Patient Monitoring During Anesthesia Flashcards
what is the motto of anesthesia
Vigilance!!
expresses the need for quick recognition of a problem
why monitor?
provide better patient care (early Dx and Tx)
prevent mortality and morbidity
protect the anesthetist (records!)
how often should you monitor?
ideally a responsible person is always available
monitor and record the results every 5 minutes
what 4 main things should be monitored
circulation
oxygenation
ventilation
temperature
common methods for monitoring circulation
mucous membrane color, CRT
palpation of pulse
ascultation of heart beat
ECG
blood pressure - recommended for all patients
when palpating the pulse, assess:
rate, rhythm and quality
subjective measure of adequacy of CO
NOT a surrogate for BP
T/F pulses at different sites may feel different
True
varible soft tissue coverage
variable distance from the heart
which artery is affected earlier by hypotension and low CO?
Distal artery/dorsal metatarsal
if it feels strong than it likely indicates good CO
common pulse palpation sites in small animals
labial
digital
dorsal pedal
metatarasal
femoral
pulse palpation sites in large animal
auricular
transverse facial
facial
ausculation of the heart assess:
heart sounds, rate and rhythm
respiratory sounds and rate
T/F the ECG does not indicate that the heart is contracting
True!
clinical uses of ECGs
determine heart rate and rhythm
aid in Dx and Tx of electrolyte disturbances (Hyperkalemia)
Dx chamber enlargement
may provide clues about myocardial oxygenationa dn perfusion abnormalities and location of certain cardiac disease
Mammalian type A conduction system
small animals
purkinjie fibers excite the endocardium only
base to apex current flow
Mammalian type B conduction system
horses, ruminants, pigs
purkinje fibers penetrate the myocardium
apex to base current flow
which lead is preferred in small animals
lead II
yeilds tallest R-wave
which lead is perferred in large animals
lead I
T/F you may need to be creative with ECG lead placement
True
surgical prepartation may prevent standard electrode placement
ECG traces that look normal will suffice for anesthesia
T/F ECG gel or saline can be used for elextrode contact but not alcohol
True
alcohol may ignite if patient had to be defibrillated, poor conductor of electricity
what is the most clinically relevant information gained from the ECG
heart rate
T/F normal HR and strong pulse indicates adequate cardiac output even if not sinus rhythm
True
what is the best way to dertermine HR
count yourself while looking at watch
asculate, palpate pulse, listen to doppler
what can effect HR/PR given by the ECG and pulse oximeter
bad signal quality
double counting
uneven HR (signal is averaged over time)
what are common arrhythmias under anesthesia
sinus bradycardia and tachycardia
AV blocks (1st and 2nd degree)
what can prevent/ reduce runs of V-tach while under anesthesia
phenoxybenzamine pretreatment
what happens to blood pressure when HR is high
plummets
when should you treat ventricular arrythmias under anesthesia
if there is severe underlying heart disease
risk of sudden death
when might you consider treating ventricular arrhythmias
severe systemic disease
if a patient has ventricular arrhythmia with moderate systemic disease or trauma should you treat the arrhythmia
only if it affects hemodynamics
what is the first line of Tx for ventricular arrhythmias
Lidocaine IV
what does blood pressure monitoring depend on
where and how it is measured
how does the BP signal change as move from central to periphery
systolic becomes higher
diastolic becomes lower
mean remains similar
systolic pressure on the BP waveform
highest point of BP curve
represents afterload for the left ventricle
mean pressure on the BP waveform
aver BP over a full cycle
determinant of tissue perfusion
diastolic pressure on BP waveform
lowest point of the BP curve
determinant of mycoardial perfusion
mean and systolic that indicate hypotension in small animals
Mean: <60
Systolic: <80
mean and systolic that indicate hypotension in large animals
Mean: <70
Systolic: <90
how should you treat hypotension under anesthesia
decrease anesthetic administration
give fluid bolus
give drugs (inotropes or vasocontrictors)
what other things does a BP measurement yeild
heart rate
BP changes with respiration: indicate hypovolemia
waveform: info about inotropy, CO and effect of arrhythmias
how can BP be calculated
BP= (HR x SV) x SVR
SV: depends on the preload and contractility; preload depends on circulating volume
CO=HR x SV
what are the 4 crucial elements of CV function
HR (and rhythm)
contractility
Circulating volume
Vasconstriction
**these elements must be normal, not maximal**
what is the gold standard for measung BP
Invasive (direct): continuously via arterial catheter
what are the most common types of non-invasive (indirect) BP measurement
oscillometric and doppler
intermittently use a pressure cuff
how do you measure IBP
insert catheter into an artery
connect to saline filled rigid tubing
connect transducer to a monitor
ensure that blood does not clot in the catheter (flush it)
IBP shoudl be used in horses if they are anesthetized for longer than:
45 min
which arteries can be used for IBP in a dog
dorsal pedal, metatarsal
which arteries can be used for IBP in a cat
dorsal pedal, coccygeal
which arteries can be used for IBP in a horse
facia, transverse facial, digital
which arteries can be used for IBP in a cattle
auricular
which arteries can be used for IBP in sheep and goats
median
where should the BP transducer be positioned
point of the shoulder in dorsal recumbency
point od sternum in lateral recumbency
what is oscillometric NIBP
arterial blood flowing under an inflated cuff generates pressure flucuations in the cuff that is detected by the monitor
what is doppler NIBP
an inflated cuff is placed over an artery
blood flow is detected distally from the cuff using a Doppler flow probe
after complete occulsion of lfow, cuff pressure is slowly decreased
pressure where blood flow reappears is systolic BP
how wide should the BP cuff be
40% of the circumference of the limb
cuff placement in small animals
distal radius
distal tibia
metatarsus
cuff placement in large animals
metacarpus, tail
what is an advantage of oscillometry
provides systemolic, mean and diastolic BP
what is the main disadvantge to oscillometry
if patient arrest in between readings you may not know
if you can only afford a single anesthesia monitor you should choose:
a doppler
how is oxygenation measured
by pulse oximeter or blood gas
what is hypoxemia
reduction of oxygenation of arterial blood
(reduction of PaO2, SaO2 or Hb content)
a patient is considered hypoxemic when
PaO2 < 60 mmHg
SaO2 < 90%
PaO2 and SaO2 should always be interpreted in light of:
inspired O2 fraction (FiO2)
a healthy air breathing animal should have a SaO2 of
>95%
what should SaO2 be if the animal is breathing pure O2
>98%
what can affect the results of a pulse oximeter
hypoperfusion
pigmentation
movement
abnormal Hb - CO poisoning, methemoglobinemia
when is it important to use a pulse oximeter
patient is breathing room air
there is V/Q mismatch
there is respiratory disease
what is ventilation defined by
PaCO2
process involved in the movement of air (gas) in and out of the alveoli
what is the normal range for PaCO2
35-45 mmHg
PaCO2 values >45 can be caused by
hypercapnia or hypoventilation
PaCO2 values <35 can be caused by
hypocapnea or hyperventilation
T/F tachypnea does not equal hyperventilation
True
there is no reliable correlation between respiratory pattern and PaCO2
a capnometer measures
only ET CO2
what does a capnograph measure
ET CO2 vs time on a graph
continuous
T/F a capnogram can be an indirect assessment of CO
True
especially during CPR - adequate CO is necessary for the transport of CO2 from the tissues to the alveoli
what factors influence ET CO2 values
CO2 production
circulation
alveolar ventilation
measurement error
what is phase I indicative of
baseline (inspiration)
What is phase II indicative of
Expiratory upstroke
what is phase III indicative of
alveolar plateau
what is phase IV indicative of
inspiration begins
what measurement is indicated by the red arrow (D)
ET CO2
what pattern is seen here
hyperventilation
what pattern is seen here
hypoventilation
what pattern is seen here
CO2 rebreathing
what pattern is seen here
spontaneous breathing during mechanical ventilation
what pattern is seen here
progressive airway obstruction
what pattern is seen here
cardiogenic oscillations
what pattern is seen here
cardiac arrest
what can be seen with hypothermia (<96º)
decrease in the MAC of the anesthetics (less ISO needed)
CV system may be depressed (bradycardia)
recovery may be prolonged
T/F hyperthermia is less common but more serrous than hypothermia
True
>102ºF, may damage the CNS
how can core body temp be measured
esophageal temperature probe entered into mid thorax
peripheral body temperature is
colder than core temp
pharyngeal, nasal, rectal
Tx for hyperthermia
find the cause
COOL!! - switch off heatng devices/blankets, decrease room temp, ice packs, ice cold infusions etc
T/F anesthetic depth should be determined without reguard to body temp
True
it would be misconduct to increase vaporizer dial setting as a “treatment” for hyperthermia
what is included in the anesthesia record
drug administration (dose, time, route)
monitored variables (HR, RR,) - min every 5 min
T/F it is ideal to have personnel that are fully and continuously dedicated for anesthesia care
True
normal limits under GA
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