Monitoring Flashcards
What is dynamic compliance?
Compliance of the lung and chest wall DURING MOVEMENT
What is static compliance?
Lung compliance while there is no airflow. It’s a function of the natural tendency of the lung/chest wall to collapse
What is plateau pressure?
Pressure in the small airways and alveoli after the target TV has been delivered.
There is NO airflow at this time, so it’s value is NOT a function of airway resistance. It instead reflects the elastic recoil of lungs and thorax during the inspiratory pause –> at this point the pressures of the lung and chest wall wanting to collapse and the pressure within the lung are equal.
Risk of barotrauma exists when plateau pressures are > ____
35cmH2O
O2 blood absorbs this wavelength
Deoxygenated blood absorbs this wavelength
O2 = 990nm (near-infrared) Deox = 660 (red)
Higher O2 content = higher wavelength
Pulse oximetry is based on this Law
Beer-Lambert:
- related to the intensity of light trimmed through a solution and the concentration of the solute within the solution.
Can pulse ox be used to look at pulse pressure variation (PPV%)?
Yes
Does pulse ox account for O2 dissolved in blood?
No
Does jaundice affect pulse ox readings?
No
Methemoglobin
Fe3+
Absorbs 990 and 660 equally
Thus, it falsely underestimates SpO2 when sat is >85%
Falsely overestimates SpO2 when
Carboxyhemoglobin
CO-Hbg (carbon monoxide)
Pulse Ox reads CO-Hgb and O2-Hgb the same. Thus, it overestimates saturation.
This is the most common method of analyzing exhaled gas in the OR
Infrared absorption
How is O2 analyzed?
O2 does not absorb infrared light, so it must be measured by electrochemical means (Galvanic Cell or Clark Electrodes) or paramagnetic analysis
The ideal BP bladder WIDTH is ___% the circumference of the pt’s arm
40%
The ideal BP blade LENGTH is ___% the circumference of the pt’s arm
80%
Do a-lines measure pressure at the site of insertion or level of transducer?
Level of transducer
Most common complication while obtaining CV access
Dysrhythmias
This is the classic presentation of PA rupture
Hemopytsis
This is the point of phlebostatic access
Mid anteroposterior level at 4th intercostal space
Where in the respiratory cycle should CVP be measured?
End expiration
Meanings of high and low CVP
Low CVP is easy: either transducer is too high or the pt is hypovolemic.
If CVP is too high, could be a million things related to
1) Hypervolemia
2) Decreased ventricular compliance
3) Increased intrathoracic pressure
How to manage Mobitz II heart block
Often unresponsive to atropine.
High risk of progression to Third Degree heart block.
Manage with pacemaker (transcutaneous, transvenous, or implantable)
Treatment of third degree heart block
Isoproterenol
Pacing
What is the most common pre-excitation syndrome?
WPW
Two types of WPW
1) Orthodromic
- Most common (90% of cases)
- Narrow complex (Goes thru AV node and his-purkinje system, then tract goes back up through atrium to stimulate AV node again)
- Treatment: Increase the refractory period of the AV node so it won’t be stimulated so frequently by the aberrant pathway.
- -> Vagal maneuvers, amiodarone, adenosine, BBs, verapamil, or cardioversion.
2) Antidromic
- Less common (10%)
- Wide Complex (Abberent pathway goes from SA, accessory pathway, ventricle, AV node, atrium). The his-purkinje system is bypassed, so it’s wide complex)
- Treatment: Increase the refractory period of the aberrant pathway
- -> Procainamide, amiodarone, cardioversion. In this case, DO NO give anything that will prolong AV refractory period –> this will cause the aberrant pathway to be favored and result in Vfib!)
Medications to avoid in Antidromic WPW (AVNRT)
AVOID ALL DRUGS THAT BLOCK CONDUCTION THROUGH THE AV NODE
- Adenosine
- Digoxin
- BBs
- Verapamil
- Lidocaine
- Diltiazem
What are the two safe options for BOTH orthodromic AND antidromic WPW?
Amiodarone and cardioversion
Effect of K+ on the QT interval
Hypokalemia can cause QT prolongation
Only narcotic that prolongs QT
Methadone
What things cause Torsades des Pointes?
POINTES
Phenothiazines (Thorazine)
Other meds (meds that are known to lengthen QT –> methadone, droperidol, halloo, zofran, VAs, amiodarone, and quinidine)
Intracranial bleed (SAH)
No known cause
Type 1 antiarrhythmics
Electrolyte Disturbances (low K+, Mg+, and Ca+2)
Syndromes
Those with chronically prolonged QTc will likely be placed on
BBs like metoprolol
SNS stimulation and precipitate torsades, and BBs are good at blocking the sympathetic response on the heart
Pacemaker designation positions
Position 1 = Chamber paced
Position 2 = Chamber sensed
Position 3 = Response to sense native cardiac activity
Position 4 = Programmability of the pacemaker
Position 5 = Indicates that the pacer can pace multiple sites
Codes for position III in pacemaker designation
Position III = pacer response to sensed native cardiac activity
0 = None T = Triggered (triggers the pacer to fire) I = Inhibited (tells the pacer NOT to fire) D = Dual (If native activity is sensed, the pacer does NOT fire. If no native activity is sensed, then the pacer WILL fire)
Codes for position IV in pacers
Position 4 = Programmability
0 = None R = Rate modulation
This describes the ability to adjust HR in response to physiologic need
Effect of magnet on Pacemaker
Changes it to asynchronous mode
Effect of magnet on ICD
Prevents shock delivery
Effect of magnet on Pacer/ICD combo
Suspends ICD shock
NO EFFECT on pacemaker
Elecromagnetic interference (EMI) can interfere with pacer function. EMI can often come from
Electrocautery
- Worse with coagulation setting than with cutting setting
- Worse with monopolar than bipolar
- If surgeon insists on monopolar, tell them to use it in short bursts (
Conditions that make the myocardium more resistant to depolarization with pacers
- High and low K+
- Hypocarbia (will cause inward K+ shift)
- Hypothermia
- MI
- Fibrotic tisue buildup around the leads
- Antiarrhythmic meds
Is lithotripsy contraindicated in those with pacer?
No, but the beam should be directed away from the pulse generator
What to do if pacer fails
Have method of backup pacing immediately available
Chemical pacing with isoproterenol, epi, and atropine
A greater than ___% reduction in cerebral oximeter readings suggests a reduction in cerebral oxygenation
25%
Can scalp hypoxia interfere with cerebral oximeter readings?
Yes
Do cerebral oximeters detect pulsatile flow?
No
Order of EEG waveforms with most awake to deepest
BAT-D
Beta Alpha Theta Delta Burst suppression Isoelectric
Amount of lag in BIS
About 20-30 seconds
BIS is less accurate in this population
Children
General anesthesia range for PSI
Similar to BIS, but uses different number
GA is 25-50
Macroshocks and their effects
1mA = threshold for touch 5 = max harmless 10-20 = Let go current 50 = LOC 100 = Vfib!
Microshock
10uA = max allowable leak in OR 100uA = Vfib!
For an electrical shock to occur in the OR, two faults must occur
1) After the first fault, the system becomes grounded
2) After the second fault, the circuit is complete and shock occurs
What is the function of the line isolation monitor (LIM)?
To alert OR staff of the first fault
When the alarm sounds, the last piece of equipment to be plugged in should be unplugged
LIM will alarm when ____mA leak current is detected
2-5mA
