Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 23 Disorders of Blood Pressure Regulation

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Arterial Blood Pressure (Definitions) Systolic pressure: pressure at the height of the pressure pulse Diastolic pressure: the lowest pressure Pulse pressure: the difference between systolic and diastolic pressure Mean arterial pressure: represents the average pressure in the arterial system during ventricular contraction and relaxation

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Arterial Blood Pressure Represents the pressure of the blood as it moves through the arterial system Cardiac output = HR x SV Vascular resistance Mean arterial pressure = CO x VR

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Mechanisms of Blood Pressure Regulation Short-term regulation: corrects temporary imbalances in blood pressure –Neural mechanisms –Humoral mechanisms Long-term regulation: controls the daily, weekly, and monthly regulation of blood pressure –Renal mechanism

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Determining Systolic and Diastolic Blood Pressure Systolic pressure –The characteristics of the stroke volume being ejected from the heart –The ability of the aorta to stretch and accommodate the stroke volume Diastolic pressure –The energy that is stored in the aorta as its elastic fibres are stretched during systole –The resistance to the runoff of blood from the systemic blood vessels

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Korotkoff Sounds Phase I: marked by the first tapping sound, which gradually increase in intensity Phase II: Period in which a murmur or swishing sound is heard Phase III: Period during which sounds are crisper and greater in intensity Phase IV: Period marked by distinct abrupt muffling or by a soft blowing sound Phase V: Point at which sounds disappear

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Influencing Mean Arterial Blood Pressure Physical –Blood volume and the elastic properties of the blood vessels Physiologic factors –Cardiac output –Systemic vascular resistance

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Which of the following does not directly affect arterial blood pressure? a. Heart rate b. Vascular resistance c. Venous constriction d. Blood volume

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer c. Venous constriction Rationale: Venous constriction will not affect arterial pressure, whereas the other factors will have immediate effects.

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins The Canadian Hypertension Education Program (CHEP) and Canadian Blood Pressure Recommendations Modifiable and nonmodifiable risk factors –Nonmodifiable risk factors Family history, gender, race, and age-related increases in blood pressure –Modifiable risk factors Sedentary lifestyle, poor dietary habits, abdominal obesity, impaired glucose tolerance or diabetes mellitus, smoking, dyslipidemia, drug use, and stress

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Affecting Hypertension Age –More common in younger men than younger women –More common in the elderly Race –The Ontario Survey of the prevalence and control of hypertension –More common in blacks and South Asians Socioeconomic group –More common in lower socioeconomic group

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Categories of Hypertension Primary hypertension (essential hypertension) –The chronic elevation in blood pressure that occurs without evidence of other disease Secondary hypertension –The elevation of blood pressure that results from some other disorder, such as kidney disease Malignant hypertension –An accelerated form of hypertension Systolic hypertension –Systolic pressure of 140 mm hg or greater and a diastolic pressure of less than 90 mm hg

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Classifications of Essential Hypertension Systolic/diastolic hypertension –Both the systolic and diastolic pressures are elevated Diastolic hypertension –The diastolic pressure is selectively elevated Systolic hypertension –The systolic pressure is selectively elevated

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Risk Factors for Hypertension Family history Age-related changes in blood pressure Race Insulin resistance and metabolic abnormalities Circadian variations Lifestyle factors

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Lifestyle Factors Contributing to Hypertension High salt intake Obesity Excess alcohol consumption Dietary intake of potassium, calcium, and magnesium Oral contraceptive drugs Stress

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Target Organ Damage The heart –Hypertrophy Brain –Dementia and cognitive impairment Systemic vascular – Atherosclerosis Kidney –Nephrosclerosis Retinal complications

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Drugs Used in the Treatment of Hypertension Diuretics β- adrenergic–blocking drugs Angiotensin-converting enzyme (ACE) inhibitors Angiotensin II receptor blockers The calcium channel–blocking drugs Central α 2 -adrenergic agonists α 1 -adrenergic receptor blockers Vasodilators

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Factors Affecting Treatment Strategies for Hypertension Lifestyle Demographics Motivation for adhering to the drug regimen Other disease conditions and therapies Potential for side effects

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Renal failure results in Na + and water retention. This results in hypertension. How would you classify this type of hypertension? a. Primary hypertension b. Secondary hypertension c. Malignant hypertension d. Systolic hypertension

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer b. Secondary hypertension Rationale: Secondary hypertension is the result of an underlying disease.

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Most Common Causes of Secondary Hypertension Kidney disease (renovascular hypertension) Adrenal cortical disorders Pheochromocytoma Coarctation of the aorta Sleep apnea

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Types of Hypertension in Pregnancy Gestational hypertension Chronic hypertension Preeclampsia-eclampsia Preeclampsia superimposed on chronic hypertension

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Diagnosis and Treatment of Hypertension in Pregnancy Early prenatal care Refraining from alcohol and tobacco use Salt restriction Bed rest Carefully chosen antihypertensive medications

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins High Blood Pressure in Children and Adolescents Blood pressure norms for children are based on age, height, and gender-specific percentiles Secondary hypertension is the most common form of high blood pressure in infants and children –Kidney abnormalities –Coarctation of the aorta –Pheochromocytoma and adrenal cortical disorders In infants, associated most commonly with high umbilical catheterization and renal artery obstruction caused by thrombosis

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Orthostatic Hypotension Definition –An abnormal decrease in blood pressure on assumption of the upright position Causes –Decrease in venous return to the heart due to pooling of blood in lower part of body –Inadequate circulatory response to decreased cardiac output and a decrease in blood pressure

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Causes of Orthostatic Hypotension Conditions that decrease vascular volume –Dehydration Conditions that impair muscle pump function –Bed rest –Spinal cord injury

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Causes of Orthostatic Hypotension (cont.) Conditions that interfere with cardiovascular reflexes –Medications –Disorders of autonomic nervous system –Effects of aging on baroreflex function

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Common Causes of Orthostatic Hypotension Related to Hypovolemia Excessive use of diuretics Excessive diaphoresis Loss of gastrointestinal fluids through vomiting and diarrhea Loss of fluid volume associated with prolonged bed rest

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Complaints Associated With Orthostatic Intolerance Dizziness Visual changes Head and neck discomfort Poor concentration while standing Palpitations Tremor, anxiety Presyncope, and in some cases syncope

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Increased vascular compliance may contribute to which condition? a. Systolic hypertension b. Orthostatic hypotension c. Orthostatic hypertension d. Diastolic hypertension

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer b. Orthostatic hypotension Rationale: Orthostatic hypotension is the result of lower pressures, and increased compliance would decrease the vascular resistance and result in lower pressures.