Patient monitoring during anesthesia Flashcards
How long does sedation take
Sedation takes: 20-30 min SQ, 15 min IM, 3-5 min IV
What can affect degree of sedation
Degree of sedation depends on drugs and environment:
Quiet, dark, familiar, owner present, other animals
Brachycephalics are at constant risk of asphyxiation when sedated-monitor continuously
Animals may be more painful when sedation wears off
How long does sedation last
Duration of sedation can last up to 8 hours
may still be sedated during recovery, at time of discharge and maybe after arriving home
What to look at for signs of sedation
T: usually constant; may be slightly decreased
P: slight ↓; severe decrease if α-2 agonist
R: slight ↓; may pant if hydromorphone (dog)
Prolapsed 3rdeyelid
Pupil size – same or relative miosis
Ataxia – mild to severe, to recumbent
Check for muscle rigidity, twitches
GI – v/d possible, ↑ saliva
What are some unacceptable signs of sedation
TPR
increase temp
sudden onset murmurs or arrhythmias
severe bradycardia (need to check BP)
MM – cyanosis or very pale
Abnormal nystagmus
http://www.youtube.com/watch?v=zLZJvqKhQBU
Blood or foreign object in vomit or diarrhea
Tremors, seizures
Weakness, stupor, unconsciousness; inability to arouse
When does induction begin and what is it
Induction begins with administration of induction agent
Goal is entry into stage 3 plane 1
Watching for changes consistent with stage 1 voluntary excitement → stage 2 involuntary excitement → stage 3, plane 1 light anesthesia
What does stage 1 look like in the animal
Stage 1: open mouth breathing, irregular depth of respiration, saliva, redness of eyes (conjunctivitis), +TPR (from fighting)
What does stage 2 look like int eh animal
Stage 2: vocalizing, tremors, twitching, paddling, rigidity
What does the animal look like while in stage 3
relaxed and recumbent
What affects the rate of induction
Faster with injectable vs mask induction
Minimal difference b/w injectables
Why monitor while under GA
Monitor for safety and monitor for anesthetic depth
Monitoring is manual (by the person) and machines are backup only
Monitor 2 parameters
Patient stability
Anesthetic depth
Anesthetic always have side effects
Purpose of monitoring is to warn early about changes in anesthetic depth and patient condition
Healthy patients are at risk; risk increases with increasing PS score
Drug selection, drug dose and duration of GA will also affect stability and depth
Risks include cardiac arrest, pulmonary arrest, brain stem depression, coma, vasogenic/cardiogenic/hypovolemic shock, drug reactions
What should you monitor while inducing
Continue to monitor heart rate and resp function, mm colour
Easy to forget when setting up monitoring equipment and intubation
Watch chest rise/fall
Check with auscultation
Minimum monitoring parameters while under GA are
HR and rhythm
Rate and depth of respiration
Mm colour, CRT
Pulse strength
BP (minimum is systolic)
*C
What are some additional monitoring that are nice to have but not needed while under GA
Diastolic, MAP, arterial BP
Oxygen saturation (SpO2)
End tidal CO2
ECG
How do you monitor for anesthetic depth while under GA
By monitoring vitals
Should remain stable
Decrease in HR< RR, BP, indicate problems
By monitoring muscle tone and reflexes
Includes eye position, pupil size, jaw tone, limb flaccidity
Goal is to find balance between sufficient anesthesia to block sensation of pain while allowing for procedure
When should you be monitoring patients under GA
Starts from the time of induction
Monitor a minimum of q5min if P1 or P2
Monitor continuously if P3 or above
Monitor continuously if a horse on inhalants or 45+ min of GA
Once patent has recovered q15min until patient can sit or lay in sternal and TPR has returned to preanesthetic values
What are some important factors when monitoring under GA
Monitoring requires manual verification of machine data and hands on check of the patient
Look at anesthetic machine: O2 flow, vaporizer, bag, pop-off valve, pressure gauges
Record O2 flow and %gas
When does stage 1 of anesthesia happen
Stage 1 occurs after giving the general anesthetic drug (proper pre- med/sedation should NEVER result in Stage 1)
Goal: to move through Stage 1 as fast as possible
End of Stage I: Can’t stand → recumbent (make sure body is properly supported)
What are the physiological responses while under stage 1 of GA
Still conscious but losing consciousness towards end)
Fear, excitement, disorientation, struggling
↑HR, ↑RR
Panting, urination, defecation
Pupil dilation
Patient is difficult to handle
What are the physiological responses while under stage 2 of GA
Unconscious
Involuntary movement (twitching, paddling, rigid muscles), moaning or other vocalization, urination/defecation
Pupils dilated
Muscle tone and reflexes present or slightly exaggerated
↑HR (should never see arrhythmia)
↑RR, irregular breathing, may be open-mouth (never cyanotic)
What does stage 2 of anesthesia look like
Patient is in unconscious “flight or flight”
Goal: to move through Stage 2 as fast as possible
End of Stage II: Muscles relax, slowing down of HR/RR, decreasing reflexes
What does stage 3 plane 1 look like under GA
Goal when inducing; time to intubate; fine for prep and moving patient; not sufficient for most surgical procedures
Unconscious
Muscles are relaxed but still have tone: limbs relaxed
Decreased jaw tone (some tone, but can easily open + close)
Decreasing reflexes
Slow PLR/palpebral/pedal (aka withdrawal)
Decreased gag/swallow → can pass ETT; start on inhalant
Decreased cardiopulmonary fxn:
Mild ↓ HR, RR, °C, BP; breathing is regular
Pupils: constricted, centrally located
Loss of tear production (need to apply an eye lubricant)
What does stage 3 plane 2 look like
Appropriate stage for cutting and painful procedures
Signs are same as Plane 1, except for these changes:
Pupils less constricted, eyes ventromedial (D,C; but not H)
No swallow/gag/palpebral/pedal
Decreased muscle tone - limbs are relaxed but not flaccid
HR, RR, BP slight decrease from Plane 1 but steady and stable
Mm still pink, CRT <2
Will continue to drop temp
What should some surgical stimulus cause
Certain surgical stimulation SHOULD cause:
Mild ↑HR, mild ↑RR, ↑BP
Patient remains unconscious and immobile
What does stage 3 plane 3 look like while under GA
Excessive CNS depression; significant cardiovascular and pulmonary depression
NO response to surgical stimulation
Decreasing HR/RR/BP; approaching minimal cut-offs
Decreased tidal volume (decrease oxygen, increasing CO2)
Low pulse strength, prolonged CRT, pale mm
Pupils moderately dilated, centrally located
Muscles are flaccid (NO jaw tone, limp)
What should you do if you notice the patient is in stage 3 plane 3
WARNING patient not stable
Decrease anesthetic
Likely requires manual ventilation (aka “start bagging”)
What does stage 4 of GA look like
BAD! Marked depression of the CNS
Pupils completely dilated, eyes centrally located
ALL reflexes absent
All muscles paralyzed or flaccid
Cardiovascular and respiratory collapse = SHOCK
VERY brief, transient sympathetic response; followed by rapidly dropping vital signs
Rapidly decreasing HR, RR, BP
Prolonged CRT, MM – pale or cyanotic
Death in 1-5 min if do nothing
How often should you monitor cat and dogs
Minimum every 5 min for P1, P2
Continuous if P3 or higher
How often should you monitor horses and exotics under GA
Continuous if on inhalants
Continuous if more than 45 min
How often do you take a temp during surgery
Every 15 mins
What are the vital sign groupings you should look for and what does these include
Circulation
- HR/P, rhythm, CRT, mm color,BP, pulse strength/quality
Oxygenation
- Mucous membrane color, oxygen saturation (SpO2), inspired oxygen , arterial blood oxygen (PaO2; blood- gas)
Ventilation
- RR and depth, breath sounds, end-tidal carbon dioxide levels (ETCO2), arterial carbon dioxide, blood pH
Temp
- Related to circulation, but other factors also contribute greatly to change in temp
What should a CRT be while under GA
Should not change under GA
Subjective indicator of peripheral tissue blood perfusion
>2 sec is reasons to report
Correlation b/w decreased perfusion and cooling of that part of body
Why might CRT be prolonged
Vasoconstriction due to epinephrine or excessively cold
Low BP – decreased cardiac output, dehydration, hypothermia, cardiac failure, excessive anaesthetic depth, blood loss, shock
What is blood pressure
Force exerted by flowing blood on arterial walls
Best measure of tissue perfusion during anesthesia
What does BP give info on
Heart function: HR, stroke volume
Vascular resistance – size of blood vessels; too much vasodilation
Blood volume
When should you alert a DVM about the blood pressure
Systolic <90
Mean <70
Diastolic <40
What does systolic pressure mean
Produced by contraction of the left ventricle
Indications of force of heart contraction; force of blood pumped out by the heart
All BP instruments give systolic pressure; Doppler is systolic
What is diastolic pressure
Pressure that remains in the arteries when the heart is in the resting phase between contractions
Not all BP monitoring instruments can measure diastolic pressure
What is mean arterial pressure
Need to know systolic and diastolic
Best indication of tissue perfusion
Most instruments provide the MAP
What are indirect BP monitors
Oscillometric – systolic, diastolic, MAP
Sphygmomanometer and cuff
Can be used with Dopplers
What are direct BP monitors
Catheter is placed in an artery and blood flow into the catheter is run through a transducer that measures the force of flow. Most accurate
What is pulse strength and why is it useful
Very rough indicator of BP
Difference between systolic and diastolic blood pressure
So, if systolic and diastolic decrease, the pulse strength will remain the same
Can’t palpate if <60mmHg
Also affected by vessel diameter, temp, SQ fat
Can palpate a peripheral artery
Lingual, dorsal pedal, femoral, carotid, facial, aural
Different arteries are appropriate for different species
Compare with pre-anesthetic pulse; should be SAME
bounding/weak/thread/absent are bad
What do you use to monitor oxygenation
Pulse oximeter which measures SpO2
What are the types of pulse oximeters
Transmission lingual probe
- Clothespin shaped
- Light emitted from one side; sensor on other
Reflective rectal probe
- Light reflects off tissue, goes back probe
- Place against rectal wall
What do you use to monitor ventilation
RR, Resp depth, resp sounds, capnograph, end tidal CO2
What does a capnograph do
Measures ETCO2
Measures RR, tidal volume
What is end tidal CO2
Measures of ventilation
Specifically measures how much CO2 is breathe out
Also takes into account: tissue metabolism, cardiac output (blood must carry the CO2 from the tissue back to the lungs), pulmonary function (tidal volume, respiration)
Changes correlate with ability to breathe and resp alkalosis/acidosis
What is a normal ETCO2
35-45mmHg
What happens if ETCO2 stays high for too long
resp acidosis
What happens if ETCO2 is over 45mmHg
Hypercapnia
Indication of hypoventilation; not enough CO2 is beijing exchanged for O2
Buildup of CO2 causes resp acidosis
Patient is also receiving less gas anesthetic and less O2
When ETCO2 >45 mmHg, a signal is sent to the respiratory center in the brain that stimulates the patient to take more/deeper breathes (CO2 drive)
If patient continues to hypoventilate or is apneic, start manual ventilation (no more than 4 deep breathes/min) until ETCO2 is around 40 mmHg
Patient is not ventilating well, too deep, acidosis and body is getting rid of excess CO2
What happens to the patient if ETCO2 is under 35mmHg
Hypocapnea
Indication of hyperventilation (sucking in O2)
Decreased CO2 causes respiratory alkalosis
Causes include stress/anxiety/pain (too light?), CNS depression (too deep), drug reaction
Remember, 40 mmHG is the cut-off level for activation of the CO2-drive
If <40 mmHg, will turn off the respiratory drive so patient may stop breathing on own until CO2 builds up to approx 40 mmHg
Why is monitoring core body temp important and when to do it
Temperature cannot tell you about oxygenation or ventilation; reflection of brainstem and hypothalamic function; may tell you some information regarding circulation
Monitor pre-anesthetic, every 15-30 minutes during anesthesia and during recovery. Monitor more often if low, small, thin, neonates, abdominal surgeries.
Hypothermia prolongs recovery and increases drug risks
Stop active warming after 37 °C; continue to monitor until back to normal
Expected drop in temperature with GA and surgery
Increased temperature is not common. Due to drug reaction (hydromorphone, fentanyl in cats; isoflurane) or vascular disease (can’t vasodilate)
What are the main systems you look at under GA
Eye position
Pupil size
Reflexes
Muscle tone
Lacrimation and salivation
HR, RR, BP, other vitals
Spontaneous movement/response to surgical stimulus
Judging Anesthetic Depth With Pupil Size and Position
Stages 1 and 2: Prolapsed 3rd eyelid
- Centrally located +/- voluntary mvmt
- Slightly dilated due to sympathetic activity
Stage 3 plane 1:
- Centrally located, constricted
Stage 3 plane 2:
- Ventro-medially located
- Constricted
Stage 3 plane 3:
- Centrally located
- Dilate
What muscle tone will you look at under GA
Typically will check
Jaw tone
Limb tone
What does muscle tone look like in stage 1 and 2
Increased muscle tone; limbs may be rigid or even spastic
What does stage 3 plane 1 muscle tone look like
Slight decrease; relaxed; slight pressure will open jaw
What does stage 3 plane 2 muscle tone under GA look like
Further decreased tone, but still require pressure to open jaw
What deos stage 3 plane 3 muscle tone look like
Limp to flaccid
What does stage 4 muscle tone look like
Flaccid
When does the palpebral reflex disapear
Disappears Stage 3, plane 2 in D, C
Disappears Stage 3, plane 3 in Eq
When does PLR decrese
Decreases and eventually gone during Stage 3, plane 2
When does the pedal/withdrawal reflex disappear
Stage 3 plane 1
When does the swallow reflex decrease and disappear
Decreased enough in Stage 3, plane 1 to intubate
Disappears in Stage 3, plane 2
When does the laryngeal reflex go away
Decreased enough in Stage 3, plane 1 to intubate
Disappears in Stage 3, plane 2
Must be gone in cats before intubation
When is the nystagmus reflex change in GA
Faster when light, slow to gone in Stage 3 plane 3 in Eq
How to test the palpebral reflex
Blink reflex in response to light tap on the medial or lateral canthus
Absent in D, C, in Stage 3 plane 2
Present, but decreased in horses in Stage 3 plane 2
What is the PLR reflex
Constriction of both pupils in response to bright light shined on one retina
Direct (pupil constricts in same eye that light is shone into)
Consensual (other eye constricts)
May be present in Stage 3 plane 2; is definitely absent in Stage 3 plane 3
What is the pedal reflex
Flexion or withdrawal of limb in response to hard pinch of digit, web between digits or pad
Also used to judge deep pain response
Small animals only
Absent in Stage 3 plane 1
What is the swallowing reflex and when does it change
Watch ventral neck region
Decreased in Stage 3 plane1
- Decreased enough to allow intubation
- If patient gags, swallow is still intact (patient needs to be deeper before intubating)
Returns just before patient regains consciousness (i.e., Stage 3 plane1)
- Extubate dogs when swallow returns
- Extubate cats before swallow returns
Laryngeal reflex is and changes when
Epiglottis and vocal cords close immediately when larynx is touched by an object
Prevents tracheal aspiration
Present, but decreased in Stage 3 plane 1
This is what makes intubation difficult
If there is too much tone in the larynx, can cause laryngospasm or trauma. Especially in cats. In these patients, intubate at Stage 3, plane 2 OR can use topical lidocaine spray
**Warning: Need to calculate the amount of lidocaine in the spray as part of maximum dose; some sprays can contain up to 12 mg of lidocaine per dose
What is different about equine patients under GA
Eyes remain central, pupils dilated
Ocular reflexes most reliable
Palpebral slows as horse deepens. Should still be present but sluggish at a surgical plane.
If completely absent they are or are becoming too deep.
Corneal reflex disappears at deeper planes. Careful when doing this one.
The horse is too light if there is a brisk palpebral, nystagmus and tearing
Ocular signs less reliable if horse develops significant periorbital edema from being in dorsal a long time or from head trauma.
What do you record during GA
Legal documents
Record pre-anesthetic patient parameters.
Give values; “Normal” or “Healthy” are never acceptable
Record dose and route of all drugs administered; AND time of each administration, person who administered
Record all fluid orders and changes in fluid orders
Monitor at least every 5 min if PS1-2; continuously if P3 or more
Pay close attention to CHANGE - this allows rapid intervention
Record all adverse events
Continue monitoring and recording until the animal is out of recovery (in sternal, responsive, vitals are back to pre-anesthetic values.
Record: start/end of surgery, when gas off, when O2 off, time of extubation.
What is the minimum acceptable HR of a small dog
> 80
What is the minimum acceptable HR of a large dog
> 60
What is the minimum acceptable HR of a cat
> 120
What is the minimum acceptable HR of a horse
30-50
What is the minimum acceptable RR of dogs and cats
8-20
What is the minimum acceptable RR of horses and ruminants
6-12
What is the minimum acceptable MAP of dogs and cats
> 70
What is the minimum acceptable MAP of horses
> 80
