CHAPTER 5 NEURO.docx

\+ Anesthetics and Sedatives Chapter 5 Care Tips After a Pet\'s Dental or Surgical Procedure \+ Nervous System: Anatomy and Physiology - To understand how anesthetic drugs work in our patients, we must review the nervous system - Command center of the body - Responsible for both au...

\+ Anesthetics and Sedatives Chapter 5 Care Tips After a Pet\'s Dental or Surgical Procedure \+ Nervous System: Anatomy and Physiology - To understand how anesthetic drugs work in our patients, we must review the nervous system - Command center of the body - Responsible for both automatic and deliberate responses - Adapts to external stimuli but also maintains internal homeostasis \+ CNS and PNS - Central nervous system (CNS) - Brain and spinal cord - Peripheral nervous system (PNS) - Cranial and spinal nerves - Communication occurs when electrical impulses travel along nerves and inform both the CNS and PNS of a stimulus and elicit an appropriate response  \+ Nervous System A diagram of the nervous system of a horse Description automatically generated \+ Neuron Anatomy - Main functional cell of the nervous system - Three types of neurons: - motor, sensory, and associative - Neuron anatomy; nucleus surrounded by cytoplasm, dendrites and axons - Dendrites are responsible for receiving messages and carrying them toward the cell body. - Axons carry messages away from the cell body. - Types of Neurons - Sensory neurons carry electrical impulses toward the CNS while motor neurons carry them away from the CNS. - Associative neurons carry impulses from one neuron to another. - Synaptic bulbs allow the neurotransmitters to be received by the dendrites.  \+ Neurotransmitters are chemical substances that facilitate the movement of an impulse from one neuron to another. Synapse.ai \+ PNS ◊ ANS and SNS - PNS is further divided - Cranial and spinal nerves - Autonomic nervous system (ANS) - involuntary - Somatic nervous system - voluntary - pairs of cranial nerves - Spinal nerves connect the spinal cord to vital organs, skeletal muscle, and skin \+ Efferent vs Afferent - Efferent (away) - Motor neurons that carry neural impulses away from the central nervous system and towards muscles to cause movement. - Efferent nerves send impulses to cardiac, smooth muscles, and glands and elicit an automatic response  - Afferent (add) - Sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain  \+ heart » drawings » SketchPort Autonomic Nervous System (ANS) - Involuntary or automatic functions - Divided into two parts: - Sympathetic nervous system - Parasympathetic nervous system - ANS is responsible for heart rate and contraction, gastrointestinal (GI) motility/secretions, pupillary response, glandular secretion, bladder control, and blood vessels \+ Autonomic Nervous System  \+ Parasympathetic and Sympathetic Nervous Systems - Parasympathetic Nervous System - Cholinergic - Responsible for both rest and (restore) energy-conserving activities - Affected by cholinergic drugs (anti-adrenergic) Promotes Rest and Repose, countered by Cholinergic or anti-adrenergic drugs - Sympathetic Nervous System - Adrenergic - "Fight or Flight" response - Affected by adrenergic drugs Fight or Flight response triggered by adrenergic drug - AKA Anti-cholinergic - When one system is stimulated, the other is inhibited (Reciprocal inhibition between the two systemS) \+ What is a Neurotransmitter Diagram Description automatically generated - Neurotransmitters endogenous chemicals that enable neurotransmission. - Chemical messenger (i.e., drug) which transmits signals across a chemical synapse - neuromuscular junction, from one neuron (nerve cell) to another \"target\" neuron, muscle cell, or gland cell. - Synapse-Axon to dendrite of another nerve cells or effector organ Nervous System Drugs - Inhibit/block the effect of neurotransmitters (NT) - Bind to the receptor site ◊ prevent binding to receptor - "-lytic" OR - Mimic the effects of neurotransmitters - Bind to receptor sites, stimulating the release of the neurotransmitter (NT) or inhibit the breakdown of the NT - "-mimetic" \+ Neurotransmitter (chemical agent-endogenous) Neurotransmitter Nervous system Acetylcholine Parasympathetic/Cholinergic Norepinephrine Sympathetic/Adrenergic Epinephrine Dopamine Serotonin GABA (gamma-aminobutyric acid) \+ List of Neurotransmitters & their action Acetylcholine Muscle contractions in motor neurons. Memory formation and learning. Stimulates the excretion of certain hormones. Involved in wakefulness, attentiveness, anger, aggression, sexuality, and thirst. Norepinephrine Excitatory chemical involved in stress. Increases heartbeat. Attentiveness, emotions, sleeping, dreaming, and learning. Epinephrine Metabolism. Regulates attention, mental focus, arousal, and cognition. Inhibits insulin excretion and raises the amounts of fatty acids in the blood. Dopamine Controls movement and posture. Modulates mood and plays a central role in positive reinforcement and dependency. Serotonin Regulation of body temperature, sleep, mood, appetite, and pain. GABA (Gamma-aminobutyric acid ) Motor control, vision, and many other cortical functions. Regulates anxiety. \+ Sympathetic - Fight or Flight - Affected by adrenergic drugs - Also known as anticholinergic - Responses correspond to responses of the sympathetic nervous system - Heart rate, force of contraction - Vasodilation (bronchioles) - motility, secretions, blood flow - Diameter of muscle blood vessels - Diameter of skin blood vessels A purple arrow pointing down Description automatically generatedA purple arrow pointing up Description automatically generated \+ Parasympathetic - Rest and Repose - Conservation and rest (opposite of sympathetic) - Affected by Cholinergic drugs or anti-adrenergic drugs - Heart rate - Bronchioles diameter - Pupil size - motility, secretions, blood flow A purple arrow pointing down Description automatically generatedA purple arrow pointing down Description automatically generated \+ Mechanism of Action - Drugs will Either inhibit or block the effect of neurotransmitter - Bind to receptor site preventing the neurotransmitter from binding to it Or - Drugs may Mimic the effects  - Drugs that mimic do so by: - directly binding to the receptor site stimulates the release of the neurotransmitter - inhibiting the breakdown of the neurotransmitter \+ Sympathetic Receptors - Alpha receptors cause excitability or increased activity in the target organ (not GI tract) - Alpha-1 - Alpha-2 - Beta receptors will decrease the activity or relax the target organ (not heart muscle) - Beta-1 - Beta-2 \+ Table 5.5 & 5.6 p 94 Alpha-1 Dilation of pupils Decrease glandular secretions Constrict arterioles and veins Decrease intestinal motility Constrict bladder sphincter Alpha-2 Skeletal muscle constriction Decrease secretion of insulin Beta-1 Increases rate, contractility, and conduction of heart Beta-2 Vasodilation of arterioles and veins Dopaminergic Vasodilation of veins in heart, kidneys, and gastrointestinal tract \+ Parasympathetic Receptors Sympathetic Receptors Parasympathetic Receptors Alpha-1 Alpha-2 Beta-1 Beta-2 Nicotinic Muscarinic \+ Parasympathomimetic and Parasympatholytic Drugs - PSM-mimic parasympathetic actions - Bladder contractility, canine glaucoma, treatment of gastroparesis, vomiting, increase peristalsis - Pilocarpine, Metoclopramide (Reglan®), bethanechol - PSL-inhibit the parasympathetic actions (anticholinergic) - Increase heart rate, decrease GI and respiratory secretions, antidote for organophosphate poisoning, CPR drug for asystole, prevents bradycardia, dilation of pupils - Atropine, Glycopyrrolate \+ Sympathomimetic (SPM)and Sympatholytic (SPL) Drugs - SPM - Increase blood pressure and cardiac output, congestive heart failure, increase renal perfusion - Epinephrine, norepinephrine, dopamine - (refer to textbook for complete table of drugs) - SPL - Acepromazine \+ Anesthetic Drugs "There are no safe anesthetic agents; there are no safe anesthetic procedures; there are only safe anesthetists." Robert Smith \+ Anesthetics Drugs:Categories/Classes - Local - Dissociative agents - Phenothiazines - Benzodiazepines - Alpha-2 agonists - Barbiturates - Opioids - Reversal agents \+ Local Anesthetics - Work by blocking pain receptors at site of action & prevent nerve impulses from being transmitted back to CNS - Prevents pain from being felt in area where local is given - Different Durations: Short acting (15-20 min) to Mod-Long acting (hours)  - Can be given directly into the desired area or in a nerve block - Can also be given in CRI or in the spinal column for epidural - Lidocaine, Bupivacaine, Mepivacaine, Proparcaine (eye) \+ Tranquilizer vs Sedative - Here are some notable differences between the two drug types: - While they both produce a calming effect, sedatives offer increased analgesia or pain relief as compared to tranquilizers. - While under sedation, most patients are relatively unaware of their surroundings - tranquilized patient is generally aware of its surroundings although doesn\'t appear to care. - Sedatives are generally used by veterinarians desiring to suppress brain activity and overall awareness to prevent movement (such as during a standing surgical procedure).  - Tranquilizers are used to reduce anxiety during some form of activity (such as breeding or loading onto a trailer or noise phobia). - Since horses are generally not going to remember or learn anything while under sedation, they are typically not asked to \"do\" anything except stand still.  - contrast, tranquilization often helps horses to perform/ learn tasks while reducing any associated anxiety(ies). \+ Anesthetic Drugs:Injectables - Uses and Advantages - Routes -- IV, IM,SQ - Induce chemical restraint - General anesthesia - Preanesthetic + induction + maintenance = multimodal protocol - More convenient and economical than inhalant anesthetic drugs - Disadvantages - Some drugs have a short duration of action - Cannot be controlled (reversals are available for some) - Not immediately eliminated \+ A close-up of a cat Description automatically generated Phenothiazines - Block dopamine receptors in the CNS (antagonist) - Sedation, pre-anesthetic (antiemetic, antiarrhythmic, antihistamine) - Acepromazine **know as a tranquilizer only** - Various forms for administration (injectable, oral tabs) - Adverse effects - Hypotension **main** - Lower the seizure threshold in epileptic patients (debatable) - Caution with geriatric patients - Hepatic or cardiac disease precautions - Boxers, sight hounds, and giant breeds are sensitive to these drugs (minimum dosage) - Prolapse of the 3rd eyelid, penile prolapse in stallions \+ 3rd eyelid prolapse  \+ 3rd Eyelid Prolapse A close up of a cat Description automatically generated \+  Benzodiazepines - Centrally acting muscle relaxant; enhance the activity of CNS inhibitory neurotransmitters (GABA agonist) - Minor tranquilizers - Anticonvulsant, 2-muscle relaxant, 3-sedation, 4-anti-anxiety, appetite stimulants (not used very often),  - Also used in combination with other anesthetic agents  - Diazepam + ketamine (dissociative) = slow IV induction - Caution in geriatric, pregnant animals, hepatic and renal disease - Diazepam, Midazolam (various forms for administration) A bottle of medicine with a label Description automatically generated \+ Alpha2-Agonists - Sedative - Benefit when compared to other sedatives/tranquilizers - Reversal - Provides some mild analgesia  \+ Alpha2-Agonists - Indications for use: Sedation, Pre-anesthetic, Analgesia, Emetic (feline) - Contraindicated in patients with: - Cardiac, hepatic, or renal diseases; seizure disorders; and debilitated patients - Adverse effects: - Bradycardia, Significant peripheral vasoconstriction, Respiratory depression, Sensitivity to loud noises - Dexmedetomidine (Dexdomitor®), Xylazine (Rompun®)  \+ Barbiturates - Effects from interaction with the CNS inhibitor/GABA receptors - Sedatives, anticonvulsants, anesthetic induction, component in euthanasia solutions - Cats are extremely sensitive to this class of drugs so caution must be utilized - Contraindicated for use in sight hounds - Lack of body fat; drugs are fat soluble - Adverse effects - Dose-dependent cardiac and respiratory depression - Hepatic, renal, and cardiac disease - administration to prevent severe tissue sloughing if administered perivascular (extremely alkaline) - dilute with NaCl, warm compress) - Phenobarbital, Pentobarbital (tx of seizures) Weekend Hound Blogging: Joey's Day to Shine -- Coyote Mercury \+ Dissociative Anesthetics - Class: Cyclohexamine - Dissociative Anesthetic - Anesthetic induction, short-term anesthesia, sedation, some analgesia (not visceral) - Contraindicated in patients with head traumas, seizure disorders, hypertension and glaucoma  - Adverse effects - Respiratory depression (apneustic breathing), ptyalism, Hyperresponsiveness, lose blink reflex, Dilated pupils,  Ataxia, Muscle tremors/rigidity, and prolonged recovery - Ketamine, Telazol (Dissociative with Benzodiazpine combo)  \+ Opioids Derived from opium poppy alkaloids Opioid receptors found throughout the body But most drugs act on receptors found in the brain and spinal cord 4 types of receptors (mu, kappa, sigma, delta) Responses are dependent on which receptor is acted upon Drugs can be agonists, partial agonists, agonist-antagonists, or antagonist \+ Opioid Receptors:Most Potent to Least Potent - Mu: analgesia, euphoria, respiratory depression, reduced GI motility, and physical dependence - Kappa: analgesia, sedation, anticonvulsant, dysphoria, depression, hallucinogenic - Sigma: vocalization and hallucinations - Delta: analgesia, antidepressant, physical dependence \+ Opioids:Uses and Precautions (Bonus) Relating To Prickly People: Part 4 - Used as pre-anesthetic, analgesic, neuroleptic analgesic, and antitussive - Use is strictly controlled (CI -- CIV) - Adverse: Respiratory & Cardiac depression - Caution with hepatic and renal disease, geriatric patients, hypothyroidism, hypoadrenocorticism, and respiratory disease - Adverse effects can be constipation, nausea and vomiting, dependence, urine retention, and sensitivity to sound - Morphine, Oxymorphone, Fentanyl, Hydromorphone (full Mu) - Buprenorphine (act as a partial agonist at mu and kappa opioid receptors and as an antagonist at delta receptors.) - Butorphanol-antagonist analgesic  \+ Nonbarbiturate Drugs or Nonclassified Anesthetics - Propofol - Ultrashort-acting, noncumulative, rapid recovery - Muscle relaxation (induction to general anesthesia) - Produces sedation-hypnosis @ IV induction - Interact with CNS GABA receptors - Alfaxan - Guaifenesin - Centrally acting muscle relaxant - Decongestant, antitussive - Minimal respiratory, cardiovascular effects - Large animal anesthesia (Triple Drip recipe) \+ Reversal Agents - Drug reversal, but analgesia may be reversed as well - Benzodiazepine antagonist - Flumazenil - Alpha2-antagonist - Yohimbine (Xyzaline/Rompun) - Atipamezole/Antisedan® ( Dexmedetomidine/Dexdormitor®) - Opioid antagonist - Naloxone \+ Behavioral Medications - Used to treat a variety of behavioral disorders in veterinary medicine - Behavior modification + Rx: - Fears and phobias - Separation anxiety - Compulsive disorders - Cognitive dysfunction - Proper client education is a necessity in cases where behavioral medications are used - "Magic Pill" \+ Behavioral Medications - Behavior Modifiers - Serotonin receptor agonist - Buspirone, Trazadone - SSRI Behavior Modifiers - Serotonin uptake inhibitor - Fluoxetine, Paraxetine - Tricyclic Behavior Modifiers (Antidepressants) - Prevent the reuptake of norepinephrine and serotonin - Amitriptyline, clomipramine, imipramine, doxepin