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Define the "Maintenance Period" of general anesthesia.
between induction and recovery
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What should the anesthetist check before anesthesia?
- check the patient's vital signs and reflexes
- know what the patient's "normal" is
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How often should the anesthestist monitor the patient?
- every 3 - 5 minutes in routine cases
- continuously for risky patients
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Describe a patient that is too light.
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Describe a patient that is too deep.
- prolonged recovery
- brain damage
- dead
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Explain the importance of monitoring vital signs.
- indicate patient's response to anesthesia
- "how well is the patient doing"
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How are vital signs monitored?
- manual monitoring
- electronic monitoring
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What kind of machines are used for electronic monitoring?
- EKG
- pulse oximeter
- blood pressure monitor
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What are the different types of vital signs that can be monitored?
- heart rate and rhythm
- blood pressure
- capillary refill time
- mucous membrane color
- respiratory rate
- blood gases
- temperature
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What is a dog's normal away heart beat?
70 - 180 bpm
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What is a dog's minimum heart rate under anesthesia?
70 bpm
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What is the normal heart rate for a cat?
110 - 200 bpm
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What is the minimum heart rate for a cat under anesthesia?
100 bpm penis
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Most anesthetic drugs cause _____ heart rate, except _____.
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What is a sinus rhythm?
heart rate is increases on inhalation and decreases on exhalation
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What animal is sinus rhythm normal in?
dogs
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What is arrhythmia?
irregular heart beat
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What is arrhythmia due to?
irritation of myocardium
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What are the causes of arrhythmias?
- anoxia (not enough oxygen)
- hypercapnia (increase in CO2)
- certain drugs (halothane, xylazine)
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How do you monitor the heart?
- feeling or hearing the heart beat, or seeing EKG of heart beating
- does not prove that the heart is beating effectively
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How do you check to see if the heart is beating effectively?
- feeling pulse
- checking CRT
- blood pressure monitor
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What is the normal systolic blood pressure for a dog and cat?
110 - 160 mmHg
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What is the normal diastolic blood pressure for a dog and cat?
60 - 100 mmHg
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What does normal blood pressure indicate?
adequate blood circulation
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What is hypotension?
low blood pressure
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What can cause hypotension during anesthesia?
- vasodilation
- anesthesia being too deep
- blood loss
- shock
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When can hypotension be serious?
if a patient is in shock or dehydrated
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What is hypertension?
high blood pressure
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Is hypertension a problem in veterinary anesthesia?
no
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Where can we palpate for a pulse during anesthesia?
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What is "pulse deficit"?
- there is not a pulse with every heartbeat
- this is abnormal
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What is a normal CRT?
under 2 seconds
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When does the CRT become prolonged?
when BP drops below 70 - 80 mmHg
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Does urine decrease or increase when the BP drops?
decreases
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Describe how to monitor BP.
- put cuff around limb
- inflate until pressuure cuts off arterial flow
- pressure is then decreased until blood flows again
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How do you detect blood reflow?
- stethoscope (done with humans)
- oscillometer
- doppler device
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What is an oscillometer?
detects vibration of blood reflow
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What is a doppler device?
detects ultrasound echo of blood reflow
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What 2 ways do we detect blood pressure?
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How do we do direct venous BP monitoring?
- find central venous pressure
- place catheter through jugular to heart (tip at right atrium)
- not usually done in veterinary medicine
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How is the rate of CRT done?
rate of return of color to mucous membrane after gentle finger pressure
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What is a normal CRT?
under 2 seconds
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What causes a prolonged CRT?
- hypotension
- shock
- dehydration
- anesthesia too deep
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What are the different locations to check the CRT?
- gums, tongue
- conjunctiva
- anus
- prepuce, vulva
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What do the different colors mean...
pink
pale pink
pale or white
blue or purple
yellow
red
black
- pink: normal for dogs
- pale pink: normal for cats
- pale or white: anemia, blood loss
- blue or purple: cyanosis - lack of O2
- yellow: icterus, jaundice - liver or hemolysis problem
- red: local inflammation or septicemia
- black: pigment - not a problem, but interferes
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How much blood can a dog or cat lose?
15% of total blood volume (about 13 ml/kg)
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How can you estimate blood loss during surgery?
3x3 sponge holds about 6 - 15 ml of blood
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What is the normal respiratory rate for a dog?
10 - 30 bpm
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What is the normal respiratory rate for a cat?
25 - 40 bpm
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What is the respiratory rate during anesthesia?
8 - 20 bpm
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What is tachypnea?
rapid RR
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What is a normal respiratory pattern?
- 1:2 ratio inspiration:expiration
- inhale 1 1/2 seconds
- exhale 3 seconds
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What is tidal volume?
volume of air taken in per breath
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What happens to tidal volume during anesthesia?
it decreases
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Why does the tidal volume decrease during anesthesia?
due to decreased ability of muscles of respiration to contract
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What is hypoventilation?
- decreased rate and depth of respiration
- patient retains CO2
- becomes acidotic
- common under anesthesia
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What is hyperventilation?
- increased rate and depth of respiration
- patient blows off CO2
- becomes alkalotic
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What are the causes of hyperventilation and tachypnea (anesthesia)?
- metabolic acidosis
- retained CO2 - bad CO2 absorber on machine
- underlying respiratory disorder
- response to pain - surgical stimulus
- recovery from anesthesia
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What is panting?
rapid rate, shallow depth of respiration
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What is the purpose of panting?
- temperature control
- CO2 levels stay normal
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What kind of drug can cause panting?
opioids
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What is atelectasis?
- partially collapsed alveoli
- not breathing deeply will cause alveoli to collapse and stick together
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What causes atelectasis?
hypoventilation under anesthesia
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What does "bagging" the patient mean?
pressure on reservoir bag to fully inflate lungs
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Whats another name for "bag the patient"?
sighing
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What is dyspnea?
difficulty breathing
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What is dyspnea due to?
- disease
- airway obstruction
- mechanical (example...blocked tube)
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Describe "rocking boat" respiration.
jerky, uneven
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When does "rocking boat" respiration occur?
occurs under very deep anesthesia
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How does "rocking boat" repiration happen?
incoordination of respiratory muscles
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What is apneustic pattern breathing?
inspiration followed by prolonged pause before expiration
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When does apneustic pattern respiration normally occur?
cats under ketamine
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What are some normal respiratory sounds?
gentle blowing sounds
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What are some abnormal respiratory sounds?
- crackles
- rales
- whistles
- squeaks
- wheezes
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What is PaO2?
- arterial O2 pressur or concentration
- is the patient getting enough oxygen?
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What is PaCO2?
- arterial CO2 pressureor concentration
- is the patient blowing off enough CO2?
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How does PaCO2 occur?
- CO2 buildup occurs under anesthesia due to hypoventilation
- causes respiratory acidosis
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What is a pulse oximeter?
measures % hemoglobin saturation with O2
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What is the normal pulse oximeter?
over 95%
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What is the normal temperature for dogs and cats?
100.5 - 102.5
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When should the temperature be checked during anesthesia?
every 30 minutes
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What is the most common place to take an animals temperature?
rectal
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What are some other locations to take a temperature?
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What are the causes of hyperthermia?
- surgical prep - shaving, scrubbing, alcohol
- unable to shiver - little muscle activity
- lower metabolic rate - less heat generation
- surgery - body opened
- certain drugs - vasodilation, heat loss
- stainless steel table - cold
- position - spread out - most heat lost through head and feet
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What causes a prolonged recovery?
slower metabolism - slower enzymatic breakdown of anesthetic drugs in the body
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What causes excessive shivering?
- during and after recovery (reflex response to hypothermia)
- increases O2 demand
- patient may get hypoxia
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What are ways to prevent hypothermia
- heating pad
- towels and blankets
- warm IV fluids
- hot water bottles
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Is hyperthermia common in anesthesia?
no
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What is the treatment for hyperthermia?
cold compresses, cold bath, alcohol rub, ice packs
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What are reflexes?
involuntary response to a stimulus - from spinal cord
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Why are reflexes important in anesthesia?
help to indicate depth of anesthesia
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What are palpebral reflexes?
blinking
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How do you test an animals palpebral reflexes?
lightly tap animal's lateral or medial canthus
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Why is the swallowing reflex important during anesthesia?
when this reflex returns during recovery, we can remove the trach tube
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How do you test an animals pedal reflex?
pinch toe and animal flexes leg
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What animal do we use the ear flick reflex for?
cats
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How do we test a cats ear flick reflex?
stroke the hair inside the ear and the ear twitches
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How do we test an animals corneal reflex?
put a drop of water in eye and the animal will blink and pull eyes back
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When does an animal lose it's corneal reflex?
stage lll, plane 4
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What is the laryngeal reflex?
vocal cords
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How do we test for the laryngeal reflex?
- touch vocal cords
- cords close
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Why is the laryngeal reflex important?
must abolish before intubation
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