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Cardiovascular > Hemodynamic monitoring > Flashcards

Hemodynamic monitoring Flashcards

1
Q

Describe the set-up for invasive arterial blood pressure monitoring

A

(summarized)
- arterial catheter
- non-compliant tubing with 3-way stopcock
- transducer (at the level of right atrium) connected to monitor
- bag of 0.9%NaCl with heparin 1 unit/mL kept pressurized at 300 mHg and running at 3 mL/h connected to circuit to prevent backflow and maintain patency
- all lines primed / flushed with the heparinized saline before connection

Need to level and zero the circuit

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2
Q

Name complications of invasive blood pressure monitoring

A
  • Hemorrhage
  • Infection
  • Distal limb necrosis
  • Thrombosis
  • Excessive heparinization
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3
Q

How to assess damping with invasive arterial pressure monitoring

A

Dynamic response / square wave test: open fast flush and count oscillations after square wave before return to baseline.

Optimal damping = 1-2 oscillations after square wave, amplitude of each oscillation no greater than 1/3 of previous one and interval between oscillations < 30 msec

Overdamping = no oscillations after square wave

Underdamping = multiple oscillations

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4
Q

How does overdamping influence the arterial waveform? Underdamping?

A

Overdamping -> lower SBP, higher DBP, loss of dicrotic notch

Underdamping -> higher SBP, lower DBP, artifacts on waveform

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5
Q

What are causes of overdamping / underdamping in invasive blood pressure monitoring

A

Overdamping: clot in catheter, catheter agains vessel wall, kinked catheter / tubing, air bubbles in system, compliant tubing

Underdamping: excessively long tubing, multiple 3-way stopcocks

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6
Q

How to calculate pulse pressure variation? What value is associated with fluid responsiveness?

A

PPV (%) = 100*(PPmax-PPmin)/[(PPmax + PPmin)/2]

Values >10% associated with fluid responsiveness, values >13% correlate with hypotension and fluid responsiveness

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7
Q

Explain why peripheral PPV overestimates central PPV

A
  • Forward (or incident) wave travels from the left ventricle to the periphery – its amplitude is based on ventricular contraction and pulse wave velocity
  • Backward (or reflected) wave travels in the opposite direction – generated by reflexion of forward wave
  • Both waves superimpose in order to create the pressure waveform
  • In the aorta, rise of systolic pressure is determined by aortic compliance and SV
  • As the arterial pressure waveform moves into the periphery (more compliant, smaller conduit), the pulse pressure is amplified
  • MAP remains unchanged to mildly decreased
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8
Q

Where should the transducer or the bottom of the manometer be placed for CVP monitoring

A

At the level of the right atrium ->manubrium in lateral recumbency / point of shoulder in sternal recumbency

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9
Q

Draw and explain a CVP waveform

A

a wave = right atrial contraction
c wave = bulging of tricuspid valve
v wave = blood flowing into right atrium
x descent = ventricular contraction / ejection
y descent = emptying of right atrium after opening of tricuspid valve

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10
Q

What is a normal CVP

A

0-5 cmH2O
(/!\ measured in cmH2O)

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11
Q

What do changes in CVP indicate

A

High > 10 cmH2O: volume overload, right sided heart failure, pericardial disease, pulmonic stenosis, marked pleural effusion / pneumothorax

Low < 10 cmH2O: hypovolemia or vasodilation

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12
Q

How will CVP change following a fluid challenge in a hypovolemic patient? Euvolemic? Hypervolemic?

A

Hypovolemic: no change in CVP or mild transient increase

Euvolemic: increase of 2-4 cmH2O and return to baseline within 15 min

Hypervolemic: increase > 4 cmH2O and return to baseline > 30 min

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13
Q

What is the normal CO for dogs and cats

A

Dogs: 125-200 ml/kg/min
Cats: 120 ml/kg/min

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14
Q

What values can be measured or calculated with a Swan-Ganz catheter

A
  • Pulmonary artery pressure
  • Pulmonary artery occlusion pressure (= pulmonary wedge pressure) -> indicates preload to left heart
  • Right atrial pressure (= central venous pressure)
  • CO with thermodilution
  • SvO2 (central venous and mixed venous)

Calculated:
- Cardiac index (= CO/body surface area)
- Stroke volume (= CO/HR)
- Stroke volume index (= SV/body surface area)
- Systemic vascular resistance (= (MAP-RAP)/cardiac index)
- DO2, O2 consumption, O2 extraction

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15
Q

Label this waveform from a Swan-Ganz catheter being inserted and indicate what are the pressures

A

See picture

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16
Q

What is the difference between mixed venous oxygen saturation (SvO2) and central venous oxygen saturation (ScvO2)

A
  • Mixed venous = measured from pulmonary artery
    Normal = 70-75%
  • Central venous = measured from jugular vein / cranial vena cava -> only reflects cranial half of the body (can be a little lower because brain consumes a lot of O2)
    Normal = 65-70%

Usually correlate quite well but in severe shock can vary up to 18% (ScvO2 will be higher than SvO2 because cerebral perfusion is prioritized over splanchnic)

17
Q

What does SvO2 indicate and how can it be used

A

It indicates oxygen extraction by tissues => reflects systemic oxygen balance and cumulative oxygen debt

SvO2 > 70% can be an endpoint of hemodynamic resuscitation.
Low ScvO2 is associated with increased mortality

18
Q

What can lead to erroneous interpretation of SvO2

A
  • Abnormal hemoglobin concentration
  • Hypoxemia (low SaO2)
  • Large difference between SvO2 and ScvO2 in severe shock
  • Impaired O2 extraction by tissues (sepsis) -> falsely elevated
19
Q

For each type of shock (hypovolemic, obstructive, cardiogenic, maldistributive) indicate if CO, contractility, and SVR are increased or decreased

A

Hypovolemic: decreased CO / increased contractility / increased SVR

Obstructive: decreased / normal to increased / increased

Cardiogenic: decreased / decreased / increased

Maldistributive: increased or decreased / increased or decreased / decreased

20
Q

What are limitations of the Fick’s methods of CO monitoring

A
  • Requires intubation (+ ventilation for NICO)
  • Requires pulmonary artery catheter for O2 consumption method
  • Requires rebreathing for CO2 production method (size limitation + issue with pulmonary disease)
  • Not real time
  • Affected by shunting (intracardiac / intrapulmonary)

CO = [Oxygen consumption (VO2) / arteriovenous oxygen difference (Ca-Cv)] x 100

21
Q

List possible complications of Swan-Ganz catheter

A
  • Gas pulmonary embolism
  • Cardiac perforation
  • Pulmonary hemorrhage
  • Arrhythmias
  • Pneumothorax
  • Thrombosis / PTE
22
Q

Name methods of CO monitoring

A
  • Fick’s method (O2 consumption or NICO for CO2 production)
  • Indicator dilution method (thermodilution and lithium dilution)
  • Arterial waveform analysis (pulse contour analysis, pulse pressure analysis = PiCCO, PulseCO)
  • Echocardiography (doppler and non-doppler)
  • Transthoracic ultrasound
23
Q

List methods to assess intravascular volume

A

Static markers:
- Physical exam findings (mentation, HR, pulse quality, MM colour, CRT, temperature, jugular vein distension, urine output)
- MAP
- Shock index
- Lactate
- CVP
- Pulmonary artery occlusion pressure
- Cardiac POCUS (left atrial size, left ventricular size, wall thickness)
- Caudal vena cava diameter

Dynamic markers:
- Any change in static markers following fluid challenge
- Caudal vena cava collapsibility
- Pulse pressure variation, systolic pressure variation, stroke volume variation
- Plethysmographic variability index

24
Q

CVC collapsibility index meaning

A

> 50% suggestive of hypovolemia
<50% suggestive of fluid overload

25
Q

What parameters (other than fluid responsiveness) affect PPV

A
  • Tidal volume
  • PIP and PEEP
  • Patient’s spontaneous respiratory efforts
  • Chest wall compliance (low compliance will increase PPV)
  • Pulmonary compliance (low compliance will decrease PPV)
  • Cardiac disorders (arrhythmias)
  • Right heart failure
  • Intra-abdominal pressure
26
Q

What is the vena cava collapsibility index

A

CVCci = (CVCd max - CVCd min) / CVCdmax

CVC diameter measured throughout inspiration and expiration to measure the index of the difference in diameter

27
Q

What influences the CVC collapsibility index (other than volume status)

A
  • Right-sided cardiac dysfunction
  • Respiratory effort
  • Intra-abdominal effort
  • Pressure artifact
28
Q

What CVC collapsibility index has been associated with fluid responsiveness

A

> 30% in dogs (50% in humans)

29
Q

True or false: patients need to be mechanically ventilated for measurement of CVC collapsibility index

A

False (spontaneous breathing is fine)

30
Q

What happens to CVP, RA pressure, SV, SBP during spontaneous inspiration and expiration?

A

Inspiration:
- CVP falls
- RA pressure falls
- SV decreases
- SBP decreases

Expiration:
- CVP increases
- RA pressure increases
- SV increases
- SBP increases

  • Reversed in PPV
31
Q

In thermodilution, how does the area under the curve relate t CO.

A

See picture

32
Q

A 2021 JVECC paper compared coccygeal and radial artery Doppler blood pressure measurements in sick cats with and without abnormalities in tissue perfusion. What was the conclusion of this study?

A
  • Median coccygeal SBP is significantly greater than radial SBP in sick cats with both normal perfusion and hypoperfusion.
  • Agreement between coccygeal and radial SBP is poor in cats and cannot be used interchangeably.
  • Recommend obtaining SBP from both sites initially and choosing to monitor and trend changes with the one site that correlates most with physical examination findings.

Cardiovascular (8 decks)

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