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Hypertension (Chapter 13, pages 289-310)
Describe age-related change in prevalence in hemodynamic characteristics in hypertension
Identify the symptoms, signs and laboratory abnormalities that are characteristic of various forms of secondary hypertension
Identify the pathological and clinical manifestations of end-organ complications of hypertension
Describe the lifestyle measures useful in treating high blood pressure
Develop the plan for initial diagnosis and treatment of an individual with elevated blood pressure; describe the rationale for diagnostic testing and mechanism of action of any recommended drugs
Intro and the basics:
Lots of people have hypertension
High BP is usually asymptomatic until something bad happens
Most of the time (95%) we don’t know the cause of the high BP
THIS IS CALLED ESSENTIAL HYPERTENSION (OR PRIMARY HTN)
When we know the cause for elevated BP, it’s called SECONDARY HTN
These cases are far less common, but are important because they have different treatment strategies and cure is often possible.
Definition: current criteria = diastolic of > 90, systolic of > 140.
These are arbitrary cut off points.
Recall that BP = CO x TPR, and CO = SV x HR. We can infer that 3 systems are important in regulating BP: heart, vessel tone, and kidney, which regulates intravascular volume, and thus preload. The kidney is especially important, because it has the amazing property of being able to return BP to normal despite very high CO and constriction of the vessels by excreting volume.
Review of the baroreceptor reflex. Feel free to skip. Also recall that the BARORECPTOR REFLEX is important in regulating blood pressure. Located in walls of aortic arch and in carotid sinus, the receptors monitor changes in BP by sensing the stretch in the vessel. With increased BP, they increase their rate of firing. The signals from the carotid sinus are sent to the medulla via the glossopharyngeal nerve (CN IX), while signals from the aortic arch are sent via vagus. The fibers converge at the TRACTUS SOLITARIUS, where upon sensing increased BP, sympathetic impulses are inhibited, and parasympathetic impulses are excited. All this results in decreased vascular resistance and decreased CO, decreased HR and force of contraction.