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ANAPHYLAXIS

emergency medicine

By Abeer AbbasPublished 2 months ago 5 min read
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shock is a life-threatening condition that occurs when body organs don't receive enough oxygen and nutrients to function properly.

shock can be grouped into four types based on the cause: hypovolemic, cardiogenic, obstructive, and disruptive shock, which can be further divided into septic, anaphylactic, and neurogenic.

now to understand anaphylactic shock let's quickly review the physiology of blood vessels, which contain smooth muscle in their walls, when the smooth muscle relaxes it increases the diameter of blood vessels called vasodilation, on the other hand, when smooth muscle contracts the diameter of blood vessels decreases, called Vasoconstriction. the contraction and relaxation of smooth muscles are primarily controlled by the sympathetic nervous system, which normally maintains a partial constriction generating enough Force to keep blood moving through the circulatory system. the sympathetic system stimulation can increase or decrease to keep up with the body's needs , increased sympathetic stimulation of the blood vessels causes Vasoconstriction and increases peripheral vascular resistance, Vasoconstriction when the total blood volume is constant raises blood pressure and allows blood to flow faster through the blood vessels , in contrast Vasodilation is typically caused by decreased sympathetic stimulation in addition to inflammatory cyto and histamine, which decrease peripheral vascular resistance, so vasodilation when blood volume is constant lowers the blood pressure and slows down the blood flow through the blood vessels.

now the main cause of anaphylaxis and anaphylactic shock is a systemic allergic reaction to an external trigger , which can be medications,insect bites , or food, for example ;nuts.

important risk factors include:

certain comorbidities such as older age , asthma and other respiratory disorders like chronic obstructive pulmonary disease or cardiovascular disease .

the pathophysiologic mechanism behind anaphylaxis and anaphylactic shock is a type 1 hypers sensitivity reaction which is mediated by IGE antibodies that bind and sensitize the mast cells and basophils, once an external trigger reaches the body it binds IG antibodies and stimulates mast cells and basophils, to degranulate and release vasoactive mediators such as histamine and bradykinin , that eventually cause massive systemic vasodilation , histamine also increases vascular permeability thereby allowing the fluid to shift from the intravascular compartment into the interstitial compartment subsequently, causing edema , in addition to histamine mast cells also release an enzyme tryptase which breaks down the proteins and causes local tissue damage.

now the next events in anaphylactic shock, are grouped into four stages: initial , compensatory , Progressive and refractory stages .

in the initial stage, systemic Vasodilation causes less blood to return to the heart through the Venus system this in turn decreases cardiac output as a consequence , body cells are not well profused so they switch to anerobic metabolism to produce energy, causing lactic acid to build up in the blood, when lactic acid builds up that lowers blood pH, causing metabolic acidosis , this activates the compensatory stage , during the compensatory stage the sympathetic nervous system increases its activity to compensate for the decreased tissue perfusion in order to maintain homeostasis , and acid base compensatory mechanisms activate to correct the acidosis. in the progressive stage these compensatory mechanisms start failing, so the body's metabolic needs can't be met, this results in lactic acid buildup in the blood more than in the initial stage, and gradually worsening metabolic acidosis. finally, the refractory stage is when shock progresses to Cellular death and multiple organ damage which can be fatal.

complications

reduced blood supply to the myocardium can result in myocardial infarction, while reduced blood supply to the brain, might cause loss of consciousness.

Additionally, the edema can affect the airway, more specifically the larynx and cause upper Airway obstruction respiratory failure as well as complications such as cardiorespiratory arrest and even death.

clinical manifestations

cardiovascular such as hypotension tacycardia and chest pain.

respiratory which are typically associated with laryngeal edema and include voice hoarseness, shortness of breath and Strider. additionally, there's often angioedema of the lips and tongue meaning these organs swell up.

skin manifestations which typically include flushing and itching.

if the cause of anaphylactic shock is an insect bite, localized signs of inflammation at the side of the bite are often present. diagnosis of anaphylactic shock starts with the patient's history and physical assessment, followed by lab tests, which might reveal High serum levels of histamine, tryptase and serum IgE antibodies, an electrocardiogram as well as Imaging studies like an x-ray or CT scan can be used to exclude possible complications of the anaphylactic shock.

finally in order to identify the allergen, skin prick test can be done. this is where small drops of allergens are pricked into the skin with a tool to see if there's evidence of an allergy like raised itchy red bumps or Wheels.

treatment for anaphylactic shock

the first step is to ensure Airway patency, which in severe cases might require intubation and administer epinephrine intramuscularly, additionally, high flow oxygen, as well as nebulized albuterol, IV Diphenhydramine and IV methylprednisolone can be administered. early resuscitation with IV fluids is also required in case of persistent hypotension, then vasopressors like norepinephrine or vasopressin should be used.

nursing care

The primary nursing goals are to maintain Airway patency and oxygenation. and promote adequate organ perfusion Begin by monitoring your patient's Airway, and oxygenation by instituting pulse oximetry and administer high flow oxygen to keep the spo2 greater than 90%. inspect their face, lips and tongue for swelling, and assess their mental status, monitor their respiratory rate depth and effort and auscultate their lung sounds.

immediately report to the health care provider if your patient experiences dyspnea, Strider or hoarseness, drooling or signs of decreased oxygenation, such as altered level of Consciousness. suction secretions and prepare to assist with rapid intubation as indicated, administer the prescribed medications such as epinephrine to help mediate the allergic reaction, next watch for signs of decreased organ profusion by assessing your patient's circulatory status, assess their Vital Signs, peripheral pulses, capillary refill, skin color and urinary output.

immediately report if your client has decreased blood pressure tacycardia, weak peripheral pulses, slow capillary refill, cool and modeled skin, decreased urine output or anuria. administer the prescribed IV fluids and medications, including an infusion of epinephrine or vasopressors as ordered and raise your patient's legs and feet to assist in promoting adequate circulation to the central part of the body.

finally assist the healthcare team in identifying the underlying cause of the anaphylactic reaction.

Counselling

first teach your client that anaphylactic shock is a life-threatening condition that occurs because of a severe allergic reaction called anaphylaxis. now if the cause of your client's anaphylactic reaction was identified stress, the importance of avoiding the allergen that caused the reaction, then teach them how to recognize signs of anaphylaxis , and demonstrate how to use their prescribed automatic injectable epinephrine device, to ask questions ensure other family members know how to use it, as well, also be sure to emphasize the importance of keeping it with them at all times, and provide information on where they can obtain a medical alert identification , finally instruct them to seek emergency medical treatment immediately after using their automatic injectable epinephrine device

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About the Creator

Abeer Abbas

I am a doctor with plenty of luck, and I love of science and beauty.

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