VETS 238Surgical Nursing and Anesthesia Spring 2006
Welcome to Surgical Nursing and Anesthesia • Dr. Bret Meckel • Graduate of Texas A&M College of Veterinary Medicine • 8 years in private practice in Southern Oregon • Three different small animal practices • Primary vet for the Oregon Tiger Sanctuary • Started teaching at Delhi in Spring ‘06
Class # 1 • Introductions • Who are you? • Name, where from, interests in veterinary medicine • VETS238 Syllabus + Lecture Outlines • VETS239 Syllabus • VETS239 Lab Guidelines • VETS239 Lab Schedule • Academic Integrity Policy • Safety Release Form
The Preanesthetic Period Read over notes and corresponding text for next class Be prepared!
Quick Survey • Currently working at a practice? • LA vs SA? • Anesthetics? • Injectable • Gas
Preanesthesia • What is it? What comes to mind?
The Preanesthetic Period • When? • The period preceding induction of anesthesia • Preanesthesia, induction, maintenance, recovery
Preanesthesia (cont) • Major functions of technician • 1) Obtain information • Preanesthetic forms, history, PE, Dx tests • 2) Patient Care • Fasting, iv catheter, walking • 3) Administering drugs • As directed by veterinarian
Patient Evaluation/ Information Collection Remember :Patients Vary Greatly So need to get standardized information • = minimum data base
Minimum Data Base • Paperwork • Patient History • Physical Examination • Diagnostic Tests
Paperwork/Information Collection • Consent Forms • Filled out/signed by owner • anesthesia consent, DNR, IV/Bloodwork waiver • Estimates • No surprises
Patient History • Information from questions to owner • “Chief Complaint” = main problem(according to O) • What’s wrong with ______ today? • How used • Observations • Objective : facts and information • ie – not urinating very much • Interpretations • Subjective: adds evaluation to information • ie – dehydrated vs blocked?
History Taking • Not yes/no questions • People avoid “I don’t know” • Not leading questions • ie - drinking too much? • Persist until adequate answer received • Ie – one cup of food per day • Examples = pg 3 VAA
Physical Examination • Signalment • 1)Species and breed–Why Important? • 2)Weight (possible complicating factor for anesthesia) • 3)Age • geriatric? Depends on breed • 4)Sex with reproductive status (M/F S/N) • ie prostate or pyometra • 5)Disposition and Activity Level • Helps determine drug choice, suture, e-collar
Hands On Exam (read section in VAA) • By body system • Front to Back • Back to Front • Top to Bottom Key is to do it the SAME every time or you’ll miss things
In Record by Body System • Temperature, heart rate and respiratory rate (TPR) • Auscultate the heart and lung and note any unusual characteristics and if necessary postpone the anesthesia until fully clear the questionable condition. • Body condition; obesity, cachexia, dehydration • Cardiopulmonary system: heart rate and rhythm, auscultate the characteristics, CRT, color of mucous membrane, exercise intolerance, coughing, dyspnea • CNS and special senses: temperament, seizure, coma, stupor, ataxia, vision and hearing impairment • Gastrointestinal: auscultate the gut sound, parasites, palpatition • Hepatic: icterus, abnormal bleeding • Renal: palpate kidneys and bladder, polyuria/polydipsia, oliguria • Integument: tumors and flea infestation • Musculoskeletal: fractures, deformity, and lameness
Diagnostic Tests • No Universal Guidelines • Will depend on work place • Clinic Policy vs Vet Decision
CBC • RBC #/ Hbg (O2 carrying capacity) • Anemia • PCV • % RBC • Low means? • TPP (TP) = albumin + immunoglobulins • High vs Low? • WBC differential • Infection (bacterial or parasitic) or Leukemia
Urinalysis (UA) • Specific Gravity • Concentration • High vs low? • Chemistries • Protein/Glucose significance? • Microscopic Exam (sediment) • Crystals, RBC, WBC, casts
Blood Chemistry Panel Checks Organ/ Hormone Function • Liver • Kidney • Diabetes Screen • Pancreas • Electrolytes • Ca,K,Na,Cl
Blood Clotting Tests • IN HOUSE • Nail cut • Buccal Bleeding • ACT (Activated Clotting Time) • TO LAB • PT/PTT • Especially consider in ?
ECG • Determines rate and rhythm of cardiac contractions
Radiography • Plain/Contrast Films, Ultrasound, CT, MRI • If warranted: • HBC • Possible Malignancy • Otherwise called for in PE
Misc. Tests • Heartworm Test • Blood Gases
Procedure to be performed • Length of time • Catheter? • Antibiotics • Open GI Tract, Urinary Tract, Orthopedic • Antibiotics!
Classification of Patient Physical Status • Used w/ minimum data base to determine appropriate anesthetic protocol • Classes I-V (see page 15 in VAA) • Example: • 1 yr old hyper young lab class I • Injectables w/ heavy sedation • 10 yr old intact male blocked cat class V • Mask down
Selection of the Anesthetic Protocol Factors that affect selection of the anesthetic protocol: (Other than the patient’s physical status) • 1. Availability of equipment and facilities • Anesthetic machine? • 2. Familiarity with the agent and the anesthetic protocol • Safest drug is the one you’re used to • 3. Nature of the procedure • Painful? Long? Local? • 4. Special patient circumstances • Pregnant animal/ C-section • 5. Cost of anesthetic agents • Important but remember #2 • 6. Speed of induction and recovery • Emergency? End of day?
Preanesthetic Patient Care 1). Withholding food and water before anesthesia Why? Don’t assume!* • Duration: food: 8 hr water: 2hr? • With GI procedures: • food: 24 hours if possible water: 8hrs? • Risks: • Dehydration – anesthesia risk factor • Hypogycemia – esp. puppies/kittens • anorexia – delays healing/recovery
Preanesthetic Patient Care 2) Correction of pre-existing problems correct if possible but weigh the risks ie UTI in blocked cat 3) Intravenous Catheter and Fluid Therapy nice to have started couple hours before surgery if possible 4) Other Care walking, antibiotics, other meds?
About any drug we discuss: • You NEED to Know: • Class and MOA • Common and Trade Name • Common route(s) • Indications (why we use) • What effects it has (good and bad) • Contraindications (when not to use) • Reversal agent if applicable
PREANESTHETIC AGENTS Reasons for use: • 1. to calm or sedate the patient • 2. to reduce or eliminate possible adverse side effects • 3. to reduce the amount of general anesthetic required • 4. to decrease pain and discomfort • BUT remember: • NO preanesthetic agent is entirely free of side effects • NO single preanesthetic agent is safe for every animal • ALL preanesthetic agents (except glycopyrrolate) cross the placenta
ANTICHOLINERGICS (parasympatholytics ) ATROPINE • Caution: • LA vs SA concentrations • Not in tachycardia or GI obstruction/constipation • Mode of action: • Acts in parasympathetic component of autonomic nervous system: • Blocks receptors for the neurotransmitter: acetylcholine at muscarinic receptors (heart, GI, bronchi, salivary glands, iris) • Inhibits parasympathetic effects parasympatholytic
Effects of atropine: • 1. Blocks stimulation of the vagal nerve • Major parasympathetic innervation to heart • Therefore increases HR • 2. Reduces production of saliva • 3. Reduces GI activity • 4. Causes dilation of pupils • 5. Reduces tear production • 6. Promotes bronchodilation • 7. May produce thick mucus within the airways
Atropine toxicity: • Signs: • Dilated pupils, tremors, ataxia • Due to excessive supression of parasympathetic response • Tx: Physostigmine • Real problem?
Use of atropine = controversial! • Needed with newer drugs? • Potential for adverse side effects/toxicity • Onset of action: • 15 min SQ/IM • Within 1 min IV • Duration of action: • 60-90 min = practical? I like it in dogs but not in cats
GLYCOPYRROLATE effects similar to atropine • Advantages of glycopyrrolate: • Effects last 2-3X as long as atropine • Less tachycardia • More effective at supressing salivation • Doesn’t cross placental barrier • BUT: Atropine superior in bradycardic situation
TRANQUILIZERS AND SEDATIVES • Main reasons for use: • Calm animal for easier handling and induction • Easier recovery for animal (ie ferals) • Four classes of Tranquilizers/Sedatives: • Phenothiazines • Benzodiazepines • Alpha 2 Agonists • Opioids
PHENOTHIAZINES = “-promazines” ACEPROMAZINE • Effects of phenothiazines: • 1.) Sedation – up to 24 hours • 2.) Anti-emetic -- decreases nausea • 3.) Anti-arrhythmic – helpful with some anesthetics (halothane) • 4.) Anti-histamine – not in allergy testing • 5.) Peripheral vasodilation – not ideal in low blood pressure/shock • 6.) Effects on personality – can cause excitement • Disadvantages of phenothiazines: • NO ANALGESIA • NO REVERSING AGENTS • LOWER SEIZURE THRESHOLDS • MANUFACTURERS’ RECOMMENDED DOSES EXCESSIVE • Decrease by 50% or risk hypotension
BENZODIAZEPINES = “-ams” examples: diazepam (valium), zolazepam (in telazol) MOA: cause release of nuerotransmitter GABA in brain Effects of benzodiazepines: 1. Reduces anxiety (little sedation) 2. Skeletal muscle relaxant (counter acts ketamine) 3. ANTICONVULSANT increases seizure threshold 4. Minimal adverse effects except in liver disease and neonates?? (poor metabolism ) 5. appetite stimulant/cats 0.05 cc IV valium = magic 6. modify behavior (inappropriate urination) BUT: NO ANALGESIA ADDICTIVE(paperwork)
Use of benzodiazepines: • Diazepam ( Valium ) IV slowly (or IM) NOT water soluble (precipitates w other drugs) • Soluble in plastics • light-sensitive • controlled substance • Commonly used in combination with drugs that induce anesthesia 2. Midazolam ( Versed ) • Advantages: • water soluble • less irritating
ALPHA 2 AGONISTS (receptor in brain) (engage these receptors) • =“thiazine derivatives” • examples: xylazine (rompun, anased), medetomidine (Domitor) • widely used in SA and LA potent sedatives not controlled substances fast onset predictable results reversible ANALGESIA • yohimbine (antisedan) • Mode of action: bind to receptors on sympathetic nerves in brain and spinal cord • stimulate these “alpha 2 adrenoreceptors” (result is decrease in norepinephrine) • yielding muscle relaxation sedation analgesia (short 20min) • metabolized in the liver, metabolites excreted in the urine • BUT: similar receptors in the heart and blood vessels >>>> side effects • decrease HR, decrease BP
Use of alpha 2 agonists: • Xylazine SA solution 2% LA solution10% mgs/mL* used alone or in combination IM or IV 2. Medetomidine ( Domitor ) 1mg/mL approved for use in dogs only commonly used in combinations: medetomidine(10ug/kg) + butorphanol(0.2mg/kg) mixed and given IM
Alpha Agonists: ADVERSE EFFECTS =significant, frightening, check your own pulse 1. BRADYCARDIA decreases cardiac output second degree heart block • sensitizes the heart to epinephrine >>>> cardiac arrhythmias • Prevention: Anticholenergics* Treatment: Yohimbine/ Atipamazole(5X dose) 2. Respiratory effects vary among animals: respiratory depression to no ill effects?? BLUE! d/t low bloodflow not hypoxia?? 3. Vomiting ~50% dogs ~90% cats (less w/ metotomidine) 4. Depress GI activity >>>> GI stasis Beware of “bloat” (giant breeds) 5. Temporary behavior and personality changes 6. Reduce secretion of insulin>>>>>transient hyperglycemia>>>>urination Use of Reversing Agents : (have drawn up) • yohimbine for xylazine (IV) atipamezole ( Antisedan ) for medetomidine (IM) • *may need to give an analgesic if reversed*
OPIOIDS aka “narcotics” or “opiates” (natural) • Versatile-- can be used for: • preanesthesia, induction, analgesia (excellent) • Very safe Wide safety margins Mode of action: four types of opioid receptors throughout body • Opioid agents differ in their action at each of these types of receptors: • agonist antagonist mixed • “pure agonists” “pure antagonists” “agonist/antagonist” • Morphine naloxone butorphanol • fentanyl reversal agent • oxymorphine
OPIOID’s (cont) • Effects: • 1. CNS effects: may cause CNS depression or excitement • dogs: usually depression, high doses >>>> narcosis • cats: may show bizarre responses; i.e., excitement, anxiety • 2. Analgesia the most effective analgesics, especially pure agonists (morphine) • Method of use: Opioid agents • Common components of preanesthetic protocols (butorphanol) • mixed with a tranquilizer and/or an anticholinergic • Used to prevent and treat postoperative pain • “Neuroleptanalgesia” = profound sedation and analgesia, for minor surgery • produced by doses of opioid (at a high dose) plus a tranquilizer
OPIOIDS: Adverse effects • 1. Respiratory depression >>>> decreases respiratory rate and tidal volume • 2. GI function: initially, increased peristalsis then, GI stasis >>> constipation • 3. Addiction physical dependence (controlled drugs =PAPERWORK) • 4. Drug interactions in patients on selegiline = FATAL • Reversibility: can reverse the effects, esp. of pure agonists w/ “antagonists” • Naloxone is preferred reversal agent, causes least respiratory depression • Molecules of reversing agents bind to the opioid receptor sites: • act as blocking agents or displace molecules of pure agonists • but, reversal of analgesia also occurs • Disadvantage: =$$$, not routinely necessary except in emergencies??