Vasovagal syncope (Vasovagal reaction, episode or attack)

24/02/2010

Condition related to stimulation of the vagus nerve.

Vagus nerve:

  • a mixed nerve that innervates the pharynx and larynx and lungs and heart and esophagus and stomach and most of the abdominal viscera.
  • it is the tenth cranial nerve.
  • originates at brainstem

Many vasovagal syncope conditions fall under this condition – they are differ in their mechanism.

Some common mechanisms:

  • Standing up very quickly
  • Stress
  • Any painful or unpleasant stimuli, such as:
    • Having blood drawn
    • Experiencing intense pain
    • Experiencing medical procedures with local anesthesia
    •  Venipuncture
    • Giving or receiving a needle immunization.
    • Watching someone give blood
    • Watching someone experience pain
    • Watching or experiencing medical procedures
    • Sight of blood
    • Occasions of slight discomfort, such as dental and eye examinations
    • Hyperthermia, a prolonged exposure to heat
    • High temperature, either in the environment or due to exercise
  • Arousal or stimulants e.g. sex
  • Sudden onset of extreme emotions
  • Hunger
  • Nausea or vomiting
  • dehydration
  • Micourination syncope or defecation syncope
  • Abdominal straining or ‘bearing down’
  • Swallowing (‘swallowing syncope’) or coughing (‘cough syncope’)
  • Pressing upon certain places on the throat, sinuses, and eyes, also known as vagal reflex stimulation when performed clinically.
  • Water colder than 10 Celsius (50° F), or ice that comes in contact with the face, that stimulates the mammalian diving reflex
  • High altitude
  • Use of certain drugs that affect blood pressure, such as amphetamines 
  • Intense laughter
  • Pathophysiology:

    In people with vasovagal episodes, the episodes are typically recurrent, usually happening when the person is exposed to a specific trigger.

    The initial episode often occurs when the person is a teenager, then recurs in clusters throughout his or her life.

    Prior to losing consciousness, the individual frequently experiences a prodrome of symptoms such as lightheadedness, nausea, sweating, ringing in the ears (tinnitus), uncomfortable feeling in the heart, weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision.

    These symptoms last for at least a few seconds before consciousness is lost (if it is lost), which typically happens when the person is sitting up or standing.

    When sufferers pass out, they fall down (unless this is impeded); and when in this position, effective blood flow to the brain is immediately restored, allowing the person to wake up.

    The autonomic nervous system’s physiologic state  leading to loss of consciousness may persist for several minutes, so:

    1. If sufferers try to sit or stand when they wake up, they may pass out again;
    2. The person may be nauseated, pale, and sweaty for several minutes.

    resulting in simultaneous enhancement of parasympathetic nervous system (vagal) tone and withdrawal of sympathetic nervous system tone.

    This results in a spectrum of hemodynamic responses:

    1. On one end of the spectrum is the cardioinhibitory response, characterized by a drop in heart rate (negative chronotropic effect) and in contractility (negative inotropic effect) leading to a decrease in cardiac output that is significant enough to result in a loss of consciousness. It is thought that this response results primarily from enhancement in parasympathetic tone.
    2. On the other end of the spectrum is the vasodepressor response, caused by a drop in blood pressure without much change in heart rate. This phenomenon occurs due to vasodilation, probably as a result of withdrawal of sympathetic nervous system tone.
    3. The majority of people with vasovagal syncope have a mixed response somewhere between these two ends of the spectrum
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    Central Lines

    18/02/2010

      

    Types of Central Lines: 

     

    1. Peripherally Inserted Central Catheter – PICC
    • typically used in patients receiving antibiotics for an extended time period
    • inserted in the antecubital fossa
    • central catheter is inserted and threaded through the peripheral catheter
    • distal catheter tip lies in the superior vena cava
    • have positive, negative pressure valves preventing the inflow of air or outflow of blood.

    Does not require heparin flushing 

    • flush with NS after each use
    • use 12ml or larger syringe

     2. Port- A- Cath 

    • A catheter connects the port to a vein.
    • Implanted venous access device
    • resembles small pacemaker in size
    • implanted in upper chest
    • tip lies in the superior vena cava
    • Huber needle access only
    • no external devices emerge from skin
    • heparin flushed

     3. Hickman aka Broviac  

    • a central line that is tunneled under the skin so that the exit site is away from where the catheter enters the blood vessel
    • has free-hanging line
    • does not have antireflux valve like PICC


    4.Tunneled catheter

    • A vascular access device whose proximal end is tunneled subcutaneously from the insertion site and brought out through the skin at an exit site
    • Passing the catheter under the skin helps keep it in place better, lets you move around easier, and makes it less visible.

     5.Implanted port

    • similar to a tunneled catheter but is left entirely under the skin.
    • Medications are injected through the skin into the catheter.
    • Some implanted ports contain a small reservoir that can be refilled in the same way.
    • After being filled, the reservoir slowly releases the medicine into the bloodstream.
    • An implanted port is less obvious than a tunneled catheter and requires very little daily care.
    • It has less impact on a person’s activities than a PICC line or a tunneled catheter

      


    Chest Ausculatation

    10/02/2010

    Cardiac Auscultation Landmarking

    Lung Auscultation Landmaring:


    Medical Fun and Games

    07/02/2010

    Like a flower waiting to bloom
    Like a lightbulb in a dark room
    I’m just sitting here waiting for you
    To come home and turn me on

    Like the desert waiting for the rain
    Like a school kid waiting for the spring
    I’m just sitting here waiting …

     – Norah Jones


    Antiemetics

    07/02/2010

     

    • treat nausea and vomiting
    • act by inhibiting dopamine or serotonin receptors in the brain
    • act to block various pathways preventing signals from reaching the VC or CTZ

     

    Physiologic vomiting triggers

    1. Stimulus of the vomiting center – VC
    2. Stimulus of the chemoreceptor trigger zone – CTZ

     

    Secondary to nausea and vomiting is dehydration

    • excessive fluid loss can lead to acid-base disturbances

     

    Types of antiemetics

    1. anticholinergics
    2. Antihistamines
    3. Benzodiazepines
    4. Cannabinoids
    5. Glucocorticoids
    6. Phenothiazines
    7. Serotonin Receptor Antagonists

     

    Acholinergics (Scopalamine)

    • block Ach receptors in the vestibular nuclei and reticular formation
    • prevent stimuli from these areas being transmitted to VC or Chemoreceptor trigger zone

     

    Antihistamines (Gravol or dimenhydrinate)

    • bind histamine receptors inhibiting the binding of Ach to vestibular nuclei and reticular formation

     

    Neuroleptic agents (Phenothiazines)

    • block dopamine receptors in the chemoreceptor trigger zone
    • meds also relieve vertilago
    • use in chemo tx of nausea and vomiting

     

    Prokinetic agents (Maxeran)

    • blocks dopamine in the CTZ and stimulates GI peristalsis
    • acts to tighten gastroesophageal sphincter preventing GERD
    • aids in gastric emptying – used for tube feed pts
    • Maxeran must be reduced if diarrhea develops
    • SE – drowsiness

     

    Serotonin blockers (Odancetron aka Zofran)

    • blocks serotonin receptors in the GI, VC and CTZ
    • often effective when gravol is not

    Benzodiazepines (Ativan)

    • decreases response in VC and CTZ
    • used as a adjunct to treat nausea and vomiting, not alone
    • uncommon in the tx of nausea and vomiting

     

    Glucocorticoids

    • action in N and V tx unclear
    • used in adjunct with other antiemetics
    • used in chemo related N and V
    • not a first line antiemetic due to it being a steroid, decreasing immunity and elevating the WBC count

     

    Antiemetic considerations:

    • liver and kidney Fx
    • Fluid and electrolyte balance (dehydration risk)
    • BP & P – hypovolemia risk

     

    Antiemetic choice considerations

    1. if vomiting occurs after a meal, administer prior to meal
    2. If gravol is ineffective use Serotonin blockers (Odancetron)

    The Common Cold

    31/01/2010

     

    Viral infection of the upper respiratory tract

    Etiology:
    1.rhinovirus
    2.parainfluenza virus
    3.respiratory syncytial virus
    4.coronaviruses
    5.adenovirus

    Modes of transmission/spread
    1.Direct contact: person to person
    most contagious in first 3 days of symptom onset
    incubation period of 5 days

    2.Indirect contact: viruses can survive more than 5 hours on the following:
    fomites
    skin
    fingers touching contaminated surfaces then mucous membranes

    3.Aerosoled
    coughing
    sneezing

    Manifestations:
    nasopharyngeal dryness and stuffiness
    excessive nasal secretions
    tearing at the eyes
    typically clear and watery secretions
    inflammation and erythmatous upper respiratory tract mucus membranes
    sore throat
    hoarseness
    headache
    generalized malaise
    chills
    fever
    exhaustion

    duration – 7 days

    Diagnosis

    Hx
    symptoms, onset, duration

    Treatment: OTC remedies

    1.Antihistamines
    used to dry nasal secretions
    may act to dry bronchial secretions
    may worsen cough
    may cause dizziness, drowsiness and impaired judgment

    2.Decongestants – sympathomimetic agents
    constrict blood vessels to decrease swelling
    may result in systemic vasoconstriction
    may elevate blood pressure
    should be avoided in those with HTN, heart disease, hyperthyroidism, diabetes

    3.Vitamin C
    studies show contradictory results
    4.Zinc Lozenges – studies also show variable results


    Inflammatory Bowel Disease

    08/01/2010

     

    Two chronic disorders:


    1.Crohn`s disease
    2.Ulcerative Colitis

    Etiology:

    Genetic susceptibility (no gene yet identified): Intolerance of normal gut flora by the body`s immune system.
    Immune response is unregulated.

    1. Ulcerative Colitis
    • Chronic inflammation of the colon that produces ulcers in its lining
    • region of affected gut is continuous

     2. Crohn`s Disease

    • A chronic form of inflammatory bowel disease that usually affects the lower small intestine (called the ileum) or the colon
    • skip lesions in small and large intestine

     

    Differentiating Characteristics of Crohn`s Disease and Ulcerative Colitis

    Characteristics Crohn`s Disease Ulcerative Colitis
    Type of inflammation Granulomatous Ulcerative and exudative:
    Level of involvement submucosa mucosa
    Area of involvement Ileum, colon Rectum and left colon
    Extent of Involvement skip lesions in small and large intestine region of affected gut is continuous
    Diarrhea common common
    Rectal bleeding rare common
    Fistuals common rare
    Stricture common rare
    Perianal abscesses Common Rare
    Development of cancer Uncommon Relatively Common

     

    Martin, Glenn and Porth, Carol, Mattson. 2009. Pathophysiology Concepts of Altered Health States. 8th ed. Lippincott Williams and Wilkins. Philadelphia