CPR First Aid

Reasons for Low Blood Volume

Reasons for Low Blood Volume

Do you always feel tired and lightheaded? It may be a sign that you have low blood volume which results in low blood pressure. This condition can cause a number of health problems if left untreated and may even lead to shock and death. In this blog post, we will discuss the reasons for low blood volume and what you can do to manage it.

What Are the Reasons for Low Blood Volume?

Having a low blood volume means having not enough fluid like blood and water to circulate in the body. As a result, you will experience low blood pressure.

According to BetterHealthChannel, these are the causes of low blood pressure:

  • Emotional stress, fear, insecurity or pain (the most common causes of fainting)
  • Dehydration, which reduces blood volume
  • The body’s reaction to heat is to shunt blood into the vessels of the skin, leading to dehydration
  • Blood donation
  • Internal bleeding, such as a perforated stomach ulcer
  • Blood loss from trauma, such as a road accident or deep cut
  • Pregnancy
  • Medications for high blood pressure
  • Diuretics, which produce fluid loss
  • Medications for depression
  • Medications for certain heart conditions
  • Allergic reactions to certain drugs or chemicals
  • Some forms of infection, such as toxic shock syndrome
  • Heart disease can hamper the pumping action of the heart muscle
  • Some nervous system disorders, such as Parkinson’s disease
  • Addison’s disease (where the adrenal glands fail to produce sufficient blood-pressure-maintaining hormones).

What are the Health Implications of Low Blood Pressure?

Low blood pressure if left untreated, leads to an emergency situation such as shock. 

What is Shock?

Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. Shock can damage multiple organs, and requires immediate medical treatment as it can worsen rapidly.

There are many specific types of shock including:

  • Hypovolemic shock
  • Cardiogenic shock
  • Anaphylactic shock
  • Neurogenic shock
  • Obstructive shock

Causes of Shock

  • Loss of blood through internal or external bleeding
  • Loss of plasma or fluids, i.e. burns, vomiting, dehydration
  • Allergic reactions (Anaphylaxis)
  • Infections
  • Heart trouble, heart attack, or stroke
  • Poisoning by chemicals, gases, alcohol, or drugs
  • Snake and animal bites
  • Respiratory problems, chest trauma
  • Lack of oxygen
  • Obstructions caused by choking
  • Injuries of all types, both severe and minor

Signs and Symptoms of Shock

The signs and symptoms will vary slightly with the specific types of shock. The most important thing is for a first aider to recognise the signs and symptoms of a casualty going into shock so that they can assist the casualty and call 000 when appropriate.

Symptoms may include:

At first:

  • Rapid pulse
  • Pale grey blue skin
  • The capillary test will be slower
  • Sweating and cold clammy skin
  • Casualty starts feeling cold (even on a warm day)
  • Weakness and giddiness
  • Nausea and vomiting
  • Thirst
  • Rapid shallow breathing
  • A weak thready pulse

As the Brain’s O2 Levels Drop:

  • Restless, anxious and even aggressiveness
  • Yawn and gasp for air
  • Unconsciousness
  • The heart will stop

First Aid for Shock

  • If unconscious and breathing, place into the recovery position
  • If conscious – lay the casualty down flat onto their back
  • Promptly control any bleeding. Manage and treat all other injuries
  • Call 000 for professional assistance
  • Make the casualty comfortable, i.e. loosen clothing
  • Keep the casualty warm. Cover with a blanket if cold
  • Reassure and keep the casualty calm
  • Continue to monitor the casualty’s physical condition
  • You may moisten the casualty’s lips – but be sure that they do not eat or drink
  • If the casualty becomes unresponsive and not breathing normally, follow DRS ABCD

How Low Can Your Blood Pressure Go Before You Pass Out?

If your blood pressure is below 90/60 mmHg, the majority of doctors will diagnose you with low blood pressure. This is referred to by your doctor as “90 over 60.”

It can be harmful when blood pressure suddenly drops. Even a small fluctuation in blood pressure, such as going from 110 mm Hg to 90 mm Hg, might result in fainting and dizziness. 

Uncontrolled bleeding and allergic reactions can cause a drop in low blood pressure and can be life-threatening. When blood pressure decreases unexpectedly or is accompanied by symptoms, it may be a sign of an underlying health condition for some people.

Meaning of Hypotension

Blood pressure (BP) is the force of blood pushing against the walls of the arteries as the heart pumps blood. Hypotension, or low blood pressure, is a condition in which the blood pressure in the arteries is lower than normal. Generally, the BP reading is less than 90/60 mmHg among Australian adults.

A person’s low blood pressure may be fine for another. There can be no noticeable symptoms but can be life-threatening. Hypotension can also be a sign of an underlying health condition, especially if it happens together with symptoms.

Types of Low Blood Pressure

Hypotension can be acute, meaning it develops suddenly and severely, or chronic, meaning it occurs gradually. Below are some of the low blood pressure types that commonly occur in Australians.

Orthostatic Hypotension

When rising from a seated position, there is a dramatic drop in blood pressure. This mostly affects seniors. We’re highlighting this type in this article.

Hypotension After Eating

This decrease in blood pressure happens one to two hours after a meal, particularly in people with excessive blood pressure or illnesses of the autonomic nervous system, including Parkinson’s disease. This scenario mostly impacts seniors.

Hypotension With Neural Mediation

Characterised by a dip in blood pressure that occurs after prolonged standing, which mostly affects children and young adults.

Orthostatic Hypotension Together With Multiple System Atrophy

An uncommon condition known as Shy-Drager syndrome affects the neurological system, which regulates involuntary processes including blood pressure, heart rate, respiration, and digestion. It is believed to be linked to extremely high blood pressure when lying down.

What Medical Conditions Causes Low BP?

  • Pregnancy
  • Conditions of the heart and heart valves
  • Illnesses relating to hormones (endocrine disorders)
  • Dehydration
  • Loss of blood
  • Septicemia – a serious infection
  • Anaphylaxis – significant allergic response
  • A diet lacking in nutrition
  • The risk of having low blood pressure may rise with cardiac issues. Severe hypotension can lower the body’s oxygen levels, which can harm the heart and the brain.

Medications That May Result in Low BP

  • Diuretics such as furosemide and water tablets, hydrochlorothiazide
  • Alpha blockers like prazosin
  • Beta blockers, such as propranolol and atenolol
  • Parkinson’s medication, such as pramipexole or levodopa-containing medications
  • Specific antidepressant medications e.g. imipramine and doxepin
  • Sildenafil and tadalafil, especially when used with the heart medicine nitroglycerin – are medications for erectile dysfunction

Fast Facts About Orthostatic Hypotension

  • Commonly known as postural hypotension
  • Occurs while getting up from a chair or lying down.
  • Can result in fainting, dizziness, or lightheadedness, as well as the possibility for a patient to fall and incur secondary trauma wounds
  • typically less severe and short
  • Long-lasting orthostatic hypotension is harmful if left untreated since it may indicate more serious issues.

What Happens During Orthostatic Hypotension?

Every time you get out of a sitting or reclining position, gravity has a significant impact on blood flow. On average, approximately 300 to 800ml of blood momentarily pools in the blood vessels of the legs. Blood pressure falls as a result of less blood returning to the heart, a consequence of blood pooling. 

Specific cells called baroreceptors, detect the decline in BP. The cardiovascular system and autonomic nervous system swiftly react in a healthy individual by speeding up the heart rate and telling the blood vessels in the legs and belly to constrict or tighten. These actions keep the brain’s blood pressure at a healthy level.

In a person with orthostatic hypotension, this compensatory process to raise blood pressure may not happen or may be delayed. They continue to have low blood pressure, which results in symptoms. Once the individual sits or lies down again, blood pressure usually recovers to normal, although this depends on how serious the underlying problem is.

Who is Prone to Orthostatic Hypotension?

Patients 65 years of age and older are most likely to experience orthostatic hypotension, in part because of diminished baroreceptor sensitivity. Within that age range, the prevalence can reach 18.2 percent.

Other Conditions Putting People At Risk

Orthostatic hypotension is also more likely to occur in patients with cardiovascular conditions such as aortic stenosis, pericarditis or myocarditis, or arrhythmias.

Younger and middle-aged patients are equally susceptible to it; however, they typically have a persistent autonomic failure in the absence of volume depletion.

Symptoms of Postural Hypotension

The most common symptom of orthostatic hypotension is lightheadedness or dizziness upon standing. Other symptoms may include: 

  • feeling faint or unsteady
  • feeling like you are going to black out
  • confusion or having trouble focusing
  • blurred vision
  • nausea and wanting to vomit
  • weakness or body malaise
  • sweating

When Do Symptoms Occur?

Here are some daily scenarios that can bring about orthostatic hypotension.

  • abrupt standing or sitting up
  • early in the day, when blood pressure naturally drops
  • after a heavy meal
  • large alcohol consumption
  • when exercising
  • straining on the toilet
  • when sick

How Do I Prevent Orthostatic Hypotension?

There are a few ways that you can treat orthostatic hypotension, depending on the underlying cause.

If you have dehydration, drinking plenty of fluids and adding salt to your diet may help to prevent postural hypotension.

If the condition is due to a medication you are taking, your doctor may be able to adjust your dosage or switch you to a different medication.

If an underlying condition is causing your orthostatic hypotension, treating that condition may help to improve your symptoms. For example, if you have diabetes, tightly control your blood sugar levels. Another circumstance would be, if a heart condition is present, such as irregular heartbeats or heart failure, treating that condition may help to reduce episodes of orthostatic hypotension.

CPR First Aid Australia’s Available Courses

Learning the management of low blood pressure and the prevention of its potential danger if left untreated is vital. Here in CPR First Aid Australia, we have course options that you may enrol at. You can choose your preferred courses below:

    • NRT LogoHLTAID009 Provide cardiopulmonary resuscitation 
    • NRT LogoHLTAID010 Provide an emergency first aid response  
    • NRT LogoHLTAID011 Provide first aid –  formerly known as Level 2 or Senior First Aid. 
    • NRT LogoHLTAID012 Provide first aid in an education and care setting
    • NRT LogoHLTAID014 Provide advanced first aid
    • NRT Logo22578VIC Course in First Aid Management of Anaphylaxis
    • NRT Logo22556VIC Course in the Management of Asthma Risks and Emergencies in the Workplace

Do You Need General First Aid Qualification?

We recommend that the NRT LogoHLTAID011 Provide first aid.

  • This also includes CPR qualification. The Australian Resuscitation Council (ARC) recommends that this qualification is updated every 3 years.

Do You Need To Update CPR Qualification?

We recommend NRT LogoHLTAID009 Provide cardiopulmonary resuscitation 

  • The Australian Resuscitation Council (ARC) recommends that this qualification is updated annually.

Do You Need First Aid Qualification To Work In The Childcare and Education Industry, that Includes Anaphylaxis and Asthma Training?

We recommend NRT LogoHLTAID012 Provide first in an education and care setting.

Are You Working With Children?

You will also be required to obtain first aid training qualifications in Asthma and Anaphylaxis. You need to check with the employer before enrolling, so that client gets the correct training for his or her circumstance.


RTO No. 21903: CPR First Aid was founded in 2007. We specialise in providing first aid training in CPR, asthma and anaphylaxis for a range of workplaces including childcare, schools and other industries in NSW, VIC, SA, WA and QLD. We are a Registered Training Organisation with the Australian Skills Quality Authority (No 21903). Our courses and Units are VET-accredited for workplaces in Australia.


Knowing the meaning and causes of low blood pressure can help you prevent it from developing into a fatal situation. Shock can happen when there’s a low blood volume in which the body suffers from poor blood circulation. Shock can damage multiple organs, and requires immediate medical treatment as it can worsen rapidly. You may consider learning more first aid tips to equip yourself, especially in life-threatening situations. CPR First Aid Australia has a variety of affordable yet high-quality courses suitable for anyone aiming to get certified. Look at our website and find the courses that best suit your needs.

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