Intraop Monitoring Flashcards
What type of monitoring are you required to use when propofol is administered during endoscopic procedures?
ETCO2
Crisis management algorithm
COVERABCD
Circulation
Oxygen
Ventilation
Endotracheal Tube
Review monitors/equipment
Airway
Breathing
Circulation
Drugs
Late stage of hypoxia
Cyanosis
Capnometry
Encompasses all means of measuring carbon dioxide
Capnography
The RECORDING of the measurement
Capnogram
The continuous display of CO2 during ventilation
Advantages/ disadvantages of non-diverting monitoring of ETCO2
Minimal sampling time delays, fewer disposable items and don’t require scavenging
Only read CO2 and N2O, increase dead space, greater risk of condensation, added weight can cause disconnect
Diverting CO2 monitoring advantages/disadvantages
Monitor multiple gases, can be used to monitor awake patients, no increase in dead space
Need for scavenging
Point on capnogram with no CO2
End inspiration and very beginning of expiration- comes from anatomic dead space and contains no CO2
2nd phase in capnogram
Upstroke of expiration
Rapid passing of expired gas through upper airways
3rd phase capnogram
Plateau
Records alveoli emptying of CO2
Fourth phase in capnogram
Rapid decrease in CO2 concentration as result of inspired Air
Impact of a large ventilation-perfusion ratio
Means large amount of deadspace=low concentration of ETCO2
V/Q mismatch with small tidal volumes
Also-small tidal volumes (inadequate ventilation) may produce ETCO2 recordings that significantly underestimate arterial CO2
Causes of failure to return to baseline in ETCO2
Inadequate FGF
Depleted CO2 absorber
Causes of increased ETCO2
Increased CO2 production- MH, fever, sepsis
Hypoventilation- COPD, paralysis, CNS depression
Equipment- Absorbent, rebreathing
Causes of Decreased ETCO2
Decreased production- hypotension/volemia, hypometabolism
Hyperventilation- pain/awareness
Equipment- disconnect, esophageal intubation
Defining intraop hyper and hypothermia
Above 38 or below 36
Risk factors for perioperative hypothermia
High ASA
Lengthy surgery
eMobile’s epidural/general
Elderly
Lean body mass
FAILURE TO MONITOR TEMP
Locations considered core temp monitoring
Tympanic membrane
Distal esophagus
Nasopharynx
Pulmonary artery
Maybe bladder
Bladder temp monitoring
Reflects core temp
Invasive/UTI
Pulmonary artery temp monitoring
Reflects core temp
Invasive/PA line
Not reliable if chest is open
Esophageal temp monitoring
Most consider it core
Slight risk of trauma
Inaccurate if too close to stomach
Can’t use in awake patients
Nasopharynx temp monitoring
Probably core
Easy to insert
Trauma/bleeding
Inaccurate if breathing through nares
Tympanic temp monitoring
Most consider it core
Accurate if contact probe used
Easy
Slight trauma risk of the membrane
Ear wax pusher
Axillary
Reasonably core
Easy
Not direct core
Influenced by IV fluids
Easily dislodged
What does an EEG measure?
The brain does NOT emit electrical waves
eeg measures the differences in electrical potentials in groups of neurons between brain regions
Basic components of an eeg
Frequency- duration btwn impulses
Amplitude- mV peak to peak measurement in a vertical plane
Morphology- this seems tricky as waves can be broken down into alpha, beta, delta and theta
2 main reasons eeg is difficult to correlate with patient outcomes
Anesthetic dose related cerebral inhibition
Environmental factors-artifact (manipulation of the brain adds to interpretation complexity)
NIRS
Cerebral oximetry via Near-infrared Spectrometry
Similar to pulse ox-utilized Beer-lambert
Can be impacted by BP, paCO2, blood volume
This is meant to be used as a trend and cannot fully reflect cerebral oxygenation-so no true values for cerebral ischemia
Nervous system structures that protect against retraction
Elastic limit of nerves
Epineurium and perineurium
20%
Indications of cerebral ischemia in EP monitoring
50% decrease in amplitude
10% increase in latency
Is the combination of IA and IV agents additive or synergistic in depressing SSEP waveforms
Synergistic
Anesthetic rec for SSEP monitoring
Narcotic based
TIVA
<0.5 MAC
Paralytics should not affect SSEP
Term for inequality of pupil diameter
Anisocoria
Neuromonitoring that is very resistant to interference
BAEP
Brain stem-auditory
BIS
Bispectral index
Analysis and processing of EEG signals with proprietary algorithm
Numeric between 0-100
40-60 suggests general anesthesia
BIS less than 40 for more than 5 minutes
Increases postoperative mortality
Anesthetic concentrations on evoked potentials
Increased latency
Decreased amplitude
Methemoglobinemia and SaO2
May cause falsely low reading when SaO2 is greater than 85%
May cause falsely high reading if SaO2 is actually less than 85%
Failure of ETCO2 to return to zero
Incompetent expiratory valve
(Or exhausted absorbent)
What does NIRS monitor?
Largely absorption of venous hemoglobin as it does not have ability to identify pulsatilla arterial component
Saturations less than 40% or changes of 25% from baseline are problematic
Why is temperature management becoming a quality indicator for anesthesia? (What does hypothermia cause)
Hypothermia- delayed drug metabolism, hyperglycemia, vasoconstriction, impaired coagulation, increased risk of surgical site infections
Hyperthermia- tachycardia, neurological injury, and vasodilation
Only time you might not use ETCO2
elective C section…
How often are you documenting HR and blood pressure?
Q5
Standard VIII as it applies to ventilators
Audible alarm with disconnect
Low concentration alarm turned on and in use
What does SpO2 analyze?
PULSATILE flow
Pulse oximetry and wavelengths
660- absorbed by deoxyhemoglobin
940- absorbed by oxyhemoglobin
Plethysmographic function of SpO2
Differentiates arterial vs venous flow and gives us heart rate
Variability can indicate fluid status
Spectrophotometric function of SpO2
Allows us to calculate SpO2 from pulsatile flow
ET vs FI
Expired vs Inspired concentration of gas…
Is ETCO2 typically higher or lower than PaCO2
Usually 2-5mmHg lower
What could cause a sudden increase in CO2
Administration of NaHCO3
Release of tourniquet
Increase in pulmonary blood flow
Sudden decrease in ETCO2
Hypotension!
Leakage
Hyperventilation
Curare cleft
Diaphragm, kicking back in
Rebreathing, think absorbent
Cardiac oscillations
COPD
Asthma
Other obstructions
Discuss dipole
Pair of charges moving together….
Positive before negative
Movement toward positive=upward deflection
Isoelectric
Extinguishment of dipole, or a dipole at right angles to the positive electrode
Pathway of cardiac conduction
SA
AV
Bundle of HIS
Bundle branches
Purkinje Fibers
What leads do we commonly monitor and why?
II and V5
90% specific in detecting ischemia
What does lead II give us a view of?
Atria
Korotkoff sounds
Result from turbulent flow in an artery
Oscillometry
Basis of automatic BP cuffs
Sizing NIBP cuff
Bladder width 40% of extremity circumference
Bladder length encircles > or = to 80% of extremity
False low readings of BP come from:
Large cuff
Positioned above heart
False high readings of NIBP come from
Small cuff or loose cuff
Extrinsic compression
2,3 DPG
Facilitates O2 transport via stabilization of deoxyhemoglobin, making it easier to release O2
Bigggg reimbursement measure in PACU
Temp>36
Most significant mechanism of heat loss in the OR
Radiation
-transfer of heat to the environment
Best practice to prevent hypothermia
PRE- warming
When should we warm the OR?
Probably all the time
Mainly in burn, pediatrics and elderly
Most common misuse of BIS monitoring
Need a baseline before you induce anesthesia
BIS awake
80-100
BIS moderate sedation
60-80
BIS general anesthesia
40-60
When will depth of anesthesia monitors not work?
Hypothermia
Hypoglycemia
Acid/base balance abnormalities
Comorbid brain pathology
How much CO2 do we produce
200ml/min
12L/hr
