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HYPOTENSION. BY PROF.DR . KAMAL MAHMOUD AHMAD. HEAD OF THE CARDIOLOGY & ANGIOLOGY UNIT MEDICAL RESEARCH INSTITUTE ALEXANDRIA UNIVERSITY. DEFINITION. Blood pressure: How low can you go? Current guidelines identify normal blood pressure as lower than 120/80
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BY PROF.DR. KAMAL MAHMOUD AHMAD
HEAD OF THE CARDIOLOGY & ANGIOLOGY UNIT MEDICAL RESEARCH INSTITUTE ALEXANDRIA UNIVERSITY
DEFINITION • Blood pressure: How low can you go? • Current guidelines identify normal blood pressure as lower than 120/80 • Many experts think 115/75 is optimal. • Some experts define low blood pressure as readings lower than 90 systolic or 60 diastolic
Normal physiology • Blood pressure is continuously regulated by the autonomic nervous system, to balance the effects of the • 1-sympathetic nervous system, which tends to raise blood pressure, & • 2-parasympathetic nervous system, which lowers it. • The vast and rapid compensation abilities of the autonomic nervous system allow normal individuals to maintain an acceptable blood pressure over a wide range of activities and in many disease states.
1 Reduced blood volume • Hypovolemia, is the most common mechanism producing hypotension. This can result from • Hemorrhage. • Insufficient fluid intake, as in starvation; • Excessive fluid losses from diarrhea or vomiting. • Hypovolemia is often induced by excessive use of diuretics.
2- Decreasedcardiac output • Severe congestive heart failure, • Largemyocardial infarction, • Bradycardia, often produces hypotension and can rapidly progress to cardiogenic shock. • Arrhythmias often result in hypotension by this mechanism. • Beta blockers can cause hypotension both by slowing the heart rate and by decreasing the pumping ability of the heart muscle.
3-Excessivevasodilation • Excessive vasodilation, or insufficient constriction of the resistance blood vessels (mostly arterioles), This can be due to; • injury to the brain or spinal cord . • dysautonomia, an intrinsic abnormality in autonomic functioning. • sepsis, • acidosis, • medications, such as nitrate preparations, calcium channel blockers, ARBS or ACE inhibitors. • Many anesthetic agents and techniques, including spinal anesthesia and most inhalational agents, produce significant vasodilation.
Causes of low blood pressure • Athletes and people who exercise regularly tend to have lower BP than do people who aren't as fit. So, in general, do nonsmokers and people who eat well and maintain a normal weight. • But in some instances, low blood pressure can be a sign of serious, even life-threatening disorders.
Causes of low blood pressure The American Heart Associationconsiders the following as possible causes of low blood pressure: 1-Pregnancy. • Because a woman's circulatory system expands rapidly during pregnancy, blood pressure is likely to drop. In fact, during the first 24 weeks of pregnancy, systolic pressure commonly drops by five to 10 points and diastolic pressure by as much as 10 to 15 points.
Pregnancy. • Hypotension during pregnancy can be as serious as hypertension. • Low systolic pressure may lead to low birth weight, death of the foetus or low intelligence quotient scores at the age of about four years. • Low diastolic pressure can also increase the risk of premature birth.
Pregnancy. 90/66
Causes of low blood pressure • 2-Medications. Many drugs can cause low blood pressure, including diuretics and other drugs that treat high blood pressure; heart medications such as beta blockers; Drugs for Parkinson's disease; tricyclic antidepressants; Sildenafil (Viagra), particularly in combination with nitroglycerine; narcotics; and alcohol.
Causes of low blood pressure • 4-Endocrine problems. hypothyroidism , adrenal insufficiency (Addison's disease), low blood sugar (hypoglycemia), and in some cases, diabetes, can trigger low blood pressure. • 5-Dehydration. • Even mild dehydration can cause weakness, dizziness and fatigue. Fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise can all lead to dehydration. • Far more serious is hypovolemic shock, a life-threatening complication of dehydration. It occurs when low blood volume causes a sudden drop in blood pressure and a corresponding reduction in the amount of oxygen reaching your tissues. • If untreated, severe hypovolemic shock can cause death within a few minutes or hours.
Causes of low blood pressure • 6-Blood loss. • Losing a lot of blood from major injury or severe internal bleeding reduces the amount of blood in our body, leading to a severe drop in blood pressure. • 7-Severe infection (septicemia). • Septicemia can happen when an infection in the body enters the bloodstream. Lung, abdomen or urinary tract infections are usually the cause of septicemia. These conditions can lead to a life-threatening drop in blood pressure called septic shock.
Causes of low blood pressure • 8-Allergic reaction (anaphylaxis). • Anaphylaxis is a severe and potentially life-threatening allergic reaction. Common triggers of anaphylaxis include foods, certain medications, insect venoms. Anaphylaxis can cause breathing problems, hives, itching, a swollen throat and a drop in blood pressure. • 9-Nutritional deficiencies. • In addition to making patients feel tired because you're not getting enough oxygen, anemia can lead to low blood pressure.
Orthostatic hypotension, • Also called "postural hypotension", • is a common form of low blood pressure. It occurs after a change in body position, typically when a person stands up from either a seated or lying position. It is usually transient and represents a delay in the normal compensatory ability of the autonomic nervous system. • It is commonly seen in hypovolemia and as a result of various medications. In addition to blood pressure-lowering medications, many psychiatric medications, in particular antidepressants, can have this side effect.
DIAGNOSIS OF ORTHOSTATIC HYPOTENSION • Simple blood pressure and heart rate measurements while lying, seated, and standing (with a two-minute delay in between each position change) can confirm the presence of orthostatic hypotension. • Orthostatic hypotension is indicated if there is a drop in 20 mmHg of systolic pressure (and a 10 mmHg drop in diastolic pressure and a 20 beat increase in heart rate.
Neurocardiogenic syncope • is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position. Neurocardiogenic syncope is related to vasovagal syncope in that both occur as a result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system.
Carotid sinus syndrome Carotid sinus syndrome (CSS) is diagnosed when carotid sinus hypersensitivity is documented in a patient with otherwise unexplained dizziness, falls, presyncope or syncope, in whom carotid sinus massage reproduces presenting symptoms.
Carotid sinus syndrome • The cardioinhibitory subtype is diagnosed if carotid sinus massage produces asystole exceeding 3 seconds, • the vasodepressor subtype if there is a fall in systolic blood pressure (SBP) exceeding 50mmHg in the absence of significant bradycardia • Mixed subtype if both are present.
Postprandial hypotension • It occurs 30–75 minutes after eating meals. When a great deal of blood is diverted to the intestines to facilitate digestion and absorption, the body must increase cardiac output and peripheral vasoconstriction in order to maintain enough BP to perfuse vital organs, such as the brain. • It is believed that postprandial hypotension is caused by the autonomic nervous system not compensating appropriately, because of ageing or a specific disorder
Symptoms • The cardinal symptom of hypotension is lightheadedness or dizziness. • If the blood pressure is sufficiently low, fainting and often seizures will occur.
