Invasive Monitoring Flashcards
What does Hypothermia does to latency?
What does Hyperthermia does to amplitude?
◦ Hypothermia increases latency
◦ Hyperthermia decreases amplitude
What does SSEP tests monitors?
SSEP tests only motors dorsal column (Sensory)
NOT MOTOR
Distance to the junction of vena cava and right atrium from cannulation Sites
What are the distances in cm?
Subclavian
Right / Lef IJ
Femoral
Right / left median basilic
How much is one marking?
10
What CVP waveform would represent diastole?
Where is the start of systole?
The Y descent probably will be dominant in diastole
The A waveform is the start of systole
What type of CVP waveform will you see in tricuspid regurgitation?
The right atrium gains volume during systole - so the “c” and “v” wave is much higher
The right atrium “sees” right ventricular pressures and the pressure curve becomes “ventricularized”
What does an overdamped system means?
What does it overestimate?
What does it underestimate?
Overdamped system: settles to baseline slowly without oscillating
Underestimates the systolic and overestimates the diastolic
You expect your arterial system to be overdamped, what do you expect your map to be?
What if your system is underdamped?
with both systems, MAP is usually accurate
SSEP (Somatosensory evoked potentials)
What does it reflect?
- SSEP (somatosensory evoked potentials): electrophysiologic responses of nervous system to the application of discrete stimulus at a peripheral nerve anywhere in the body
- SSEP’s reflect the ability of a specific neural pathway to conduct an electrical signal from the periphery to the cerebral cortex
Central Venous Anatomy
What do we worry about when cannulting a patient?
We worry about accidentally puncturing the apex of the lungs
- that can lead to pneumothorax
- always ASPIRATE when putting a needle in
Absence of an A wave on the CVP waveform might mean?
AFIB
Hemothorax happens in what approach?
what causes this?
Hemothorax with subclavian approach due to subclavian artery laceration
A short time in diastole such as in tachycardia may cause?
it may also cause what waves to merge?
short “y” descent
tachycardia can make “v” and “a” waves to appear to merge
Identify the relation between the a line waveform and the EKG
what complication do we worry about with IJ approach?
CAROTID PUNCTURE
What happens to the CVP waveform on cardiac tamponade?
- CVP becomes monophasic with a single, prominent “x” descent with a muted “y” descent
- Similar to pericardial constriction but not exactly the same
Where do we measure the CVP monitoring?
why?
What is the normal range?
The CVP monitoring is measured at the level of tricuspid valve
At this level, hydrostatic pressures caused by
changes in body position almost zero
Normal 1- 15 mmHg
most common cannulation sites of thr areterial line
Radial
What cvp waveform will you associate with a junctional rhythm?
LARGE/ CANNON “A” wave
–> also seen with A-V dissociation , ventricular pacing
What does 50% or greater decrease in amplitude may indicate in SSEP monitoring?
Amplitude: measured from baseline to peak. Any decrease in amplitude (50% OR greater) may indicate disruption of the sensory nerve pathways.
What does the A wave represent?
What does the Y descent represent?
What does the V wave represent?
Waveforms:
A wave: follows p wave on EKG
- Due to atrial contraction
- Absent in Afib and exaggerated in junctional rhythms
C wave: due to triscuspid valve elevation during early
ventricular contraction
X wave: reflects right ventricular ejection, which causes an emptying of blood from the ventricle and a sharp decrease in pressure
V wave: reflects venous return against a closed triscuspid valve
Y wave: reflects triscuspid valve opening, causing blood flow into the ventricle and a decrease in pressure in the right atrium
GIANT V wave that replaces normal c,x,v may mean?
TRICUSPID REGURGITATION
What is the most common complication that we see with a subclavian and low anterior IJ approach?
Pneumothorax
Where does the motor pathway’s get its blood supply
How about the sensory pathway?
- *Motor** pathways: blood supply from anterior spinal artery
- *Sensory pathways:** blood supply from posterior spinal artery
What complication do we worry about with a left IJ site? why?
Thoracic duct puncture
Thoracic duct wraps around Ij as high as 3-4 cm above the sternal end of clavicle
What changes in latency indicates a disruption of the sensory pathway?
Latency: time from onset of stimulus to occurrence of a peak. Any increase in latency (10% or greater) may indicate disruption of the sensory nerve pathways.
How long can the spinal cord tolerate ischemia before we lose SSEPs?
The SPINAL CORD can tolerate ISCHEMIA for 20 minutes before SSEP’s are lost
What does these arterial waveforms represent
slope of upstroke –>
Respiratory variations –>
Slope of downstroke –>
Dicrotic notch –>
Arterial
upstroke represents myocardial contactility
respiratory variations –> large variations maybe indicative of hypovolemia
Slope of downstroke–> SVR
Dicrotic Notch –> AV closure
What causes decreases in Amplitude?
Hypoxia
Hypotension
Anemia if Hct <10% –> decreased amplitude (probably R/T tissue hypoxia)
What causes an INCREASE in Latency?
Hypothermia
Hypocarbia –> increased latency with ETCO2 <25
Anemia if Hct <15%
What can Bradycardia do to your CVP waveforms?
Causes each wave to become more distinct
“h” wave may become evident – plateau wave in mid or late diastole
PAP monitoring
What are the distances from the right IJV to the distal cardiac and pulmonary structure?
What is the most life-threatening complication of PAP insertion?
PA RUPTURE
What does an underdamped system represent?
What does it overestimate?
What does it underestimate?
Underdamped system: continues to oscillate for 3-4 cycles
Overestimates the systolic and underestimates the diasolic BP
What is the leading complication of placing PAP catheters?
Catheter-related bloodstream infection (CRBSI) ranks as third most common nosocomial infection in ICU’s
A short PR interval can cause?
tachycardia
- “a” and “c” waves to fuse
- short y descent [shorten time spent in diastole]
- v and a waves appear to merge
What do you expect the waveform of an arterial line of a patient that has a low EF ?
Slurred upstroke
- patient that has a low contractility
What does VAA do to amplitude and latency?
- All VAA cause dose-dependent decreases in amplitude and increases in latency
- The above can be worsened with the addition of N2O
- If possible, bolus injections of drugs should be avoided, especially during critical stages of surgery
- Continuous infusions are preferable
What would you expect to see on the arterial waveform of a patient on hypertensive crisis?
Slurred downstroke –> indicative of increased SVR/ afterload
This is inline with your thumb?
Where do arteries anastamose?
Radial Artery
Arteries anastamose via 4 arches in the hadn and wrist (superfcial and deep parmal arches)
What CVP waveform do you see in tricuspid stenosis?
- Mean CVP is elevated
- “a” wave is usually prominent as it tries to overcome the barrier to emptying
- “y” descent muted as a result of decreased outflow from atrium to ventricle
What type of waveform would I expect as the site of cannulation moves from the aorta peripherally to the arterial trea?
What causes the pressure changes?
How much would the SBP in the radial artery compared to the pressure of aorta?
exaggerated waveform
Pressure changes result from decrease in arterial wall compliance and from resonance
SBP in radial aretery may be as much as 20-50
What are the Normal Pressure ranges?
Right Atrial CVP
Right Ventricle
