Your Eyes, Their Hearts, Can't Lose: Navigating Anesthesia Without Monitors
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Your Eyes, Their Hearts, Can’t Lose. Navigating anesthesia without monitors
Kristen Cooley BA, CVT, VTS (Anesthesia/Analgesia)
University of Wisconsin School of Veterinary Medicine
Madison, Wisconsin
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Anesthesia
- Our goal
- Unconsciousness
- Amnesia
- Analgesia
- Muscle relaxation
- Compromises homeostasis
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Why Monitor?
- Difficult to predict emergencies
- Proactive vs. reactive
- There is NO safe anesthesia, only safe anesthetists!
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Morbidity and Mortality
- Morbidity
- The rate of complications
- Renal failure post-anesthesia – Blindness etc.
- Mortality
- The rate of anesthetic death
- Human vs. Veterinary
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M & M
- Common intra-operative complications
- Excessive bradycardia
- Cardiac depression
- Vasodilation
- Hypotension
- Arrhythmias
- Hypoventilation
- Hypoxemia
- Hypothermia
- Diligent monitoring is essential!
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Monitoring Basics
- Mandatory ACVAA guidelines
- Continuous awareness
- Heart rate
- Pulse quality and vasomotor tone
- Respiratory rate and character
- Reflexes and muscle tone
- Eye position
- Body temperature
- Multiple parameters
- Mechanical monitors
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Heart Rate
- Know what is normal
- Stay away from extremes...
- Bradycardia
- Too slow when...
- Decreased cardiac output
- Hypotension
- Poor perfusion
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Heart Rate
- Bradycardia
- Medium-large dogs 50 bpm
- Small dogs
- Normal blood pressure
- Cats 100 bpm
- Normal blood pressure
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Heart Rate
- A few common causes of bradycardia
- Anesthetic overdose
- Opioid administration
- Alpha-2 agonist administration
- Hypothermia
- Hypoxia
- 1st and 2nd degree AV block
- High vagal tone
- Hyperkalemia
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Heart Rate
- Tachycardia
- Decreases filling time
- Increased myocardial
oxygen consumption
- Dog tachycardia
-180-200 bpm
- Size dependent
- Cat tachycardia
- 200-240 bpm
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Heart Rate
- A few common causes of tachycardia
- Too light
- Painful
- Drug administration
- Hypovolemia
- Hyperthermia
- Hypoxemia
- Hypercarbia
- Anesthesia recovery
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Pulse Quality and Vasomotor Tone
- Pulse palpation
- Approximating blood pressure
- Bounding pulse = vasodilation
- Sepsis and hypovolemia
- Easily collapsible
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Pulse Quality & Vasomotor Tone
- Pulse palpation
- Weak and thready pulse = vasoconstriction
- Alpha-2 administration
- Poor cardiac function
- small stroke volumes
- Tachycardia
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Pulse Quality and Vasomotor Tone
- Pulse quality is largely dependent on...
- Stroke Volume
- Vasomotor tone
- Vessel size
- Vasoconstriction vs.Vasodilation
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Vasomotor Tone
- Regulates perfusion
- Peripheral
- Visceral
- Vasodilation
- Improves peripheral perfusion
- Causes hypotension
- Vasoconstriction
- Impairs peripheral perfusion
-Improves blood pressure
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Vasomotor Tone
- Assessing Vasomotor Tone
- MM and CRT
- Pale = vasoconstriction (anemia?)
- CRT < 1 sec
- Pink = normal
- CRT 2 sec
- Red = vasodilation
- CRT > 2 sec
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Causes
- Vasodilation
- Vasoconstriction
- Sepsis
- Hypercapnia
- Hyperthermia
- Systemic inflammation
- Drugs
- Hypovolemia
- Heart failure
- Hypothermia
- Drugs
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Pulses
- Femoral artery
- Large vessel
- Central
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Pulses
- Dorsal metatarsal (dorsal pedal)
- Very accessible
- Peripheral
- Arterial catheterization
- Vasoconstricted
- Hypovolemic
- Small patients
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Pulses
- Coccygeal artery
- Ventral tail
- Strongest at the base
- Central
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Pulses
- Radial artery
- Just proximal to the metacarpal pad
- Vasoconstricted, hypotensive, or small
- Peripheral
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Pulses
- Lingual artery
- Medial aspect of ventral tongue
- Anesthesia necessary
- Intra-op
- Peripheral
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Respiratory Rate and Character
- Anesthetic drugs
- Respiratory depression
- Change in breathing pattern
- Change in status
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Respiratory Rate and Character
- Respiration is comprised of...
- Tidal volume (TV) or (Vt)
- 10-20 ml/kg
- Respiratory rate (RR) or (f )
- 8-15 br/min
- Minute volume (MV) or (VE)
- 150-250 ml/kg/min
- TV x RR = MV
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Respiratory character
- Shallow breaths
- Decreased TV
- Increase in RR
- Normalize MV
- Deep breaths
- Increased TV
- Decrease in RR
- Normalize MV
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Respiratory Character
- Apnea
- Lack of spontaneous breathing
- Rapid induction
- Too deep
- Hypothermic
- Over-ventilated
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Respiratory Character
- Bradypnea
- Slow RR
- EtCO2
- Assist or sigh
- Possible causes
- Hypothermia
- Depth
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Respiratory Character
- Tachypnea
- Increased respiratory rate
- Many possible causes
- Too light
- Too deep
- Hypoxia
- Hypercapnia
- Hyperthermia
- Hypotension
- Painful
- Septic...
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Respiring
- Ventilation
- How well are we breathing?
- EtCO2
- Blood gas
- Physical process
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Reflexes and Tone
- Presence of reflexes
- Palpebral
- Brisk vs. Absent
- Corneal
- Always present
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Reflexes and Tone
- Tone is characterized as...
- No tone
- Some tone
- Lots of tone
- Jaw tone
- Anal tone
- General muscle tone
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Eye position
- Centrally facing
- Too deep vs. too light
- Pupil size
- Medium pupil
- Dilated pupil
- Constricted pupil
- Ventral-medial
- Good anesthetic plane
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- Eye center with medium pupil
Light plane of anesthesia
- Eye center with dilated pupil
Deep plane of anesthesia
Opioids can cause mydriasis in cats
Anticholinergic can cause mydriasis in cats and dogs
- Eye ventral-medial with medium pupil
Surgical plane of anesthesia
- Eye center with constricted pupil
Deep plane or CNS disease
IV opioid administration(dogs)
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Temperature
- Anesthesia
- Muscle activity
- Metabolism
- Thermoregulation
- 98-102 degrees F
-dogs and cats
- Anesthetic properties
- Decrease doses
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Temperature
- Hypothermia
- < 98 degrees F
- 96-98 is mild hypothermia
- 94-96 is moderate
- 90-94 is severe
- Decreased anesthetic requirements
- Prolonged recovery
- < 90 is moribund
- CNS depression - death is imminent
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Temperature
- Hyperthermia
- > 103.5 degrees F
- Cell damage
-108 degrees and above
- Metabolic oxygen requirement
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Wrapping it up
- You are an excellent monitor!
- Look at the whole picture
- Know normals
- Be aware
- Seek knowledge
- Have confidence
- Enjoy yourself
- Anesthesia is fun!
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Thank you!
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