The drop in blood pressure, called arterial hypotension, can manifest itself as palpitations, sweating, great weakness, dizziness, paleness, or even syncope. The causes can be very diverse and must be identified to define the appropriate treatment.
Definition of drop in blood pressure or hypotension
The drop in blood pressure expresses a decrease in the pressure of the blood pumped by the heart against the wall of the arteries. According to the MSD Manual, this hypotension results from the dilation of small arteries, heart problems, or an insufficient volume of blood pumped by the heart. Blood pressure is measured by a blood pressure monitor, which will record two measurements: systolic pressure (maximum pressure when the heart contracts) and diastolic pressure (minimum pressure when the heart is at rest). Normal blood pressure is between 90/60 mmHg and 130/80 mmHg, specifies the Amelis Institute. We speak of a drop in blood pressure when it falls below the threshold of 90/60 mmHg. In this respect, we distinguish between different types of hypotension: postprandial hypotension which follows a very copious meal, and orthostatic hypotension linked to a sudden change of position (sitting/standing, lying down/standing).
The causes of the dilation of the small arteries causing the drop in blood pressure
Several factors can lead to dilation of small arteries and therefore a drop in blood pressure. The main causes of arteriole dilation are:
- Medications: certain drug treatments can have side effects on blood pressure and cause it to fall. This is the case for antihypertensives when they are dosed too high, but also for diuretics, anxiolytics and even antidepressants.
- A serious infectious disease, leading to septic shock or toxic shock.
- Lesions in the spinal cord, which will impact the nerves responsible for contracting the small arteries.
- Anaphylactic shock: that is to say a serious, even potentially fatal, allergic reaction which occurs in the presence of an allergen (food, venom, latex, medication, etc.).
- The particular case of orthostatic hypotension: it corresponds to a sudden drop in blood pressure when moving from a sloping position to an upright position. Often transient, it can however be the cause of falls.
Heart problems, possible causes of blood pressure drop
As the Center Hospitalier Universitaire Vaudois explains, the heart is a muscle responsible for pumping blood, in order to distribute it to organs and tissues throughout the body, through the arteries and veins. So, when the heart no longer performs its functions properly, then blood pressure can drop. This is the case if you suffer from heart problems, such as valvulopathy (pathology that affects the mitral valve or the aortic valve), tachycardia (too fast heart rate), bradycardia (too slow heart rate), arrhythmia ( irregular heartbeat) or even a myocardial infarction. The heart then no longer pumps enough blood to oxygenate the body properly, and the blood pressure against the artery walls decreases.
Insufficient blood volume causes hypotension
If the blood volume circulating in the veins and arteries is insufficient, then you also risk having a drop in blood pressure. This insufficient blood volume may be the consequence of insufficient hydration, a common phenomenon among the elderly, because they perceive the sensation of thirst less well. It can also be a side effect of excessive alcohol consumption, as alcohol causes dehydration of the body. This deficit in blood volume can also result from hemorrhage. Finally, it can be indicative of a kidney problem. A kidney pathology, in particular a dysfunction of the adrenal glands, will lead, through insufficient secretion of cortisol, to a drop in blood pressure.
Neurological disorders, responsible for the drop in blood pressure
A drop in blood pressure can be indicative of neurological pathologies. Indeed, when the nerves responsible for transmitting information between the heart, the vessels and the brain do not properly fulfill their role, because they are affected by a neurological disorder, then this can lead to a drop in blood pressure. This happens if you have autonomic neuropathies. These autonomic neuropathies can have various causes, such as uncontrolled diabetes, amyloidosis (rare disease which results in an abnormal accumulation of proteins in the tissues), or even an autoimmune disease (rheumatoid arthritis, systemic lupus erythematosus, syndrome of Guillain-Barré, Hashimoto’s thyroiditis, Parkinson’s disease, multiple sclerosis, vasculitis, etc.).
Sources
- Arterial hypotension: causes, symptoms and treatments, Amelis InstituteDecember 18, 2023
- Low blood pressureThe MSD Manual, June 2022
- The drop in pressure when you get upMontreal University Hospital Center, March 20, 2019
- Arterial pressureVaud university hospital center
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