Monitoring Aneasthesia Flashcards
why should we monitor anaesthesia?
anesthesia depresses many homeostatic mechanisms
- hypothermia
- hypoventilation
- hypotension
- reduced cardiac output
monitor and manage
manage depth and plane
monitor analgesia need
are compromised patients tolerating the procedure?
why is a pre-anesthetic assessment useful?
provides baseline value
see whether changes/adaption are needed
identifies any problems prior to anesthetic
have done by person monitoring
- learn the patient
what is basic monitoring?
you monitoring
examples
- reflexes
- respiratory
- CV - pulse/MMs/CRT/HR etc
what is intermediate monitoring?
the use of additional equipment for more readings
examples
- ECG
- capnograph
- blood pressure
- pulse-ox
- glucometer
- lactate testing
what is advanced monitoring?
additional tests if any concerns/complications
eg PCV and TS checks if hemorrhaged
how is the neurological system impacted under GA?
how do we monitor this?
reduction of consciousness
immobility
check with reflexes
to define plane of anaesthesia
how is the CV system impacted under GA?
how do we monitor this?
anaesthtic agents effect
- autonomic function
- vascular tone
- heart rate and contractibility
monitor these with
- BP
- ECG
- Pulse/heart rate
- MMs
what considerations need to be made when monitoring heart rate?
affected by pain/bleeding
pulse palpitation - tells us perfusion but doesn’t mean good BP
ECG - doesn’t mean heart working
SPO2 - affected by alpha-2 drugs (vasoconstriction)
what can impact mucus membrane colour?
blue/grey = cyanosis
- hypoxic
pale
- anaemic
- vasodilation
pinker
- vasoconstriction
yellow = jaundice
- issue with liver
cherry red
- toxicity
- carbon monoxide
how to check for perfusion?
MM
CRT
HR
Pulse Quality
Extremity temperature
lactate
- high = lack of perfusion
what is pulse oximetry?
what do we need to consider when using?
read pulse rate
- ensure PR = HR
reads saturation of hemoglobin
- can still be anemic (just less hemoglobin travel)
place on gums, tongue, ear etc
- effected by hair/dirt/pigments
- move regularly as pressure on tissues with decreases perfusion
carbon monoxide/ toxictity patients
- detects bright red MMs
- reads as good hemoglobin
- will still be hypoxic
reasons for bad perfusion/saturation?
- hypoventilation
- lighten anesthetic and give IPPV - insufficient FiO2
- increase oxygen delivery - ventilation:perfusion mismatch
- treat cause
what is electrocardiography?
measure electrical activity of the heart
- not cardiac output
- doesn’t mean patient is alive - carries on after heart stops
detects arrhythmias/abnormalities
things to consider when using an ECG?
positioning
- right = right fore
- yellow = left fore
- green = back left
heart rate can be double or triple counted
- or sometimes not at all - common with brachys and cats
continue checking pulse
what features on a normal ECG?
P wave
- atrial depolarisation
- should be followed by atrial contraction
QRS complex
- ventricular depolarisation
- should be followed by ventricular contraction
T wave
- ventricular repolarisation
how to interpret an ECG
morphology
- can you identify all parts of complex?
uniformity
- do they all look the same
- if not: narrow and wide or wide and bizarre?
regular or irregular
- if irregular: regularly (sinus arrhythmia) or irregularly (atrial fibrillation)?
output
- is there a palpable pulse for each complex?
types of sinus rythms?
sinus rhythm
- normal
sinus tachycardia/ brachycardia
- can be normal - patient/drug dependent
sinus arrhythmia
- variable intervals
- regular pattern
- associated with breathing
- not normal in cats
types of bradyarrythmias?
AV blocks - disconnect between SA node and AV node
type 1 = delay between P wave and QRS
type 2 = some P wave conduction, some missed
type 3 = complete disconnection
- causes ventricular escape rhythm - lethargic/collapse
- needs pacemaker
alpha-2 can cause block
- give atropine
types of tachyarrythmias?
Ventricular tachycardia
- more than 3 wide and bizarre complexes in a row
- HR over 260
- heart not going back to baseline - no time to refill
- poor perfusion and hypoxia
- convert with lidocaine bolus
atrial fibrillation
- P wave absent
- irregular and fast rhythm of atria
- defibrillation or cardiac meds
types of death rhythms
asystole
- no electrical activity
pulseless electrical activity (PEA)
- electrical activity with n cardiac output
- can look normal
pulseless ventricular tachycardia
- wide and bizarre complexes - HR over 180
- very strong v-tack so no cardiac output or pulses
- fix with defib
ventricular fibrillation
- no cardiac output or pulses
- heart is quivering
- start CPR and fix with defib
What can blood pressure tell us?
indicates cardiac output and tissue perfusion
but increased vascular tone will increase blood pressure but not always perfusion
a MAP over 60 allows autoregulation
- maintain blood flow to brain and kidneys
MAP <60 = hypotension
- can go lower with neonates/pediatrics
- if mild correct with fluids
- if severe (below 45) get diagnosis and management
MAP >110 = hypertension
- often pain
- could be renal disease, hyperthyroidism or hyperadrenocorticism - geriatrics
how to solve hypotension?
flow chart to fix
- lost fluid/hypovolemic shock?
- IVFT - bradycardia?
- reverse alpha-2s - vasodilation?
- reduce inhalant - give agent - reduced venous return?
- obese, pregnant, ascites
- change positioning or deflate stomach - poor cardiac contractility?
- cardiac drugs
types of blood pressure monitoring equipment?
doppler
- cuff 40% limb width
- gives HR and BP reading
- note trends
Oscillometrics
- not ideal if brady/tachycardic, arrhythmias or hypo/hypertensive
- make sure accurate - matches HR
direct arterial
- arterial catheter - fluid line with transducer
- continuous monitoring - good if unstable
- very accurate
- but more cost, equipment and risks
what do we check for when monitoring the respiratory system?
resp pattern, effort and rate
manual inflation of lungs
- check lung compliance
- forceful = compromised
thoracic auscultation
- crackles - edema
- wheezes - bronchoconstriction
- dullness - pleural effusion
what can a capnograph tell us?
measure end tidal CO2
- expired CO2
- indicates cardiac output and perfusion
normocapnia = 35-45
stages of a capnograph waveform?
phase 1 = inspiratory baseline
phase = expiratory upstroke
phase 3 = expiratory plateau
- point of reading
phase 4 = expiratory downstroke
must return to 0
- otherwise rebreathing
- breathing in expired CO2
how to manage abnormal capnographs?
patient stopped breathing
- give IPPV - likely apneic phase
- check if arrest - pulse?
patient rebreathing CO2
- increase FGF/O2
- change/check soda-lime and bag
‘fin-like’ shape = ET tube partially obstructed
- mucus production
- suction or change tube
reasons for hypo/hypercapnia?
hypocapnia = <35
hyperventilation (main)
- light anesthesia
- pain
reduced CO2 production
- hypothermia - reduces perfusion
- hypotension - more alveolar dead space
- pulmonary thromboembolism
equipment
- sampling error from leaks
- inflate cuff and leak test
hypercapnia = >45
hypoventilation (main)
- too deep
- obesity, pregnancy, ascites
- positioning
- underlying disease
increased CO2 production
- hyperthermia
- pain
- shivering
- seizures
increased inspired CO2
- rebreathing
- dead space
- exhausted sodalime
reason for sudden drop in CO2 when monitoring?
equipment disconnection
- calibration
oesophageal intubation
apneoa
cardiac arrest
reasons for changes in temperature under GA?
low temp
- no CNS response to change
- no ability to shiver
- skin prep solutions - esp. spirit
- loss of heat from body cavity - eg abdomen surgery
high temp
- unable to pant
- vasoconstrictors reduce peripheral heat loss
- common with brachys and double-couted/fluffy breeds
why is hypothermia a problem?
increased post-op infections
reduced coagulation
- increase hemorrhage
altered drug metabolism
- prolonged recovery
shivering
- increased O2 consumption
- so increased CO2 production
why manage urinary output under GA?
reducing urine production avoids hypotension
- hypotension reduces renal blood supply and function
