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Nurs 400;ICU > Critical CV Physiology > Flashcards

Critical CV Physiology Flashcards

1
Q

What is the equation for cardiac output?

A

CO = SV x HR

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2
Q

What is normal stroke volume?

A

Around 70mls; 60-90mls

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3
Q

What is normal cardiac output? Cardiac index?

A

Co = 4- 8l/ min
C.i. = 2.5- 4.5 L/m/m2

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4
Q

How do you assess stroke volume or adequacy of cardiac output in your patient?

A

Using blood pressure

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5
Q

What do each of the blood pressure measurements mean?

A

DBP = the pressure in the vessel at relaxation; circulating volume and arteriolar resistance (normal is 60 -80 mm Hg

PP = amount of pressure each stroke creates in the vessel; created by SV; normal is 30-40

SBP = sum of DBP + PP

Mean arterial pressure = actual perfusion pressure over time
(2xdiastolic) + systolic/3
—minimum map to maintain perfusion is 65mmHg

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6
Q

What is preload? What is the frank-starling law?

A

The stretch created by volume in the ventricles just before they contract- often referred to as filling pressure
—preload is the most important factor in determining SV and therefore CO

Frank-starling law: the more you stretch the myocardial fibers, the stronger they contract… to a point
— overstretching the fibers will produce a lower stroke volume

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7
Q

What factors affect preload?

A

Circulating blood volume
Venous return
-atrial kick
-filling time
-vascular tone (squeeze factor)
-intrathoracic pressure (more pressure in the thoracic
Cavity means decreased venous return)
Ventricular compliance and contractility

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8
Q

What does low preload indicate about your patient? What are interventions?

A

Low preload= decreased venous return and Hypovolemia
It will decrease both SV and CO

Interventions:
Give fluids
Vasopressors

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9
Q

What does high preload indicate about your patient? What are interventions?

A

High preload = hypervolemia and decreased ventricular compliance
It will decrease strove volume and cardiac output, creating pulmonary congestion

Interventions:
Diuretics
Vasodilators
Ultrafiltration, dialysis, fluid removal

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10
Q

What is afterload?

A

The force ejection must oppose ( vascular resistance)
—afterload is the major factor affecting myocardial workload and myocardial oxygen demand

Diastolic blood pressure measures afterload

In low afterload, the same preload will produce a higher stroke volume
In high afterload, the same preload will produce a lower stroke volume

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11
Q

What factors affect afterload?

A

Value function- stenosis or atherosclerosis
Vascular tone
-vascular health/condition
- ANS stimulation
- medications like vasodilators, ACE/ARB, calcium channel blockers

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12
Q

What does low afterload indicate about a patient? Interventions?

A

Low afterload= vasodilation
Decreased blood pressure, low preload, decreased blood flow

Interventions:
Vasopressors
Fluids

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13
Q

What does high Afterload indicate about a patient? Interventions?

A

High afterload= vasoconstriction or value stenosis
Myocardial workload will increase
Interventions:
-vasodilators
- treat aggravating factors such as pain or anxiety

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14
Q

What is contractility? What factors affect contractility?

A

Contractility = force of muscular contraction-inotropy
Better the contraction, the higher the SV… To a point

Factors affecting:
-preload
-Afterload
- muscular ability
-viable muscle mass
- oxygen supply/demand ratio
– myocardial metabolic state
-_ neurohormonal influences

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15
Q

What does low contractility indicate? Interventions?

A

Low contractility= preload is too high or too low, Afterload is too high or too low, ventricular failure
Decreased stroke volume and cardiac output leading to pulmonary congestion

Interventions:
-Optimize preload
- optimize Afterload
-Optimize 02, ph, electrolytes, coronary circulation
- inotropes it necessary
- mechanical assist device it needed to maintain life

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16
Q

What are clinical assessments that tell us about preload (fluid status)?

A

Meds, physical findings (skin, mucous membranes, edema, lung sounds)

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17
Q

What are the direct measurements of preload?

A
  1. Volume in the ventricle at the end of diastole
    - known as RV preload = RVEDV and LV preload= LVEDV
  2. Pressure in the ventricle at the end of diastole
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18
Q

How is pressure (preload) measured?

A

Measuring the pressure in the atrium at the end-diastole.
- rv preload (RAP or CVP) is measured via central venous catheter (CVC)
- LV preload (LAP or PAOP) is measured via Pulmonary artery catheter (PAC)

19
Q

Which of the direct measurements of preload is the most accurate?

A

PAOP (pulmonary artery occlusion pressure)
- but it has a poor risk/benefit ratio

20
Q

What does PAOP measure?

A

LV preload

21
Q

What is a central venous catheter and what does it measure?

A

Catheter inserted via subclavian, jugular, or femora vein
Measures right atrial pressure (RAP aka CVP) and RVEDP
- also used as an indicator of LVEDP

Normal RAP (CVP) = 2-8 mmHg (8-12 cm H2O)

22
Q

What is a pulmonary artery catheter (PAC)? What values does it measure?

A

A catheter inserted into subclavian, ij, or femoral vein. Measures pulmonary artery pressures and cardiac output

Values:
RAP
PA Systolic (PAS)
PA Diastolic (PAD)
PA Occlusion Pressure (PAOP)
—measures LV preload

23
Q

What is wedging?

A

In a pulmonary artery catheter, it uses pulmonary capillary wedge pressure (PCWP) to measure LVEDP
Catheter goes up the pulmonary artery towards the lung to measure the pressure on the left side of the heart

24
Q

What are complications of a central line?

A
  • Electrical hazards, infection, pneumo/hydrothorax
    Circulatory impairment
    -hemorrhage: dislodgement, disconnect, open stopcock
  • air embolism: air sucked in and occludes rr outflow leading to circulatory collapse (50% mortality)
    ** turn on left side immediately **
    -Pulmonary embolism

Ventricular irritability (cath too long, insertion or displacement problems )

25
Q

How do you assess preload responsiveness?

A

Passive leg raise: reversible increase in venous return of about 300mls blood Bolus that lasts 2-3 min
- if BP improves, they’re fluid responsive

26
Q

What is an arterial line? What does it measure?

A

Line that enters through the radial or femoral artery
Gives direct, continuous BP values
-, DBP,sbp, map

27
Q

What are some complications of arterial lines?

A
  • Electrical hazards and infection
    Circulatory impairment
    Hemorrhage: disconnect, dislodgement
    -Peripheral limb ischemia: embolism, vasospasm
    Radial nerve palsy
28
Q

What is contractility?

A

The force of muscular contraction (inotropy)

29
Q

What factors affect contractility?

A

Preload
Afterload
Muscular ability
-Viable muscle mass
- oxygen supply/demand ratio
- myocardial metabolic state
-Neuro hormonal influences

30
Q

What are the direct measurements of contractility?

A

Ejection fraction using echo or cardiac cath
-Ratio of SV to end diastolic volume (% ejected)

Cardiac output and cardiac index

Stroke work index (LVSWI or RVSWI)
- must sensitive indicator!
-Requires PAC, special artenalline, or biopedance device

31
Q

Physiological symptoms of low cardiac output

A

Decreased heart rate or way too high heart rate
Decreased stroke volume

Preload will be decreased or increased too much
Afterload is increased or decreased so much that preload is low
Contractility will be decreased

32
Q

What are physical assessment findings of low cardiac output?

A

Low BP
LowCO/CI
Tachycardia
Metabolic Acidosis from low tissue perfusion

33
Q

Physiological changes from high cardiac output

A

Increased heart rate
Increased stroke volume

Increased preload (to a point)
Decreased Afterload (to a point)
Increased contractility

34
Q

Physical assessment findings for high cardiac output

A

High BP
Bounding pulses
Flushed, warm skin

35
Q

What components are blood flow made up of?

A

Pressure gradient/resistance

Pressure gradient creates flow
Resistance impedes flow

36
Q

What is critical closing pressure?

A

The point at which the vessel collapses and flow stops

37
Q

How is tissue perfusion clinically evaluated?

A

Map: it is a determinant of perfusion but not an indicator or guarantee of adequate perfusion

Physical findings:
- capillary refill
- skin color
- skin temp

38
Q

What are direct measurements of tissue perfusion?

A

Tissue oxygenation (invasive measurement)
Serum lactate (lactic acidosis = tissue breakdown)
Organ function:
- bowel movement
- bun, Cr
-Loc

39
Q

Why do you level the invasive hemodynamics monitor?

A

The transducer air/fluid interface must be level with the heart
-Eliminates the effects of hydrostatic forces on the measured pressures

Must be level with the phlebostatic axis

40
Q

Where is the phlebostatic axis?

A

At the level of the left atrium
4th ICS an 1/2 the AP diameter

41
Q

When should you level the transducer system?

A

Relevel with any change in the patient’s position

42
Q

What is the second step in setting up the transducer system?

A

Zeroing the system
Open the transducer to air the “zero” the display
This calibrates the equipment to atmospheric pressure

43
Q

What is the third step in setting up the transducer system?

A

Fast-flush square wave test
To test the accuracy of the system to reproduce pressures

Should do this at the beginning of each shift

44
Q

What are the receptors of the sympathetic nervous System?

A

The adrenergic receptors:
- alpha and beta receptors

Stimulation of alpha receptors = vasoconstriction

Nurs 400;ICU (6 decks)

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