Hypertension is recognized as a major risk factor for several potentially lethal cardiovascular conditions, including myocardial infarction, heart failure, and stroke. Guidelines urge more active prevention and treatment of hypertension. According to the guidelines, average systolic pressure greater than 120 but less than 130 mm Hg is considered elevated, pressure equal to or greater than 130/80 but less than 140/89 mm Hg is considered stage 1 hypertension, while pressures equal to or greater than 140/90 mm Hg are considered stage 2 hypertension. Increased systolic pressure is now considered at least as important as elevated diastolic. Both stage 1 and stage 2 hypertension are deserving of treatment in most patients and the guidelines urge that causes and treatment of atherosclerosis also be considered (see Chapter 35).
Many drugs are available for treatment of hypertension and in most patients blood pressure can now be controlled effectively and with minimal adverse effects. Antihypertensive drugs are organized around a clinical indication—the need to treat the disease—rather than a single receptor type. The drugs covered in this unit have a variety of mechanisms of action including diuresis, sympathoplegia (interference with the sympathetic nervous system), vasodilation, and antagonism of the renin-angiotensin-aldosterone system, and many agents are available in most of these categories.
High-Yield Terms to Learn
|Baroreceptor reflex ||Primary autonomic mechanism for blood pressure homeostasis; involves sensory input from carotid sinus and aorta to the vasomotor center and output via the parasympathetic and sympathetic motor nerves (see Figures 6–4 and 11–2) |
|Catecholamine reuptake pump ||Nerve terminal transporter responsible for recycling norepinephrine after release into the synapse; also called norepinephrine transporter (NET) |
|Catecholamine vesicle pump ||Storage vesicle transporter that pumps catecholamine from neural cytoplasm into the storage vesicle; also called vesicle monoamine transporter (VMAT) |
|End-organ damage ||Vascular damage in heart, kidney, retina, or brain resulting in diminished perfusion and impaired function |
|Essential hypertension ||Hypertension of unknown etiology; also called primary hypertension |
|False transmitter ||Substance, for example, octopamine, stored in vesicles and released into synaptic cleft but lacking the effectiveness of the true transmitter, norepinephrine |
|Hypertensive emergency (“malignant hypertension”) ||An accelerated form of severe hypertension associated with rising blood pressure and rapidly progressing damage to vessels and end organs. Often signaled by renal damage, encephalopathy, and retinal hemorrhages or by angina, stroke, or myocardial infarction |
|Orthostatic hypotension ||Hypotension on assuming upright posture; postural hypotension |
|Postganglionic neuron blocker ||Drug that blocks transmission by an action in the terminals of the postganglionic nerves |
|Rebound hypertension ||Elevated blood pressure (usually above pretreatment levels) resulting from loss of antihypertensive drug effect |
|Reflex tachycardia ||Tachycardia resulting from lowering of blood pressure; mediated by the baroreceptor reflex |
|Secondary hypertension ||Hypertension caused by a diagnosable abnormality, eg, aortic coarctation, renal artery stenosis, adrenal tumor, etc. Compare essential hypertension |
|Stepped care ||Progressive addition of drugs to an antihypertensive regimen, starting with one (usually a diuretic) and adding in stepwise fashion ...|