SA pre-med and sedation

Question 1

Why pre-medicate?

Answer 1

1. In preparation for general anesthesia
   >To provide sedation and pre-emptive analgesia
2. Sedation but animal remains conscious in a situation for diagnostics or minor surgery
   >They can swallow and maintain airway and breathing on their own
   >Analgesia

Question 2

when is monitoring important during sedation?

Answer 2

• When drugs taking effect
• During maximal sedation
• Recovery phase

Question 3

Advantages of pre-medication

Answer 3

1. Facilitate safe handling
2. Provide analgesia
   * Pre-emptive or before surgery
3. Balanced general anesthetic approach
   * Lowers the dose of anesthetic induction drugs
   * Smooth induction & endotracheal intubation
   * Lowers the dose of inhalational anesthetics

§ 2 and 3 will minimize –ve CV and Resp effects

4. Contributes to a smooth recovery

Question 4

Disadvantages of Premedication

Answer 4

§ Cost
* Relative disadvantage because you save on
induction and inhalational anesthetic doses

§ Time delays
* Have to wait for onset of effects

Question 5

Patient Considerations for Drug Selection

Answer 5

1. Presenting complaint of animal
   * Duration of procedure/Sx
   * Sedation level required
2. Signalment
   * Age; Breed; Personality
3. Health status
   * CV, resp, liver, renal, endocrine, CNS
   § ASA status framework for drug choice
   * ASA I-V
   § Patients with higher ASA —-> higher risk
   * ASA I -normal to an ASA V-not expected to survive
4. Level of pain
5. Last time animal has eaten
   * Vomiting a concern?

Question 6

drug classes used as pre-anesthetic sedatives in SA

Answer 6

1) anticholinergics
2) phenothiazines
3) alpha2 agonists
4) benzodiazepines
5) opioids
6) others, eg, ketamine, propofol, alfaxalone

Question 7

common anticholiergics used as pre-anesthetic sedatives

Answer 7

Atropine, glycopyrrolate (IM, SC, IV)

Question 8

common phenothiazines used as pre-anesthetic sedatives

Answer 8

Acepromazine (IM, SC, IV)

Question 9

common alpha2-agonist used as pre-anesthetic sedatives

Answer 9

Dexmedetomidine, Medetomidine (IM or IV)

Question 10

common benzodiaepines used as pre-anesthetic sedatives

Answer 10

Diazepam (IV only) - Midazolam (IM, SC, or IV)

Question 11

common opioids used as pre-anesthetic sedatives

Answer 11

• Mu-agonists – morphine, hydromorphone, fentanyl, oxymorphone (IV, IM or SC) or meperidine (not IV)
• Kappa-agonists – butorphanol (IM, SC, IV)
• Partial Mu-agonists – buprenorphine (IM, SC, IV)

Question 12

what is neuroleptanalgesia? how do we achieve it and what are the advantages?

Answer 12

§ Sedation/tranquilization + Analgesia

• Drugs from different classes given together
• Offers better sedation
• Provide added benefit of the other class
• Lowered doses of each

Question 13

some possible combinations to achieve neuroleptanalgeisa

Answer 13

• Acepromazine + Opioid
• Alpha2-agonist + Opioid
• Benzodiazepine + Opioid

Question 14

drugs that can be used for sedation when there is no IV access

Answer 14

§ Alfaxalone or Ketamine

Question 15

signs of sedation: none, mild, moderate, profound

Answer 15

None:
Bright and alert - no sedation and/or patient is even more excitable - dysphoric (excited, anxious, difficult to restraint in lateral recumbency, very interactive and responsive, vocalizing, very reactive to noise or touch

Mild:
Calm - minimal sedation, quiet but still alert and aware of surroundings, can hold head up, mild resistance to restraint in lateral recumbency, moderate response to noise or touch

Moderate:
Moderate sedation - quiet, relaxed, minimal restraint required to position in lateral recumbency, mild response to noise or touch, but head is mainly down and relaxed

Profound:
Profound sedation - quiet, very relaxed, no restraint necessary in lateral recumbency, no response to noise or touch and head remains down.

Question 16

characteristics of the ideal premedication or sedative agent

Answer 16

1. Provide reliable and consistent sedation & anxiolysis
2. Minimal to no negative effects
3. Provide analgesia
4. Be Reversible
5. Reduce the dose of other sedatives or anesthetics

Question 17

two common anticholinergics

Answer 17

glycopyrrolate and atropine

Question 18

effect of anticholinergics on Parasympathetic tone, and why they are given? effect on salivary secretions?

Answer 18

-Administered to reduce parasympathetic tone
-Vagal tone may be increased with opioids, endotracheal intubation, IV anesthetics or surgery
> Anticholinergics are given to maintain HR during anesthesia and surgery
-reduce salivary secretions

Question 19

anticholinergics cardioresp effects on HR, CO, contractility, BP, RR?

Answer 19

HR: up up
CO: up
contractility: NC
BP: NC or up
RR: NC

Question 20

anticholinergics are given with:
not given with:

Answer 20

Given with
* Opioid and acepromazine drug combinations
* Anticholinergics ARE NOT indicated with α2-agonists

Question 21

most popular phenothiazine

Answer 21

acepromazine

Question 22

acepromazine acts on what receptors, and how? What are the effects?

Answer 22

Dopamine (D2) receptor antagonist
-Gives sedation, anxiolysis, anti-emetic, reduces MAC, Anti-arrhythmic
-Calming effect even at lowered doses

Alpha1-antagonist
– vasodilation & may produce hypotension
>Especially in sick or dehydrated patient

Question 23

higher doses of acepromazine correspond to? when would we give a high dose?

Answer 23

longer duration of action, but not necessarily higher sedation level
-not typically given, as generally combined with an opioid

Question 24

when do we give low doses of acepromazine

Answer 24

-Given for mild effects before or after surgery -In stable patients

Question 25

acepromazine cardioresp effects on HR, CO, contractility, BP, RR?

Answer 25

HR: down (or up) CO: down (or up) contractility: +/- BP: down down down RR: NC or down

Question 26

how does acepromazine effect body temp?

Answer 26

decrease

Question 27

when should we not administer acepromazine? ie what clinical signs.

Answer 27

shock or dehydration

Question 28

α2-agonists Mechanism of Action, and effects

Answer 28

* Bind to α2-adrenergic receptors in the central nervous system * decrease NE and epinephrine levels * Sedation, analgesia, and muscle relaxation

Question 29

xylazone, romifidine, and dexmedetomidine act on what receptor, and how?

Answer 29

α2-agonists

Question 30

α2-agonists – Central Effects

Answer 30

* Produce sedation centrally Presynaptic α2 – adrenoreceptor reduces release of epinephrine and norepinephrine

Question 31

how does using higher doses of dexmedetomidine change the effect of the drug?

Answer 31

* Sedation level plateaus – using high doses outside of recommended range increase the duration of sedation and negative effects but does not increase sedation level

Question 32

what can we mix an alpha2 agonist with to ensure a stressed, anxious animal will have consistent sedation?

Answer 32

opioid, benzodiazepine

Question 33

effect of alpha2 agonist on inhaled anesthetic

Answer 33

-dramatic MAC reduction, inhalant sparing properties

Question 34

α2-agonists – Peripheral BP Effects

Answer 34

* Biphasic blood pressure response - seen more with IV than IM administration Pre-synaptic α2 * Reduces NE resulting in decrease BP > Low doses used in people > This effect predominates in people Post-synaptic α1 and α2 * Causes contraction * This effect predominates > Doses used in veterinary medicine > Difference in receptor subtype & # > α2B

Question 35

α2-agonist - Dexmedetomidine cardiovascular effects (BP, HR, CO)

Answer 35

Increase in BP * > dogs than cats * Wanes over time and in combination with inhalants or other drugs that vasodilate * As a sedative we DO NOT see clinical hypotension Reduction in HR and associated bradyarrhythmias * From the increase in BP * And central sedation effects Reduction in Cardiac output is from the reduction in HR * Using anticholinergic in sedation phase is not indicated * Treating HR with anticholinergic increases cardiac workload with period of worsened bradyarrhythmias without improving Cardiac output

Question 36

α2-agonists - Dexmedetomidine disadvantages

Answer 36

the cardiovascular effects

Question 37

α2-agonists - Dexmedetomidine advantages

Answer 37

1. Analgesia and sedation 2. Injectable and inhalant sparing properties 3. Reversible 4. Not scheduled

Question 38

dexmedetomidine cardioresp effects (HR, CO, contractility, BP, RR)

Answer 38

HR: down down down, bradyarrhythmias CO: down down, due to low HR Contractility: NC BP: up up up up when IV, species variation RR: slight down

Question 39

dexmedetomidine effect on temp, vomiting, urinary volume, endocrine, alalgesia

Answer 39

temp: NC or down vomiting: possible urinary: volume up endocrine: hyperglycemia analgesia: +++

Question 40

Benzodiazepines – Diazepam & Midazolam disadvantages

Answer 40

* Unreliable or poor sedation alone > Unless sick or older small animal * Scheduled – records required * Potential for abuse * NOT an analgesic

Question 41

Benzodiazepines – Diazepam & Midazolam advantages

Answer 41

* Minimal negative cardio-respiratory effects * Reversible - flumazenil

Question 42

bensodiazepnies cardioresp effects (HR, CO, contractility, BP, RR)

Answer 42

Minimal negative cardio-respiratory effects

Question 43

use of opioids for sedation: what animals are they good for? what can they be combined with to increase efficacy? what animal are they not great for?

Answer 43

Opioids provide mild sedation * Even in healthy or young dogs * Better sedation when administered with sedative > Acepromazine or α2 - agonist * Healthy cats – poor sedation alone * Sick animals better sedative effects > Opioid alone gives very good sedation in ASA 3-4 patients > Additional strong sedative such as acepromazine or dexmedetomidine is not required

Question 44

opioids advantages

Answer 44

1. Effective Analgesia with sedation 2. Minimal CV depression 3. Reversible 4. Relatively inexpensive

Question 45

opioids disadvantages

Answer 45

1. Scheduled / require records 2. Potential for abuse (staff) 3. Side effects

Question 46

opioid side effects

Answer 46

* Dysphoria, panting * Respiratory depression in sick or high doses > pure mu-agonists only more common as CRI * Nausea, vomiting, defecation * Inability to ambulate * Ileus (rare SA, problem in equine) * Hyperthermia in cats with general anesthesia

Question 47

opioid cardioresp effects (HR, CO, contractility, BP, RR)

Answer 47

HR: down, > mu-agonists CO: NC or down contractility: NC BP: NC to mild down RR: down down, panting

Question 48

opioid effects on temp, vomiting, antitussive, analgesia

Answer 48

temp: down, or up in cats vomiting: ++ mu-agonists - hydromorphone/morphine anti-tussive: ++ analgesia: ++++

Question 49

when is resp depression most pronounced with opioids?

Answer 49

high doses or CRI’s - thoracic disease, very young or old, in combination with inhalant or general anesthetics

Question 50

resp depression from opioids leads to what? why?

Answer 50

Hypoventilation * An increase in PaCO2 – carbon dioxide levels in the blood * Not a reason to withhold in a sick or painful patient, but need to monitor * The sicker the patient more monitoring required related to ventilation especially when with GA

Question 51

what drugs are given as sedatives if: 1. Included after when the original sedation doesn’t work 2. Initially in a very aggressive/scared animal 3. In cases where more immobility deemed necessary * Benefit is short duration immobility * Cardio-respiratory depression dose related

Answer 51

ketamine, propofol, alfaxalone

Question 52

ketamine advantages

Answer 52

* ADV: can use in cats and dogs, small volumes

Question 53

ketamine disadvantages

Answer 53

Ketamine behavioural effects in recovery, rough recoveries possible, no reversal, not ideal in CKD or HCM

Question 54

propofol advantages

Answer 54

* ADV: short duration; rapid metabolism even liver dz; cats and dogs

Question 55

propofol disadvantages

Answer 55

* DISADV: Need IV; Cannot start with this protocol if animal aggressive

Question 56

alfaxalone advantages

Answer 56

* ADV: IM route possible – NOT contraindicated in sick patients with renal or cardiac disease