Cardiac Output monitoring Flashcards

1
Q

What is the normal CO in dogs and cats?

A

120-200 mL/kg/min

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2
Q

What is the cardiac index?

A

CO divided by the animal’s body surface area in L/min/m2

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3
Q

Explain the Frank-Starling principle and curve

A

Explains that stroke volume increases as cardiac end-diastolic volume increases, i.e., more blood means increased stretych of cardiac myofibrils –> improves contractility

myofibrils have a maximal stretch –> when starling-curve reaches plateau, i.e., fluid-unresponsive state

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4
Q

List 5 differentials for elevated CVP

A
  • increased blood volume
  • poor ventricular function
  • increased vascular tone
  • increased intrathoracic pressure (PPV)
  • increased intraabdominal pressure
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5
Q

Explain the Fick’s principle of cardiac output measurement

A

Considered the orignial gold standard

goes by the principle that VO2 must equal CO x (CaO2 - CvO2)

can rearrange this equation to:

CO = VO2 / (CaO2 - CvO2)

CaO2 and CvO2 measured (CvO2 with mixed venous sample ideally via pulmonary atery catheter) - in volume/volume (mL/L)

VO2 - determined by measuring inspired by expired volume of O2 per min (mL/min)

–> L/min CO

modified technique with CO2 measurement, teremd “noninvasive CO mon.”

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6
Q

Name 3 examples of indicators used for indicator dolution method for CO monitoring

A
  • lithium
  • cold saline (thermo dilution)
  • dye
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7
Q

What are the two different methods of indicator dilution methods for CO monitoring? Describe the methods

A

Transpulmonary thermodilution
- patient receives indicator into bloodstream (e.g., jugular vein)
- indicator is sampled downstream (e.g., femoral artery)
- time-dilution curve of indicator found in the downstream sample is generated - used to derive CO

Pulmonary artery thermodilution
- patient receives indicator into the RA
- indicator is sampled downstream in the pumonary artery

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8
Q

Explain pulse contour analysis

A

Arterial blood pressure waveform is measured and analyzed in conjunction with traditional CO monitoring, i.e., thermodilution (PiCCO) or lithium dilution (LiDCO).

The traditional CO measurement is used for calibration - then software uses pulse contour analysis of the arterial waveform for continued CO monitoring

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9
Q

Describe Pulse Pressure Analysis for CO monitoring

A

Similar to pulse contour analysis but does not require a traditional dilution technique for callibration

software uses variation in arterial blood pressure waveform to calculate SV –> is then multiplied by HR to get CO

found to be unsuitable in anesthetized dogs compared to transpulmonary or pulmonary artery thermodilution

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10
Q

Describe how CO can be estimated with transthoracic echocardiography

A

SV calculated from:
- velocity of blood flow in the left ventricular outflow tract
- x cross-sectional area of the left ventricular outflow tract

… x HR = CO

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11
Q

Explain how CO measured using esophageal Doppler

A

esophageal doppler measure blood flow velocity in the descending aorta x aortic diameter …. = SV

… x HR = CO

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12
Q

What is USCOM?

A

Ultrasound CO monitor

  • uses transortic and transpulmonary blood flow tracings to then calculate CO and SV

Problem: standard aortic diameter is pre-dermined in the machine (for adult and pediatric human patients) –> would need to first peform an echo in veterinary patients and enter aortic diameter into the machine

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13
Q

What is bioimpedance and bioreactance?

A

Bioimpedance
- applies high-frequency electric current of a known amplitude and frequency across the thorax
- amount of resistance/impedance varies in relation to amount of fluid in the thorax

Bioreactance
- electric current of known frequency is applied across the thorax
- measures reactance/frequency or phase shift of the electric current
- delay in phase shift = increased SV

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14
Q

Describe a traditional fluid challenge using CVP and how to interpret its results

A

CVP measurement whil giving 20 mL/kg isotonic crystalloids or 5 mL/kg colloids

normal blood volume –> CVP should increase by 2-5 cm H2O and return to baseline within 15-20 min

fluid overload/ poor cardiac function –> CVP increased by > 5 cm H2O

fluid responsive –> CVP does not increase or decreases to baseline quickly

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15
Q

Where should the tip of a central venous catheter used to measure CVP be located?

A

within the vena cava, just proximal to the right atrium

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