INTRODUCTION TO ANESTHESIA & PRE-ANESTHETIC AGENTS CHAPTERS 1 & 3

TERMINOLOGY OF ANESTHESIA _______________ may be defined as “loss of sensation”, but this only describes one of its effects. It is used daily in most veterinary practices to provide sedation, tranquilization, immobility, muscle relaxation, unconsciousness, and pain control for a diverse range of indications including surgery, dentistry, grooming, diagnostic imaging, wound care, and capture/transport of wild animals

TERMINOLOGY OF ANESTHESIA __________________ refers to drug-induced CNS depression and drowsiness that vary in intensity from light to deep. Patient can be aroused by noxious stimuli _______________________ is a drug-induced state of calm in which the patient is reluctant to move and is aware of but unconcerned about its surroundings. Often used interchangeable with sedation

TERMINOLOGY OF ANESTHESIA ________________ is a sleeplike state from which the patient can be aroused with sufficient stimulation. _____________________ refers to a drug-induced sleep from which the patient is not easily aroused and that is most often associated with the administration of narcotics.

TERMINOLOGY OF ANESTHESIA __________________________________may be defined as a reversible state of unconsciousness, immobility, muscle relaxation, and loss of sensation throughout the entire body produced by administration of one or more anesthetic agents. _______________________________ is a specific stage of general anesthesia in which there is sufficient degree of analgesia(loss of sensitivity to pain) and muscle relaxation to allow surgery to be performed without patient pain or movement.

Fully conscious Awake Light sedation Moderate sedation Sedation Deep sedation Border between Consciousness and unconsciousness Hypnosis Narcosis Light surgical anesthesia Unconscious Moderate surgical anesthesia General anesthesia Deep surgical anesthesia Anesthetic overdose

TERMINOLOGY OF ANESTHESIA __________________ anesthesia refers to loss of sensation in a small area of the body produced by administration of a local anesthetic agent in proximity to the area of interest. _________________ anesthesia is the loss of sensation of a localized area produced by administration of a local anesthetic directly to a body surface or to a wound. _________________ anesthesia refers to a loss of sensation in a limited area (larger area than with local anesthetics)of the body produced by administration of local anesthetic agent in proximity to sensory nerves.

TERMINOLOGY OF ANESTHESIA ___________________ anesthesia refers to the practice of administering multiple drugs concurrently in smaller quantities than would be required if each were given alone. Maximizes benefits of each drug Minimizes adverse effects Allows anesthetist to produce CNS depression, immobilization, and pain relief that is appropriate for the patient and the procedure.

PRE-ANESTHETIC AGENTS & ADJUNCTS ANESTHETIC AGENT: any drug used to induce a loss of sensation with or without unconsciousness. _________________: a drug that is not a true anesthetic but that is used during anesthesia to produce other desired effects such as sedation, muscle relaxation, analgesia, reversal, neuromuscular blockade, or parasympathetic blockade Ex: muscle relaxants, neuromuscular blockers, reversal agents

PRE-ANESTHETIC AGENTS & ADJUNCTS CHOOSING THE APPROPRIATE AGENTS ____________________: most clinics will not have the option of choosing from every drug on the market. ____________________: drugs are often chosen based on the veterinarian’s familiarity ____________________: drugs that are appropriate for one procedure may not be appropriate for another Some drugs are short-acting and would not be appropriate for long surgeries Some drugs may be appropriate for a spay but not a c-section

PRE-ANESTHETIC AGENTS ___________: It is ok to use a cheaper anesthetic as long as it is just as safe as the more expensive one. ______________________________: in emergency situations, fast-acting drugs may be necessary The anesthetic protocol, dose, and route are chosen by the veterinarian Many clinics have a routine protocol, but is important to consider all aspects of the patient’s minimum database

PRE-ANESTHETIC AGENTS Drugs that are administered to an animal prior to general anesthesia May be a single drug or combination of drugs Do not mix two or more drugs unless you have reliable evidence that it is safe to do so. REASONS TO ADMINISTER PRE-ANESTHETIC AGENTS _________________________________________

PRE-ANESTHETIC AGENTS REASONS TO ADMINISTER PRE-ANESTHETIC AGENTS _______________________________________________ Ex: some anesthetic agents cause hypersalivation, we can use atropine or glycopyrrolate to counteract this effect. ________________________________________________ If the patient is already sedated, it takes less drug to bring them into the unconscious state. This is a safer practice than using large amounts of drugs Using smaller amount of both pre-anesthetics and anesthetic agents in combination is known as balanced anesthesia.

PRE-ANESTHETIC AGENTS REASONS TO GIVE PRE-ANESTHETIC AGENTS _______________________________: some pre-anesthetic agents last long enough to be effective post-operatively

CLASSES OF PREANESTHETIC AGENTS ANTICHOLINERGICS TRANQUILIZERS and SEDATIVES Phenothiazines Benzodiazepines Alpha-2 agonists OPIOIDS Agonists Partial agonists Agonist-antagonists antagonists

ANTICHOLINERGICS aka parasympatholytics or sympathomimetics

ANESTHETIC & SURGICAL TECHNIQUES MAY STIMULATE THE VAGUS NERVE The ______________ nerve provides parasympathetic innervation to numerous target organ such as: Heart Lungs GI tract (viscerovagal reflex) Secretory glands Iris(oculovagal reflex) The vagus nerve can stimulated by endotracheal intubation, GI traction, or manipulation of the eye

ANTICHOLINERGICS Acetylcholine is the primary neurotransmitter in the PNS responsible for parasympathetic effects (cholinergic effects) Ach Ach

ANTICHOLINERGICS These drugs are given to counteract the effects caused by vagal stimulation EXAMPLES: Atropine, Glycopyrrolate

ANTICHOLINERGICS Ach Ach ANTICHOLINERGICS ONLY AFFECT _________________RECEPTORS ON THE TARGET ORGANS

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS? EFFECTS: ADVERSE EFFECTS:

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS? EFFECTS: ADVERSE EFFECTS:

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS? EFFECTS: ADVERSE EFFECTS:

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS? EFFECTS: ADVERSE EFFECTS:

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS?

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS?

WHAT EFFECT DO ANTICHOLINERGICS HAVE ON THE VARIOUS BODY SYSTEMS?

ATROPINE vs. GLYCOPYRROLATE: A COMPARISON Both drugs can be given SQ or IM (preanesthetic purposes) or IV (emergency treatment of bradycardia/cardiac arrest) ______________ is generally preferred for emergencies due to the quicker onset of action Onset of Action/Duration of Action Atropine IM: 5min, peak @ 10-20min, duration 60-90min Atropine IV: 1 min, peak @ 3-4 min, duration several minutes Glycopyrrolate IM: similar onset time to atropine, peak @ 30-45min, duration 2-3 hrs

ATROPINE vs GLYCOPYRROLATE: A COMPARISON Glycopyrrolate causes less tachycardia ______________ is better at decreasing salivation TOXICITY With overdoses drowsiness, excitement, dry mouth, ataxia, muscle tremors, dilated pupils, hyperthermia, and tachycardia may be seen REVERSED with PHYSOSTIGMINE Reversal is uncommon ANTICHOLINERGICS _____________CONTROLLED

TRANQUILIZERS and SEDATIVES PHENOTHIAZINES BENZODIAZEPINES ALPHA-2 AGONISTS

GENERAL INFO ON TRANQUILIZERS/SEDATIVES _________________ reduce anxiety, but may not decrease awareness _________________ reduce mental activity and awareness and induce sleepiness These terms are often used interchangeably Patients that have received a tranquilizer/sedative may still be easily aroused and could potentially get aggressive or injure themselves http://www.youtube.com/watch?v=AkaGWwTHD5g

ACEPROMAZINE CHLORPROMAZINE PHENOTHIAZINES ACEPROMAZINE CHLORPROMAZINE

GENERAL INFO on PHENOTHIAZINES These drugs have no _____________ effects These drugs are not controlled These drugs do not have a ____________ agent Examples: Acepromazine, Chlorpromazine

WHAT ARE THE EFFECTS THAT PHENOTHIAZINES HAVE ON THE VARIOUS BODY SYSTEMS? ADVERSE EFFECTS: EFFECTS: ADVERSE EFFECTS:

WHAT ARE THE EFFECTS THAT PHENOTHIAZINES HAVE ON THE VARIOUS BODY SYSTEMS? ADVERSE EFFECTS: EFFECTS: ADVERSE EFFECTS:

OTHER EFFECTS & ADVERSE EFFECTS of PHENOTHIAZINES: ANTIHISTAMINE EFFECT PENILE PROLAPSE DECREASED PCV Onset of action/duration of action 15min after IM injection, peak@ 30-60 min Duration: 4-8 hrs( could be up to 48hrs)

THINGS TO CONSIDER WITH PHENOTHIAZINES Sedative effects can be overridden if patient is stimulated to a sufficient degree Use a max of 3mg in dogs and 1mg in cats Boxers and giant breed dogs by have increased sensitivity Terriers and cats are more resistant to its effects Chlorpromazine is used in veterinary medicine as an antiemetic, but not as an anesthetic adjunct.

DIAZEPAM MIDAZOLAM ZOLAZEPAM BENZODIAZEPINES DIAZEPAM MIDAZOLAM ZOLAZEPAM

GENERAL INFO ON BENZODIAZEPINES Benzodiazepines depress the CNS by increasing activity of endogenous ____________________________, an inhibitory neurotransmitter in the brain. These drugs are ________________ These drugs can be reversed ______________________ is the benzodiazepine antagonist. It is rarely used due to the very low incidence of adverse effects and the high cost. These drugs provide no ______________ These drugs have unreliable sedative effects & could induce dysphoria, excitement, or ataxia in young, healthy animals, esp. when given alone EXAMPLES: DIAZEPAM, MIDAZOLAM, ZOLAZEPAM

WHATEFFECTS DO BENZODIAZEPINES HAVE ON THE VARIOUS SYSTEMS OF THE BODY? ADVERSE EFFECTS:

WHAT EFFECTS DO BENZODIAZEPINES HAVE ON THE VARIOUS SYSTEMS OF THE BODY?

THINGS TO CONSIDER ABOUT BENZODIAZEPINES Diazepam is not __________-soluble and cannot be mixed with water- soluble agents except ketamine Midazolam and zolazepam are water-soluble and can be mixed with other agents Diazepam is painful and poorly absorbed when administered intramuscularly Midazolam is more readily absorbed via IM and SQ routes Zolazepam is available only mixed with tiletamine to produce the combination product ____________. Diazepam is very soluble in plastic and over time is absorbed by syringes, IV bags, and IV tubing

THINGS TO CONSIDER ABOUT BENZODIAZEPINES Diazepam and midazolam are light-sensitive Onset of action/duration of action Less than or equal to 15 min after IM injection Duration: 1-4 hours

XYLAZINE DEXMEDETOMIDINE ALPHA-2 AGONISTS XYLAZINE DEXMEDETOMIDINE

GENERAL INFO ON ALPHA-2 AGONISTS These drugs ________controlled These drugs ___________reversed These drugs do provide _____________ effects These drugs act on alpha-2 adrenergic receptors in the CNS and PNS causing a decrease in the neurotransmitter norepinephrine The sedation is actually a paradoxical effect on the SNS. It decreases release of the neurotransmitter norepinephrine. The sedative effect is potent. The analgesic effects are relatively short-lived (~20 minutes) and should be supported by other agents

WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON THE VARIOUS BODY SYSTEMS? ADVERSE EFFECTS: EFFECTS: CV: vasoconstriction with a reflex bradycardia followed by a decrease in cardiac output, hypotension, and further decrease in heart rate due to decrease in sympathetic tone. Resp: depress respirations, effects are dose-dependent MS: muscle relaxation GI:vomiting esp in cats and xylazine>dexmedetomidine Other drugs: increased effects of other anesthetic agents, reduce the amount of other drugs given ADVERSE EFFECTS: EFFECTS:

WHAT EFFECTS DO ALPHA-2 AGONISTS HAVE ON THE VARIOUS BODY SYSTEMS? ADVERSE EFFECTS: CNS:temporary behavior changes, aggression, excitement CV: pronounced bradycardia; don’t use in debilitated animals or those with heart dz RESP:pronounced depression esp when given with other agents and in brachycephalic breeds Other: increased urination,gas distension of the stomach, premature labor, accidental absorption through the skin EFFECTS: ADVERSE EFFECTS:

OTHER EFFECTS OF ALPHA-2 AGONISTS Hyperglycemia: alpha-2 agonists reduce the secretion of insulin by the pancreas Hypothermia: alpha-2 agonists decrease thermoregulation and shivering Premature parturition Can be absorbed through the skin and abrasions – as little as 0.1ml of dexmedetomidine can cause hypotension and sedation in humans.

THINGS TO CONSIDER ABOUT ALPHA-2 AGONISTS Xylazine is largely reserved for use in large animals Cattle are sensitive and only require 1/10 of the dose used in horses ___________________ is largely used in small animals and is _______ potent than xylazine Both drugs are commonly mixed with other drugs such as ketamine, and an opioid such as butorphanol or morphine Animals can undergo minor and major surgical procedures with these combinations

THINGS TO CONSIDER ABOUT ALPHA-2 AGONISTS These drugs can be reversed with Yohimbine (reverses xylazine) and ______________ (reverses dexmedetomidine) Atipamezole is sold in combination with dexmedetomidine and is given in a __________ ratio It is not recommended to treat bradycardia with anticholinergics, but rather the appropriate reversal agent Reversal takes only 5-10min

AGONISTS PARTIAL AGONISTS AGONIST-ANTAGONISTS ANTAGONISTS OPIOIDS AGONISTS PARTIAL AGONISTS AGONIST-ANTAGONISTS ANTAGONISTS

GENERAL INFO ON OPIOIDS MODE OF ACTION 3 Primary receptor in the brain and spinal cord Mu, kappa, delta SEDATION ONSET OF ACTION:15min after IM administration DURATION: 1-3 hrs for most (buprenorphine 6-8 hrs) ANALGESIA *excellent somatic and visceral analgesia Agonists their effects on the mu and kappa receptors; partial agonists only partially stimulate the receptors; agonist-antagonists do not stimulate the mu, but stimulate the kappa; pure antagonists bind to but do not stimulate the mu & kappa receptor

WHAT EFFECTS DO OPIOIDS HAVE ON THE VARIOUS BODY SYSTEMS? ADVERSE EFFECTS: CV: bradycardia, esp with other agents RESP: minimal resp depression, panting due to effect on thermoregulatory center EFFECTS: ADVERSE EFFECTS:

WHAT EFFECT DO OPIOIDS HAVE ON THE VARIOUS BODY SYSTEMS? EFFECTS: ADVERSE EFFECTS: EFFECTS: ADVERSE EFFECTS:

OTHER EFFECTS OF OPIOIDS Allergic reactions: morphine for example may cause facial swelling and hypotension after rapid Iv administration Changes in body temperature: there is a resetting of the thermoregulatory center in the brain resulting in the dog panting and possibly lowering the body temperature Cats may have an elevated body temperature for unknown reasons. Miosis in dogs; mydriasis in cats CNS: anxiety, disorientation, dysphoria, increased response to noise CV: pronounced bradycardia RESP: dose dependent respiratory suppression, esp with other agents GI:initally vomiting, salivation, diarrhea, flatulence, followed by prolonged constipation ALLERGIES: morphine, meperidine, facial swelling, hypotension

GENERAL INFO on OPIOIDS These are controlled substances with human abuse potential Opioids used in combination with a tranquilizer achieve a state of profound sedation and analgesia termed ________________________ These drugs can be reversed with the opioid antagonist _________________ (works within 2 min IV and 5 min IM) Agonist-antagonists such as butorphanol can also be used to reverse the effects of pure agonists These will be discussed further and in more detail in week 5-6