What Is Postural Hypotension?

Introduction

Postural hypotension is a drop in your blood pressure when you stand up or change position. Postural means the position in which you hold your body when you are standing or sitting.

Hypotension is a term for low blood pressure. Blood pressure refers to the force of blood against the walls of your arteries through your circulatory system.

When you go from a sitting to standing position, blood draws into your lower legs due to gravity and this in turn causes your blood pressure to drop naturally. Your body has automatic coping mechanisms to compensate for this drop by increasing your heart rate and causing narrowing in your blood vessels to increase your blood pressure to its normal levels. However, sometimes certain medications and other factors can alter this coping mechanism causing postural hypotension.

Experiencing this condition can be debilitating and have an impact on your quality of life as adaptations to daily life may be required to manage symptoms and triggers. By understanding the condition and how it affects you can enable you to live a normal life without being too impacted by this condition.

Types of postural hypotension

In postural hypotension, your bodies’ response to the natural drop in blood pressure on change of position is inadequate or delayed. There are two recognised types of postural hypotension, these are:

• Classic postural hypotension – blood pressure drop occurs within three minutes of position change
• Delayed postural hypotension – this occurs when the drop in blood pressure is over three minutes following position change¹

Classic postural hypotension appears to be the most common form and most of the clinical research on this condition has been into classic presentations.

Causes of postural hypotension

As mentioned, certain medications can interrupt the coping mechanism of the body’s blood pressure response. Medications include:

• Some chemotherapy medications
• Vasodilation drugs such as calcium channel blockers and ACE inhibitors used to treat high blood pressure, heart failure and angina.
• Some antidepressants
• Some antipsychotics
• Diuretics also water tablets
• Medications used to treat Parkinson’s

Other causes of postural hypotension include:

• Dehydration – when the body does not have enough fluid circulating in the blood, this can reduce the volume of the blood circulating which can lower your blood pressure
• Underlying heart conditions – some heart conditions cause an inability to pump sufficient blood through the circulation. In heart failure, this can be due to a weakened heart muscle. This can reduce the blood pressure due to insufficient force when blood is pumped out of the heart
• Other underlying conditions that affect your hormones and nervous system including Parkinson’s and Diabetes can influence your body’s ability to maintain your blood pressure

Symptoms of postural hypotension

On standing, you may experience a number of symptoms including:

• Dizziness or feeling lightheaded
• Syncope (fainting)
• Feeling weak
• Nausea
• Falls
• Fatigue
• Shortness of breath
• Blurry vision

Everyone experiences symptoms differently so you may experience one or all of these symptoms and variations in severity of these.

Diagnosis of postural hypotension

History taking

The first part in achieving a diagnosis of postural hypotension is by understanding the context that the symptoms occurred and any influencing factors. It is important to tell your healthcare professional as much detail as possible such as how much fluid you had drank on the day, any medications you have taken and how the symptoms started. This allows for an understanding of the triggers of the symptoms and to assess the full picture.

Blood pressure measurements

A key measurement in diagnosing postural hypotension is through blood pressure measurement. This involves attaching your upper arm to a blood pressure cuff, air is then pumped into the cuff to temporarily cut off the blood flow. The cuff will feel tight on your arm. Air is removed slowly out of the cuff to produce a sound, which can be picked up by an automatic blood pressure machine.

This sound is the flow of blood returning to the vessel. The first sound that is registered is called your systolic blood pressure (the top reading). This indicates the pressure in your arteries when the heart is beating to send blood through your arteries. As the sound disappears, this represents your diastolic blood pressure (the bottom reading).

Postural hypotension is described as a drop in systolic blood pressure >20 millimetres of mercury (mmHg) and >10 mmhg drop in diastolic pressure. Normal blood pressure is around 120/70 mmhg so a drop of 20 mmhg in systolic blood pressure would be 100/70 mmhg. The drop may be present in just the systolic reading or with a drop in both systolic and diastolic.

You may have your blood pressure taken when you are lying down and then within three minutes of standing to identify if and when a drop in blood pressure occurs. These measurements may be repeated in order to obtain the most accurate recordings.

Heart rate measurement

It can also be important to record heart rate at the same time as blood pressure recordings. By measuring the heart rate, it can demonstrate how quickly the body's coping mechanism is kicking in when the blood pressure drops. The heart rate is measured by placing two fingers on the wrist and counting the beats that are felt in one minute.

Normal heart rate can range between 60-100 beats per minute (bpm). An increase in the heart rate of <15 beats per minute in postural hypotension is said to potentially represent an underlying neurological cause.² Whereas an increase >15 bpm indicates the body's coping mechanism is functioning correctly and therefore other causes can be explored.

An electrocardiograph (ECG) test may be performed to examine the electrical impulses through the heart to identify any underlying issues.

Blood tests

Standard blood tests can be performed to rule out any other abnormalities or potential contributing factors such as a low blood or iron level count known as anaemia.

Physical tests

A tilt table test may be performed to aid diagnosis. This is where you lay flat on a table and your health care professional uses an electronic remote to tilt the table into different positions to see if this causes your symptoms or any fainting.

Management and treatment options

Once the underlying cause and a diagnosis has taken place, measures can be put into place to prevent and reduce the impact of occurrences.

Lifestyle modifications

Monitoring and increasing your fluid intake can help with symptoms of postural hypotension. If dehydration is a contributing factor to episodes, by keeping an eye on how much you are drinking and actively trying to drink more could have a positive impact on this.

Having an awareness when you are changing positions and actively moving more slowly can reduce the impact of episodes by giving your blood pressure time to adjust to the change.

If medications are contributing to postural hypotension, a review of these with your healthcare professional could be beneficial, as reducing doses or changing medications, where possible can have a positive impact.

Physical manoeuvres

In some cases, compression stockings may be recommended. These stockings compress the lower parts of your legs in an attempt to reduce the effects by gravity. Stockings must be recommended for use by a healthcare professional.

Medication

In severe cases you may be prescribed medications to help to increase the volume of your blood or constrict blood vessels including fludrocortisone and midodrine.

Summary

Postural hypotension is caused when your blood pressure drops on changing position, usually when standing. This can cause a number of unpleasant symptoms including weakness and dizziness that can lead to fainting. Prompt diagnosis through a range of clinical techniques including blood pressure measurement, history taking and ECG can ensure early adjustment to lifestyle factors and improved quality of life.