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2011-04 HRV Papers Review (Subject: Unstable blood
pressure, hypotension, broreflex failure, and dysautonomia)

The clinical problems in cardiovascular control following spinal cord injury: an overview.
Prog Brain Res.  2006; 152:223-9 (ISSN: 0079-6123)
Krassioukov A; Claydon VE
International Collaboration on Repair Discoveries (ICORD), University of British Columbia, Vancouver, BC V6T
1Z4, Canada.

Editor’s note: Patients with cervical and upper thoracic spinal cord injury face the challenge of
managing their unstable blood pressure, which frequently results in persistent hypotension and/or
episodes of uncontrolled hypertension.

On a daily basis, individuals with cervical and upper thoracic spinal cord injury face the challenge of managing
their unstable blood pressure, which frequently results in persistent hypotension and/or episodes of
uncontrolled hypertension. This chapter will focus on the clinical issues related to abnormal cardiovascular
control in individuals with spinal cord injury, which include neurogenic shock, autonomic dysreflexia and
orthostatic hypotension. Blood pressure control depends upon tonic activation of sympathetic preganglionic
neurons by descending input from the supraspinal structures (Calaresu and Yardley, 1988). Following spinal
cord injury, these pathways are disrupted, and thus spinal circuits are solely responsible for the generation of
sympathetic activity (Osborn et al., 1989; Maiorov et al., 1997). This results in a variety of cardiovascular
abnormalities that have been well documented in human studies, as well as in animal models (Osborn et al.,
1990; Mathias and Frankel, 1992a, b; Krassioukov and Weaver, 1995; Maiorov et al., 1997, 1998; Teasell et
al., 2000). However, the recognition and management of these cardiovascular dysfunctions following spinal
cord injury represent challenging clinical issues. Moreover, cardiovascular disorders in the acute and chronic
stages of spinal cord injury are among the most common causes of death in individuals with spinal cord injury
(DeVivo et al., 1999).

Management of blood pressure instability in severe tetanus: the use of clonidine.
Intensive Care Med.  1997; 23(8):893-5 (ISSN: 0342-4642)
Gregorakos L; Kerezoudi E; Dimopoulos G; Thomaides T
Department of Respiratory Insufficiency, Chest Hospital of Athens, Greece.

Editor’s note: Clinical results suggest that clonidine is effective in the treatment of blood pressure
instability in severe tetanus.

OBJECTIVE: To evaluate the effectiveness of clonidine in the management of unstable blood pressure in
severe tetanus. DESIGN: Patients with severe tetanus and blood pressure instability were treated with
clonidine and the results were compared with those of other patients with severe tetanus who were not treated
with clonidine. SETTING: Intensive care unit of the Chest Hospital of Athens. PATIENTS: We studied 27
patients with severe tetanus and autonomic dysfunction. INTERVENTIONS: Patients were managed according
to a protocol. MEASUREMENTS AND RESULTS: Clonidine was administered until blood pressure stability was
the fully restored and the dose was then gradually reduced. Five patients from the nonclonidine group and 2
from the clonidine group died. CONCLUSIONS: These results suggest that clonidine is effective in the
treatment of blood pressure instability in severe tetanus.

Baroreflex failure syndrome: a rare complication of bilateral carotid body tumor excision.
Turk Kardiyol Dern Ars.  2010; 38(4):267-70 (ISSN: 1016-5169)
Onan B; Oz K; Onan IS
Lutfi K?rdar Kartal Education and Research Hospital, Istanbul, Turkey.

Editor’s note: Patients suffered baroreflex failure syndrome after bilateral carotid body tumor

Baroreflex failure syndrome is a rare disorder seen after bilateral carotid body tumor resection. Iatrogenic
injuries to the baroreceptor reflex arc cause fluctuations in blood pressure with hypertensive attacks or
hypotensive episodes. A 43-year-old woman underwent bilateral carotid body tumor resection with one-week
interval for a hypervascular tumor, 78 x 50 x 45 mm in size, at the right carotid artery bifurcation and a smaller
tumor (50 x 30 x 20 mm) in the contralateral neck. Blood pressure of the patient became significantly unstable
after excision of the second tumor, with hypertensive attacks up to 220/140 mmHg, accompanied by episodes
of severe frontal headache, nausea, vomiting, skin flushing, and synchronous sinus tachycardia of 130
beats/min. Intermittent episodes of hypotension and bradycardia were also noted. The patient was clinically
diagnosed as having baroreflex failure syndrome. The symptoms of the patient improved with medical therapy
including clonidine, low dose beta-blocker, metoprolol, and a sedative. During 10 months of follow-up, she was
generally well with residual episodes of hypertension about twice a month. In patients with bilateral carotid body
tumors, unilateral excision of the greater tumor and a conservative approach for the contralateral tumor seem to
be a more convenient approach to prevent baroreflex failure.

Recurrent hypertensive crises associated with severe orthostatic hypotension due to
baroreflex failure syndrome
Z Kardiol.  2002; 91(11):946-50 (ISSN: 0300-5860)
Frantz S; Lührs H; Allolio B; Koller ML
Medizinische Universitätsklinik Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany. s.frantz@mail.uni.

Editor’s note: the authors reported a clinical case of baroreflex failure following bilateral carotid
artery surgery and radiation with symptoms of drastic changes in sympathetic activation and
unstable blood pressure

The baroreflex mechanism is a central part of the regulation of the cardiovascular system, particularly in the
control of vagal and sympathetic outflow to the heart and the peripheral circulation. Failure of the baroreflex is a
rare cause of secondary hypertension. It is characterized by drastic changes in sympathetic activation and
blood pressure following complete denervation of the baroreflex. Here, we report a case of baroreflex failure
following bilateral carotid artery surgery and radiation. Moreover, postoperative orthostatic hypotension with
recurrent syncope suggests a rare subform, the selective baroreflex failure, where efferent parasympathetic
activity is preserved. Both high blood pressure and orthostatically induced syncope improved substantially after
treatment with clonidine.

Understanding Low Blood Pressure -- the Basics
(From WebMD)

What Is Low Blood Pressure?

Hypotension is the medical term for low blood pressure (less than 90/60) with no symptoms.
A blood pressure reading appears as two numbers. The first and higher of the two is a measure of systolic
pressure, or the pressure in the arteries when the heart beats and fills them with blood. The second number
measures diastolic pressure, or the pressure in the arteries when the heart rests between beats.
Normal blood pressure is usually in the range of 120/80 (systolic/diastolic). In healthy people, especially
athletes, low blood pressure is a sign of good cardiovascular (heart and blood vessel) health. But low blood
pressure can be a sign of an underlying problem -- especially in the elderly -- where it may cause inadequate
blood flow to the heart, brain, and other vital organs.
Chronic low blood pressure with no symptoms is almost never serious. But health problems can occur when
blood pressure drops suddenly, and the brain is deprived of an adequate blood supply. This can lead to
dizziness or lightheadedness. Sudden drops in blood pressure most commonly occur in someone who's rising
from a prone or sitting position to standing. This kind of low blood pressure is known as postural hypotension,
orthostatic hypotension, or neurally mediated orthostatic hypotension.
Postural hypotension is considered a failure of the autonomic nervous system -- the part of the nervous system
that controls involuntary vital actions, such as the heartbeat -- to react appropriately to sudden changes.
Normally, when you stand up, some blood pools in your lower extremities. Uncorrected, this would cause your
blood pressure to fall. But your body normally compensates by sending messages to your heart to beat faster
and to your blood vessels to constrict. This offsets the drop in blood pressure. If this does not happen, or
happens too slowly, postural hypotension results.
The risk of both low and high blood pressure normally increases with age, due in part to normal changes during
aging. In addition, blood flow in the brain declines with age, often as a result of plaque buildup in blood vessels.
An estimated 10% to 20% of people over age 65 have postural hypotension.

What Causes Low Blood Pressure?
The cause of low blood pressure isn't always clear. It may be associated with the following:
•        Pregnancy
•        Hormonal problems such as an underactive thyroid (hypothyroidism), overactive thyroid
(hyperthyroidism), diabetes, or low blood sugar (hypoglycemia)
•        Over-the-counter medications
•        Overdose of high blood pressure drugs
•        Heart failure
•        Heart arrhythmias (abnormal heart rhythms)
•        Widening, or dilation, of the blood vessels
•        Heat exhaustion or heat stroke
•        Liver disease

What Causes a Sudden Drop in Blood Pressure?
Sudden drops in blood pressure can be life-threatening. Causes of this type of hypotension include:
•        Loss of blood from bleeding
•        Low body temperature
•        High body temperature
•        Heart muscle disease causing heart failure
•        Sepsis, a severe blood infection
•        Severe dehydration from vomiting, diarrhea, or fever
•        A reaction to medication or alcohol
•        A severe allergic reaction, called anaphylaxis

Who Gets Postural Hypotension?
Postural hypotension, which is low blood pressure when standing up suddenly, can happen to anyone for a
variety of reasons, such as dehydration, lack of food, prolonged standing in the heat, or being overly fatigued. It
can also be influenced by genetic make-up, aging, medication, dietary and psychological factors, and acute
triggers, such as infection and allergy.
Postural hypotension occurs most frequently in people who are taking drugs to control high blood pressure
(hypertension). It can also be related to pregnancy, strong emotions, hardening of the arteries (atherosclerosis),
or diabetes. The elderly are particularly affected, especially those who have high blood pressure or autonomic
nervous system dysfunction.
Hypotension after meals is a common cause of dizziness and falls after eating. It’s believed to be caused by
blood pooling into he vessels of the stomach and intestines.
Several drugs are commonly associated with postural hypotension. These medications can be divided into two
major categories:
•        Drugs used to treat high blood pressure, such as diuretics, beta-blockers, calcium-channel blockers, and
angiotensin-converting enzyme (ACE) inhibitors.
•        Drugs that have hypotension as a side effect, including nitrates, drugs for Parkinson's disease,
antipsychotics, neuroleptics, anti-anxiety agents, sedative-hypnotics, and tricyclic antidepressants.
Common causes of naturally occurring postural hypotension include:
•        Dehydration and electrolyte loss, which may result from diarrhea, vomiting, excessive blood loss during
menstruation, or other conditions
•        Age-associated decline in blood pressure regulation, which may be worsened by certain health conditions
or medications
Certain diseases can cause postural hypotension. These include:
•        Central nervous system disorders, such as Shy-Drager syndrome or multiple system atrophy
•        Nerve problems, such as peripheral neuropathy or autonomic neuropathy
•        Cardiovascular disorders
•        Alcoholism
•        Nutritional diseases
Less common diseases that can cause postural hypotension include amyloidosis (caused by deposits of a waxy
substance called amyloid in the body), vitamin deficiencies, spinal cord injuries, and neuropathies associated
with cancer, particularly lung or pancreatic cancer.

What is Neurogenic Shock

From Wikipedia, the free encyclopedia

Neurogenic shock is a distributive type of shock resulting in hypotension, occasionally with bradycardia, that is
attributed to the disruption of the autonomic pathways within the spinal cord. Hypotension occurs due to
decreased systemic vascular resistance resulting in pooling of blood within the extremities lacking sympathetic
tone. Bradycardia results from unopposed vagal activity and has been found to be exacerbated by hypoxia and
endobronchial suction.[1] Neurogenic shock can result from severe central nervous system damage (brain
injury, cervical or high thoracic spinal cord).[2] In more simple terms: the trauma causes a sudden loss of
background sympathetic stimulation to the blood vessels. This causes them to relax (vasodilation)[3] resulting
in a sudden decrease in blood pressure (secondary to a decrease in peripheral vascular resistance).
Neurogenic shock can be a potentially devastating complication, leading to organ dysfunction and death if not
promptly recognized and treated. It is not to be confused with spinal shock, which is not circulatory in nature.
[edit] Treatment
•        Fluid is always the initial treatment of shock, especially since concomitant hemorrhagic shock must be
excluded following trauma. Most institutions will additionally utilize pressor agents to achieve hemodynamic
•        Dopamine (Intropin) is often used either alone or in combination with other inotropic agents.
•        Vasopressin (antidiuretic hormone [ADH])[4]
•        Certain vasopressors (ephedrine, norepinephrine). Phenylephrine should be avoided as it can worsen
bradycardia often seen in neurogenic shock.
•        Atropine (speeds up heart rate and cardiac output)