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Do you have     
hypertension?
- are you monitoring   
frequently?
- are you taking
prescription drugs?
- are you aware of drug
side effects on ANS?
- self-improvement tips
Read more......
Feeling dizzy      
or even fainted?
- are you low in blood
pressure or heart rate?
- are you taking
prescription drugs?
- You may experience
Baroreflex failure
Read more......
Irregular heartbeats?
- often noticing abnormal
heartbeats (missing,
uneven, or super-fast)?
- Yo might have cardiac
arrhythmias
- Most sudden death
events are preceded by
irregular heartbeats
Read more......
Mitral Valve Prolapse?
- Mitral valve is the
bicuspid valve between left
atrium and ventricle
- If mitral valve is not
closed properly (called
mitral valve prolapse
MVP), the blood may
backflow during pumping
- there is a strong
connection between panic
attackes and MVP
- How to detect it?
Read more......
Am I having   
dysautonimia?
- autonomic nervous
system works to fine tune
body conditions depending
on physiological needs
- ANS consists of two
branches: sympathetic and
parasympathetic
- do you have balanced
ANS?
- what are the symptoms of
dysautonomia?
Read more......
Hypotension and Baroreflex Failure
Glimpse of Facts on Hypotension



  • The range of systolic blood pressure for most healthy adults falls between 90 and 120
    millimeters of mercury (mm Hg). Normal diastolic blood pressure ranges between 60 and 80
    mm Hg
  • Hypotension or low blood pressure is hard to define, because a lowered blood pressure can
    occur naturally in persons who exercise regularly, keep a normal weight, and eat a healthy diet.
  • Many experts use the arbitrary criteria of a systolic (top) pressure of 90 or lower or a diastolic
    (bottom) pressure of 60 or less to be the cutoff levels used to define low blood pressure.
  • Regardless of definition on hypotension, blood pressure in some people is so low it causes
    symptoms or signs due to the low flow of blood through the arteries and veins. When the flow of
    blood is too low to deliver enough oxygen and nutrients to vital organs such as the brain, heart,
    and kidney, the organs do not function normally and may be temporarily or permanently
    damaged
What are the causes of low blood pressure?

  • Conditions that reduce the volume of blood, reduce cardiac output (the amount of blood
    pumped by the heart), and medications are frequent reasons for low blood pressure.
  • Dehydration is common among hypotension patients with prolonged nausea, vomiting, and
    diarrhea. Other causes of dehydration include exercise, sweating, fever, and heat exhaustion,
    or heat stroke.
  • Moderate or severe bleeding can quickly deplete an individual's body of blood, leading to low
    blood pressure or orthostatic hypotension. Bleeding can result from trauma, surgical
    complications, or from gastrointestinal abnormalities such as ulcers, tumors, or diverticulosis.
  • Severe inflammation of organs inside the body such as acute pancreatitis can cause low blood
    pressure. In acute pancreatitis, fluid leaves the blood vessels to enter the inflamed tissues
    around the pancreas as well as the abdominal cavity, concentrating blood and reducing its
    volume.
  • Weakened heart muscle can cause the heart to fail and reduce the amount of blood it pumps.
    Other heart diseases as common causes of weakened heart muscle include heart attack,
    medications that are toxic to the heart, infections of the muscle of the heart by viruses
    (myocarditis), and diseases of the heart's valves such as aortic stenosis.
  • Pulmonary embolism is a condition in which a blood clot in a vein (deep vein thrombosis)
    breaks off and travels to the heart and eventually the lung. A large blood clot can block the
    flow of blood into the left ventricle from the lungs and severely diminish the blood returning to
    the heart for pumping. Pulmonary embolism is a life-threatening emergency.
  • A slow heart rate (bradycardia) can decrease the amount of blood pumped by the heart.
    Bradycardia (resting heart rates slower than 60 beats/minute) does not always cause low
    blood pressure. In fact, some highly trained athletes can have resting heart rates in the 40s
    and 50s (beats per minute) without any symptoms. (The slow heart rates are offset by more
    forceful contractions of the heart that pump more blood than in non-athletes.) But in many
    patients bradycardia can lead to low blood pressure, lightheadedness, dizziness, and even
    fainting.
  • Drug toxicity: Drugs such as digoxin (Lanoxin) or beta blockers for high blood pressure, can
    slow the transmission of electricity in the heart chemically and can cause bradycardia and
    hypotension
  • An abnormally fast heart rate (tachycardia) also can cause low blood pressure. The most
    common example of tachycardia causing low blood pressure is atrial fibrillation. Atrial fibrillation
    is a disorder of the heart characterized by rapid and irregular electrical discharges from the
    muscle of the heart causing the ventricles to contract irregularly and (usually) rapidly.  Other
    abnormally rapid heart rhythms such as ventricular tachycardia also can produce low blood
    pressure, sometimes even life-threatening shock.
  • Medications such as calcium channel blockers, beta blockers, and digoxin (Lanoxin) can slow
    the rate at which the heart contracts. Some elderly people are extremely sensitive to these
    medications since they are more likely to have diseased hearts and electrical conduction
    tissues.
  • Medications used in treating high blood pressure (such as ACE inhibitors, angiotensin receptor
    blockers, beta blockers, calcium channel blockers, and alpha-blockers) can excessively lower
    blood pressure and result in symptomatic low blood pressure especially among the elderly.
  • Water pills (diuretics) such as hydrochlorothiazide furosemide (Lasix) can decrease blood
    volume by causing excessive urination.
  • Medications used for treating depression, such as amitriptyline (Elavil), Parkinson's disease,
    such as levodopa-carbidopa (Sinemet), erectile dysfunction (impotence), such as sildenafil
    (Viagra), vardenafil (Levitra), and tadalafil (Cialis) when used in combination with nitroglycerine,
    can cause low blood pressure.
  • Alcohol and narcotics also can cause low blood pressure.
How is low blood pressure treated?

  • Low blood pressure in healthy subjects without symptoms or organ damage needs no
    treatment.
  • However, all patients with symptoms possibly due to low blood pressure should be
    evaluated by a doctor. (Patients who have had a major drop in blood pressure from
    their usual levels even without the development of symptoms also should be evaluated.)
  • The doctor needs to identify the cause of the low blood pressure; remedies will depend
    on the cause. For example, if a medication is causing the low blood pressure, the dose
    of medication may have to be reduced or the medication stopped, though only after
    consulting the doctor. Self-adjustment of medication should not be done.
Symptoms of Low Blood Pressure

  • If insufficient blood flows to the brain, brain cells do not receive enough oxygen and nutrients,
    and a person can feel lightheaded, dizzy, or even faint.
  • Going from a sitting or lying position to a standing position often brings out symptoms of low
    blood pressure. This occurs because standing causes blood to "settle" in the veins of the lower
    body, and this can lower the blood pressure. If the blood pressure is already low, standing can
    make the low pressure worse, to the point of causing symptoms. The development of
    lightheadedness, dizziness, or fainting upon standing caused by low blood pressure is called
    orthostatic or postural hypotension.
  • When there is insufficient blood pressure to deliver blood to the coronary arteries (the arteries
    that supply blood to the heart's muscle), a person may develop chest pain (a symptom of
    angina) or even a heart attack.
  • When insufficient blood is delivered to the kidneys, the kidneys fail to eliminate wastes from the
    body, for example, urea (BUN) and creatinine, and increases in their levels in the blood occur.
  • Shock is a life-threatening condition where persistently low blood pressure causes organs such
    as kidney(s), liver, heart, lung, and brain to fail rapidly.
Hypotension and ANS

  • Vasovagal reaction is a common condition in which a healthy person temporarily develops low
    blood pressure, slow heart rate, and sometimes fainting. A vasovagal reaction typically is
    brought on by emotions of fear or pain such as having blood drawn, starting an intravenous
    infusion, or by gastrointestinal upset. Vasovagal reactions are caused by activity of the
    involuntary autonomic nervous system, especially the vagus nerve (i.e. the parasympathetic
    branch in ANS), which releases hormones that slow the heart and widen the blood vessels.
  • Postural (orthostatic) hypotension is a sudden drop in blood pressure when an individual stands
    up from a sitting, squatting, or supine (lying) position. When a person stands up, gravity causes
    blood to settle in the veins in the legs so that less blood returns to the heart for pumping, and,
    as a result, the blood pressure drops. The body normally responds automatically to the drop in
    blood pressure by increasing the sympathetic tone which raises heart rate and narrows the
    blood vessels. In patients with postural hypotension, this compensating reflex fails to occur,
    resulting low blood pressure and its symptoms. Postural hypotension can occur in persons of all
    ages but is much more common among the elderly, especially in those on medications for high
    blood pressure and/or diuretics.

  • Baroreceptors (or baroceptors) are sensors located in the blood vessels.  They are a type of
    mechanoreceptor that detects the pressure of blood flowing through them, and can send
    messages to the central nervous system to increase or decrease total peripheral resistance
    and cardiac output. Baroreceptors act immediately as part of a negative feedback system
    called the baroreflex, as soon as there is a change from the usual mean arterial blood pressure,
    returning the pressure to a normal level. They are an example of a short-term blood pressure
    regulation mechanism (see Figure 1)
  • Baroreceptors detect the amount of stretch of the blood vessel walls, and send the signal to the
    nervous system in response to this stretch
  • Baroreflex Failure is a rare disorder characterized by change of blood pressure with episodes
    of severe hypertension (high blood pressure).  There can be increased heart rate during stress
    and hypotension (low blood pressure) with normal or reduced heart rate during rest.
  • The baroreflex normally serves to buffer blood pressure against excessive rise or fall.
    Baroreflex failure occurs when afferent baroreceptive nerves or their central connections
    become impaired. In baroreflex failure, there is loss of buffering ability, and wide excursions of
    pressure and heart rate occur. Such excursions may derive from endogenous factors such as
    stress or drowsiness, which result in quite high and quite low pressures, respectively. They may
    also derive from exogenous factors such as drugs or environmental influences.
  • Symptoms may include headache, excessive sweating, extremely high or volatile blood
    pressure and heart rate with spikes in blood pressure in response to stress, with periods of
    normal or low blood pressure during rest
  • Possible causes of baroreflex failure may include surgery and radiation for cancer of the throat,
    injury to glossopharyngeal and vagus nerves (nerves involved in sensing blood pressure), cell
    loss on both sides in the nuclei of the solitary tract (NTS, a column of cells located in the
    medulla) in the setting of a degenerative neurologic disease of the brain.  But for many patients,
    the cause of Baroreflex Failure is not known.
  • Baroreflex Failure resembles other more common disorders, so its diagnosis is challenging. The
    physician will conduct a physical examination, which will include checking blood pressure and
    heart rate in specific circumstances, such as during daily activity and with medication challenges
  • Treatment for Baroreflex Failure involves medications to control blood pressure and heart rate
    and to reduce stress.
Figure 1: Schematic of Baroreceptors and Baroreflex