Chp 40 Canine Breed-Specific Problems Flashcards
What is a breed?
Particular group of domestic animals related by descent from common ancestors –> visibly similar in most characteristics, usually incapable of maintaining distinctive characteristics in nature
–Familial sensitivity to certain drugs may be present
Sighthounds
- Classification of a dog breed as a sighthound = purely subjective
- Based on body conformation similarities, breed purpose
- Dogs bread to hunt by sight +/- used for racing
- Considered to be oldest breed of dogs
Examples of Hounds per AKC
Afghan Hound Borzoi Greyhound Ibizan Hound Italian Greyhound Irish Wolfhound Pharaoh Hound Saluki Scottish Deerhound Whippet
What are two other breeds sometimes included in the sighthound group?
Rhodesian Ridgeback
Basenji
What are some characteristics of sighthounds that might affect anesthesia?
Nervous, more prone to develop stress-related clinical complications including GI upset, hyperthermia
What are hematological characteristics of sighthounds that will influence GA?
- Higher PCVs (50-60%)
- Lower serum protein concentrations (6.5mg/dL)
- Lower serum albumin concentrations may result relatively increased effect of drugs that are highly protein bound (ie anesthetics)
What are the two factors that will play important role in recovery from effects of drugs in sighthounds?
- Lack of fat tissue that will affect redistribution of drugs
- Different abilities to metabolize drugs used to induce/maintain GA
What environmental factor is essential to control with sighthounds?
BODY TEMPERATURE!
Why is body temperature essential to be conscious of in sighthounds?
Lean animals with low body fat to muscle ratio –> susceptible to hypothermia, esp when thermoregulatory mechanisms depressed by GA
- -Heat loss exacerbated by short, thin coat in whippets, GHs
- -Prevention essential -> cool down very rapidly, can have problems associated with hypothermia that can be significant (eg bradycardia that unresponsive to anticholinergics)
How is the hepatic metabolism of drugs different in sighthounds vs MBDs?
- -Alteration in the activity of liver enzymes in the cytochrome P450 family
- -Mostly affected metabolism of thiobarbiturates (significantly slower), but propofol and methohexital also cleared more slowly
Why should we avoid thiobarbiturates in GHs and why?
- Recovery from thiobarbiturate ax: redistribution of drug from brain tissue to muscle/fat with concomitant liver metabolism and elimination of the drug
- GHs: Absence of adipose tissue for redistribution, alterations of liver metabolism of the drug
- Rate of elimination = nonlinear -> suggests saturation of enzymatic clearance process
What is another drug should consider avoiding in GHs due to potential for poor, prolonged recoveries?
- telazol
Are large-breed dogs more sensitive to CV/respiratory depressant effects of drugs used in an anesthesia protocol?
-LBDs = more easily overdosed –> effect, duration of action of drugs will be increased
Ideally, how should calculate drug doses for LBDs?
- Body surface area instead of weight
- Equation for estimation: metabolic weight = Body Weight (kg) ^ (3/4)
Newfies do not respond well to anesthesia, tend to be overly depressed by anesthetic drugs. Is this statement true?
- Hypothyroidism = frequently present as subclinical disease in NFs –> tend to be easily depressed
- Can be due to hypothyroid state, associated with depression of physiologic functions
- When in doubt, assess with thyroxine (T4), triiodothyronine (T3) +/- TSH
Is it true that toy breeds are more sensitive to effects of isoflurane?
- No!
- Iso = potent, hypotensive ax
- rate of rise of alveolar concentration of this agent when using high oxygen flow rate on a NRB system (eg Bain) = rapid –> equilibration time for small body sizes/weights much faster than for LBDs
- Mask induction also more rapid than in M/LBDs
What is meant by boxer sensitivity to acepromazine or boxer acepromazine syndrome?
-Admin of acepromazine to some boxers can induce profound bradycardia assoc with hypotension, collapse of the animal
-Esp seen in UK
-Appears to be related to certain strains of the breed
-Seen with doses even as low as 0.01mgkg
SQ -> induced collapse in otherwise healthy dogs
-Explanation not documented
What are the brachycephalic breeds?
Boston Terrier Chinese Shar Pei English Bulldog Pug French Bulldog Lhasa apso Pekinese Shih Tzu Any cross-breds from these breeds can also experience BAS
What is BAS?
Upper airway obstruction process characterized by one or more of the following anatomical or functional abnormalities:
- Stenotic nares
- Elongated soft palate
- Laryngeal saccule eversion
- Laryngeal collapse
- Hypoplastic Trachea
What are clinical signs of BAS?
Snoring, stridor, exercise intolerance, cyanosis, collapse
How induce brachycephalic dogs
- Preoxygenate
- Rapid IV induction technique
- Intubate mandatory
Why is pre oxygenating important for BAS dogs?
Provides additional reserve of oxygen in case intubation is difficult and airway obstruction occurs
–Want to pre oxygenate for at least 5min
Why is a rapid IV induction technique advised for BAS dogs?
- -Allows for rapid control of the airway
- -Generally not advised to use slow indiction techniques like mask, chamber induction
- -Ensure have assortment of endotracheal tubes available
What are preanesthetic considerations when performing anesthesia on BAS dogs?
- Preferable to avoid deep sedation –> associated with excessive relaxation of upper airway muscles and exacerbation of obstruction
- Strong vagal tone –> consider using anticholinergic both to prevent bradycardia, clear airway from salivary secretions
What are the two strategies to extubate a BAS dog?
- Rapid extubation
2. Prolonged extubation
Advantages of a rapid recovery/extubation in BAS dog?
- BAS patient at greater risk of upper airway obstruction, but thought is that obstruction much easier to manage than in a dysphoric animal emerging from GA
- Correct head positioning, reintubation will be accomplished smoothly if patient still anesthetized
Advantages of slow recovery/extubation in BAS dog?
- Lower risk of obstruction
- Good protection of airway at moment of extubation
- If obstruction does occur, good protection of airway at moment of extubation
- If patient does obstruct, greater risk of panic from patient –> need to be ready for rapid reintubation
- Constant monitoring
What special consideration should you have in mind during preanesthetic assessment of a Doberman pinscher?
-Highly susceptible to von Willebrand Disease
What is von Willebrand disease?
- Genetic disorder affecting platelet function
- Lack of synthesis of/abN fxn of vWF
- vWF = essential to activity of factor VIII, required for platelet adhesion.
- Can check BMBT or plasma levels of vWF
Can stored whole blood or pRBCs be used to provide vWF?
No –> pRBCs do not contain vWF, blood that has been stored for >6hrs does not contain therapeutic levels of vWF
What drugs should be avoided in ax management of vW-positive Doberman Pinscher?
- Little info in vet ax on effects of drugs on coat
- Reportedly, phenothiazine tranquilizers decrease platelet aggregation - avoid
- NSAIDS - avoid, increase clotting time
Are Doberman Pinschers the only dogs affected by vW disease?
- No -> reported in >60 dog breeds
- Shetland Sheepdogs, Pembroke Welsh corgi, Scottish terrier, Airedale, standard poodle
- DNA detection test available for all these breeds
Can carprofen be used in labs?
Idiosyncratic hepatotoxicosis in 21 dogs following carprofen administration –> half in labradors. Use caution.
Why are small breed dogs more susceptible to hypothermia?
- Lower body weight to surface ratio –> larger surface exposed to heat loss
- Initiate active warming, reduce anesthesia time
What are some complications associated with hypothermia?
-increased postoperative infection, coagulopathies, cardiac morbidity
