Circulatory System Conditions
Subtopic:
Hypertension
Hypertension: Elevated Blood Pressure
Definition
- Hypertension, derived from “hyper” (above normal) and “tension” (pressure), refers to persistently high blood pressure.
- Hypertension is defined as a consistent elevation of blood pressure beyond what is considered normal for an individual’s age, typically above 140/90 mmHg. A diagnosis is confirmed when either the diastolic or systolic pressure (or both) are repeatedly measured above the normal range across at least three separate clinic visits.
Blood Pressure Explained
Blood Pressure: The force exerted by circulating blood against artery walls, measured in millimeters of mercury (mmHg) using a sphygmomanometer.
Diastolic Pressure: The pressure in the arteries when the heart relaxes between beats.
Systolic Pressure: The pressure in the arteries when the heart contracts and pumps blood.
Blood Pressure Classification (Adults)
| BP Classification | Systolic BP (mmHg) | Diastolic BP (mmHg) |
|---|---|---|
| Normal | <120 | <80 |
| Pre-hypertension | 120 – 139 | 80 – 89 |
| Stage 1 Hypertension | 140 – 159 | 90 – 99 |
| Stage 2 Hypertension | ≥160 | ≥100 |
| Isolated Systolic Hypertension | ≥140 | <90 |
Accurate Blood Pressure Measurement
To ensure reliable blood pressure readings, follow these steps:
Correct Equipment: Use a properly calibrated sphygmomanometer with an appropriate cuff size.
Rest Period: Allow the patient to rest quietly for 5-10 minutes before measurement.
Avoid Talking: The patient should remain silent during measurement.
Arm Position: Position the arm at heart level.
Multiple Readings: Obtain 2-3 readings over separate visits before confirming a diagnosis.
Patient Communication: Explain the blood pressure reading to the patient.
Documentation: Record and provide a copy of the results.
Types of Hypertension
Hypertension is classified into two categories:
1. Essential (Primary) Hypertension
No identifiable underlying medical condition.
Accounts for approximately 90% of hypertension cases in Uganda.
Historically considered a natural adaptation to aging, but this view is outdated.
Risk Factors for Essential Hypertension
Family History: Close relatives with hypertension or cardiovascular disease.
Diabetes Mellitus: Increased risk among diabetics.
Physical Inactivity: A sedentary lifestyle.
Overweight or Obesity: BMI ≥30 kg/m².
Smoking: Raises blood pressure and cardiovascular risk.
Advanced Age: More common in individuals over 60.
High Cholesterol: Elevated cholesterol levels.
2. Secondary Hypertension
Elevated blood pressure caused by an underlying medical condition.
Common causes include:
Kidney Disease
Medications: Steroids, oral contraceptives
Pregnancy Complications: Pre-eclampsia, eclampsia
Obstructive Sleep Apnea
Coarctation of the Aorta (narrowing of the main artery)
Diabetic Renal Disease
Management focuses on treating the primary condition alongside blood pressure control.
Management of Hypertension
Non-Pharmacological Measures (Lifestyle Changes)
Patient Education: Inform patients about hypertension and its long-term management.
Weight Management: Encourage weight loss.
Regular Exercise: 30 minutes of activity, 5 days a week.
Smoking Cessation: Strongly advised to improve medication effectiveness and cardiovascular health.
Healthy Diet: Encourage fruits and vegetables.
Moderate Alcohol Consumption: Limit to moderate levels.
Low Sodium Diet: Reduce salt intake.
Limit Saturated Fats: Avoid high-fat foods.
Drug Therapy (Pharmacological Measures)
Monotherapy (Single Drug): For mild hypertension.
Combination Therapy: If blood pressure remains uncontrolled, a second medication may be added.
Stage 2 Hypertension: Often requires two medications initially, adjusted based on response.
Choosing Antihypertensive Medications
Considerations:
Co-existing Conditions: Certain drugs are contraindicated in pregnancy, asthma, diabetes, etc.
Medication Accessibility & Cost: Assess affordability.
Allergies: Check for known drug allergies.
Target Organ Damage: Evaluate if organs are affected by hypertension.
Antihypertensive Drug Choices in Specific Conditions
| Condition | Recommended Antihypertensive |
| Pregnancy | Methyldopa (Aldomet) |
| Diabetes Mellitus | Captopril, Lisinopril |
| Asthma | Amlodipine, Nifedipine |
| Pre-eclampsia/Eclampsia | Hydralazine (Apresoline) |
| Angina Pectoris | Nifedipine, Amlodipine |
| Heart Failure | Frusemide, Lisinopril, Captopril |
Resistant Hypertension
Defined as persistently high blood pressure (≥140/90 mmHg) despite using three or more antihypertensive medications, including a diuretic at full doses.
Causes of Resistant Hypertension
Advanced Age: Individuals over 60 years are at higher risk.
Medication Non-Adherence or Misuse: Not taking prescribed blood pressure medication correctly or as directed.
Lifestyle Factors: Ongoing engagement in risk behaviors like smoking, excessive alcohol intake, and being overweight or obese.
Drug Interactions: Using certain other medications concurrently that can raise blood pressure, such as certain decongestants, NSAIDs (like diclofenac) for pain relief, or some cold remedies.
Underlying Health Conditions: Presence of other medical issues that contribute to high blood pressure, such as kidney disease.
Malignant hypertension, hypertensive emergency, hypertensive urgency
Malignant hypertension
This is a serious condition marked by a sudden, significant increase in blood pressure leading to damage in small blood vessels, potentially affecting multiple organs.
Clinical features may include disorientation or confusion, severe headache, loss of vision, and in severe cases, coma.
It is a medical emergency requiring immediate hospitalization and rapid, but controlled, lowering of blood pressure, typically over 12 to 24 hours, to a safe level.
Hypertensive emergency
Defined as severe elevation of blood pressure (typically above 180/120 mmHg) accompanied by acute, ongoing damage to target organs. These organs can include the brain (stroke, encephalopathy), kidneys (acute kidney injury), heart (heart attack, heart failure), and eyes (retinopathy).
Patients require admission to an intensive care unit if possible for close monitoring. Blood pressure must be promptly reduced to prevent further organ damage, but the reduction must be cautious. Rapid reduction (more than 40% in the initial 24 hours) can risk reduced blood flow to the brain (cerebral hypoperfusion).
Medications used for these critical situations, particularly intravenously, may include Hydralazine or Labetalol.
Hypertensive urgency
Characterized by very high blood pressure but without clinical evidence of new or worsening target organ damage.
Blood pressure should be lowered more gradually than in an emergency, typically reduced over 24 to 48 hours. Oral medications are commonly used in this setting. Examples include Nifedipine (sometimes administered sublingually for faster effect), Captopril, or Labetalol tablets.
Drugs used in the treatment of hypertension
Common classes of antihypertensive medications used include:
Beta blockers
Calcium channel blockers
Diuretics
Angiotensin-converting enzyme inhibitors (ACE inhibitors)
Angiotensin II receptor blockers (ARBs)
Centrally acting antihypertensives
Direct acting vasodilators
1. Beta blockers
These are frequently prescribed drugs for hypertension management, often due to their widespread availability and affordability.
Examples
Propranolol
Atenolol
Carvedilol
Labetalol
Mechanism of Action
Beta blockers primarily work by blocking beta-1 receptors, particularly those found in the heart. This action leads to a slower heart rate and a reduced force of heart muscle contraction, thereby lowering blood pressure. Some also block beta-2 receptors or alpha receptors.
Indications
High blood pressure (hypertension)
Chest pain due to reduced blood flow to the heart muscle (angina pectoris)
Certain types of headaches (migraine prophylaxis)
Management of chronic heart failure (specific agents like Carvedilol or Metoprolol)
Following a heart attack (post-myocardial infarction)
Side effects
Difficulty with sexual performance (impotence)
Wheezing or shortness of breath, especially in susceptible individuals
Sensation of coldness in hands and feet (cold extremities)
Slow heart rate (bradycardia)
Decreased ability to tolerate physical activity (reduced exercise tolerance)
Fatigue or tiredness
Potential to worsen or precipitate heart failure in some cases, particularly if started inappropriately
Contraindications
Individuals with asthma or significant reactive airway disease
Patients experiencing acute, decompensated heart failure
Certain heart rhythm abnormalities (heart block, specifically 2nd or 3rd degree)
Chronic obstructive pulmonary disease (COPD)
Patients with diabetes mellitus, as they can mask the warning signs of low blood sugar (hypoglycemia)
Clinical depression (caution advised)
Pregnancy and breast feeding
Some beta blockers are generally considered for use during pregnancy when necessary, although prolonged use may potentially affect fetal growth. Certain beta blockers are considered compatible with breastfeeding.
2. Calcium channel blockers
Often used as initial therapy for hypertension, these agents can be used alone or in combination with other blood pressure medications. They are generally safe for use in patients with certain co-existing conditions like asthma or kidney dysfunction, but caution is needed in severe heart failure.
Examples
Nifedipine
Amlodipine
Felodipine
Mechanism of Action
Calcium channel blockers reduce the influx of calcium ions into vascular smooth muscle cells. This action causes the blood vessels to relax and widen (vasodilation), which in turn lowers blood pressure. Some also affect calcium channels in the heart, affecting heart rate and contractility.
Indications
High blood pressure (hypertension)
Chest pain due to reduced blood flow to the heart muscle (angina pectoris)
Side effects
Facial redness and warmth (flushing)
Swelling, particularly in the ankles and legs (oedema)
Headache
Drop in blood pressure upon standing (postural hypotension)
Feeling lightheaded or unsteady (dizziness)
Feeling weak or lacking energy (weakness)
Sensation of burning in the chest (heart burn)
Rapid heart rate (tachycardia), particularly with some short-acting agents
Contraindications
Significant heart rhythm abnormalities (2nd or 3rd degree heart block)
Known allergic reaction or hypersensitivity to any drug in the class
Severe, decompensated heart failure
Extremely low blood pressure (severe hypotension)
Pregnancy and breast feeding
Specific calcium channel blockers, notably Nifedipine, are commonly used in the management of hypertension during pregnancy.
3. Diuretics
Diuretics are a cornerstone of antihypertensive therapy and are often considered first-line agents.
Thiazide diuretics, such as Bendrofluazide, are known for being safe, inexpensive, and effective in treating hypertension. Diuretics can be used alone or combined with ACE inhibitors, beta blockers, or other antihypertensives.
Classification of diuretics
| Class | Example |
| Thiazide diuretics | Bendrofluazide, Metolazone |
| Loop diuretics | Furosemide (Frusemide) |
| Potassium-sparing diuretics | Spironolactone |
Mechanism of action
Diuretics work primarily by increasing the amount of water and salt excreted by the kidneys into the urine. This process, called diuresis, helps reduce the total volume of fluid in the bloodstream, which in turn lowers blood pressure.
Indications
High blood pressure (hypertension)
Fluid overload, such as in heart failure (reducing swelling and congestion)
Note: Thiazide diuretics are primarily used for hypertension, but they may also be beneficial in managing mild heart failure symptoms. Loop diuretics are potent diuretics commonly used for significant fluid retention (oedema), particularly in heart failure, and are typically reserved for hypertension when associated with fluid overload or renal insufficiency.
Side effects
| Class | Common side effects |
| Thiazide diuretics | Low potassium levels (hypokalaemia), Elevated uric acid levels (hyperuricaemia), High blood sugar (glucose intolerance), Erectile dysfunction (impotence), Weakness, Dehydration |
| Loop diuretics | Dehydration, Dry mouth, Low potassium (hypokalaemia), Low sodium (hyponatraemia), Low magnesium (hypomagnesemia), Hearing problems (ototoxicity – rare but possible with high doses/rapid infusion) |
Contraindications
Thiazide diuretics should generally be avoided in patients with:
A history of Gout (due to potential increase in uric acid levels).
Certain types of Diabetes mellitus (can sometimes affect blood sugar control).
Existing Low potassium levels (hypokalaemia).
Significant Elevated blood lipid levels (hyperlipidaemia).
Previous Known hypersensitivity or allergic reaction to thiazides or sulfonamide-derived drugs.
Pregnancy and breast feeding
Caution is advised when using diuretics during pregnancy and breastfeeding, and their use should be carefully considered based on the clinical situation.
4. Angiotensin converting enzyme inhibitors (ACE inhibitors)
These are considered a preferred class of drugs for treating hypertension, including in patients with diabetes due to their kidney protective effects. They can be used alone or in combination with other agents like diuretics or beta blockers.
Examples
Captopril
Ramipril
Lisinopril
Enalapril
Mechanism of action
ACE inhibitors work by blocking the enzyme responsible for converting Angiotensin I to Angiotensin II. Angiotensin II is a powerful substance that constricts blood vessels (vasoconstrictor). By inhibiting its formation, these drugs cause blood vessels to relax and widen (vasodilation), leading to a reduction in peripheral resistance and a decrease in blood pressure. They also reduce aldosterone secretion, which helps reduce salt and water retention.
Indications
High blood pressure (hypertension)
Management of heart failure
Protection of kidney function in patients with diabetes (diabetic nephropathy)
Side effects
Common side effects associated with ACE inhibitors include:
A Persistent, dry, irritating cough
Skin rash
Alteration in taste perception (taste disturbance)
A potentially life-threatening swelling of the face, lips, tongue, or throat (Angioedema)
Contraindications
ACE inhibitors should generally not be used in:
Pregnant women (especially in the later stages due to risk of harm to the fetus).
Patients with moderate to severe renal impairment, particularly bilateral renal artery stenosis.
Individuals with a prior history of angioedema linked to ACE inhibitor use.
Known hypersensitivity or allergic reaction to any drug within this class.
Breastfeeding mothers (use is generally discouraged).
5. Centrally acting antihypertensive
Historically used for hypertension treatment, these medications are now less commonly the first choice for general hypertension management due to a higher incidence of certain side effects compared to newer agents.
Examples
Methyldopa
Clonidine
In some regions, Methyldopa remains the primary choice for treating hypertension in pregnant women due to its established safety profile in this population.
Mechanism of action
These drugs work by stimulating alpha-2 adrenergic receptors in the brainstem. This action reduces the outflow of sympathetic nerve signals, leading to decreased total peripheral resistance and a consequent lowering of blood pressure.
Indications
Hypertension during pregnancy
May be used for severe hypertension, sometimes as a third-line option
Side effects
Feeling tired or fatigued (Tiredness)
Headache
Erectile dysfunction (Impotence)
Feeling lightheaded or unsteady (Dizziness)
Mood changes or clinical depression (Mental depression)
Drowsiness or Sedation
A sudden, significant increase in blood pressure if stopped abruptly (Rebound hypertension on withdrawal)
Contraindications
Severe liver disease
Known hypersensitivity or allergic reaction to Methyldopa
6. Angiotensin II antagonists
This class of drugs represents a more recent development in hypertension therapy. They are often used as an alternative to ACE inhibitors, particularly in patients who experience side effects like cough with ACE inhibitors, as they are equally effective in lowering blood pressure.
Examples
Losartan
Telmisartan
Valsartan
Candesartan
Mechanism of action
Angiotensin II antagonists work by specifically blocking Angiotensin II from binding to its receptors (AT1 receptors) in blood vessels and other tissues. By preventing Angiotensin II’s action, they cause blood vessels to relax and widen (vasodilation), reducing peripheral resistance and lowering blood pressure. Unlike ACE inhibitors, they do not interfere with the enzyme that breaks down bradykinin, which is why cough is less common.
Indications
High blood pressure (hypertension)
Management of heart failure
Side effects
Common side effects associated with Angiotensin II antagonists include:
Low blood pressure (Hypotension)
Feeling lightheaded or unsteady (Dizziness)
Elevated potassium levels (Hyperkalaemia)
Contraindications
These medications should be strictly avoided during pregnancy, especially during the second and third trimesters, as they are known to cause fetal malformations and injury.
Generally not recommended for breastfeeding mothers.
7. Direct acting vasodilators
This group includes medications that relax the blood vessel walls directly.
Common examples include:
Hydralazine
Minoxidil
In some regions like Uganda, Hydralazine may be registered and recommended for treating hypertension that hasn’t responded adequately to other drug classes.
Long-term use of Hydralazine for hypertension can sometimes lead to fluid retention and a compensatory increase in heart rate (reflex tachycardia). These effects can often be managed by combining Hydralazine with beta blockers (to counteract the increased heart rate) and/or diuretics (to reduce fluid retention).
Mechanism of action
Direct acting vasodilators work by directly relaxing the smooth muscle in the walls of blood vessels, causing them to widen (vasodilation). This increased vessel diameter reduces resistance to blood flow, resulting in a decrease in blood pressure.
Indications
Severe hypertension
Management of hypertensive emergencies
Treatment of hypertension associated with pre-eclampsia and eclampsia during pregnancy
Side effects
Side effects commonly observed with Hydralazine include:
Headache
Rapid heart rate (Tachycardia)
Facial redness and warmth (Flushing)
Difficulty breathing or shortness of breath (Dyspnoea)
Swelling, particularly in the ankles (Oedema)
Drop in blood pressure upon standing (Postural hypotension)
Contraindications
Chest pain due to reduced blood flow to the heart muscle (Angina pectoris) – can worsen symptoms due to reflex tachycardia.
Patients with significant heart failure
Known hypersensitivity or allergic reaction to the drug.