Anesthesia: Anesthetic Agents and Adjuncts

Define anesthetic agent:

Any drug used to induce a loss of sensation with or without unconcsiousness.

Define adjunct:

A drug that is not an anesthetic, but can produce desired effects.

• Adding in Cerenia to prevent vomiting.

What are some ways that we classify anesthetic agents and adjuncts?

• Route of administration

• Time of administration

• Principle effect

• Chemistry

Define agonist:

Hint: agonists have action.

Binds to receptors AND stimulates.

Define antagonist:

Binds to receptors, but does NOT stimulate.

Reversal drug.

Define partial agonists:

Binds to receptor and partially stimulates.

Define agonist-antagonist:

Binds and stimulates to one receptor, and then binds to another receptor, but does not stimulate.

Why is it important to stick with the same class?

If you use one class, and then administer another, you could potentially reverse it.

When should you provide analgesics?

Pre AND post operatively.

You should always treat pain __________ it starts!

Before.

Is it okay to administer a drug combination if there is precipitation present?

• Will look like a snow-globe.

No.

How many drug schedules are there? Which is the most controlled?

• 5.

• 2.

What schedule is Morphine?

Schedule 2.

Who dispenses drugs in the US?

CSA- controlled substance act

Who enforces drugs in the US?

DEA- drug enforcement agency.

How often does the DEA inspect?

Every 2 years.

When storing controlled drugs, how should you do so?

• Keep them securely locked in a cabinet

• You should also lock up the antagonists

• Also lock up prescription pads

How often should you check your scheduled drugs?

• check daily

How much loss does the DEA allow? What should you do if it exceeds this limit?

• Allow 10% or less

• Report anything greater than 10%

What are the pre-anesthetic categories?

• Anxiolytics

• anti-emetics

• anticholinergics

• tranquilizers

• sedatives

• opioids

What are the reasons to pre-medicate?

• Calm or sedate

• Reduce doses of other drugs— reduces side effects

• Induction and recovery goes smoother

• Muscle relaxation and analgesia

Describe the SQ route of administrations onset and duration:

SQ- slowest onset, longest duration.

Describe the IM route of administrations onset and duration:

(most common)

IM- faster onset, shorter duration

Describe the IV route of administrations onset and duration:

IV- fastest onset, shortest duration

Why is IM the preferred method of administration?

It allows to sedate a little before IV catheterization.

Gabapentin and Trazodone are:

Anxiolytics.

What does Maropitant (Cerenia) do?

Prevents vomiting.

What routes can cerenia be given?

• PO

• SQ- stings

• IV

The injectable version of cerenia should be ______________, and can provide _______________.

• Refrigerated

• visceral pain relief.

Describe what is happening during vasoconstriction:

• vessels get smaller

• bp increases

• HR decreases

• body temperature decreases

Describe what happens during vasodilation:

• vessels enlarge

• bp decreases

• HR increases

• body temperature decreases

Describe what happens during hypoventilation:

• RR decreases

• Decrease tidal volume.

  • how much air is taken in with every breath

What do anticholinergics do?

Decrease the action of the parasympathetic nervous system.

Block acetycholine.

What are anticholinergics used for?

• Prevent and treat bradycardia.

• Decrease salivary secretions.

What is the DOC for emergencies?

Atropine.

Atropine has a ___________ onset and a ___________ duration.

• quicker onset

• shorter duration.

Which anticholinergic is good for use in geriatric patients?

Glycopyrrolate.

Glycopyrrolate causes _______ arrhythmia than atropine does.

Fewer arrhythmias.

Glycopyrrolate has a ________ onset and a _________ duration.

• slower/longer onset

• longer duration

Anticholinergic cardiovascular effects:

• Prevent bradycardia

• Faster HR

• Treat 2nd degree AV block

Anticholinergic adverse effects:

• Atropine is more likely to cause

• Not good to use in patients with cardiac disease

• Transient bradycardia

• 2nd degree AV block

GI stasis is an adverse effect of anticholinergics. Who is it important to note/ keep an eye on?

• Horses

• Rabbits

• Guinea pigs

• Other small exotics

Who should you avoid the use of anticholinergics in?

Ruminants

What are the following drugs an example of?

• Phenothiazines

• Benzodiazapines

Tranquilizers.

What do tranquilizers do?

Reduce anxiety/not awareness.

What are the following drugs examples of?

• Alpha-2-agonists

Sedatives.

Acepromazine:

• Injectable- IV, IM, SQ

• Metabolized by the liver

Is acepromazine reversible?

NO.

Does acepromazine provide analgesia?

NO.

CNS effects of acepromazine?

• Anxiolysis

• Aware, but cannot respond.

• NO analgesia

Cardiovascular effects of acepromazine:

• Hypotension

• Anti-arrhythmic

• Vasodilation

Acepromazine prevents the release of ___________. Which may be indicated in MCT cases prior to anesthesia.

Prevents histamine release.

Why is acepromazine contraindicated in seizure patients?

It may lower the seizure threshold.

Why should acepromazine not be used in STALLIONS?

Prone to penile prolapse

• Have to have a procedure to fix it and they will lose function.

You should avoid use of acepromazine in:

• ASA III- V

• MDR-1 mutation

• Boxers- sensitive

Are benzodiazepines tranquilizers or sedatives?

Tranquilizers.

Are benzodiazepines controlled?

Yes!

List 3 common benzodiazepines:

• Diazepam- Valium

• Zolazepam (component of Telazol)

• Midazolam— seziures

Benzodiazepines produce ___________ side effects.

Unreliable side effects.

• dysphoria and aggression— cats

• excitement— dogs

• ataxia

Effects of benzodiazepines:

• Muscle relaxation

• Potentiate general anesthetics

• Anti-convulsant properties (Midazolam)

• NO analgesia or sedation

Diazepam key points:

• Benzodiazepine

• NOT water soluble— contains propylene glycol

  • Precipitation

• can be used with ketamine

• IV ONLY

• Reversal— flumazenil

Midazolam key points:

• Benzodiazepine

• Mixes well with other drugs— water soluble

• IM, IV, or SQ

• Excellent sedative for swine, ferrets, rabbits and birds

• Reversal— flumazenil

Zolazepam key points:

• Benzodiazepine

• Only available in a drug combo— Telazol

• Reversible with flumazenil

  • neuro side effects

What is the reversal for benzodiazepines?

Flumazenil.

Alpha 2 agonists provide:

• Sedation

• Analgesia

• Muscle relaxation

Adverse effects of the cardio system with alpha 2 agonists:

Early stages:

• Vasoconstriction

• Hypertension

• Bradycardia

• 2nd degree Av block

Late stage:

• Hypotension

• Bradycardia

Repiratory effects of alpha 2 agonists:

• Hypoventilation

  • Decreased RR

  • Decreased tidal volume

Who should you avoid the use of alpha 2 agonists in?

• Geriatrics

• Diabetics

• Pregnant

• Pediatric

• Ill

Xylazine (alpha 2 agonist) keypoints:

• Rompun rage in horses

• Primarily used in LA

• Reversal agent- Yohimbine

Dexmedetomidine (alpha 2 agonist) keypoints:

• SA

• Reversal agent- Antisedan (atipamazole)

• Severe bradycardia

List 2 other alpha 2 agonists:

• Detomidine (Dormosedan)

• Romifidine (Sedivet)

What happens when alpha 2 agonists are reversed?

It reverses both the desirable and non-desirable effects.