1. Anesthetic and Analgesic Agents
Tessa Bowers, LVT

2. What do you really know about the drugs you use?
Name
Strength
Dosage ranges (species specific)
Common uses
Systemic effects
Reversibility
Routes

3. Drug “Categories” Inhalant Benzodiazepine
Pure Opioid and partial agonist/antagonist
Dissociative
Tranquilizer/Alpha-2 Agonist
Hypnotic
Non-barbiturate
Anticholinergic
Local
Non-steroidal Anti-inflammatories (NSAID)
Agonists

4. Cookie cutter drug protocols
It is imperative to limit the use of “cookie cutter” dosage protocols.
Every patient is different.
Drugs along with their dosages should be adjusted base on their species, age, PE, blood work, past anesthetic experiences, and procedure.

5. Inhalants
Isoflurane
Allows for rapid changes in induction, depth transition, and recovery
Causes respiratory depression, depression of cardiac contractility, vasodilatation, increases ICP
Contraindicated for pets in shock or history of malignant hyperthermia
MAC 1.3% in dogs and 1.6% in cats, surgical plane 1 – 1.5x MAC

6. Sevoflurane
Allows for very rapid changes in induction, depth transition, and recovery
Causes respiratory depression, depression of cardiac contractility, vasodilation, increase ICP
Contraindicated in animals in shock or history of malignant hyperthermia
MAC 2.4% in dogs and 2.6% in cats, surgical plane 1 – 1.5x MAC
Does not cause larynospasm

7. Benzodiazepines Diazepam Anticonvulsant Excellent muscle relaxant
Minimal CV depression
Minimal respiratory depression
Reduces ICP
When used in conjunction with other medications, reduces required doses necessary

8. Diazepam Causes Delayed recovery in pets with hepatic dysfunction
Excitation in young, health patients
Potentates respiratory depression of opioids
Occasional PVC after IV dose (due to propylene glycol solvent)
Significant thrombophelbitis with rapid IV
False urine glucose

9. Diazepam Uses
IM administration is accompanied by poor and erratic absorption
Non water soluble, will sting if given IM
Crosses the blood brain barrier
Metabolized in the liver, eliminated primarily in the urine.
Reversible by Flumazenil (0.1 mg/kg IV)
Dosage 0.1 – 0.2 mg/kg IV
May be used as a CRI but binds to plastic and should be protected by light

10. Midazolam Delayed recovery in pets with hepatic dysfunction
Highly protein bound
Excitation in young, health patients
Potentates respiratory depression of opioids
Nearly 3x times as potent as diazepam
Crosses the blood brain barrier

11. Midazolam Uses Well absorbed after SC and IM injections
Water soluble, does not sting after IM injections
Shorter duration than Diazepam
Metabolized in the liver
Reversible by Flumazenil (0.1 mg/kg IV)
Dosage 0.1 – 0.3 mg/kg IV, IM, SC
CRI 0.3 mg/kg/hr, protect from light

12. Butorphanol Synthetic partial agonist/antagonist opioid
Minimal organ toxicity
More rapid onset then morphine
Does not cause histamine release
Does not induce vomiting
Minimal respiratory depression then other opioid agonists
Antitussive
Antiemetic

13. Butorphanol Undesirable Effects
At high doses will cause dysphoria, nystagmus, salivation, hyperthermia, and decrease GI motility
Ceiling effect to analgesic action
Analgesic and sedation effects are short lived due to drug duration
Unless frequent dosing, does not provide aid in inhalant reduction needs

14. Butorphanol Uses Parenteral analgesia for mild pain in dogs and cats
Opioid partial antagonist or reversal agent
Onset of action approximately 5 minutes
Peak analgesic and sedation effects 15 – 30 minutes
Reversible by Naloxone (0.04 – 0.1 mg/kg IV/IM)
Dosage 0.1 – 0.5 mg/kg IV, IM, SC (alone)
Sedation effects prolonged when combined with other drugs

15. Morphine Agonist at mu opiate receptor Minimal organ toxicity
Histamine release with IV injection, sometimes causing pronounced vasodilation/hypotension
Induces vomiting with IM or SC injection
Antitussive

16. Undesirable effects from Morphine
Slow onset of action
Induces bradycardia (or tachycardia due to coronary vasoconstriction)
Miosis in dogs
Decreased GI motility (may have immediate defecation, then GI slows)
Respiratory depression
Dysphoria at high doses in cats
Constipation
Bronchoconstriction
Hyperthermia in cats and hypothermia in dogs

17. Wait there’s more....
Morphine causes a decrease in sympathetic nervous tone, which can lead to decreased venous tone, decreased CO, pooling of blood, decreased arterial pressure secondary to decrease return
GI side effects include nausea, vomiting, decreased intestinal peristalis

18. Morphine Uses Parenteral analgesia for moderate pain
Epidural analgesia for abdominal and hind body surgical procedures (exploratory, PU, orthopedic are some examples)
Contraindicated in head trauma, respiratory disease or acute respiratory dysfunction
Crosses the placenta
Provides better sedation THEN analgesia

19. Sedation does not = pain control
Morphine needs to be protected from light
Incompatible with heparin
Increase Amylase and Lipase upto 24 hours following administration
Reversed by naloxone
Dogs: 0.1 – 1 mg/kg IM, SC (IV 10% of this)
Cats: – 0.2 mg/kg IM, SC
Epidural: 0.1 mg/kg, duration 12 to 24 hours

20. Hydromorphone Agonist at mu opiate receptor Minimal organ toxicity
5x more potent then morphine
Mild histamine release with IV injection
More rapid onset then morphine
Induces vomiting with IM or SC injection
Antitussive

21. Undesirable effects of Hydro
Dose dependant respiratory depression
Dysphoria at high doses, use a tranquilzer with
Side effects include: sedation, bradycardia, slight decrease in cardiac contractility and blood pressure, panting
Do not use with patients that have head trauma, increased ICP, acute abdomen, respiratory disease
Do not use with patients that are bradycardic
Be careful with GDV and other obstructive disease

22. Hydromorphone Uses
Use for analgesia for moderate to severe pain in dogs and cats
Epidural analgesia for abdominal and hindlimb body surgical procedures
Increase Amylase and lipase up to 24 hours

23. Hydromorphone Dosage Sedation onset (route dependant) 5 – 10 minutes
Analgesic onset (route dependant) 15 – 30 minutes
Metabolized in the liver, excreted by the kidneys
Reversible by naloxone
Dogs 0.05 mg – 0.4 mg/kg IV, IM, SC q 2 -4
Cats 0.02 mg – 0.2 mg/kg IV, IM, SC q 2 – 6
CRI

24. Fentanyl Pure mu opioid agonist
Extremely rapid onset with extremely short duration
Neuroleptanalgesia in dogs when combined with a benzodiazepine or acepromazine
Reversible by naloxone, but normally not necessary due to it’s short duration

25. Fentanyl effects
Excitatory at high doses or alone in young/healthy dogs or cats
Respiratory depression
Dose related bradycardia
Urine retention, possible constipation, possible ileus
Increase Amylase/Lipase up to 24 hours
Dosage 2 – 10 mcg/kg IV as bolus, then CRI
Recent studies with patches show 18 hours till effect

26. Buprenorphine A partial opiate agonist
Because of the above may not provide appropriate analgesia for moderate to severe pain. (thoracotomy and orthopedic procedures)
Slower onset of action (30 min – 1 hour)
Do not give SC, poor erratic absorption
IV, IM, SL every 4 to 8 hours, BUT does have a ceiling effect.

27. Buprenorphine Effects
Incompatible with diazepam
Side effects include decrease blood pressure, HR, and rarely respiratory rate
Highly plasma protein bound (not albumin)
Crosses the placenta
Dogs – 0.02 mg/kg
Cats – 0.01 mg/kg

28. Dissociative
Ketamine can be used SC, IM, IV for anesthesia/chemical restraint
Inhibits NMDA receptors for adjunct use to control pain
Inhibits GABA and may block serotonin, norepiniephrine, and dopamine
Superficial analgesia
Rapid onset of effects, no matter the route
Sympathetic stimulation

29. Ketamine effects Muscle rigidity if given alone
Seizures in 20% of cats
Increase ICP, IOP, BP, salivation, temperature
Increase CO = increase in HR, increase in MAP and in CVP
Eyes remain open, mild jaw tone once induced
Pain with IM injections
Sensitive to noise during induction/recovery

30. Ketamine Use
Do not use in patients with shock, renal/liver impairment, alone, hypertension, ICP, hyperthyroidism
Decreases airway resistance. Do not use for airway procedures
Good for patients in wind up. Low dose CRI.
Dogs and Cats 10 mg/kg IV
CRI 0.1 – 0.6 mg/kg/min

31. Tranquilizer Acepromazine antiarrhythmic, antiemetic, antihistamine
slow onset, even in IV (up to 15 minutes)
duration (12 – 24 hours)
Occasional bradycardia (or reflex tachycardia)
Lower dosage in giant breeds and greyhounds
Incompatible with diazepam and glycopyrrolate
dogs and cats – 0.5 mg/kg IV
0.025 – 0.1 mg/kg IM/SC

32. Alpha 2 Domitor (medetomidine)
Primary use for restraint and quick procedures at regular veterinarians
Beneficial for wind up patients
At bottle dosage causes cardiac depression, decrease BP (or hypertension caused by vasoconstriction)
At much lower dosage plus and opiod, decreases these side effects
Reversible with atipamazole (IM only)

33. Hypnotic Propofol Rapid and short acting Reduces ICP, IOP
Transient apnea (worsened by other drugs)
Hypotension and bradycardia
Repeated doses in cats may cause increase Heinz body production, slow recoveries, anorexia, lethargy, diarrhea
Repeated doses in dogs may cause autoimmune problems

34. Propofol uses
Do not use with patients that are anemic, dehydrated, hypovolemic, shock, hypoproteinemia
Onset within 1 minute, duration 2-5 minutes
Dosage 4 – 6 mg/kg IV, give over 60 – 90 seconds.
CRI intra-op 0.4 mg/kg IV
Side effects may be less if given while administering crystalloid therapy

35. Non-Barbiturate: Etomidate
IV anesthetic agent useful in patients with pre-existing cardiac dysfunction or the critically ill
Little effect on CV system, RR, decreases cerebral blood flow and O2 consumption
Do not use with hypoproteinemic patients
Pain at IV site, retching, transient hemolysis
Pre-treating with diazepam and/or opioid reduces the above effects along with dosage

36. Etomidate
Give via rapid IV injection, via an IV line to reduce pain and chance of hemolysis
Protect from light at room temperature
Duration of hypnosis 3 -5 minutes
Recovery slower then propofol
Onset 15 to 30 seconds
Duration 5 to 15 minutes
Etomidate alone: mg/kg IV
Etomidate 1 mg/kg IV + diazepam 0.5 mg/kg IV

37. Anticholinergic Atropine Glycopyrrolate
Protects the heart from bradycardia of reflex vagal stimulation and bradycardia induced by the effects of drugs
Glycopyrrolate
Anticholinergic of choice for patients with hyperthryoidism and HCM
Incompatible with dex sp and diazepam (+ others)

38. Glycopyrrolate and Atropine
Will not cross blood brain barrier
Marginally crosses
Tachycardia (some)
IV peak 1 – 5 minutes
IM, SC peak min
Vagalytic effects 2 -3 hr
mg/kg IV
mg/kg IM, SC
Atropine
Crosses the blood brain barrier
Crosses the placenta
Tachycardia (raging)
IV peak 3-4 minutes
Antihistamines may enhance effects
mg/kg IV
0.02–0.04 mg/kg IM, SC

39. Local anesthetics Lidocaine Bupivacaine Rapid onset
Duration 60 – 120 min
Quickly absorbed
Given IV to fast may cause rapid pressure drop
Decrease general anesthetic needs
Local and systemic use
Bupivacaine
4x more potent then lidocaine
Used for regional & epidural nerve blocks
Onset slow to intermediate
Duration 3-10 hours
Cardiac toxicity higher

40. NSAIDs These drugs as a class share common therapeutic actions:
anti-inflammatory
analgesic effects
antipyretic effects
Are effective to both acute and chronic pain with minimal side effects
COX-1 inhibitors are more commonly known for their side effects. (ie: piroxacam)
COX-2 inhibitors oral longer acting, less SE.
Do not alter the patients CNS, respiratory, CV system

41. General Info
The use of NSAIDs predisposes animals to gastric erosions and ulceration, especially those the GI disease.
On the ER side of things we see worst case scenario......
PO SID: Rimadyl, Etogesic, Metacam, Deramaxx, Previcox
IV SID: Rimadyl, Metacam
Do not change from one to another w/out waiting a minimum of 48 to 72 hours.

42. Antagonists Flumazenil Benzodiazepine antagonist
Antagonizes the sedative and amnestic qualities
May benefit treating encephalopathy with severe hepatic failure
May cause vomiting, cutaneous vasodilation, vertigo, ataxia, blurred vision
Discard once in syringe after 24 hours
Antagonist: mg/kg IV

43. Naloxone Pure opioid antagonist, reverse apomorphone
Reversal of CNS and respiratory depressant
Being investigated to treat septic, hypovolemic, or cardiogenic shock
At high doses increases dopamine levels and seizures may be seen
Sudden reversal can cause a catecholamine surge, resulting in tachycardia, hypertension, dysrhythmias, and pulmonary edema

44. Use of Naloxone Crosses the placenta
IV onset is 1-2 minutes, duration 20-40min
IM onset w/in 5 min, duration min
Duration of reversal is normally shorter then the drug you are reversing
IV 0.01 mg/kg and IM 0.04 mg/kg
Protect from light

45. Questions?