lec 10 chemical restraint

Chemical Restraint

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

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


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 Physical factors Age Sex Physical condition

PregnancyAnatomy

Brachycephalic

Emotional status Fearful? Aggressive?

Environment Noise Odors Other patients

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,

buprenorphine, 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

Inhalant Anesthesia

lec 10 chemical restraint

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