PathoPhysiology Chapter 16

1. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
CHAPTER 16
ALTERATIONS IN BLOOD
PRESSURE

2. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE
• It is the pressure differences between the left and
right sides of the heart that produce the gradient
allowing systemic movement of blood
• Arterial blood pressure is produced by the force of
left ventricular contraction overcoming the
resistance of the aorta to open the aortic valve

3. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE (CONT.)
Determinants of Systemic Blood Pressure
• Cardiac output and the resistance to the ejection
of blood from the heart
• CO = SV (stroke volume) x HR (heart rate)
• End-diastolic volume is the preload
• Systemic vascular resistance (afterload) is
determined by the radius of arteries and degree of
vessel compliance

4. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE (CONT.)
Measurement of Blood Pressure
• Components of blood pressure measurement
• Systolic blood pressure—peak pressure during cardiac
systole
• Diastolic blood pressure—lowest pressure during cardiac
diastole
• SV is the primary factor influencing systolic pressure
• SVR is the major determinant of diastolic pressure

5. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE (CONT.)
• Components of blood pressure measurement
• Mean arterial pressure is the calculated average pressure
within the circulatory system throughout the cardiac cycle
• MAP = (2 x diastolic pressure) + systolic pressure
3

6. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE (CONT.)
Direct Measurement of Blood Pressure
• Requires intraarterial catheter to transduce arterial
fluid pulsations into electrical signals (waveforms)
• Catheter commonly placed in radial artery
• Most accurate method of measuring blood pressure

7. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
ARTERIAL BLOOD PRESSURE (CONT.)
Indirect Measurement of Blood Pressure
• Commonly measured indirectly via the brachial
artery using a stethoscope and
sphygmomanometer or automated oscillometric
system
• Requires careful technique to ensure accuracy
• Auscultation of Korotkoff sounds

8. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
MECHANISMS OF BLOOD PRESSURE
REGULATION
• Affected by neural, humoral, and renal factors
• Blood pressure fluctuates over 24 hours due to
physiologic changes associated with circadian
rhythm

9. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
MECHANISMS OF BLOOD
PRESSURE REGULATION (CONT.)
Short-Term Regulation of Systemic Blood
Pressure
• Changes in BP are mediated through activation of
the sympathetic nervous system
• Results in release of neurotransmitters epinephrine
and norepinephrine
• Vasomotor center indirectly activated via
baroreceptors
• Activates α1 receptors in smooth muscle of arterioles
• Activates β1 receptors of the heart

10. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
SHORT-TERM REGULATION OF
SYSTEMIC BLOOD PRESSURE

11. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
MECHANISMS OF BLOOD
PRESSURE REGULATION
Long-Term Regulation of Systemic Blood
Pressure
• Increase in extracellular fluid volume = increased
CO and SVR = elevated BP
• Increased serum sodium level = increased
osmolality = increased ADH secretion
• Renin–angiotensin–aldosterone system (RAAS)
important regulator of BP

12. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
LONG-TERM REGULATION OF
SYSTEMIC BLOOD PRESSURE

13. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
MECHANISMS OF BLOOD
PRESSURE REGULATION
Long-Term Regulation of Systemic Blood
Pressure
• Angiotensin II produces an increase in SVR
• Atrial natriuretic peptides cause kidneys to increase
sodium and water excretion by increasing the
glomerular filtration rate
• Intrarenal arteriolar constriction leads to increased
tubular reabsorption of sodium and water

14. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
LONG-TERM REGULATION OF
SYSTEMIC BLOOD PRESSURE

15. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
MECHANISMS OF BLOOD
PRESSURE REGULATION
Normal Fluctuations in Systemic Blood
Pressure
• Suprachiasmatic nuclei in the brain govern daily
variations in bodily functions
• Neural and hormonal regulation influences BP
• Lifestyle influences can affect BP

16. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION
• Most common primary diagnosis in the United States
• Increases morbidity and mortality associated with
heart disease, kidney disease, peripheral vascular
disease, and stroke
• Responsible for an annual worldwide death rate of
7 million

17. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Definition and Classification
• Determined by the Joint National Committee on
Prevention, Detection, Evaluation, and Treatment of
High Blood Pressure
• Prehypertension is a range of pressures between
normal and stage 1 hypertension in an effort to
initiate interventions early enough to prevent or
deter progression of the disease process

18. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

19. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

20. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Primary Hypertension
• Idiopathic disorder
• Most common form of hypertension
• Rare prior to the age of 10

21. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Primary Hypertension
• Subtypes
• Isolated systolic hypertension
• Isolated diastolic hypertension
• Combined systolic and diastolic hypertension
• SBP is a major risk factor for subsequent cardiovascular
disease

22. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Primary Hypertension
• Risk factors
• Nonmodifiable
• Family history
• Age
• Modifiable
• Dietary factors
• Sedentary lifestyle
• Obesity
• Metabolic syndrome

23. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Primary Hypertension
• Outcomes
• End-organ damage
• Increased myocardial work results in heart failure
• Glomerular damage results in kidney failure
• Affects microcirculation of the eyes
• Increased pressure in cerebral vasculature can result in
hemorrhage

24. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

25. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Primary Hypertension
• Treatment interventions
• Lifestyle modifications are first and most important
prevention and treatment strategy
• Drug therapy for hypertension address heart rate, SVR, and
stroke volume

26. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

27. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

28. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

29. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Secondary Hypertension
• Hypertension attributed to a specific identifiable
pathology or condition
• Most common form in children <10 years of age
• May be related to:
• Renal disease
• Coarctation of the heart
• Pregnancy
• Obesity/obstructive sleep apnea
• Endocrine disorders

30. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)

31. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
HYPERTENSION (CONT.)
Hypertensive Emergencies and Urgency
• Hypertensive emergency: sudden increase in either
or both systolic or diastolic blood pressure with
evidence of end-organ damage
• Rapid but controlled reduction of blood pressure using
parenteral antihypertensive agents under close monitoring
(typically in ICU setting)
• Hypertensive urgency: similar blood pressure
elevation without evidence of end-organ damage
• Oral medications to bring blood pressure under control over
24-48 hours

32. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
LOW BLOOD PRESSURE
• Orthostatic (postural) hypotension is a decrease in
systolic blood pressure (>20 mm Hg or >10 mm Hg
within 3 minutes) when moving to an upright
position
• Excessive increase in heart rate (by 20-30
beats/minute) may also be diagnostic
• May be a result of:
• Problem with vasomotor or baroreceptor response
• Adverse effect of drug therapy
• Arterial stiffness
• Volume depletion
• Secondary disease process

33. Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.
LOW BLOOD PRESSURE (CONT.)
Treatment
• Review medication history
• Slow positional changes
• Avoid hot environments
• Avoid large or carbohydrate-heavy meals
• When symptoms begin, squatting/bending forward
or crossing legs may reduce effects