Lec 10 Chemical Restraint

Anesthesia
 The absence of sensation
 General anesthesia
• Unconsciousness and insensibility to feeling and pain
• Used for general surgery and painful procedures
 Local anesthesia
• Loss of sensation in a localized body part or region
• No loss of consciousness

Copyright © 2010 by Saunders, an imprint of Elsevier Inc. All rights reserved. 3

More Terminology
 Sedation
 State of calm or drowsiness
 Tranquilization
 State of relaxation and reduced anxiety
 Neuroleptanalgesia
 State of profound sedation and analgesia
 Produced by administration of an opioid and a
tranquilizer
 Used to perform minor procedures


Balanced Anesthesia
 Concurrent administration of two or more
anesthetic drugs to achieve the desired
anesthetic state
 Loss of sensation
 Muscle relaxation
 Analgesia
 Altered consciousness
 Patient safety
 Minimal adverse effects
• Especially respiratory and cardiac functions


Anesthetics
 Complete loss of sensation – often loss of
consciousness. Provides depression of nervous
tissue, local or general
• Be prepared to intubate
• Typically metabolized by hepatic or pulmonary
systems

Extravasation is bad

 Drugs can cause tissue damage if given
perivascular (around the vein)
 Examples: Ketamine, Chemotherapeutics, 10% Dextrose
 If it happens:
 Inform DVM
 May infuse equal amount isotonic saline or may
watch/wait (benign neglect) then treat PRN

Reasons for Chemical Restraint

 Reduce anxiety
 Reduce fear related aggression, so improved
safety for handlers
 Immobilization
 Reduce stress
 Reduce struggling, so less potential for injury
to patient or handler during procedure

Routes of Administration
 Oral
 Spray
 Pill/liquid
 Parenteral
 S.Q. Subcutaneous
 I.M. Intramuscular
 I.V. Intravenous
 Darts

Disadvantages

 Most are CNS depressants
 Many are CV and/or respiratory depressants
 Hypothermia is common
 If sedation for handling, may be unexpected 
P may have eaten recently  > chance of V
 Injury can occur during induction or recovery
 Patient requires monitoring after procedure

Considerations
 Species  Emotional status
Fearful?
Physical factors


 Aggressive?
Age  Environment
Sex  Noise
Odors
Physical condition 

 Other patients
Pregnancy
Anatomy
Brachycephalic

What does the RVT do?

 Prepare supplies for sedation & procedure
 Controlled Substance Log
 Prepare area to maximize P comfort
 Position P appropriately
 Induce anesthesia or assist DVM in inducing
 Monitor P during & after procedure
 Keep DVM informed of any changes in P status

Controlled Substances
 Schedule Drugs
 I – no accepted medical use (PCP, LSD)
 II – high abuse potential, severe physical dependence
(many opioids, pentobarbital)
 III – moderate/low physical dependence, less abuse
potential (ketamine, Telazol, buprenorphine,
euthanasia - pentobarbital)
 IV – low abuse potential, limited physical dependence
(phenobarbital, benzodiazepines, butorphanol)
 V – lowest abuse potential of controlled drugs

Patient Care
 During induction and maintenance of general
anesthesia, the positioning, comfort, and
safety of the patient must be considered
 Prevent trauma by supporting patient’s body
 Check endotracheal tube for proper placement
 Make sure the tube cuff is inflated
 Don’t hyperflex or hyperextend neck or limbs
 Don’t compress chest
 Make sure patient stays warm
 Sterile lubricant in eyes every 90 minutes


Vital Signs
 Used to evaluate cardiovascular and
respiratory systems
 Heart rate and rhythm
 Respiratory rate and depth
 Mucous membrane color
 Capillary refill time
 Blood pressure
 Body temperature


Reflexes and Other Indicators
of Anesthetic Depth
 Reflex: Involuntary protective responses to
stimuli that can be used to determine
anesthetic depth
 Palpebral reflex
 Swallowing reflex
 Pedal reflex
 Corneal reflex
 Muscle tone
 Eye position and pupil size


Anesthetic Recovery
 Time between discontinuation of anesthetic
and time when patient is able to walk unaided
 Factors
 Length of procedure
 Anesthetic protocol used
 Patient condition
 Body temperature
 Patient must be watched continually during
recovery


Level of Consciousness Terms

 BAR – bright, alert, responsive
 Obtunded – slow, lethargic, dull
 Stuporous – aroused by strong stimuli
 Comatose – no cerebral response to stimuli

19

Anesthetic Recovery
 Rubbing, patting the chest, and turning the
animal may hasten recovery
 Gentle movement of endotracheal tube will
stimulate breathing
 Recovery involves reverse movement
through the planes and stages of anesthesia
 Deflate the cuff and untie the tube before the
animal shows signs of recovery to allow
removal when animal swallows


Anesthetic Recovery
 Horses must stand shortly after recovery
 Some horses will try to stand too early and
have a rough recovery
 Ruminants will stay in sternal recumbency
during recovery
 Try to prevent bloat in recovering ruminants


Anesthetic Problems
 Adverse drug reactions
 Equipment malfunction
 Anesthetic overdose
 Complications of surgery
 Blood loss
 Human error
 Apnea or hypoventilation
 Hypotension
 Cyanosis or low oxygen saturation

Anesthetic Emergencies
 The animal won’t stay anesthetized
 Check the machine and endotracheal tube
 Excessive anesthetic depth
 Stop anesthetic delivery; give pure oxygen
 Cardiopulmonary arrest (CPA)
 No heartbeat, pulse or respirations
 Requires immediate CPCR
 Vomiting or regurgitation
 Can result in aspiration into the lungs


What if something goes wrong?

 Do not panic
 Breathe
 Inform DVM
 Take action
 Keep detailed records
 Include drugs administered, times
given, amount (mg, ml)

How can I convince my doctor
to let me do more?
 Show DVM they can TRUST you
 Attention to detail
 Always be prepared
 Knowledge of anesthesia
 Patient care, monitoring
 Procedure, medicine

 Drugs used

 Always clean up

Injectable Anesthetic Agents
 Phenothiazine tranquilizers
 To calm and sedate patients before general anesthesia
 Reduced anxiety during induction and recovery
 Does not diminish P consciousness
 Example: acepromazine alone or in combination with
other drugs


Phenothiazine Tranquilizers

• Often see hypotension, sometimes profound
• Depresses CNS
• No analgesia
• Anti-emetic
• Potent – long lasting
• May not always work as anticipated
• Cats, horses, some dogs
• Avoid in P w/ seuizure hx, in stallions

 α2-adrenergic drugs
 Sedatives used with other drugs to produce
effects from sedation to general anesthesia
 Examples:
• Xylazine and medetomidine and dexmedetomidine in SA
• xylazine, detomidine, and romifidine in LA


Alpha-2 agonists
 Xylazine, Detomidine, Meditomidine, Dexmeditomidine
 Initial hypertension, then HYPOtension
 Bradycardia
 Use for sedation and analgesia
 Ruminants VERY sensitive (small dose)
IM on aggressive animals, IV if can handle animal
IV-sedation in 3-5 min; IM -5 to 15 min
 Quiet, calm environment IMPORTANT

Alpha-2 antagonists

 Yohimbine, Atipamezole, Tolazoline
 Used to reverse effects of alpha-2 agonists
(anesthesia, analgesia)
 Typically takes effect in 3-5 minutes after IM
injection

Benzodiazepine + dissociative

 Telazol - Equal parts zolazepam (benzodiazepine) +
tiletamine (dissociative, cyclohexanone)
 Acidic (can burn/sting)
 Provides analgesia & muscle relaxation
 Not okay as sole agent for major surgery
 Can do TKX (telazol + ketamine + xylazine)

 Effect in 1-10 minutes following IM injection
 Mostly used IM, but Plumb lists an IV dose

 Benzodiazepine tranquilizers
 Used with other drugs to produce effects from
sedation to general anesthesia
 Controlled substances
 Examples: Diazepam, midazolam, zolazepam


Benzodiazepines

 Diazepam (valium)
 Anti-convulsant

 Muscle relaxant
 Can cause excitement in some spp if given alone
(Feline, equine)
 M99 (Etorphine)
* Synthetic opiate
* Highly analgesic

 Dissociatives
 Used alone to immobilize patients for minor or
brief procedures
 Produce immobilization, not surgical anesthesia
 Example: ketamine


Disassociatives, cyclohexanones

 Produces trance like state with some reflexes
intact.
 Ketamine, tiletamine
 Some analgesia (poor visceral analgesia)
 Rigidity of muscles (catalepsy)
 May cause seizures in dogs when used alone
 IV, IM, (SQ)

 Opioids
 Narcotics related to morphine
 Used as sedatives, analgesics and
neuroleptanalgesics (with tranquilizers)
 Cats and large animals: experience
anxiety, excitement, hyperthermia, and mydriasis
 Dogs and primates: experience
sedation, hypothermia, and miosis
 Examples:
fentanyl, hydromorphone, oxymorphone, buprenorphin
e, butorphanol, naloxone (reversal)

Narcotics (opiods)

 Provide sedative, hypnotic and analgesic
properties
 Decrease respiration
 Emesis
 (note: apomorphine – substance used to induce vomiting)

 Hypersensitivity to noise
 Can be given IV, IM, SC

 Propofol
 Short-acting IV anesthetic
 Used to induce general anesthesia
 Has anticonvulsant and antiemetic properties
 Rapid induction can cause apnea and hypotension


Propofol
 Non-barbiturate, non-dissociative IV anesthetic agent
 Used for sedation, induction and/or anesthetic
maintenance by repeated bolus injection
 Transient apnea after rapid IV injection
 No analgesia
 Not controlled
 May cause myoclonus (some like to give w/ diazepam)
 Discard 6h after reconstituting (new 28d formula)

 Imidazole derivatives
 Short-acting sedative/hypnotic
 Used to induce anesthesia in dogs and cats
 Example: etomidate
 Minimal CV effects
 Minimal respiratory effects
 Good to pre-med w/ benzodiazepine
• Minimize excitement, myoclonus


 Guaifenesin
 AKA glyceryl guaiacolate or GG
 A muscle relaxant and sedative
 Used in combination with other drugs in large
animals
• Must give rapidly
• Extravasation  tissue necrosis, sloughing
 Also used as an expectorant


 Barbiturates
 Are used for induction of general
anesthesia, treatment of seizures, and euthanasia
 Are controlled substances
 Thiopental sodium methohexital: ultrashort-acting
for induction of general anesthesia
 Pentobarbital sodium: intermediate acting used for
euthanasia


Anticholinergics
 Not true anesthetic agents
 Counteract effects of the parasympathetic nervous
system – work to prevent/counteract bradycardia and
excessive salivation
 May be part of premedication for surgical procedures
 Examples: atropine and glycopyrrolate


Lec 10 Chemical Restraint

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