Long Term Arterial Pressure Regulation & Hypertension Dr. Wasif Haq

Important Concepts Changes in arterial pressure for weeks and months. Arterial pressure & urinary output: Direct relationship. Whenever arterial pressure rises, urinary output is also increased. Increased arterial pressure not only causes excess water loss (pressure diuresis) but also increased Sodium ion loss (pressure natriuresis)

Renin-Angiotensin System Drop in arterial pressure stimulates Renin release from Kidney Juxtaglomerular cells. Prorenin splits to form Renin which acts on Angiotensinogen to form “Angiotensin 1”. Splitting of amino acids from Angiotensin 1 forms “Angiotensin 2”. Angiotensin converting enzyme (A.C.E.) mostly in lungs. Kidneys and blood vessels may also have. Angiotensin 1 mild vasoconstrictive properties while Angiotensin 2 extremely vasoconstrictive.

Actions of Angiotensin 2 Strong vasoconstriction in arterioles rises total peripheral resistance and therefore arterial pressure. Mild vasoconstriction in veins promote increased venous return to heart. Retention of Sodium & water to increase body fluid volume that rises arterial pressure through release of Aldosterone from adrenal glands. More significant step in long term regulation. Angiotensinases inactivate Angiotensin 2 within 1-2 minutes.

Mechanism of action Angiotensin constricts renal arterioles which lead to reduced blood flow in kidneys. This causes greater reabsorption of sodium and water, decreasing urinary output. Aldosterone-Sodium conserving hormone. It’s release prevents Sodium loss.

Hypertension

Hypertension Repeatedly elevated blood pressure exceeding 135mm over 90 mm Hg. Mean arterial pressure greater than 110 mm Hg (normal: 90 mm Hg). If mean arterial pressure rises above 150 mm Hg= Severe hypertension. Blood pressure can change depending on whether a person is lying down or standing up. Exercise can temporarily raise blood pressure. Feeling nervous or excited also can cause a temporary increase.

Types Primary Hypertension Secondary Hypertension (Unknown cause, (Renal artery stenosis, also called “Essential monogenic causes= hypertension”) mutation of single gene)

Symptoms Mostly asymptomatic-hence called ‘silent killer’. Common symptoms are headache, dizziness, blurred vision, nausea & shortness of breath.

Effects of Hypertension A. Risk of coronary disease: Excessive workload on heart can cause heart failure and death. B. Cerebral infarction: High blood pressure can rupture cerebral vessels which can lead to death of part of brain called cerebral infarction or stoke. Stroke can cause paralysis, dementia & blindness. C. Damage to kidneys: Can cause kidney failure, uremia and death due to renal tissue destruction.

Prevention & Treatment 30 minutes daily exercise. What’s the best exercise? Avoiding high intake of Sodium & fat containing foods. No smoking. Regular checkup. Diuretics & A.C.E. inhibitors.

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