US Pharm. 2014;39(2):2-4.
Hypotension (low blood pressure) can be just as serious
as hypertension. But the good news is that low blood pressure can be
easily recognized by key signs and symptoms. Low blood pressure occurs
when blood pressure drops below a normal range (120/80 mmHg). Though it
varies from person to person, a reading of 90 mmHg or lower of systolic
blood pressure or 60 mmHg or lower of diastolic blood pressure is
generally considered hypotension. Low blood pressure is often an
indicator of an underlying problem and is especially dangerous when the
pressure drops suddenly. Hypotension causes an inadequate flow of blood
to the body organs and may cause stroke, heart attack, kidney failure,
and shock if not treated.1
The main causes of low blood pressure
include decrease in cardiac output, dilation of blood vessels, decrease
in blood volume, inhibition of brain centers that control blood
pressure, impairment of the autonomic nervous system, and certain
medications. Treatment is determined by the cause of the low blood
In this clinical review, we will look at the signs and symptoms, causes, risk factors, and treatment of this condition.
Normal Blood Pressure
The human body has certain mechanisms to
maintain blood pressure and blood flow at a normal level. Artery walls
sense blood pressure and send signals to the heart, the arterioles, the
veins, and the kidneys to make flow adjustment and increase or decrease
blood pressure. Heart mechanisms adjust the amount of blood pumped by
the heart into the arteries (cardiac output), the amount of blood in
the veins, the volume of blood, and arteriole resistance.2
Heart contractions can eject more blood
into the arteries and increase blood pressure. Veins can expand and
narrow and store more blood. The arterioles can also expand and narrow
and cause more or less resistance to the flow of blood. The kidneys
respond to these changes by increasing or decreasing the amount of
urine that is produced, which in turn changes the volume of blood. The
kidney mechanism takes much longer to affect the blood pressure than
All of these adaptive mechanisms keep the blood pressure in normal range.
Signs and Symptoms
Low blood pressure will not deliver
enough blood to the organs of the body. The organs can be damaged
temporarily or permanently.3 Lightheadedness, dizziness, and
even fainting (orthostatic hypotension) can happen due to insufficient
blood flow to the brain. The brain malfunctions first because it is
located at the top of the body and blood has to fight gravity to reach
it. Changing position from sitting or lying to standing to often
produces the symptoms of low blood pressure. This is due to the
settlement of blood in the veins of the lower body. An insufficient
amount of blood delivered to the coronary arteries may cause chest pain
or even a heart attack. Low blood flow to the kidneys will reduce the
elimination of waste from the body, and urea (measured as blood urea
nitrogen, or BUN) and creatinine levels will increase in the blood. In
addition, the major organs of the body, such as the brain, kidneys,
liver, and heart, may collapse rapidly owing to prolonged low blood
pressure. Fatigue, nausea, thirst, rapid and shallow breathing, cold,
clammy and pale skin, and blurred vision are some of many early signs
of low blood pressure. In general, compensatory mechanisms try to
increase blood pressure that is low.
Knowing the four major types of hypotension may help to diagnose a person’s condition.4
Postural or orthostatic hypotension (OH):
This is low blood pressure that occurs when one stands up from sitting
or lying down. Orthostatic hypotension is strongly age-dependent, with
prevalence ranging from 5% to 11% in middle age to 30% or higher in the
elderly. Current guidelines suggest a wide range of treatments, but
systematic reviews of the evidence-based literature for such
recommendations are lacking. Postural hypotension was traditionally
classified as neurogenic (less common but often more severe) or
nonneurogenic (more common, with no direct signs of autonomic nervous
occurs when blood pressure drops suddenly after eating. The intestines
require a large amount of blood for digestion. Postprandial is more
common than postural hypotension and occurs mainly in the elderly. Some
risk factors for this are Parkinson disease and autonomic neuropathy.
Drugs such as octreotide reduce the amount of blood flowing to the
intestines. Certain nonsteroidal anti-inflammatory drugs (NSAIDs) cause
salt to be retained and thus increase blood volume.
Neurally mediated hypotension:
This occurs when blood pressure drops after standing for a long period of time.
Multiple system atrophy with orthostatic hypotension:
This is also known as Shy-Drager syndrome.
Marked by progressive damage to the autonomic nervous system, this
condition causes hypotension when standing and hypertension when lying
Causes of Low Blood Pressure
Anyone can be affected by hypotension,
especially those who are over the age of 65 years. The following
conditions, and the taking of certain medications, increase the risk of
mild cases of dehydration can cause low blood pressure. Dehydration can
result from prolonged nausea, vomiting, or severe diarrhea. In
situations like this, a large amount of water is lost and blood shunts
away from the organs to the muscles. Patients with mild dehydration may
experience only thirst and dry mouth. Moderate dehydration may cause
orthostatic hypotension, and severe dehydration (hypovolemia) can lead
to shock, kidney failure, confusion, acidosis, coma, and even death.
major injury or internal bleeding can quickly deplete an individual’s
body of blood, leading to low blood pressure. Bleeding can occur from
injury, trauma, gastrointestinal diseases including as diverticulitis,
or surgical complications. The severe and rapid bleeding from a
ruptured aortic aneurysm can cause shock and death. Plasma loss (from
burns) is also a major hypovolemic factor.
valve problems such as aortic stenosis, low heart rate, heart attack,
medications that are toxic to the heart, and infection of the heart
muscle by viruses (myocarditis) can all lead to hypotension.
Bradycardia can lead to low blood pressure, light-headedness,
dizziness, and even fainting. Causes of bradycardia include sick sinus
syndrome, heart block, and drug toxicity (digoxin). Many of these
conditions happen in the elderly, and the problem usually lies in the
heart’s failure to circulate enough blood.
Severe allergic reactions:
Also known as type 1 immunoglobulin E (IgE)-mediated hypersensitivity reaction or anaphylaxis, this reaction can suddenly cause the blood pressure to drop.
acute pancreatitis, fluids leave the blood vessels to enter the
inflamed tissues around the pancreas as well as the abdominal cavity,
concentrating the blood and reducing its volume (pooling of unavailable
Also known as gram-negative septicemia, any infections that enter the bloodstream can cause potentially fatal drops in blood pressure.
under- or overactive thyroid gland can trigger hypotension. Diabetes,
postgastrectomy (or dumping) syndrome, primary hypoaldosteronism, and
pheochromocytoma are other endocrine factors that cause hypotension.
women often experience hypotension because the circulatory system
rapidly expands during pregnancy. Blood pressure typically returns to a
normal level after childbirth.
beta-blockers, alpha-blockers, calcium channel blockers, certain
antidepressants (e.g., amitriptyline), drugs for Parkinson disease
(carbidopa and levodopa), and erectile dysfunction drugs such as
sildenafil, when used in combination with nitroglycerin, can cause
Diagnosis and Evaluation
In many healthy individuals, symptoms of
weakness, dizziness, and fainting can be due to low blood pressure.
Measuring the blood pressure is generally the first step in diagnosing
this condition. A decrease in blood pressure upon standing causes the
heart rate to increase. In many cases, the cause may be apparent as
mentioned above, but at other times, the cause may be identified by the
following tests and techniques: CBC, blood electrolyte measurement,
cortisol levels, blood and urine cultures, radiologic studies,
electrocardiogram, Holter monitor (to record intermittent episodes of
brady- and tachycardia), echocardiogram, ultrasonography examinations
of the leg veins, CT scan of the chest, and tilt-table tests.5,6
In some cases, the symptoms of
hypotension may be very mild and may not signal the need for immediate
medical attention. However, low blood pressure can be an indicator of a
more serious health condition. For more serious cases of hypotension,
the underlying cause is treated first, such as endocrine problems,
heart problems, dehydration, or use of certain medications.
Mild dehydration is treated with fluids
and electrolytes. Moderate-to-severe dehydration is usually treated in
the hospital or emergency room with IV fluids and electrolytes.7
Low blood pressure from severe bleeding
needs to be treated immediately. Hypotension due to bradycardia may be
caused by a medication, and the dosage of such a medication must be
adjusted. Bradycardia due to a sick sinus rhythm or heart block is
normally treated with a pacemaker. Blood pressure medications or
diuretics that cause low blood pressure may be changed or stopped
altogether by the physician.
Fludrocortisone is recommended as
first-line drug therapy. This is a drug that prevents dehydration by
causing the kidneys to retain water. This drug boosts the blood volume,
which raises the blood pressure. Fludrocortisone is a very potent
mineralocorticoid with high glucocorticoid activity, used primarily for
mineralocorticoid effects. It promotes increased reabsorption of sodium
and loss of potassium from renal distal tubes. This drug is given as
0.1 mg daily in conjunction with a high salt diet and adequate fluid
intake and may be increased in increments of 0.1 mg per week; the
maximum daily dose is 1 mg.8
Midodrine is used to raise standing
blood pressure levels in patients with chronic orthostatic hypotension.
This is recommended for monotherapy or combined therapy with
fludrocortisone. It forms an active metabolite, which is an alpha1
agonist. This agent increases arteriolar and venous tone, resulting in
a rise in standing, sitting, and supine systolic and diastolic blood
pressure in patients with orthostatic hypotension. The dose is 10 mg
three times per day during daytime hours when the patient is upright
(maximum dose is 40 mg/day). In the prevention of hemodialysis-induced
hypotension (unlabeled use), 2.5 to 10 mg is given 15 to 30 minutes
prior to a dialysis session. The major side effect of this drug is
supine hypertension (7% to 13%).9
Norepinephrine is a vasoactive agent used in the treatment of severe hypotension and shock. It stimulates beta1
adrenergic receptors and alpha-adrenergic receptors, causing increased
contractility and heart rate and thereby increasing systemic blood
pressure. Dosage administration requires the use of an infusion pump,
and the drug is therefore used in emergency room and inpatient
settings. The initial adult norepinephrine dose is 8 to 12 mcg/min, and
it is then titrated to the desired response.10
Octreotide is a somatostatin analogue
that inhibits release of gastrointestinal peptides, some of which may
cause vasodilation. Subcutaneous doses given 30 minutes before a meal
may be used to reduce postprandial orthostatic hypotension. Octreotide
does not increase supine hypotension. Nausea and abdominal cramps may
Not all cases of hypotension are preventable, but taking the following steps can reduce the risk of developing the condition.
Water Intake: Drinking
water helps combat dehydration and increases blood volume. In addition,
dehydrating drinks like alcohol and coffee and triggers such as a high
temperature environment must be avoided.
are elastic stockings that are commonly used to relieve pain and
swelling of varicose veins and can reduce pooling of blood in the legs
and, in certain cases, prevent hypotension.
Patients should sit up and breathe deeply as they get out of bed in the
morning or when standing up from a sitting position. Dorsiflexing their
feet first and even crossing the legs while upright can be helpful.
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9. Prakash S, Garg AX, Heidenheim AP, et al. Midodrine
appears to be safe and effective for dialysis-induced hypotension: a
systematic review. Nephrol Dial Transplant. 2004;19(10):2553-2558.
10. Dellinger RP, Levy MM, Rhodes A, et al. Surviving
sepsis campaign: international guidelines for management of severe
sepsis and septic shock. Crit Care Med. 2013;41(2):580-637.
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