Chapter 16: Alterations in Blood Pressure PDF

CHAPTER 16 ALTERATIONS IN BLOOD PRESSURE 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 blo...

CHAPTER 16 ALTERATIONS IN BLOOD PRESSURE 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 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 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 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 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 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 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 Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Long-Term Regulation of Systemic Blood Pressure Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Hypertensiv e Medications 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 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 Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Hypertension (Cont.) 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 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 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 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 Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Hypertension (Cont.) 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 Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc. Hypertension (Cont.) 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 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 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 Elsevier items and derived items © 2010, 2005 by Saunders, an imprint of Elsevier Inc.