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BCPS Exam > Critical Care: Hemodynamic Parameters > Flashcards

Critical Care: Hemodynamic Parameters Flashcards

1
Q

Arterial blood pressure is the product of _____ and _____

A
  1. Cardiac Output (CO)

2. Resistance to flow (systemic vascular resistance, SVR)

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2
Q

Cardiac output is the product of ____ and _____. What are the units?

A
  1. Cardiac output (mL of blood pumped per minute) is product of
  2. Stroke volume (mL of blood ejected from left ventricle per beat)
  3. Heart rate (beats per minute)
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3
Q

Stroke volume is determined by what 3 factors?

A
  1. Preload (amount of blood available to eject)
  2. Afterload (resistance to ejection)
  3. Contractility (amount of force generated by the heart)
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4
Q

Three different ways to express arterial blood pressure?

A
  1. Systolic BP (SBP)
  2. Diastolic BP (DBP)
  3. Mean arterial pressure (MAP)
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5
Q

MAP is an indication of _____ perfusion pressure

A

Global perfusion pressure

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6
Q

A MAP of at least ___ is necessary for adequate cerebral perfusion in most patients

A

65 mm Hg

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7
Q

MAP can be calculated by equation, but what is a more timely and accurate what to get it?

A

Direct measurement from an arterial line

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8
Q

Define preload

A

Ventricular end-diastolic volume

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9
Q

Due to the Frank-Starling mechanism, preload is one of the three main factors that directly influences _____

A

Stroke volume

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10
Q

List two common measures of preload and two new measures of preload

A 
Common:
1. Central Venous Pressure (CVP)
2. Pulmonary Capillary Wedge Pressure (PCWP) or Pulmonary artery occlusion pressure (PAOP)
New:
1. Stroke volume variation (SVV)
2. Pulse pressure variation (PPV)
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11
Q

Central Venous Pressure (CVP) is the pressure in the _____ at the point of blood returning to the _____.

A

CVP is the pressure in the

  1. Vena cava at the point of blood returning to the
  2. right atrium
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12
Q

CVP may reflect _____ status, but is a poor predictor of ______ responsiveness

A

CVP may reflect

  1. Volume status, although it is a poor predicator of whether a patient’s low
  2. blood pressure (volume responsiveness) will improve with an increase in intravascular volume.
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13
Q

Historically, a CVP of __ to ___ mm Hg has been considered optimal for a patient with hypoperfusion from sepsis

A

8 to 12 mm Hg

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14
Q

A higher CVP goal of ___ to ___ mm Hg has been considered optimal for patients on a ventilator due to increased ______ pressure.

A

12 to 16 mm Hg due to increased intrathoracic pressure

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15
Q

Data on the use of CVP is _______. It is known to be a poor predictor of _______ and _______

A
  1. Lacking
  2. Volume responsiveness
  3. Volulme status
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16
Q

CVP values at the extremes and volume status?

A
  1. Less than 2 mm Hg reflect hypovolemia

2. Greater than 18 mm Hg reflect hypervolemia

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17
Q

PCWP or PAOP is the pressure when __________________

A

Pulmonary capillary wedge pressure or pulmonary artery occlusion pressure is the pressure when a balloon is inflated (wedged) in one of the pulmonary artery branches.

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18
Q

Why might PCWP be a more accurate measure of volume status than CVP?

A

The pulmonary artery branches are closer to the left ventricle than the inferior vena cava.

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19
Q

Measuring preload: What’s used to measure right heart? What’s used to measure left heart?

A
  1. Central Venous Pressure (blood returning to heart from vena cava) used to measure right atrial pressure; estimate right ventricle preload.
  2. Pulmonary artery occlusion pressure (aka pulmonary capillary wedge pressure) blood returning to heart from pulmonary vein.
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20
Q

Describe the frank starling mechanism and frank starling curves. (e.g. why is there a family of curves)

A
  1. Cardiac output is directly proportional to end-diastolic volume (i.e. preload).
  2. The proportionality constant (e.g. slope of the curve) is dependent on contractility (i.e. inotropy, the force pushing with) and afterload (i.e. resistance, the force pushing against.)
  3. Cardiac output represented by a family of curves. There is a family of curves. You slide up a curve based on preload, and you shift between curves (e.g. change slope of curve) based on inotropy and afterload.
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21
Q

Why has the utility of pulmonary artery occlusion pressure been diminished recently?

A

The use of pulmonary artery catheters has diminished in favor of bedside echocardiography.

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22
Q

What are two examples of functional hemodynamic monitoring used to assess a patient’s position on the Starling curve and their fluid responsiveness?

A
  1. Stroke volume variation (SVV)

2. Pulse pressure variation (PPV)

23
Q

The simplest measurement of adequate oxygen delivery is assessment of _____ function

A

Assessment of end organ function

24
Q

List three signs of end organ dysfunction that may be first signs of inadequate oxygen delivery

A
  1. Changes in mental status
  2. Decreased urine output (less than 0.5 ml/kg/hour)
  3. Cold extremities
25
Q

What is the driving force behind oxygen delivery?

A

Blood pressure

26
Q

The organ’s ability to autoregulate blood flow is generally lost at MAP less than ___ mm Hg

A

65 mm Hg

27
Q

List four indicators of oxygen delivery

A
  1. Assessment of end organ function
  2. Blood pressure
  3. Lactic acid
  4. Venous oxygen saturation
28
Q

Why is lactic acid an indicator of oxygen deliverY?

A

Lactic acid is formed during anaerobic metabolism, and during states of hypoperfusion, the tissues receive less blood and therefore less oxygen.

29
Q

In shock states, ____ clearance can be used as a therapeutic end point

A

Lactate clearance

30
Q

The oxyhemoglobin saturation of venous blood returning to the right atrium is ____%. Normal arterial oxygen saturation is ___%. This idnicates that the normal oxygen extraction ratio is ____%.

A
  1. Venous blood: 70-75%
  2. Arterial blood: 99-100%
  3. Oxygen extraction ratio: 25-30%
31
Q

A decrease in venous oxygen saturation occurs when when there is an increased extraction ratio because:

A

Decreased oxygen delivery to hemoglobin (e.g. anemia, carbon monoxide poisoning) than what is being consumed by cells.

32
Q

Two ways to measure venous oxygen saturation

A
  1. Central venous oxygen saturation (ScvO2)

2. Mixed venous oxygen saturation (Svo2)

33
Q

Where is Scvo2 measured?

A

Superior vena cava

34
Q

Where is Svo2 measured?

A

Pulmonary artery

35
Q

Which is higher, Scvo2 or Svo2, and why?

A

Svo2 is about 5% lower than Scvo2 because it has mixed with venous blood from coronary sinus.

36
Q

Hypoperfusion may still be present in patients with a normal Svo2 but who have an impaired ________. Give an example

A
  1. Oxygen extraction

2. Sepsis

37
Q

How can you measure hypoperfusion in a patient for whom measurement of venous oxygen saturation is not reliable (e.g. sepsis)

A

Lactate concentration

38
Q

Normal range for: SBP

A
  1. Systolic BP

90-140 mmHg

39
Q

Normal range for: DBP

A
  1. Diastolic BP

60-90 mmHg

40
Q

Normal range for: MAP

A
  1. Mean Arterial Blood Pressure

70-100 mmHg

41
Q

Normal range for: SVR

A
  1. Systemic vascular resistance

800-1200 dynes/s/cm5

42
Q

Normal range for: HR

A
  1. Heart rate

60-80 beats/min

43
Q

Normal range for: CO

A
  1. cardiac output

4-7 L/min

44
Q

Normal range for: CI

A
  1. cardiac index

2. 5-4.2 L/min/m2

45
Q

Normal range for: SV

A
  1. stroke volume

60-130 mL/beat

46
Q

Normal range for: PCWP or PAOP

A
  1. Pulmonary capillary wedge pressure or Pulmonary artery occlusion pressure
    5-12 mm Hg
47
Q

Normal range for: CVP

A
  1. Central venous pressure

2-6 mm Hg

48
Q

Normal range for: lactic acid

A

Less than 1 mmol/L

49
Q

Normal range for: Scvo2

A
  1. Central venous oxygen saturation

70-75%

50
Q

Calculation for Mean Arterial Blood Pressure?

A

1/3 SBP + 2/3 of DBP

51
Q

Calculation for Systemic Vascular resistance?

A

[(MAP-CVP)/CO] times 80

52
Q

Calculation for Cardiac Output?

A

HR * SV

53
Q

Calculation for Cardiac Index?

A

CO divided by BSA

54
Q

Calculation for Stroke volume?

A

CO/HR

BCPS Exam (34 decks)

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