Exam 2

Question 1

Pulse Pressure

Answer 1

determined by the interaction of the stroke volume of the heart, compliance of the aorta, and the resistance to flow in the arterial tree

Question 2

Mean Arterial Pressure

Answer 2

Actual mean is determined by the area under the arterial pressure curve divided by the beat period

Calculus: integration of the area under the curve

Question 3

Why is MAP a good assessment tool?

Answer 3

• mean pressure the same in all parts of the arterial tree
• mean pressure not significantly affected by overshoot, artifact and the frequency response characteristics of the system
• pulmonary and SVR values are calculated using the mean pressure
• mean pressure represents the inlet pressure to the systemic and cerebral capillary networks

Question 4

Causes of False-High Reading

Answer 4

Cuff too small
cuff not centered over the brachial artery
cuff not applied snugly
arm below heart level
Very obese arm
cone-shaped arm

Question 5

Causes of False-Low Reading

Answer 5

Cuff too large
arm located above heart level
Failure to correctly determine the onset of the first Korotkoff sound

Question 6

Auscultation

Answer 6

May be up to 20 mmHg lower than direct
Proper cuff size: obese or patients with cone-shaped arms
Deflate cuff at at approx. 3mmHg/sec
Diastolic reading muffled (hyperdynamic)
Problems with damping of sounds in pt w. reduced stroke volume and severe vasoconstriction
concerns with frequency of pressure determination

Question 7

Complications of deflating cuff too fast or slow?

Answer 7

Too fast- underestimate values

Too slow creates venous congestions which distorts Korotkoff sounds

Question 8

Indirect BP Manual Techniques

Answer 8

Auscultation 
Palpation- determine systolic only
Auscultation assisted by Doppler- determine systolic only; easier to determine pressure in "shocky" patients
Manometer oscillation observation
Photoelectric devices

Question 9

Photoelectric Devices

Answer 9

Indirect manual technique
pulse ox is an example
determines sytolic only
patient motion is a problem
problems when arterioles of extremities are constricted

Question 10

Manometer oscillation observation

Answer 10

Indirect Manual Techniques
Determine systolic and mean/first oscillation
systolic/maximal oscillation
mean/minimal oscillation in hypotensive patients

Question 11

Indirect Automated Technique Examples

Answer 11

oscillometery- detection of pulsatile arterial wall vibrations/most commonly used
Infrasound- detect pulsatile vibrations via microphone
Ultrasonic determination of axial flow- use doppler to detect sound of flowing blood (TEE)
Arterial tonometry-pressure sensor over radial artery detects pusatile forces

Question 12

Indirect Automated Technique Characteristics

Answer 12

Depend on adequate pulsatile blood flow to extremities
Many determine mean pressure
Good for following trends in stable patients
Poor results in hypotension or pts receiving potent vasoactive drug titration

Question 13

Indirect vs. Direct: Patient Factors

Answer 13

Regional arterial pressure gradients due to: atherosclerosis, peripheral vascular disease, aortic dissection, arterial embolism, surgical retraction, patient position

Generalized arterial pressure gradients due to: severe vasoconstriction and shock, peripheral vasodilation with rewarming during and after CPB, normal widening of the peripheral pressure pulse

Question 14

Indirect vs. Direct: Technical Factors

Answer 14

Cuff problems: too small, arm shape, extrinsic cuff compression, limb position relative to heart
Rapid deflation (underestimation)
Physiologic problems and method limitations- rapid P changes, dysrhythmias, severe vasoconstriction and shock, shiver and pt movement, BTBV

Question 15

Vasoconstricted patients with low stroke volume

Answer 15

Obtained pressures with indirect method underestimate true systolic pressure

oscillometry, palpation, and auscultation: indirectly measure blood pressures tend to underestimate systolic BP and overestimate diastolic pressure (dampened)

Question 16

Adequacy of tissue perfusion in direct method

Answer 16

difficult to determine by direct method based on pressure readings

Question 17

Direct Continuous Intra-Arterial Pressure Monitoring

Answer 17

Most reliable method of determining real-time systemic arterial systolic, diastolic and mean pressures
Relatively pain-free
Simple
Relatively low-risk access for arterial blood sampling

Question 18

Indications for Arterial Cannulation

Answer 18

Need continuous arterial pressure monitoring

Patient has a need for serial blood gases

Question 19

Who needs continuous arterial pressure monitoring?

Answer 19

critically ill, injured, undergoing major surgery

Provides ability to detect sudden changes, evaluate changes in the trend, immediately assess effects of therapy

Question 20

Who needs serial blood gases?

Answer 20

Respiratory failure
Management of ventilator support
Treatment of severe acid-base disturbances
Need more than three or four arterial blood samples on a daily basis

Question 21

Contraindications for Arterial Cannulation

Answer 21

Peripheral Vascular Disease
Hemorrhagic disorders
On anticoagulants or receiving thrombotic agents

Question 22

Where should you not insert a catheter?

Answer 22

area of infection
site previous vascular surgery (cutdown)
through synthetic vascular graft material

Question 23

Pressure Wave Generation

Answer 23

Ventricular ejection creates blood flow and a pressure wave
Pressure wave precedes the actual blood flow of blood
Creation of pressure wave-form is affected by this relationship

Question 24

Speeds of Pressure Wave & Blood flow

Answer 24

pressure wave: 10 m/s
blood flow: 0.5 m/s
Almost sound like a phase shift-out of sync

Question 25

True Pressure Wave Phases

Answer 25

Phase 1: Inotropic component Phase 2: Volume Displacement Curve Phase 3: Late Systole and Diastole

Question 26

Phase 1: Inotropic Component

Answer 26

Aortic Valve Opens Energy created by contracting LV transferred to the aorta Pressure wave created- starts moving down arterial tree Simultaneously- first part of stroke volume pumped into aortic root Anacrotic rise (dP/dT)- steepness, rate of rise & heigh of rise related to rate of acceleration of blood (indication LV contractility)

Question 27

What dose Anacrotic rise indicate?

Answer 27

LV contractility

Question 28

Phase 2: Volume Displacement

Answer 28

Movement of blood into aorta fills out and sustains the pressure pulse Rounded appearance results from: continued ejection of the SV, displacement of blood, distention of arterial walls Anacrotic notch: may be present, mark change from inotropic component to displacement Low stroke volume (curve narrow with low amplitude)

Question 29

What marks change from inotropic component to displacement?

Answer 29

Anacrotic notch

Question 30

Phase 3: Late Systole & Diastole

Answer 30

Sloping decline- rate of peripheral runoff exceeds vol input Closure of aortic valve: start of diastole, dicrotic notch Continuous decline as blood moves from aortic root to the peripheral vessels Undulations may result from reflected pressure waves

Question 31

High amplitude of inotropic spike

Answer 31

Increase rate of LV pressure generation & increased acceleration of aortic blood flow Increased reflection of pressure waves from the periphery: vasoconstriction Overshoot artifact

Question 32

Decreased amplitude of inotropic spike

Answer 32

myocardial depression hypovolemia decreased reflection of pressure wave from the periphery (vasodilation)

Question 33

High Pressure, Low Flow

Answer 33

Low flow: might be perfusing core but periphery gets acidotic

Question 34

Low Pressure, High Flow

Answer 34

Perfusing all tissues; not much downside

Question 35

Maintain flow using drugs

Answer 35

never change flow and give systemic vasoconstrictor making extremities hypoxic

Question 36

Overshoot

Answer 36

Overshoot of systolic pressure most common artifact seen in clinical practice May come and go (changing HR, development of hyperdynamic conditions) Due to underdamping or inadequate frequency response

Question 37

Effects on Pressure Waves

Answer 37

Gravitational Effects Reflected Waves Effects Physiological Effects

Question 38

Gravitational Effects

Answer 38

Vertical patient vs. supine Vertical: pressure decreases moving upward from heart Pressure increases moving downward from heart pressure the same at all points at same vertical level Supine: no differences due to gravity "Orthostatic Hypotension"

Question 39

Standard Reference Level for blood pressure

Answer 39

Heart!

Question 40

Reflected Pressure Waves

Answer 40

Pressure waveform precedes the actual flow of blood: ventricles generate tension then contract Pressure waves reflected back toward aortic root by smaller distal vessels: added to pressure waveform as tit travels down the arterial tree (fourier analysis) Pulse pressure increases as wave travels down the arterial tree (sys higher, diastolic lower)

Question 41

Since pulse pressure increases as it goes down the arterial tree: underdamping or overdamping?

Answer 41

Underdamping | Systolic higher, diastolic lower

Question 42

Normal Pulse Pressure

Answer 42

Greater than 40 mmHg is abnormal

Question 43

High Pulse Pressure

Answer 43

``` Heart Problems (older adults) Stiffness of aorta (calcification) Athersclerosis Aortic dissection Endocarditis Chronic aortic regurgitation (AI) Fever Anemia Pregnancy Anxiety Heart Block Raised ICP ```

Question 44

Low (Narrow) Pulse Pressure

Answer 44

Poor Heart function (see this a lot) Most common cause: drop in LV stroke volume In trauma: significant blood loss (insufficent preload leading to reduced CO) If extremely low: 25mmHg or less the cause may be low SV as in CHF or shock

Question 45

Physiological Factors affecting Waveforms

Answer 45

``` Arrythmias Hypertension Hypotension Age Vasoconstriction Hypovolemia Respiration Variation ```

Question 46

Effect of Hypotension on Arterial Waveform

Answer 46

Peak of inotropic component and dicrotic notch disappear | Waveform looks to be damped

Question 47

Aging

Answer 47

Difference between central aortic and distal systolic pressures decreases -minimal change in the pressure pulse -loss of arterial compliance Inotropic component tends to be dominant

Question 48

Direct Arterial Cannulation Locations | See pg 151-152 chart in book

Answer 48

``` Radial artery Brachial artery Axillary artery Femoral artery Dorsalis Pedis Artery ```

Question 49

Direct Arterial Complications

Answer 49

``` Embolism Vascular insufficiency (distal ischemia) Iscemic necrosis of overlying skin Infection Hemorrhage Accidental intra-arterial drug injection Vasculitis Arterial dissection ```