Low Blood Pressure (Hypotension): Causes, Symptoms, and Treatment

Blood pressure is one of the most critical indicators of cardiovascular health. While high blood pressure (hypertension) is widely discussed, low blood pressure, or hypotension, can also cause concern and require attention. Hypotension is a condition in which blood pressure drops below normal values (typically below 90/60 mm Hg), which can lead to inadequate blood supply to organs and tissues.

What is Hypotension and Why Does It Occur?

Hypotension can be a physiological feature of the body that causes no discomfort, or it can be a symptom of more serious medical conditions. When blood pressure drops too low, the brain and other vital organs may not receive enough oxygen and nutrients, leading to characteristic symptoms.

Key causes that can lead to the development of hypotension include:

• Dehydration and water balance disorders. A lack of fluids in the body reduces the volume of circulating blood, which directly affects blood pressure.
• Endocrine disorders. Certain hormonal imbalances can affect blood pressure regulation.
• Cardiovascular diseases. Heart problems, such as heart failure, can reduce the heart's ability to pump blood effectively.
• Certain medications. A number of medications have a hypotensive effect as a side effect.

The Link Between Hypotension and Water-Salt Balance

One of the significant causes of hypotension is disturbances in the body's water and salt balance. These disturbances can be triggered by various conditions:

• Central Diabetes Insipidus (CDI). This is a clinical syndrome caused by the loss or impairment of function of vasopressinergic neurons, leading to a deficiency of arginine vasopressin (AVP). AVP deficiency results in the kidneys' inability to concentrate urine and excessive water loss, causing hypotonic polyuria (excretion of large volumes of diluted urine) and compensatory thirst [7]. As a result of such excessive fluid loss, dehydration and, consequently, hypotension can develop. Patients with CDI, especially hospitalized ones (e.g., with COVID-19), are at high risk of mortality due to fluid volume loss [5].
• Hyponatremia (low blood sodium levels). This condition can be caused by various factors. For example, dilutional hyponatremia is a major complication of desmopressin treatment in diabetes insipidus, when excess water is retained in the body, diluting sodium [5]. Hyponatremia is also common in patients with COVID-19 (accounting for up to 20-30% of cases according to studies) and is primarily caused by the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or hypovolemia (decreased blood volume) [5].

Under conditions of hyponatremia and dehydration, the body experiences a fluid deficit, which directly leads to a drop in blood pressure.

Medications and Hypotension: The Role of Diuretics

Certain medications can cause hypotension as a side effect. One such class is diuretics (water pills), which are widely used, for example, in heart failure to relieve symptoms associated with fluid retention [6].

Although guidelines recommend using the lowest possible dose of loop diuretics to maintain euvolemia (normal fluid volume), data on the safety of this practice are limited [6]. A study showed that changing diuretic doses (both increasing and decreasing) in stable heart failure patients may be associated with the risk of adverse events, such as hospitalization or death, within 30 days [6]. This emphasizes the importance of careful selection and monitoring of diuretic dosages to avoid an excessive drop in blood pressure and associated complications.

Symptoms and Diagnosis of Hypotension

Symptoms of low blood pressure can range from mild to significantly impairing quality of life. The most common include:

• Weakness, fatigue
• Dizziness, especially upon sudden postural changes (orthostatic hypotension)
• Fainting or pre-syncope states
• Pale skin
• Cold extremities
• Impaired concentration

Diagnosis of hypotension begins with measuring blood pressure and taking a medical history. The doctor may order additional tests to identify the underlying cause. For instance, when water balance disorders such as hypotonic polyuria are suspected, a copeptin test can be useful, as it improves the accuracy and acceptability of the diagnostic approach [7]. It is also important to monitor plasma sodium levels, especially in patients receiving desmopressin [5].

Approaches to Treating Hypotension

Treatment for hypotension is always aimed at eliminating its underlying cause. General recommendations may include:

• Increasing fluid intake. In cases of dehydration, this is a key step.
• Adjusting medication therapy. If hypotension is caused by drugs, the physician may adjust the dose or switch the medication.
• Dietary changes. In some cases, a moderate increase in salt intake may be recommended (under medical supervision).

For patients with central diabetes insipidus receiving desmopressin, it is crucial to carefully monitor the dosage to avoid dilutional hyponatremia. In situations where monitoring plasma sodium levels is difficult (e.g., during the COVID-19 pandemic), it is recommended to withhold desmopressin once a week until aquaresis (excretion of excess water) occurs, which allows the retained fluid to be eliminated. Patients should monitor their weight daily, and after pituitary surgeries, drink according to thirst and know the symptoms of hyponatremia for early recognition [5].

When using diuretics, particularly in patients with heart failure, it is essential to strictly follow medical recommendations and undergo regular check-ups to assess the efficacy and safety of the therapy [6].

The Importance of an Individualized Approach

Hypotension is not always a harmless condition. If you experience symptoms of low blood pressure, it is important to consult a physician for accurate diagnosis and selection of appropriate treatment. Self-treatment can be dangerous. Only a specialist can determine the cause of hypotension and develop an individualized treatment plan that takes into account all the characteristics of your body and concomitant diseases.

Sources

1. [1] The efficacy and safety of low-dose triple combination for hypertension treatment: a systematic review and meta-analysis of randomized controlled trials. https://pubmed.ncbi.nlm.nih.gov/39912900/
2. [2] Hypertension Treatment and Control in Canadians With Diabetes. https://pubmed.ncbi.nlm.nih.gov/40447187/
3. [3] Hidden barriers: obesity bias in hypertension treatment. https://pubmed.ncbi.nlm.nih.gov/39160218/
4. [4] Cardiac response to hypertension treatment: an advanced echocardiographic evaluation. https://pubmed.ncbi.nlm.nih.gov/39014266/
5. [5] ENDOCRINOLOGY IN THE TIME OF COVID-19-2021 UPDATES: The management of diabetes insipidus and hyponatraemia. https://pubmed.ncbi.nlm.nih.gov/34292875/
6. [6] Exploring safety of down-titrating diuretics in heart failure management. https://pubmed.ncbi.nlm.nih.gov/40600695/
7. [7] Diagnosis and Management of Central Diabetes Insipidus in Adults. https://pubmed.ncbi.nlm.nih.gov/35771962/
8. [8] What Have We Learned From the Idiopathic Intracranial Hypertension Treatment Trial the William F. Hoyt Lecture. https://pubmed.ncbi.nlm.nih.gov/42133960/

The information provided in the article is for reference purposes only and cannot replace an in-person consultation with a qualified medical professional. Always consult a physician for diagnosis and treatment.