Hypotension


Hypotension refers to low blood pressure.


A systolic blood pressure of less than 90 millimeters of mercury (mm Hg) or diastolic of less than 60 mm Hg is generally considered to be hypotension.


A mean arterial pressure <65mmHg is considered hypotension.


Intra-operative hypotension <65 mmHg can lead to an increased risk of acute kidney injury, myocardial injury or post-operative stroke.


Blood pressure is considered too low only if noticeable symptoms are present.


It is best understood as a physiological state rather than a disease.


Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients: shock.


Hypotension can be caused by: low blood volume, hormonal changes, dilating of blood vessels, anemia, heart or endocrine problems, and medication effects.


Some medications can also lead to hypotension.


Syndromes associated with hypotension include:  orthostatic hypotension, and vasovagal syncope, among others.


Low blood pressure can cause dizziness, fainting or indicate the presence of serious heart, endocrine or neurological disorders.


Exercise can induce hypotension and water-based exercise can induce a hypotensive response.


Treatment of hypotension may include:  intravenous fluids or vasopressors. 


The primary symptoms of hypotension are lightheadedness or dizziness, and if 

blood pressure is sufficiently low, fainting (syncope) may occur.


Low blood pressure is sometimes associated /caused by:


chest pain


shortness of breath


irregular heartbeat


High fever


headache


stiff neck


severe upper back pain


cough with sputum


prolonged diarrhea or vomiting


dyspepsia


dysuria 


acute, life-threatening allergic reaction


seizures


loss of consciousness


profound fatigue


temporary blurring or loss of vision


black tarry stools


Reduced blood volume, is the most common cause of hypotension.


Reduced blood volume can result from:


hemorrhage; 


insufficient fluid intake, 


excessive fluid losses from diarrhea or vomiting. 


excessive use of diuretics.


Hypotension may be attributed to heat stroke.


Medications can produce hypotension:  alpha blockers or beta blockers.


Beta blockers can cause hypotension both by slowing the heart rate and by decreasing the pumping ability of the heart muscle.


Decreased cardiac output due to severe congestive heart failure, myocardial infarction, heart valve abnormalities, arrhythmias bradycardia often produce hypotension and can rapidly progress to cardiogenic shock.


Excessive vasodilation causes hypotension, and can be due to decreased sympathetic nervous system output or to increased parasympathetic activity occurring as a consequence of injury to the brain or spinal cord.


Dysautonomia, an intrinsic abnormality in autonomic system functioning, can also lead to hypotension.


Excessive vasodilation can also result from sepsis, acidosis, or medications, such as nitrate preparations, calcium channel blockers, or angiotensin receptor antagonists.


Many anesthetics, and anesthesia techniques, including spinal anesthesia and most inhalational agents, produce significant vasodilation.


Meditation, yoga, or other mental-physiological disciplines may produce hypotension.


Lower blood pressure is a side effect of certain herbal medicines.


((Orthostatic hypotension)), also called postural hypotension is a common form of hypotension.


Postural hypotension occurs after a change in body position, typically when a person stands up from either a seated or lying position.


Postural hypotension is usually transient and represents a delay in the normal compensatory ability of the autonomic nervous system.


Postural hypotension is commonly seen in hypovolemia and as a result of various medications: blood pressure-lowering medications, many psychiatric medications, and antidepressants.


Vasovagal syncope is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position.


((Vasovagal syncope)) is result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system.


Vasovagal syncope is associated sudden, unprovoked lightheadedness, sweating, changes in vision, and finally a loss of consciousness.


Consciousness will often return rapidly once patient is lying down and the blood pressure returns to normal.


Postprandial hypotension is associated with a decline in blood pressure that occurs 30 to 75 minutes after eating substantial meals.


Blood diverted to the intestines facilitates digestion and absorption, the body must increase cardiac output and peripheral vasoconstriction to maintain enough blood pressure to perfuse vital organs, such as the brain.


Postprandial hypotension  can be caused by the autonomic nervous system’s inability to compensate.


The Flammer syndrome, which is characterized by cold hands and feet and predisposes to normal tension glaucoma and hypotension.


Hypotension can be a symptom of relative energy deficiency in sport.


Blood pressure is continuously regulated by the autonomic nervous system, using an elaborate network of receptors, nerves, and hormones to balance the effects of the sympathetic nervous system, which tends to raise blood pressure, and the parasympathetic nervous system, which lowers it.


The abilities of the autonomic nervous system allow normal individuals to maintain an acceptable blood pressure over a wide range of activities and in many disease states.


Alterations in these networks can lead to hypotension.


The  ideal blood pressure for most people is at or below 120/80 mmHg. 


Even a small drop in blood pressure, as little as 20 mmHg, can result in transient hypotension.


Asymptomatic hypotension in healthy people usually does not require treatment: the addition of electrolytes to a diet can relieve symptoms of mild hypotension, as can caffeine.


Laying a person in dorsal decubitus position and lifting the legs increases venous return, thus making more blood available to critical organs in the chest and head.


The Trendelenburg position, is no longer recommended.


Hypotensive shock treatment in terms of mortality is directly linked to the speed that hypotension is corrected.


Blood pressure support with a vasopressor are all equivalent with respect to risk of death, with norepinephrine possibly better than dopamine.


Achieving  a mean arterial pressure (MAP) of greater than 70 mmHg does not appear to result in better outcomes than trying to achieve a MAP of greater than 65 mm Hg in adults.


To ensure adequate tissue perfusion maintaining SvO2 >70 with use of blood or dobutamine is the goal.


Mixed venous oxygen saturation (SvO2) is the percentage of oxygen bound to hemoglobin in blood returning to the right side of the heart. 


Addressing the underlying etiology of hypotension: antibiotic for infection, stent or CABG for myocardial infarction, and steroids for adrenal insufficiency.


Determining if fluids will benefit hypotension  occurs by passive leg raise followed by measuring the output from the heart.


Chronic hypotension medications: used Fludrocortisone, Erythropoietin, and sympathomimetics such as Midodrine and Noradrenaline and precursor (L-DOPS).


Fludrocortisone is the first-line therapy for patients with chronic hypotension or resistant orthostatic hypotension: 

It works increases the intravascular volume.


Midodrine is a therapy used for severe orthostatic hypotension, and works by increasing peripheral vascular resistance.



Noradrenaline and its precursor L-DOPS are used for primary autonomic dysfunction by increasing vascular tone.


Erythropoietin can be used with neurogenic orthostatic hypotension and works by increasing vascular volume and viscosity.


Hypotension changes in the pediatric population depend on the child’s age


Age Systolic Pressure


Term Neonates <60 mmHg


Infants <70 mmHg


Children 1 – 10 years <70 + (age in years x 2) mmHg


Children >10 years <90 mmHg



Symptoms of hypotension for children include increased sleepiness, not using the restroom as much, having difficulty breathing or breathing rapidly, or syncope.


The treatment for hypotension in pediatric patients is similar to the treatment in adults.


Children are more likely to undergo intubation during the treatment of hypotension because their oxygen levels drop more rapidly than adults.





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