Circulation

1
Circulation
2
Figure 49.2 Structures of the heart. The
diagram shows the vena cava, right atrium,
tricuspid valve, right ventricle, pulmonic valve,
pulmonary arteries, pulmonary veins, left atrium,
mitral valve, left ventricle, aortic valve, and
the aorta.
3
Figure 49.4 The electrical system of the heart.
The impulse is initiated by the SA node, then
travels to the AV node, the bundle of His, and
finally to the Purkinje fibers.
Cardiac muscle can generate an electrical impulse
and contraction independently of the nervous
system. This is known as automaticity.
Cardiac Conduction System
4
Cardiac Cycle Terminology

• Systole
• Contraction
• Heart ejects blood into the pulmonary and
  systemic circulations
• S1 sound
• Caused by the closure of the tricuspid and mitral
  valves

5
Cardiac Cycle Terminology

• Diasystole
• Relaxation
• Ventricles fill with blood
• S2 sound
• Caused by the closure of the aortic and pulmonic
  semilunar valves

6
Table 49-1 Cardiac Cycle and Heart Sounds
7
Table 49-2 Factors Related to Cardiac Functions
8
Stroke Volume

• The amount of blood ejected from the ventricles
  into the circulation

9
Cardiac Output

• Indicates how well the heart is functioning as a
  pump
• Vital for tissue perfusion, oxygenation, and
  nutrient delivery at the cellular level
• Stroke volume X heart rate CO

10
Cardiac Output Affected By

• Heart rate
• Preload
• Contractility
• Afterload

11
Heart Rate Influenced By

• Autonomic nervous system
• Blood pressure
• Hormones such as thyroid hormone
• Certain medications

12
Preload

• The degree to which muscle fibers in the
  ventricle are stretched at the end of the
  relaxation period (diastole)
• Increased volume causes increased stretch and
  more forceful contraction (Frank-Starling Law of
  the Heart)

13
Contractility

• Inherent ability of cardiac muscle fibers to
  contract
• Positive inotropic drugs increase contractility
• Negative inotropic drugs decrease contractile
  strength

14
Afterload

• The resistance against which the heart must pump
• Right ventricle pumps blood into the
  low-resistance pulmonary system
• Left ventricle pumps blood into the high pressure
  systemic arterial system

15
Cellular Level

• Oxygen diffuses into blood from capillary
  networks that encompass the alveoli
• Carbon dioxide diffuses into the alveoli from the
  blood
• Oxygen nutrients exchanged for waste products
  in the capillary beds

16
Veins

• Tunica intima inner layer of endothelium that
  facilitates blood flow
• Tunica media middle layer of elastic fibers and
  smooth muscle
• Tunica adventitia outermost layer of connective
  tissue

17
Arteries

• Walls have three layers, but tunica media is
  thicker and more muscular to help maintain blood
  pressure and continuous circulation to tissues
• Unlike veins, arteries do not have valves

18
Blood Pressure

• The force exerted on arterial walls by the blood
  flowing within the vessel

19
Mean Arterial Pressure

• The pressure that maintains blood flow to the
  tissues throughout the cardiac cycle
• It is a product of the cardiac output times the
  peripheral vascular resistance
• CO x PVR MAP

20
Hemoglobin

• Component of RBCs (erythrocytes)
• Transports oxygen to cells
• Anemia occurs when there are too few RBCs or RBCs
  with too little or abnormal hemoglobin
• Result is fatigue and activity intolerance

21
Lifespan Considerations

• Pressure changes
• Foramen ovale between atria closes
• Ductus arteriosus between pulmonary artery and
  aorta closes

22
Pulse Rates

• Resting heart rates for neonates range from
  80-200 beats per minute
• 80-150 in infancy early childhood
• 55-100 by 10 yrs

23
Blood Pressures

• 1-3 days old BP avg. 65/40
• 1 mo. avg. 90/55
• Adult avg. 120/80
• Arteriosclerosis with aging

24
Risk Factors for CVD

• Non-Modifiable
• Heredity
• Age
• Gender

• Modifiable
• Serum lipid levels
• Smoking
• Diabetes
• Obesity
• Sedentary lifestyle

25
CV Function Also Influenced By

• Heat and cold
• Health status
• Stress and coping

• Diet
• Alcohol
• Elevated homocysteine level

26
Table 49-3 Risk Factors for Coronary Heart
Disease
27
Myocardial Infarction

• Chest pain and/or pain radiating to left arm or
  jaw
• Nausea
• Shortness of breath
• Diaphoresis

28
Heart Failure

• Pulmonary congestion SOB
• Adventitious lung sounds
• Increased HR
• Increased resp rate
• Cold, pale extremities
• Distended neck veins

29
Table 49-4 Examples of Conditions That May
Precipitate Heart Failure
30
Impaired Tissue Perfusion

• Ischemia may lead to TIA or stroke
• Peripheral vascular disease
• Pulmonary emboli

31
Peripheral Vascular Disease

• Ischemia of distal tissues
• Decreased peripheral pulses
• Pale skin color
• Cool extremities
• Hair loss

32
Pulmonary Embolism

• Sudden onset of shortness of breath
• Pleuritic chest pain

33
Nursing Management

• Nursing history
• Physical assessment
• Diagnostic studies

• Cardiac monitoring
• Blood tests
• Hemodynamic studies

34
Unnumbered Box 49-2 Assessment Interview
35
Nursing Diagnosis

• Ineffective Tissue Perfusion (Cardiopulmonary)
  Decrease in oxygen resulting in the failure to
  nourish the tissues at the capillary level

36
Nursing Diagnosis

• Decreased Cardiac Output Inadequate blood pumped
  by the heart to meet metabolic (demands) of the
  body

37
Nursing Diagnosis

• Activity Intolerance Insufficient physiological
  or psychological energy to endure or complete
  required or desired daily activities

38
Medications

• To reduce workload and prevent vasoconstriction
• Nitrates
• Calcium channel blockers
• Angiotensin-converting enzyme inhibitors (ACE
  inhibitors)

39
Medications

• To increase the contractile strength of the heart
• Positive inotropic drugs such as digitalis

40
Medications

• To block the sympathetic nervous system action on
  the heart and decrease oxygen consumption
• Beta adrenergic blocking agents
• Propranolol
• Metoprolol

41
Medications

• For clients with peripheral vascular disease and
  sometimes clients with hypertension
• Direct vasodilators

42
Monitoring After Meds

• Diuretics Check IO, K levels
• Positive inotropics Check BP, HR, peripheral
  pulses, lung sounds as indicators of cardiac
  output
• Antihypertensives Check BP

43
Figure 49.6 The sequential venous compression
device enhances venous return. They are available
in knee-high or above the knee length.
44
Figure 49.7 Applying a sequential compression
device to the leg.
Also known simply as SCD
45
Unnumbered Box 49-5 Teaching Wellness Care
Promoting A Healthy Heart
46
Chapter 49, Discussion Point 1
How does the cardiovascular system transport
gases to and from the tissues?
47
Chapter 49, Discussion Point 2
What are the parts of the cardiovascular system?
48
Chapter 49, Discussion Point 3
What are the parts of the cardiac cycle?
49
Chapter 49, Discussion Point 4
How is a persons cardiac output calculated?
What diagnostic tests might be indicated to
validate a clients cardiac output? What
medical conditions might cause a clients cardiac
output to fall?
50
Chapter 49, Discussion Point 5
What is used to provide continuous information
about a clients heart?
51
Chapter 49, Discussion Point 6
What are some ways to increase blood flow back
to a clients heart?
52
Chapter 49, Discussion Point 7
What diagnostic tests are used to determine
cardiac functioning? Which ones are specific
for a myocardial infarction?