96 terms

Anesthesia

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Adverse effects of atropine
Drying of mm and eyes
Constipation
Reflex tachycardia
Thickens mucus secretions and can block ET tube
When to avoid atropine
Preexisting tachycardia
Preexisting constipation or ileus
Colic in horses
Glycopyrrolate
Anticholinergic
Similar to atropine
Lasts 2x longer than atropine
Less likely to produce tachycardia
Benzodiazepines
Tranquilizer
Effect CNS
No analgesia
Minimal cardio and resp effects
Not for neonates or liver dysfunction
Valium
Diazepam
Benzodiazepine
Appetite stimulant (also midazolam)
Drug for status epilepticus
Telazol
Cyclohexamine
tiletamine and zolazepam
No analgesia
Decreases risk of seizures
Promote muscle relaxation
Alpha 2 agonists
Tranquilizer
Thiazine derivatives
(Xylazine, dormosedan, dexdomitor)
Dormosedan
Detomidine
Alpha 2 agonist
Approved in horse for sedation, analgesia, muscle relaxation
Analgesic properties
Sedation
Muscle relaxation
Xylazine
Rompun
alpha 2 agonist
Short period of analgesia (ACE doesn't)
Emetic of choice in cats
Yohimbine is reversal
Small and large animal dosages
Dexdomitor
Dexmedetomidine
Alpha 2 agonist
Reversed with antisedan (atipamazole)
When to avoid thiazines
Kidney/liver disease
CV/resp dz
Nenates
Pregnant
Opiods
Drug of choice for analgesia relief
Ex are morphine, oxy, meperidine, fentanyl, butorphanol, buprenorphine
Antagonist is naloxone
Can cause CNS depression or excitement
Increase IOP, ICP
Neuroleptanalgesia
profound state of sedation and analgesia induced by simultaneous administration of an opioid and a tranquilizer
Animals are still awake and can feel pain
Analgesia
Loss of sensitivity to pain
Anesthesia
Total loss of sensation to a body part or entire body
Occurs by giving drugs that decrease sensitivity of nervous tissue peripherally or centrally
balanced anesthesia
Administration of multiple drugs to same patient
Maximize benefits of each drug
Minimize adverse effects
Produces muscle relaxation, analgesia, and immobilization
What is physical status classification?
Decided what anesthetic protocol is selected and which special monitoring techniques will be used
ASA class 1
Minimal risk patient
Normal healthy p, no underlying dz
Ex are elective procedures
ASA Class II
Slight to mild systemic disturbances
P can compensate
No clinical signs
Ex neonates/geriatrics, fracture w/o shock, low grade heart murmur, skin tumor removal
ASA class III
Moderate risk
Moderate to severe systemic dz
Mild clinical signs
Ex anemia, moderate dehydration, kidney dz, low grade heart murmur, moderate fever
ASA class IV
High risk
Pre-existing systemic dz or severe disturbance
Ex severe dehydration, shock, anemia, uremia, high fever, uncompensated heart dz, ruptured bladder, pyo, hemorrhage, pneumothorax
ASA class V
Grave risk
Sx performed in desperation on p with life threatening systemic dz
Includes all p not expected to survive 24 hours
Ex HBC, severe head trauma, GDV, major organ failure
Why fast p
P fed before anesthesia may vomit
P under anesthesia are hyporeflexive and won't swallow (aspiration pneumonia)
Adults fasted for 8-12 hours and no water 2-4 hrs before sx
Neonates/toys fasted less time
Anticholinergics
Parasympatholytics
Block acetylcholine
Not sedatives
Bronchodilator
Atropine
Anticholinergic
Prevent and treat bradycardia, decrease secretions, bronchodilator
Slow GI motility
Dilate bronchi
Glycopyrrolate
Anticholinergic
No reflex tachycardia
Lasts twice as long as atropine
Phenothiazines
Acepromazine/chlorpromazine
Not analgesic
Antiemetic
Suppress sympathetic nervous system
Acepromazine
Phenothiazine
Tranquilizer
Antihistamine
Antiemetic
Antiarrhythmic
Peripheral vasodilation
Reduce seizure threshold
Not analgesic
Metabolized in liver
Paraphampsis in stallions
Thiopental
Barbiturate
Induction med
Signthounds have long recovery
Always give to effect (cumulative effect)
Vesicant
No analgesia
Decrease IOP, ICP, and seizures
Who shouldn't get thiopental?
Sighthounds (ex greyhound)
Hypoproteinemic p
Propofol
Non-barbiturate
Induction and short term maintenance of general anesthesia
Only white liquid given IV
Must titrate to effect
Pros of propofol
CNS depression
Muscle relaxation
Decrease IOP and ICP
Antiemetic effect
Safe in liver and kidney p
Cons of propofol
Not analgesic
Bradycardia
Hypotension
Respiratory depression
Muscle twitching during induction
Ketamine
Cyclohesamine
Controlled class 2
Cons of ketamine
Not effective if blocking visceral pain
Excreted unchanged by kidney (not good for renal p)
Metabolized by liver (not good for neonates/failure)
Increase IOP and ICP
Increase hr, bp, co
Apneustic breathing in cats
Color of oxygen tanks
Green
Size of reservoir bag
6 x tidal volume
60 ml/kg
Oxygen and anesthesia flow for induction box
4-5 L/min
4% anesthesia
Oxygen and anesthesia flow for mask induction
Oxygen 2-3L
Anesthesia 3-4 %
Most reliable sign of inadequate anesthesia
Responsive movement
Why are cats difficult to intubate?
Laryngeal spasms
Stage 1 of anesthesia
Period of voluntary movement
Immediately after induction agent
Patient still conscious
Patient disoriented
Decreased sensitivity to pain
Swallow and cough reflexes present
Stage 2 of anesthesia
Period of involuntary movement
Begins with loss of consciousness
Swallow/cough reflexes present
Pupils dilated
Excitatory phase
Can be skipped with premed
Stage 3 plane 1 of anesthesia
Time for intubation
Eyeball moves ventrally
Swallow/cough reflex decreased
Blink reflex present
Stage 3 plane 2 of anesthesia
Surgical plane
Regular shallow respirations
Decrease in hr and rr
Relaxation in muscle tone (some jaw)
Protective reflexes lost
Stage 3 plane 3 of anesthesia
Deep anesthesia plane
Too deep
Decreased hr and pulses
Stage 3 plane 4 of anesthesia
Early anesthetic OD
Fixed dilated pupils
Very very low hr
Abdominal breathing
Pale mm
Prolonged CRT
Stage 4 anesthetic plane
Anesthetic OD
Death
Do you assume that a p is too light or too deep?
Too deep
What to monitor every 5 minutes
Resp depth character and rate
Mm color and crt
Heart rate and rhythm
Pulse strength
Jaw tone
Eye position, palpebral reflex, light reflex
Oxygen flow rate and inhalant %
Fluid drip rates
Temp (every 30 minutes)
Surgical fluid rate
Dogs are 60ml/lb/day
Cats are 45 ml/lb/day
What does central eye position tell you?
Too light or too deep
How can you measure perfusion?
BP
CVP
Mm/CRT
Pulse strength
Normal non-anesthetized systolic bp
110-160 mmHG
Normal non-anesthetized diastolic bp
50-70 mmHG
What does Doppler measure?
blood pressure
What to do when BP systolic drops below 70
Increase fluid rate
How much blood can 1 gauze sponge hold?
5 ml
How many ccs of crystalloids replace 1 ml of blood?
3 cc
What does tachypnea indicate?
P is too light or too deep
Can be result of surgical stimulation
If soda lime is exhausted p may hyperventilate/become hypercapnic
What does soda lime do?
Removes CO2 from the breathing circuit
Notate number of hours it was used
Change after 6-8 hrs or color change
Why give PPV every 5 minutes?
Help prevent atelectasis (partial collapse of alveoli)
Hypoxia
SpO2 is less than 95%
What does end tidal CO2 measure?
Expired CO2
hypercapnia
Greater than 40 mmHg
What can cause ETCO2 to drop?
Hyperventilation
P is too light, too deep, or in pain
What can cause ETCO2 to increase?
Hypoventilation
Malignant hyperthermia
Fatal syndrome of anesthetized pigs
Oxygen gas cylinder
Provides O2 from tank to machine
Replace when less than 200 psi
Pressure reducing valve
Decreases pressure of O2 from 2200 psi to 50 psi
Flow meter
Determines amount of O2 being delivered to patient
Measures flow in L/min
Pressure guage
Tells you how much gas pressure is in system in mmHg
Amount of pressure in breathing system
Vaporizer
converts liquid anesthetic agent to a gas that can be inhaled by a patient
Adds controlled amounts of gas to O2 (carrier)
Oxygen flush
Allows O2 to bypass flow meter and vaporizer and go into circuit and bag
Reservoir bag
Monitors p breathing and give PPV
Allows p to breath in the system and not rely on O2 flow
undirectional valve
Flutters on inspiration
Pop off valve
Allows excess gas to exit the breathing circuit and enter scavenge
Prevent increase in pressure in system
Close to check for leaks and to give PPV
Common gas outlet
O2 and anesthetic gas exit anesthetic machine and go to breathing circuit
CO2 absorber
Removes excess CO2 from breathing circuit so gas can be reused
Scavenge system
Removes excess gas
Pulling the ET tube
Dogs- pull when dog swallows
Brachycephalics- pull when head is up and p is sternal
Cats- pull when voluntary movement or swallow
total rebreathing system
Pop off closed
Increased pressure in circuit
Slow response to vaporizer changes
All gas exhaled by p remains in circuit
Gas recirculated
Requires small amounts of fresh O2
Partial rebreathing
Pop off semiclosed
Some gases exhaled remain in circuit, some to scavenge
Cons of closed/semiclosed
Requires more monitoring
Risky
Increase CO2
Increase pressure
Slow to respond to change mi
open system
Pop off valve open
Fast response to vaporizer change
High O2 levels
Rebreathing circuit
Flow meter
Vaporizer
Common gas outlet
Unidirectional inspiratory valve
Breathing circuit
Pop off valve
CO2/scavenge/reservoir bag
Non-rebreathing circuit
Flow meter
Vaporizer
Common gas outlet
Inspiratory hose
Patient
Reservoir bag (with pop off attached)
Scavenge
Bains system
No rebreathing
For patients under 7 kg
Little or no exhaled gases recirculated
Offers little resistance for p
Fresh gas in inner tube
Exhaled gas in outer tube
High O2 rate
Methoxyflurane
More potent
More fat soluble
High solubility (doesn't like gas phase- doesn't go into blood well)
Low MAC
Slow induction and recovery
Inhalants and lipid solubility
The more lipid soluble an inhalant is, the more potent it is
Vapor pressure and inhalants
Inhalants with high vapor pressure require a precision vaporizer so right amount of gas is delivered
Precision vaporizers work best out of circuit
Inhalants and solubility coefficient
Low solubility coefficient likes to be in gas phase
Does not like to be dissolved in blood
Builds up high gradient
Low solubility means yay Gad
Gradient drives fast induction and recovery
Minimum Alveolar Concentration (MAC)
Lowest concentration at which there is no response to pain in 50% of p
Low MAC means more potent
ISO maintenance is 1.8%
Halothane
Requires precision vaporizer
Low solubility/mod fat solubility
Associated with malignant hyperthermia
Isoflurane
Precision vaporizer
Low solubility coefficient
Low fat solubility
Good for old p/liver disease
99% eliminated by lungs
Sevoflurane
Low solubility coefficient
Low lipid solubility
Eliminated only by lungs
Expensive