Anesthesia Monitoring Flashcards
Why do we monitor patients?
assess data indicating:
patient’s physiologic status (homeostasis)
patient response to therapeutic intervention
What AANA standard is monitoring?
Standard 9:
monitoring, evaluate and document patient’s physiologic condition as appropriate for the procedure and anesthetic technique.
Alarms are turned on and audible
Document blood pressure, heart rate, and respiration at least every 5 minutes for all anesthetics
What is standard 9?
monitor ventilation, continously (O2 and continous ETCO2)
monitor cardiovascular status continously
monitor thermoregulation continously
monitor neuromuscular function
monitor and assess patient positioning
How long do CRNAs stay with their patients?
remain with patients until care is responsibly transferred to another qualified healthcare provider
Alarm Settings
alarms reflect changes in patient or equipment status
variable pitch
threshold alarms on and audible
Alarm fatigue
National patient safety goal 2017
goal 6: reduce harm associated with clinical alarm systems
What is Vigilance?
a state of clinical awareness whereby dangerous conditions are anticipated or recognized and promptly corrected
What is more important then monitors?
Look
Listen
Feel
Smell
Look
inspection
retractions, color, mucous membranes
Listen
Ausculate
heart and lung sounds, wheezing
continous suction intraoperatively
Feel
palpate
pulses, color, edema, crepitus, muscle tension, resistance and compliance
Smeel
smoke/burning, volatile anesthetic
List of Monitors
pulse oximeter capnography NIBP or arterial line EKG Temperature oxygen analyzer stethoscope PA catether ICP urine output Peripheral nerve stimulator BIS Precordial Doppler TEE/TTE SSEPs
Oxygenation
continously monitor oxygenation by clinical observation and pulse oximetry
the surgical or procedure team communicates and collaborates to migate the risk of fire
Most important aspect of anesthesia
AIRWAY
ventilation
continously monitor ventilation by clinical observation and confirmation of continous expired CO2 during moderate sedation, deep sedation or general anesthesia
Oxygenation implies
oxygen analyzer pulse oximetry skin color color of blood ABG (when indicated)
O2 analyzer
Measures FiO2 (inspired gas/inspiratory limb) low concentration alarm <30% calibrate to room air and 100% required for any general anesthetic useful for calculating PaO2
Alveolar Gas Equation
PAO2= FiO2 x (Pb-47)-PaCO2
Oxgen analyzer
electrochemical sensor (Cathode and anode embedded in electrolyte gel)
separated from O2 gas by oxygen permeable membrane
o2 reacts with electrodes, generates electrical signal proportional to O2 pressure in sample gas
Pulse oximetry
standard of care for continous non-invasive monitoring of oxygenation
provides early warning of hypoxemia; cynaosis= late sign
measures arterial O2 saturation coming principles of oximetry and plethysymography
What does pulse oximetry require
pulsatile arterial bed
plethysmography, pulsatile measurement
finger, toe, ear lobe, bridge of nose, palm of foot in children
continuous measurement of pulse rate and oxygen saturation of peripheral hemoglobin
Lambert-Beer Law of spectrophotometry
absorption of red and infrared light differs in oxygenated and reduced Hgb
HbO2 absorbs
more infrared 960nm
Reduced HbO2 absorbs more
red at 660nm
How does oximeter calculate O2 saturation
ratio of infrared and red transmitted to a photodetector) by comparison of absorbances of these wavelengths
What is the basis of oximetry?
change of light in absorption during arterial pulsations
Factors that effect pulse ox accuracy
high intensity light patient movement electrocautery peripheral vasoconstriction hypothermia cardiopulmonary bypass (need pulsatile bed) presence of other hemoglobins IV injected dyes Hemoglobin less <5
What does CoHb do to the pulse ox reading?
false increase in reading
What does MetHb do to pulse ox reading?
depends can increase or decrease
depends on SaO2
What dye causes the largest decrease in SpO2?
methylene blue
PO2 30=
SaO2 60
PO2 60=
SaO2 90
PO2 of 40
SaO2 75
What is ventilation?
movement of volume; inhalation/exhalation
Minute volume
elimination of CO2
Ventilation Monitors include
continuous ausculation (stethoscope)
chest excursion
end tidal capnography
spirometry
Precodial stethoscope
suprasternal notch or apex left lung (where heart and lung sounds are audible)
easily detects changes in breath sounds or heart sounds
What do you hear with a pericordial stethoscope?
airway/circuit disconnect
endobronchial intubation
anesthetic depth/increase HR, contractility
Esophageal Stethoscope
soft plastic catheter balloon covered distal opening limited to intubated patients better quality heart & breath sounds incorporated temperature probe place through mouth or nose into esophagus (distal 1/3) ONLY in general anesthesia
C/A with esophageal stethoscope
esophageal varices or structures
Respiratory Gas Analysis
gas sampling line
allows measurement of volatile anesthetics
non-dispersive infrared (NDIR) most common
What are characteristics of nondispersive infrared?
side streaming sampling
gas absorbs infrared energy at specific wavelength
complex algorithm and micropressor
rate of absorbance
many gases absorb at different wavelengths and the microchip can determine what the gas
Modern gas analyzer rate
250ml/min
Principles of Capnography
confirms ETT placement and adequate ventilation
average adult produces 250ml CO2/min
Capnography changes d/t
patient’s condition
anesthetic depth
temperature
Sidestream sampling
most common
airway gas aspirated and pumped into measuring device
sample flow rates of 50-250ml/min
limitations of side streaming
H20 condensation can contaminate the system and falsely increase readings
lay time between sample aspiration and reading
kinked line
PACO2-PaCO2 gradient
normal 2-10mmHg
Abnormal PA-Pa Co2 gradient
gas sampling errors prolonged expiratory phase V/Q mismatch airway obstruction embolic states COPD hypoperfusion
Phase 1 of Capnograph
corresponds to inspiration
anatomic/apparatis dead space devoid of CO2
level should be zero unless re-breathing
When is the baseline elevation of phase 1 of capnograph elevated?
CO2 absorbent exhausted
expiratory valve is missing/incompetent
bain circuit
Phase 2 of Capnograph
early exhalation/ steep upstroke
mixing of dead-space with alveolar gas
What cause a prolonged upstroke in phase 2 of caphnograph?
mechanical obstruction (kinked ETT)
COPD
bronchospasm
This indicates CO2 isn’t able to escape as readily
Phase 3 of capnograph
CO2 rich alveolar air
horizontal with mild upslope
What disrupts the 3rd phase of the capnograph
steepness is function of expiratory resistance
COPD, Bronchospasm
Not able to release CO2 due to airway resistance or diffusion issue
Low plateau
low CO2, decrease CO, increase RR rate increase dead space
High Plateau
hypoventilation increase CO2 (ie MH)
Important alarms for the mechanical ventilator
tidal volume- integrated spirometry
airway pressure: in-circuit pressure gauge, peak inspiratory pressure, sustained elevated pressure
Disconnect alarm: low airway pressure
Electrocardiogram
standard of care requires continuous monitoring and display
heart rate with audible indicator
Heart rate detects
cardiac dysrhythmias conduction abnormalities myocardial ischemia/ST Depression electrolyte changes pacemaker function/malfunction
three lead EKG system
typically monitor in lead 2
limited in detection of myocardial ischemia
Five lead EKG system
allows recording of six standard limb leads (1,2,3, avr, avf, avl)
better in detecting myocardial ischemia
allows better differiental diagnosis of atrial and ventricular dysrhythmias
Lead 2
yields max P wave voltages
superior detection of atrial dysrhythmias
detects inferior wall ischemia/ ST depression
V5
5 ICS/ anterior axillary line
detection of anterior and lateral wall ischemia
Lead One
Patient’s
R hand negative L hand positive
Lead 2
Patient’s
R hand negative and Foot positive
Lead 3
Patient’s L hand negative
foot position
Avr
patient R hand positive
foot negative
AvL
patient’s L hand positive
foot negative
5 lead EKG placement
white: 2nd ICS R mid clavicular line
green: 6-7th ICS R midclavicular line
Brown: 4 ICS R sternal border
Black: 2nd ICS L midclavicular line
Red: 6-7 ICS L midclavicular line
Arterial Blood Pressure
palpation
ausculation (korotkoff sounds)
automated indirect blood pressure (NIBPM)
oscillometry easy, accurate, versatile in children and obses may be used no calf or thigh oscillometric device air pump inflates cuff micropressor open deflation valve oscillations are sampled
NIBP Errors
surgeon leans on cuff inappropriate cuff size large cuff to low reading small cuff to high reading shivering or excessive motion
atherosclerosis and HTN with NIBP
systolic low
diastolic too high compared with invasive arterial pressure
Indications for arterial monitoring
any patient requiring BP measurement > minute to minute
critically ill
anticipated rapid blood loss
major procedures: cardiopulmonary bypass aortic cross clamping
intracranial surgery
carotid sinus manipulation
Frequent ABG
Arterial Line Site Selection
radial artery ulnar artery (technically more difficult/ more tortuous) brachial artery (complications, predisposed to kinking) femoral artery (prone to pseudoaneurysm & atheroma formation) dorsalis pedis(may have distorted waveform) axillary artery (potential for plexus/nerve damage from hematoma or traumatic cannulation
Indications for CVP
fluid management of hypovolemia and shock
infusion of caustic drugs
aspiration of air emboli
insertion of pacing leads
TPN
venous access in patients with poor peripheral veins
Site selection
IJ (R)
subclavian
external jugular
antecubital (special kit with long catether)
Pulmonary Artery Catheterization
via CVL poor LV function EF <0.4, CI <2L/min evaluate response to: fluid administration, vasopressors, vasodilators, inotropes Potential indications valvular heart disease recent MI ARDS Massive trauma Major vascular surgery
RA
2-6mmHg
RV 20-
20-30mmHg/0-5mmHg
PA
20-30mmHg/5-15mmHg
PCWP
4-12 mmHg
Factors effecting thermoregulation
ambient room temperature (cool or tropical)
scope and length of surgery (open or laproscopic)
Hypothalamic depression
intraoperative fluid replacement (blood and IVF being warmed)
viligiance in maintaining core temperature
RT RBCs decrease body temp by
0.2 degrees C
RT Crystalloids decrease body temp by
0.4 degrees C
4 Methods of heat loss
evaporation
radiation
convection
conduction
List the methods of heat loss from greatest to least
radiation> convection> conduction> evaporation
Radiation
heat radiated from patient into room
Convection
heat loss due to air velocity
Conduction
contact with OR table, black, touch
Evaporation
heat loss to dry inspired gases
Unintentional Hypothermia
GA can’t regulate temperature
Phase 1-3
Phase 2- altered perception by dermatones (hours1-4)
hypothalamus
controls temperature by intrathreshold range
inhibited by anesthetics
Hypothermia
heat loss outpaces metabolic heat production
anesthesia impairs normal response
body temperature may decrease 1C to 4C
may delay awakening
may cause shivering (increase O2 consumption by what %)
Who is greatest risk of hypothermia?
elderly, burn patients, neonates and patient’s with spinal cord injuries
Mild hypothermia
33-36 degrees
reduced enzyme function
coagulopathy
Moderate hypothermia
= to 32C
fibrillatory threshold
Hyperthermia
rarely develops under anesthesia
late sign of malignant hyperthermia
Other causes of hyperthermia
endogenous pyrogens
thyrotoxicosis or pheochromocytoma (increase metabolic rate)
anticholinergic blockade of sweating
excessive environmental warming
Monitoring Temperature Sites
esophagus (lower 1/3) accurately reflects blood temperature (most often, trended) nasopharynx rectum bladder tympanic blood (PA catheter) skin
Superifical warming modalities
Active warming
forced air warmer
most effective
warming blanket (water circulates, miniminally effective)
radiant heat unit (no impact on body temp)
heated liquids (IV bags or bottles on patient-very dangerous; burns
Watch with joint surgeries because heat can cause infection
Core warming modalities
Active warming
intravenous fluid warmers
warmed liquid transfer of heat (hotline) to infusate
delivers fluids at highest temperature of any technology
Gastric lavage- warms body core, impractical in surgery
peritoneal irrigation- encourage use of warm irrigation during intra-abdominal procedures
Passive warming modalities
ambient temperature- highest effect on maintaining body heat
ambient tem > 24C
insulation (head and extremities)
heat and moisture exchanger (artificial nose, retains moisture)
coaxial breathing circuit
Ambient temperature >24
most adults remain normotheramic w/o requiring other measures
coaxial breathing circuit
warms and humidifies inspiratory gases
Neuromuscular function
monitor NM response and assess depth of blockade and degree of recovery
Peripheral Nerve Stimulator
monitors effect of NM blocking agent on NM junction
- know and compare to baseline
-quantify by feel
Delivers electrical stimulation to a peripheral motor nerve
evokes mechanical response
permits titration of drug to optimal effect
quantifies recovery from NM blockade
Monitoring sites of PNS
ulnar nerve facial nerve posterior tibial nerve peroneal nerve place electrode near nerves to avoid direct muscle stimulation
Ulnar Nerve
innervates the adductor pollicis muscle
-adducts thumb
electrodes placed at wrist or elbow
- negative (depolarizing) placed distally
common monitoring site
inaccurate reflection of degree of block (diaphragm or airway muscles)
- these muscles less sensitive to ND block
-adductor pollicis paralysis and still have coughing, breathing, vocal cord movment
When is it best to utilize the ulnar nerve?
onset of recovery
Facial Nerve
lies within the parotid gland
electrodes in front of tragus of ear and below
avoid direct muscle stimulation
-negative electrode placed over nerve
-facial hair contact interference
Better indicator and ND blockade of diaphragm and airway then peripheral muscle
monitor contraction of orbicularis oculi
orbicularis oculi controls
closes eyelid
currugator supercilli
furrows brow
Posterior Tibial Nerve
places electrodes behind medial malleolus of tibia
results in plantar flexion
flexor hallucis brevis muscle
sole of foot
flexes big toe
Peroneal nerve
electrodes on lateral aspect of knee
response= dorsiflexion of the foot
Patterns of Stimulation
single twitch TOF tetanic stimulation Post tetanic stimulation double-burst stimulation
Singel twitch stimulation
single pulse delivered every 10 seconds at 0.1-1Hz
increasing block results in diminishing response
Twitch heights will be normal til 75% Nachr receptors are blocked
90% no twitch
TOF
most common
4 repetitive stimuli
twitches progressively fade as relaxation increases
2Hz every 0.5 seconds for 5 seconds
ration of responses to 1st adn 4th are sensitive indicator of ND relaxation
Loss of 4th twitch
75% receptors blocked
Loss of 3rd twitch
80% of receptors blocked
Loss of 2nd twitch
90% of receptors blocked
Clinical relaxation requires
75-95% block
Depolaring NM
every twitch will be same height
Partial NMB
inversely proportional to degree of block
Tetanic Stimulation
tetany at 50-100Hz
-50 Hz Q5seconds evoked tension approximates tension developed during maximal voluntary effort
in presence of NM Relaxants, fade occurs
sustained response occurs when TOF >70%
Post Tetanic Count
apply tetanus @ 50Hz for 5 seconds
wait 3 seconds
apply single twitches every second up to 20
# of twitches inversely related to depth of block
When is post tetanic count useful?
when all twitches are suppressed
Double Burst Stimulation
less painful than tetany
more sensitive than TOF for visual evaluation of fade
DBS3,3
3 short 50 hz impulses followed by 750msec by another 3 burst
PNS method during Induction
Single twitch
TOF
PNS method intraop
TOF
Post tetanic cound
PNS method for Emergence
TOF
double burst stimulation
Relative Sensitivities of muscle groups to ND muscle relaxants
Most sensitive: extraocular pharyngeal masseter adductor pollicis abdominal rectus Orbicularis oculi diaphragm vocal cord- most resistant (least sensitive)
Orbicularis occuli measures
onset
Adductor pollicis measure
recovery
In TOF, 1 of 4 twitches indicates reversal will be
as long as 30 minutes
In TOF, 2-3 twitch indicates reversal will be
10-12 minutes following a long acting relaxants, 4-5 minutes after immediate relaxants
In TOF, 4 of 4 twitches indicates
adequate recovery within 5 minutes of neostigmine, within 2-3 minutes of edrophonium
Limitations of NM monitoring
responses may appear normal despite receptor occupancy
wide variabiltiy in evoked responses, some exhibit weakness at TOF ration of 0.8-0.9
valves of adequate recovery do not guarantee adequate ventilatory function or airway protection
perioperative hypothermia increases skin impedence, limiting interpretation of evoked responses
Unreliable signs of clinical recovery
sustained eye openign tongue protrusion arm life to opposite shoulder normal tidal volume normal or near normal vital capacity max insp pressure <40-50cmH20
Most reliable signs of clinical recovery
sustained headlift x 5 seconds
sustained leg lift for 5 seconds
sustained handgrip x 5 seconds
max inspiratory pressure 40-50 cm H20 or >
Quantitative Nerve Monitoring
device that quantifies the degree of NM blockade
reliable, accurate, objective
post stimulation, muscle response objectively quantified
Acceleromyography (AMG)
piezoelectric sensor measures muscle acceleration (voltage generated upon muscle contraction)
Electromyography (EMG)
muscle action potentials recorded, electrical activity proportional to the force of contraction
- more specific then mechanical
Kinemyography
quanitifies muscle movement with motion sensor strip containing piezoelectric sensors
Mechanomyography
detects contraction force, converts to electrical signal, signal amplitude reflects contraction strength
Phonomyography
muscle contraction produces low-frequency sounds, calculates muscle response
Bispectral Index Score
used to assess depth of anesthesia (optional) EEG signal index ranges from 0-100 100=awake CNS >70 greater recall risk 40-60 general anesthesia 0= isoelectic EEG
Advantage of BIS score
reduced risk of awareness
better management of responses to surgical stimulation
faster wake up (controversial)
more cost effective use of anesthetics
BIS readings are affected by
electrocautery EMG pacer spikes patient movement #s asosciated with reduced risk of recall levels >70 associated with less recall
Cerebral Oximetry
assess cerebral oxygen saturation using near infrared spectrophotometry (NIRS)
noninvasive monitor
detects decreases in CBF in relation to CMRO2
intensity difference between transmitted and received light, determines regional oxygen saturation (similar to oximetry and Beer lambert law
light source adheres to forehead, light transmits through tissue adn cranium
