Blood pressure (low)

Low blood pressure, also known as hypotension, refers to an abnormally reduced force of blood pushing against the artery walls. While blood pressure naturally fluctuates throughout the day depending on activity, stress, hydration, and other factors, consistently low readings may cause symptoms such as dizziness, fainting, blurred vision, or fatigue. In some cases, hypotension may be benign, especially in healthy individuals, but it can also signal underlying medical problems requiring evaluation and treatment.

---

Definition and Diagnostic Thresholds

• Normal blood pressure: around 120/80 mmHg.

• Hypotension: generally defined as systolic blood pressure below 90 mmHg and/or diastolic blood pressure below 60 mmHg.

• Severity is context-dependent; for some individuals, these readings may be normal and asymptomatic, while for others they may cause organ hypoperfusion.

---

Types of Hypotension

1. Orthostatic (Postural) Hypotension

   • A sudden drop in blood pressure when standing up from sitting or lying down.

   • Caused by impaired autonomic regulation, dehydration, medications, or neurological conditions.

2. Postprandial Hypotension

   • Occurs after meals due to excessive diversion of blood to the digestive tract.

   • More common in older adults.

3. Neurally Mediated Hypotension (Vasovagal Syncope)

   • Triggered by stress, pain, or prolonged standing.

   • Causes sudden slowing of the heart rate and dilatation of blood vessels.

4. Severe Hypotension (Shock)

   • Associated with life-threatening conditions such as sepsis, major blood loss, severe allergic reactions (anaphylaxis), or heart failure.

   • Requires emergency management.

---

Causes of Low Blood Pressure

• Physiological: Naturally low readings in young, fit individuals.

• Dehydration: Loss of fluids from vomiting, diarrhea, or excessive sweating.

• Blood loss: Trauma, surgery, or internal bleeding.

• Heart problems: Arrhythmias, heart valve disease, or heart failure.

• Endocrine disorders: Addison’s disease, hypothyroidism, adrenal insufficiency, or hypoglycemia.

• Medications:

  • Antihypertensives (e.g., ACE inhibitors, beta-blockers, diuretics).

  • Antidepressants (tricyclics, SSRIs).

  • Parkinson’s medications.

• Sepsis: Infection-induced systemic inflammation.

• Neurological disorders: Autonomic neuropathy (common in diabetes).

• Nutritional deficiencies: Lack of vitamin B12 or folate.

---

Symptoms of Low Blood Pressure

• Lightheadedness or dizziness

• Blurred vision

• Fatigue

• Fainting (syncope)

• Nausea

• Confusion (especially in older adults)

• Cold, clammy skin (in shock states)

• Rapid, shallow breathing

---

Diagnosis

1. Blood pressure measurement: Supine and standing (to detect postural drops).

2. History and examination: Assess medication use, hydration, and symptoms.

3. Blood tests: To check for anemia, hormonal disorders, and electrolyte imbalances.

4. Electrocardiogram (ECG): To evaluate arrhythmias or structural heart disease.

5. Tilt-table test: For recurrent syncope suspected to be vasovagal or autonomic in origin.

---

Management and Treatment

Treatment depends on the cause and severity.

1. Lifestyle Measures

• Increase fluid intake to maintain blood volume.

• Add more salt to the diet (under medical supervision).

• Small, frequent meals to avoid postprandial hypotension.

• Slow position changes (e.g., rising gradually from bed).

• Compression stockings to improve venous return.

• Elevating the head of the bed to reduce morning hypotension.

2. Treatment of Underlying Causes

• Correcting dehydration with oral rehydration solutions or intravenous fluids (0.9% sodium chloride infusion).

• Treating anemia with iron supplements or vitamin B12/folate replacement.

• Adjusting or discontinuing medications contributing to hypotension.

• Treating endocrine disorders (e.g., hydrocortisone for Addison’s disease, levothyroxine for hypothyroidism).

• Managing infections with antibiotics if sepsis-related.

3. Pharmacological Treatments

When lifestyle adjustments are insufficient:

• Midodrine (generic: midodrine hydrochloride)

  • Alpha-adrenergic agonist that raises blood pressure by vasoconstriction.

  • Typical dose: 2.5–10 mg orally three times daily.

  • Avoid giving close to bedtime due to risk of supine hypertension.

• Fludrocortisone (generic: fludrocortisone acetate)

  • Synthetic corticosteroid that helps retain sodium and expand blood volume.

  • Typical dose: 0.1–0.2 mg orally daily, titrated based on response.

  • Requires monitoring for hypokalemia, fluid overload, and hypertension.

• Droxidopa (generic: droxidopa)

  • Prodrug converted to norepinephrine, improving blood vessel tone.

  • Typical dose: 100–600 mg orally three times daily.

  • Used mainly in neurogenic orthostatic hypotension.

• Caffeine (as adjuvant therapy)

  • Mild pressor effect, sometimes used for episodic hypotension.

---

Complications of Severe Hypotension

• Syncope and risk of falls, leading to fractures or head injuries.

• Shock (cardiogenic, hypovolemic, septic, or anaphylactic) leading to multi-organ failure.

• Chronic organ hypoperfusion may contribute to kidney dysfunction and cognitive decline in older adults.

---

Prognosis

• Many people with naturally low blood pressure and no symptoms require no treatment.

• Symptomatic hypotension can usually be managed successfully with lifestyle adjustments and medications.

• Prognosis depends on underlying causes—e.g., chronic illnesses (heart failure, endocrine disorders) may require lifelong management.