Ex 3 - Common misconceptions in the practice of anesthesia

Question 1

Are many breeds “sensitive” to anesthesia?

Answer 1

No, very few breed-specific anesthetic idiosyncrasies

Question 2

Thiobarbiturates in greyhounds

Answer 2

• Delayed recovery (3-4x longer)
• mostly due to decreased liver metabolism
• we assume all sighthounds react the same, but not studied yet

Question 3

What mutation is common in Collies?

Answer 3

MDR1 mutation (70% of Collies)

• Nonfunctional P-glycoprotein –> drugs able to cross BBB –> excessive CNS exposure

Question 4

What anesthetic drugs are we concerned about in Collies?

Answer 4

Acepromazine and butorphanol

Question 5

Boxers and Acepromazine

Answer 5

• Anecdotal reports of collapse
• Maybe genetics? (British/European lines)
• CAUTION in these dogs is recommended

Question 6

Brachycephalic breeds and Anesthesia

Answer 6

“Brachycephalic Syndrome”

• upper airway obstruction
• challenging intubation and recovery
• you should pre-oxygenate
• Extubation: actively objecting the ETT

Question 7

Do opioids cause excitation/dysphoria in cats?

Answer 7

This only happens with really HIGH doses (studies tested super high doses)

• very unlikely at clinical doses
• we recommend using opioids to treat pain in cats
• can use during pre and post-op
• euphoria is common

Question 8

Are opioids dangerous and do they cause serious adverse effects?

Answer 8

In reality, opioids are extremely safe analgesics.

• good CV stability and minimal depression
• potent anesthetic sparing effect
• reversible! yay!
• Resp. depression not as severe as in people
• Bradycardia - but easily managed
• V/defecation not common
• can interfere with thermoregulation, but easily managed

Question 9

Can burtophanol be used to treat severe pain?

Answer 9

No! it should only be used for MILD pain

• not as efficacious as pure mu agonists
• short duration (1-2 hr max)

Question 10

Hydromorphone is more potent than morphine, therefore must be a better analgesic

Answer 10

False! Potent does NOT equal efficacy

Hydromorphone is more potent, but it is equally as efficacious as morphine

Question 11

Can low doses of a2-agonist have CV effects?

Answer 11

Yes! even very low doses can cause severe CV depression

e.g. Dexmedetomidine
1ug/kg decreases CO > 50%

Only use in young healthy animals

Question 12

is mask induction the best method?

Answer 12

No! its slow, stressful, and has greater CV depression (have to use higher doses)

Question 13

Is propofol the safest induction drug?

Answer 13

No! Therapeutic index similar to thiopental

Cardiorespiratory effects similar to this

• more vasodilation (hypotension)
• less arrhythmias

Increased risk of overdose and apnea (preoxygenate!)

*It does have rapid and smooth recovery and extra hepatic sites of metabolism (good)

Question 14

Is Sevo better than Iso?

Answer 14

Clinically not significantly different

• sevo has lower solubility and thus faster induction/recovery time (but not significantly different)

Sevo has potentially toxic by-products

Question 15

If ECG is normal, the heart is pumping, right?

Answer 15

No!
ECG can appear normal even when the heart is not pumping effectively (or at all!)

ECG’s are useful for detection of arrhthymias, but we should always be monitoring BP

Question 16

Does a strong pulse indicate good BP and tissue perfusion?

Answer 16

No! it only indicates the difference between systolic and diastolic pressures

It does not rule out hypertension!!

Question 17

Do only old and sick animals get hypotensive during anesthesia ?

Answer 17

Nope! Many young and healthy patients get hypotensive during routine procedures

Question 18

How can you tell if a patient is hypotensive?

Answer 18

ONLY if you MEASURE it!

Hypotensive animals can appear clinically normal

Question 19

Recovery from anesthesia - potential problems

Answer 19

Most recover without “obvious” problems

But there can be internal organ damage that can go undetected
e.g. 75% of nephrons must be dead before BUN or creatinine increase

Question 20

Can anesthesia for dental procedures pose a risk?

Answer 20

YES!

Mostly older patients
- coexisting diseases

Perform careful pre-anesthetic eval (PE and BW)

Have adequate support (fluids and O2) and monitoring

Question 21

Does bradycardia always mean the patient is too deep?

What are the most common causes of bradycardia?

Answer 21

No, there are many causes of bradycardia

Most common causes:

• hypothermia
• vagal stimulation
• anesthetic drugs: opioids and a2 agonists

Question 22

Does O2 administration delay recovery?

Answer 22

O2 administration has minimal to no effect on recovery time

Just remove IA from the breathing circuit when finished –> empty bag and refill with O2

It prevents hypoxemia

Some say “animals at room air seem to breathe better” but this is just a hypoxic drive! bad!

Question 23

“I would know if my patient was in pain after sx” true or false?

Answer 23

False! Recognizing pain can be challenging –> esp in the post-op period

ALWAYS give the benefit of the doubt