a salt, so there is no metabolism in the liver
- Elimination → via kidney
If the patient suffers from kidney failure,
- lower dose (by 25%) to avoid the accumulation of salt
- Can induce vomiting, can reduce this by splitting the dose to 2x a day with food
Half-life = 35-46 days (admin. 1x daily),
Plasma steady-state = 3 months
Potassium Bromide
Side effectss
Side effects:
- Polyphagia
- Pruritus (itchy)
- Paraparesis (weakness of HL)
- Pancreatitis (pancreas inflammation)
Imepitoin
- First line
- Failure → combination
- Quite safe
- Kidney failure → lower dose
Levetiracetam
- Second line (in combinations
- Oral tablet (3x a day, sometimes 4x)
Side effects:
- Sedation
- Ataxia
- Loss of appetite
Diazepam
- Ø recommended long term in fe
(individuals can be very sensitive! It’s hepatotoxic and can induce irreversible liver damage if given ~7 days)
- Ca → appropriate dose can be effective
Side effects:
- Polyphagia (fe, ca)
- Ø depth perception
- Sedation
Zonisamide
- Success: limited date (~60%), used mostly in Humans
- Second line (in combinations)
Side effects:
- Sedation
- Ataxia
Other alternatives
- N. vagus stimulation → implant (Hu), placed near or on N. vagus so that it doesn’t stimulate repetitive muscle contractions
- CBD, Gabapentin → supportive
- The ketogenic diet (high fat, moderate protein, low carbohydrates)
- Not proven to be safe and effective
- Pancreatitis!! (Ø recommended)
- . Acupuncture, homeopathy: NO!
Not recommended substances
- 1. Primidone
- Very hepatotoxic
- 2. Lamotrigine
- Hepatotoxicity
- 3. Phenytoin
- Myocardial damages
- 4. Carbamazepine
- Bad pharmacokinetics
- 5. Oxcarbazepine
- Bad pharmacokinetics
- 6. Vigabatrin
- Not enough data
- 7. Tiagabine
- Not enough data
Situation task 1
Dog with severe trauma
Stabile general condition (3 years old, no known disease)
Amputation inevitable
Which drugs should we use?
- *Phenothiazine** → potentiate analgesic effect
- *⍺-2 agonist** → increase pain killing efficacy
- *Benzodiazepines** → can prevent pre & post anesthesia excitement
- *Ketamine** → IV & has analgesic effect (NMDAr antagonist), given at a continuous rate (at subanesthetic dose), decreases sensitization of pain
- *Lidocaine** → local anaesthetic, use around nerve where you’re going to cut the leg off
Situation task 2
Dog with severe liver failure
Idiopathic epilepsy
Phenobarbital was administered earlier
What kind of agents can be used for monotherapy of epilepsy control?
Potassium bromide
Potassium bromide
