Transcript VETS 238 Surgical Nursing and Anesthesia

Spring 2006
VETS 238
Surgical Nursing and
Anesthesia
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
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VETS238 Syllabus + Lecture Outlines
VETS239 Syllabus
VETS239 Lab Guidelines
VETS239 Lab Schedule
Academic Integrity Policy
Safety Release Form
Any Questions?
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)
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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!*
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Duration: food: 8 hr
water: 2hr?
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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:
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1. Blocks stimulation of the vagal nerve
• Major parasympathetic innervation to heart
• Therefore increases HR
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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
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• Effects of phenothiazines:
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1.) Sedation – up to 24 hours
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2.) Anti-emetic -- decreases nausea
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3.) Anti-arrhythmic – helpful with some anesthetics (halothane)
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4.) Anti-histamine – not in allergy testing
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5.) Peripheral vasodilation – not ideal in low blood pressure/shock
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6.) Effects on personality – can cause excitement
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• Disadvantages of phenothiazines:
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NO ANALGESIA
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NO REVERSING AGENTS
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LOWER SEIZURE THRESHOLDS
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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:
1. Diazepam ( Valium )
IV slowly (or IM)
NOT water soluble (precipitates w other drugs)
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Soluble in plastics
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light-sensitive
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controlled substance
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• Commonly used in combination with drugs that induce anesthesia
2. Midazolam ( Versed )
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Advantages:
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water soluble
less irritating
ALPHA 2 AGONISTS
(receptor in brain)
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(engage these receptors)
=“thiazine derivatives”
– examples: xylazine (rompun, anased), medetomidine (Domitor)
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widely used in SA and LA
potent sedatives
fast onset
predictable results
Mode of action:
bind to receptors on sympathetic nerves in brain and spinal cord
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not controlled substances
reversible
ANALGESIA
yohimbine (antisedan)
– stimulate these “alpha 2 adrenoreceptors” (result is decrease in norepinephrine)
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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:
1. Xylazine
SA solution 2%
LA solution 10%
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
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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
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Use of Reversing Agents : (have drawn up)
• yohimbine for xylazine (IV)
atipamezole ( Antisedan ) for medetomidine (IM)
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*may need to give an analgesic if reversed*
OPIOIDS
aka “narcotics” or “opiates” (natural)
• Versatile-- can be used for:
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preanesthesia, induction, analgesia (excellent)
• Very safe
Wide safety margins
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Mode of action: four types of opioid receptors throughout body
• Opioid agents differ in their action at each of these types of receptors:
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agonist
• “pure agonists”
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Morphine
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fentanyl
• oxymorphine
antagonist
mixed
“pure antagonists” “agonist/antagonist”
naloxone
butorphanol
reversal agent
OPIOID’s (cont)
• Effects:
– 1. CNS effects:
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may cause CNS depression or excitement
dogs: usually depression, high doses >>>> narcosis
cats: may show bizarre responses; i.e., excitement, anxiety
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2. Analgesia the most effective analgesics, especially pure agonists
(morphine)
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• Method of use:
Opioid agents
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Common components of preanesthetic protocols (butorphanol)
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mixed with a tranquilizer and/or an anticholinergic
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Used to prevent and treat postoperative pain
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“Neuroleptanalgesia” = profound sedation and analgesia, for
minor surgery
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produced by doses of opioid (at a high dose) plus a tranquilizer
OPIOIDS: Adverse effects
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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
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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
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Disadvantage: =$$$, not routinely necessary except in emergencies??