Many tranquilizers produce some state of sedation.
Muir 4th Ed Handbook of Veterinary Anesthesia
Each practice will set its own protocols but they will most often include:Pre-medication drug (e.g., acepromazine) Induction drug (e.g., ketamine-diazepam mixture)Maintenance drug (e.g., sevoflurane gas)Analgesic (e.g., morphine)
A complete list of considerations is listed on page 927.
Vital signs are used to assess if a patient is safe while under anesthesia.They are loosely correlated to depth of anesthesia.Vital signs can be affected by specific agents used and preexisting illness.Many anesthetic agents are respiratory depressants.Hypothermia is experienced by most anesthetized patients and should be prevented.
Palpebral reflex: gently tapping the skin at the medial or lateral canthus causes animal to blink.Swallowing reflex: normal reflex to saliva or food in the pharynx; watch the throat for swallowing motions.Pedal reflex: vigorously pinch a toe; limb should withdraw.Corneal reflex: place a drop of sterile artificial tears on the cornea; eyeball will retract slightly within the orbit.Muscle tone: resistance to opening jaw or observing the anal opening.Eye position and pupil size: nystagmus indicates a light surgical plane.
Recovery should take place where the animal can be extubated and monitored.Monitor vital signs every 5 minutes.
Be prepared for excitement stage as animal recovers.Gently talk to the animal to calm it down.
Horse recoveries can be dangerous to the horse and to the anesthetist.Ruminant recoveries are less traumatic; they will stay in sternal recumbency for some time.
Most problems can be corrected by carefully watching the anesthetic machine, the patient, and monitoring devices.Make sure the animal is correctly hooked up to the anesthetic machine.Watch all gauges, the reservoir bag, and the carbon dioxide canister.
Chapter 34 explains CPCR (cardiopulmonary-cerebral resuscitation).If animal vomits during surgery, move its head lower than the body so vomitus flows into the oral cavity and away from the pharynx.Keep endotracheal tube cuff inflated during surgery to prevent aspiration of vomitus.
Anticholinergics prevent bradycardia and excessive salivation.BAG = butorphanol, acepromazine, and glycopyrrolateRAT = xylazine (Rompun), acepromazine, and butorphanol (Torbugesic)
CNS depression, analgesia, and muscle relaxation are the main therapeutic effects of α-adrenergic drugs.Xylazine can be used to induce vomiting in cats after toxin ingestion.
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
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
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
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
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
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)
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 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)