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FNH 477 > Hypertension > Flashcards

Hypertension Flashcards

1
Q

What is hypertension?

A
  • Blood pressure: force blood exerts against arterial walls; expressed in mmHg systolic/diastolic
    • <120/<80 = normal
    • ≥140/≥90 = hypertension
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2
Q

What is blood pressure directly related to?

A

Blood volume

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3
Q

When does blood pressure increase?

A

When resistance to blood flow is increased

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4
Q

Name 3 ways resistance to blood flow increases.

A
  • Lumen of vessel is decreased
  • Length blood must travel is increased
  • Viscosity of blood is increased
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5
Q

Describe nervous system control of blood pressure. [3]

A
  • BP regulated by cardiovascular center in medulla oblongata
  • Receives input from baroreceptors
  • Regulates heart rate & force of contraction, vessel dilation/constriction
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6
Q

Describe endocrine control of blood pressure. [4]

A
  • Renin-angiotensin-aldosterone system (RAAS) - increases BP
  • Epinephrine & norepinephrine - increases BP
  • Antidiuretic hormone (vasopressin) - increases BP
  • Atrial natriuretic peptide - decreases BP
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7
Q

What is renin released in response to? [3]

A
  • Low blood pressure
  • Low extracellular fluid (ECF) volume
  • Low plasma sodium
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8
Q

What does aldosterone stimulate?

A

Sodium reabsorption→ increases extracellular fluid osmolality → promotes fluid retention → rise in BP

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9
Q

Describe the RAAS response to decreased blood pressure.

A
  1. Decreased blood pressure
  2. Renin (an enzyme) is released; angiotensinogen from liver
  3. Angiotensin I results from renin action of angiotensinogen; conversion takes place primarily in the lungs
  4. Angiotensin II formed from angiotensin I
  5. Aldosterone is released from the adrenal gland; blood vessel contriction by angiotensin II
  6. Aldosterone stimulates increased sodium retention by the kidney
  7. Increased water retention by the kidney

Result = increased blood pressure

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10
Q

What is the body’s response to dehydration?

A
  • Dehydration = decreased ECF; decreased ICF; increased osmotic pressure
  • RAAS system activated and hypothalamus stimulated
  • RAAS → adrenal cortex → aldosterone → increased sodium and water retention by the kidney
  • Hypothalamus → Pituitary gland → ADH → increased water reabsorption by the kidney

Result = increased ECF and ICF

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11
Q

Hypertension has signs and symptoms.
True or False?

A

False.
There are usually no symptoms or signs.

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12
Q

Hypertension usually has no signs or symptoms.
True or False?

A

True.

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13
Q

What does hypertension tend to rise with?

A

Age

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14
Q

What does hypertension commonly co-exist with? [2]

A

Type II diabetes
Obesity

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15
Q

What occurs over time with hypertension?

A

Damage to blood vessels, heart, and kidneys

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16
Q

What is hypertension a risk factor for? [4]

A
  • Heart disease
  • Aneurysm
  • Stroke
  • Kidney failure
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17
Q

Describe hypertension as a global issue.

A
  • Low in North America
  • Higher in South America and Africa
  • Highest in central Africa, East European countries, and Russia
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18
Q

Describe hypertension prevalence in women.

A

Compared to men; more countries in 20-30% range; most below 50%; mean ~40%

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19
Q

Describe hypertension prevalence in men.

A

Compared to women, less in 20-30% range, more over 50%; mean ~35%

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20
Q

Discuss hypertension in Canada.

A
  • Hypertension has been cited as the most common reason for doctor’s visits & most common reason for taking medications
  • 2018 - 25% of Canadian adults over 20 years of age live with diagnosed hypertension
  • Approximately 20% of indivdiuals with hypertension are not aware of their condition, so the true prevalence is likely higher
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21
Q

Describe the potential for dietary intervention for hypertension treatment.

A
  • Dietary changes can serve as first-line therapy, before antihypertensive medication, for treating uncomplicated hypertension.
  • Among hypertensive individuals who are already taking medication, dietary changes can further lower BP and make it possible to reduce the number and dose of antihypertensive medications.
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22
Q

Which diet-related factors have well-established antihypertensive efficacy? (either adverse [3] or protective [2])

A

Adverse effect on BP:
* Body weight (increased visceral fat)
* Salt
* Alcohol

Protective effect on BP:
* Potassium
* DASH-type dietary pattern

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23
Q

Why is body fat a concern with hypertension?

A
  • For each extra pound of body fat, an estimated 400 miles of additional blood vessels develop
  • Recall - blood pressure is directly related to blood volume.
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24
Q

What is the key regulator of blood volume and blood pressure?

A

Sodium!

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25
Q

What is the main cation in extracellular fluid?

A

Sodium!

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26
Q

What is sodium’s role in maintenance of fluid homeostasis?

A
  • Balance of ECF and ICF
  • More sodium in blood = increased osmolarity, pulls more water into blood → increases blood pressure
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27
Q

How is sodium balance in the body maintained?

A
  • Sodium is conserved by renin-angiotensin aldosterone system
  • Sodium is excreted with increased atrial natriuretic peptide
28
Q

What is the relationship between sodium & hypertension?

A

Multiple studies (animal, observational, and experimental) have shown a direct relationship between dietary sodium and hypertension.

29
Q

What were the conclusions from the following study:
Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and metaanalysis of randomised trials. BMJ. 2020

A
  • The magnitude of blood pressure lowering achieved with sodium reduction showed a dose-response relation
  • was greater for older populations, non-white populations, and those with higher blood pressure.
  • Short term studies underestimate the effect of sodium reduction on blood pressure
  • Each 50 mmol reduction in 24 hour sodium excretion was associated with a 1.10 mm Hg reduction in systolic BP and a 0.33 mm Hg reduction in diastolic BP.
  • Suggests 3 g salt/day (~1/2 g sodium/day) as population target
30
Q

What are the AI and UL for sodium intake for adults?

A

AI for adults = 1500 mg/day
UL for adults = 2300 mg/day

31
Q

What is the difference between sodium and salt?

A
  • ~90% of dietary sodium comes from sodium chloride
  • Salt is about 40% sodium by weight
32
Q

What is the difference between sodium and salt?

A
  • ~90% of dietary sodium comes from sodium chloride
  • Salt is about 40% sodium by weight
Recall: UL = 2300 mg/day
33
Q

How many people are exceeding the UL for sodium?

A
  • 85% of men
  • 60-80% of women
34
Q

Who has the highest median sodium intake?

A

Men aged 19-30 years = 4046 mg/day

35
Q

Where does sodium in Canadian diets come from?

A

Mostly processed foods

36
Q

Compare sodium content in processed versus homemade meals.

A
37
Q

Describe the dietary intake of sodium for children in Vancouver (determined using FFQ).

A
  • 91.6% exceeded AI
  • 85% of children 1-3 and 54% of children 3-6 exceeded UL

AI: 1000 mg/d for children 1-3 years; 1200 mg/d for 3-6
UL: 1500 mg/d for children 1-3 years; 1900 mg/d for 3-6

38
Q

What are the AI and UL for sodium for children 1-3, children 3-6, and adults?

A

AI: 1000 mg/d for children 1-3 years; 1200 mg/d for 3-6; 1500 mg/d for adults

UL: 1500 mg/d for children 1-3 years; 1900 mg/d for 3-6; 2300 mg/d for adults

39
Q

What are the terms of the NASEM Committee to Review the Dietary Reference Intakes for Sodium and Potassium? [2]

A
  • UL = toxicological risk
  • CDRR = chronic disease risk reduction; intake for sodium to describe the ‘intake above which intake reduction is expected to reduce chronic disease risk within an apparent healthy population’
40
Q

Discuss the CDRR for children.

A

49% of children 1 to 3 years old and 72% of children 4 to 8 years old were consuming sodium at levels exceeding age-specific CDRR intake thresholds.

41
Q

Lower sodium intake was associated with increased total mortality in Italian adults with high sodium intakes.
True or False?

A

True.

42
Q

Lower sodium intake was associated with decreased total mortality in Italian adults with high sodium intakes.
True or False?

A

False.

43
Q

What is the rationale for population-wide decrease in sodium intake?

A
  • Sodium may increase blood pressure, which is a known risk factor for CVD.
  • It has been estimated that if the Canadian average sodium intake is decreased by ~1800 mg/day
    • High blood pressure prevalence would decrease by 30%
    • ~23,500 CVD events could be prevented per year
    • Could result in direct and indirect savings of $3 billion per year
44
Q

What is the rationale against population-wide decrease in sodium intake?

A
  • Benefit of reducing salt at individual level is variable
  • Some studies show no effect or even increased risk for death due to cardiovascular disease among those with lower sodium intakes
The study by Alderman et al. challenged: Why? - Low number of events recorded - Methodological inadequacies (e.g., evaluation of habitual salt consumption using 24 hour urine collection obtained shortly after the study participants had been instructed to reduce their usual sodium intake)
45
Q

Describe individual response to dietary sodium reduction.

A

It lies along a continuum.

46
Q

What does individual sodium response depend on? [5]

A
  • Current blood pressure
  • Age
  • Race
  • Potassium intake
  • Renin-angiotensin-aldosterone system
47
Q

How does sodium intake relate to CVD risk?

A

Lowest tertile of sodium excretion (g/day) had a significantly increased risk of CVD

Editorial response in The Lancet “This study is disappointingly weak and contributes little to our understanding of salt and disease. It is likely to confuse public perceptions of the importance of salt as a risk factor for high blood pressure, heart disease, and stroke. Questions of intervention and outcome, such as sodium intake and CVD events, cannot be answered by small observational studies. It is dangerous to jump to conclusions on the basis of single studies and ignore the totality of evidence. At a time when CVD is the world's leading cause of death and excess dietary sodium has convincingly been shown to be a serious public health hazard, the results of this work should neither change thinking nor practice.”
48
Q

Risk of CVD was lowest among those with the lowest, moderate or high sodium excretion?

A

Moderate ~ 4.00 g/day

Note the J shaped curve

“an estimated sodium intake corresponding to sodium excretion between 3 and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake. ”

49
Q

What are some possible limitations of studies on sodium & CVD? [5]

A
  • Observational studies - cannot show causation
  • Small sample sizes, few cases of CVD
  • Reverse causation
    • Individuals at risk (or diagnosed with) a disease may change their diet/lifestyle as a result of medical advice or to prevent recurrence or complications from occurring
  • Errors in estimating sodium intake
  • Short term studies underestimate the effect of sodium reduction on blood pressure
50
Q

Do short term studies under or over estimate the effect of sodium reduction on blood pressure?

A

Underestimate (BMJ 2020, Systematic review and meta-analysis of randomized trials)

51
Q

How is sodium intake estimated? [2]

A
  • Dietary estimates (Dietary recalls/ records/ FFQ)
  • Urinary sodium excretion (approximates dietary intake; collection at one time point or over 24 hours)
52
Q

What are sources of error for estimating sodium intake by the urinary excretion method? [8]

A
  • Medical conditions
  • Incomplete collection
  • Hydration
  • High participant burden (may lead to drop-out)
  • Differences in losses in sweat & feces
  • Lab error
  • Day to day variation
  • Modifying intake since cognizant of being measured

ONE 24-hr urinary collection or dietary recall may not
be representative of usual intake due to INTRAindividual variation in sodium intake.

53
Q

What are sources of error for estimating sodium intake by the dietary sodium method? [5]

A
  • Over/underestimate portion sizes
  • Missed addition of salt/condiments at table
  • Differences in sodium content of similar foods
  • Accurate database for sodium content of foods
  • Single recall may not be representative of usual intakes
54
Q

Reduction in systolic blood pressure of 3 mmg Hg results in 8% reduction in stroke mortality.
True or False?

A

True.

55
Q

Reduction in systolic blood pressure of 3 mmg hG is not enough to reduce stroke mortality.
True or False?

A

False.
Reduction in systolic blood pressure of 3 mmg Hg results in 8% reduction in stroke mortality.

56
Q

Reduction in systolic blood pressure of at least 5 mmg Hg is needed to result in any reduction in stroke mortality.
True or False?

A

False.
Reduction in systolic blood pressure of 3 mmg Hg results in 8% reduction in stroke mortality.

57
Q

Reduction in systolic blood pressure of 3 mmg Hg results in no reduction in stroke mortality but decreases mortality due to CHD by 5%.
True or False?

A

False.
Reduction in systolic blood pressure of 3 mmg Hg results in 8% reduction in stroke mortality.

58
Q

Salt intake and cardiovascular disease: why are the data inconsistent? [5]

A
  • Method of measuring sodium
  • Effects may differ by geographical region, depend on range of sodium intakes
  • ‘Salt sensitivity’ of individuals
  • Influence of other dietary factors
  • Sodium > BP > CVD may be too simplistic
59
Q

What is the bottom line for sodium and CVD risk? [3]

A

Bottom Line:
* High dietary sodium intake (>5 g/d) associated with increased CVD risk
* Moderate sodium intake may or may not be associated with increased CVD risk
* More research is needed to understand relationship between sodium and CVD and whether there is a safe lower threshold of sodium intake

60
Q

Potassium is a major intracellular cation. How does it influence blood pressure?

A
  • Higher intakes associated with lower blood pressure
  • Has opposing effects from sodium on fluid and blood pressure regulation
61
Q

What is the interaction between sodium and potassium on blood pressure?

A
  • Effects of potassium are greatest when sodium intake is also high
62
Q

What is the best source of potassium?

A

Fruits and vegetables

63
Q

What are dietary approaches to stopping hypertension?

A
  • Emphasizes vegetables, fruits, and fat-free or lowfat dairy products
  • Includes whole grains, fish, poultry, beans, seeds, nuts, and vegetable oils
  • Limits sodium, sweets, sugary beverages, and red meats
  • Consistent with dietary habits associated with reduced risk for chronic conditions such as cancer, heart disease, osteoporosis, etc.

The DASH diet

64
Q

What are clinical recommendations for antihypertensive dietary therapy? [6]

A
  • For overweight and obese sugjects, lose weight
  • For lean individuals, maintain weight
  • Keep salt as low as possible, ideally less than 3.8 g/day (corresponding to 65 mmol or 1.5 g of sodium per day)
  • Get at least 120 mmol or 4.7 g potassium per day
  • Drink less than 2 drinks a day (men) or 1 drink a day (women)
  • Ensure your diet is rich in fruits, vegetables, and low-fat dairy products, and low in saturated fat
65
Q

What is reverse causation?

A

Individuals at risk (or diagnosed with) a disease may change their diet/lifestyle as a result of medical advice or to prevent recurrence or complications from occurring.

FNH 477 (11 decks)

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