Lec 4 - Pre-Anesthetic and Multi-Modal Pain Management

What are the general objectives for an anesthetic?

- Pt does not move

- Pt is not aware

- Pt does not feel pain

- Pt has no memory of the procedure

What are some benefits of using pre-medication?

Reduced FAS, reduced nausea/vomiting, easier to place IV catheter, smoother induction, starts pain control early

What are three common mixtures used as pre-anesthetic drugs?

BAG, BAA, and HAG

What route of administration does gabapentin use?

PO

When is gabapentin used in reference to Sx?

Pre-anesthetic

What are two examples of anxiolytics?

Gabapentin and Trazodone

How does gabapentin work?

Dampens abnormal nerve signalling involved in pain and seizures

What are some effects of gabapentin?

Decreased anxiety, some sedation, ataxia, anticonvulsant

What are some effects of trazodone?

Decreased anxiety, sedation, lethargy, ataxia

How does trazodone work?

Inhibits the release of other neurotransmitters that increase anxiety, like norepinephrine

What is an example of a pre-anesthetic antiemetic?

Maropitant (Cerenia)

How does maorpitant reduce vomiting?

Blocks the neurotransmitter responsible for triggering vomiting from binding in the vomiting center and the CRTZ in the brain

What are examples of pre-anesthetic tranquillizers/sedative categories?

Phenothiazines, benzodiazepines, and alpha2 agonists

What types of animals should we be cautious about using or avoiding phenothiazines with?

MDR-1 dogs, sight hounds, Boxers, brachycephalics, dogs with a history of seizures, and stallions

What is an example of a phenothiazine?

Acepromazine

Are phenothiazines controlled drugs?

No

Is there a reversal available for phenothiazines? If so, what is it?

No

What are the expected effects of phenothiazines?

Vasodilation, hypotension, increased heat losses, anti-emetic, anti-histamine

How are phenothiazines commonly used?

With an opioid as a pre-med

What are some examples of benzodiazepines?

Diazepam, midazolam, and zolazepam

Are benzodiazepines controlled drugs?

Yes

Is there a reversal available for benzodiazepines? If so, what is it?

Yes - Flumazenil

What route of administration should benzodiazepines be given?

IV

What effects do benzodiazepines commonly have?

Increases the effects of other sedatives/analgesics, and an anti-convulsant

What is a common use of benzodiazepines?

Diazepam IV before Propofol induction or mixed with ketamine as an IV induction agent

Are alpha2 agonists controlled drugs?

Yes

Is there a reversal available for alpha2 agonists? If so, what is it?

Yes - Atipamezole (for Dexmed), Yohimbine (for Xylazine), and Tolazoline (for Xylazine in ruminants)

What are some examples of alpha2 agonists?

Dexmedetomidine (Dexdomitor) and Xylazine (Rompun)

What are the principal effects of alpha2 agonists?

Sedation, muscle relaxation, short-acting analgesia, CV effects (dec. HR), vasocontriction, respiratory system depression, GI upset

What route of administration should be used for Dexmedetomidine (Dexdomitor)?

IV (dogs) or IM (cats), SQ at GV20 site, or oral gel

What route of administration should be used for Antipamezole (Antisedan; Dexdom reversal)?

IM only

Are opioids considered a controlled drug?

Yes

Is there a reversal available for opioids? If so, what is it?

Yes - Naloxone

What route of administration should be used for naloxone (opioid reversal)?

IM or IV slowly

What state can a patient enter when an opioid is given with a tranquillizer?

Neuroleptanalgesia (state of sedated analgesia - immobilization and insensitivity to pain)

What are the principal positive effects of opioids?

Analgesia and sedation

What are some issues associated with giving opioids?

Decreased HR and RR, hypothermia in dogs and hyperthermia in cats, vomiting (esp. dogs), and serotonin syndrome

What is an example of a dissociative anesthetic?

Ketamine

What can ketamine be combined with for profound sedation and analgesia in cats?

hydromorphone or methadone and dexmedetomidine (DKH, DKM, or DKB)

What are some common drug mixtures used as dissociative anesthetics?

KetVal (Ketamine and Diazepam) and Telazol (Tiletamine and Zolazepam)

What are the effects of dissociative anesthetics?

Pt does not blink, increased HR and cardiac output, increased salivation, analgesia to skin and limbs (not abdomen)

What are some examples of injectable induction agents?

KetVal (Ketamin and Valium), Telazol (Tiletamine and Zolazepam), Barbiturates, Propofol, Etomidate, and Alfaxalone

When should an injectable anesthetic be given?

Repeated IV boluses 3-5 mins apart, or as a CRI

Does propofol provide analgesic effects?

No

Is propofol a short-acting or long-acting anesthetic? Is it a barbiturate or not?

Short-acting barbiturate anesthetic

What route of administration should be used for propofol?

slow IV bolus

What are some contraindications for propofol?

Hypotension and hypoproteinemia

What are the effects of propofol?

Bradycardia, decreased cardiac output, transient hypotension, respiratory depression, apnea, and muscle twitching

What are some examples of cautions associated with propofol?

Will cross the placenta and exert effects on the fetus, may cause Heinz body anemia or hemolysis in cats

How long does propofol typically last?

10-20mins (~30mins in cats)

Is alphaxalone (Alfaxan) a short-acting or long-acting anesthetic? Is it a barbiturate or not?

Short-acting non-barbiturate

What route of administration should be used for alphaxalone (Alfaxan)?

Slow IV bolus (or IM or SQ with higher doses), or CRI

What are some contraindications for using alphaxalone (Alfaxan)?

Hypotension

What are the effects of alphaxalone (Alfaxan)?

Bradycardia, decreased cardiac output, transient hypotension, respiratory depression, apnea, and muscle twitching

How long does alphaxalone (Alfaxan) typically last?

10mins (dogs) and 25mins (cats)

What is a caution of using alphaxalone (Alfaxan)?

Will cross the placenta and exert depressive effects on the fetus

What kind of patients would be at high risk if given etomidate?

Cardiac patients

What are some effects associated with etomidate?

Muscle tremors, paddling, and vocalization

What is dissociative anesthesia?

Anesthesia with a feeling of detachment from reality