Ventilation, Perfusion and Shock

Dec 25, 2012 – Uploaded by WCTCEMS << OVERVIEW OF SHOCK VIDEO<<

typesofshock

Initial symptoms of shock include:
  • Cold, clammy hands and feet.
  • Pale or blue-tinged skin tone (cyanosis)
  • Weak, fast pulse rate (tachycardia)
  • Fast breathing rate (tachypnea)
  • Low blood pressure (hypotension)

 

Cardiogenic shock is literally shock of cardiac origin. It is also the physiologic end point of all other causes of shock. Cardiogenic shock can therefore, regardless of its etiology, be thought of as shock caused by failure of the heart as a forward pump. Modern advances in medical care have made cardiogenic shock less common than it once was, but it is still a life-threatening reality. For example, in the 1970s, approximately 15% of all patients suffering from acute myocardial infarcts developed cardiogenic shock; today, the incidence of cardiogenic shock has dropped to about 5%.

Shock occurs when the circulatory system doesn’t have enough pressure to allow oxygen to reach all of the organs. Supplying organs and body tissues with oxygenated blood is known as perfusion. Components responsible for maintaining perfusion include the heart, blood vessels and blood. Shock should be considered a sign, not a diagnosis. Treatment is based on the underlying cause. There are five types of shock: cardiogenic, distributive, obstructive, dissociative and hemorrhagic.

Cardiogenic shock occurs when the heart fails to pump adequately. Decreased cardiac output can be caused by extremes in heart rate — either too slow or too fast, a decrease in force of pumping caused by a myocardial infarction (MI) or damaged heart valves.

hypovolemic-shock-chart

Hypovolemic shock, also known as hemorrhagic shock, is a life-threatening condition that results when you lose more than 20 percent (one-fifth) of your body’s blood or fluid supply. This severe fluid loss makes it impossible for the heart to pump a sufficient amount of blood to your body. Hypovolemic shock can lead to organ failure. This condition requires immediate emergency medical attention.

Hypovolemic shock is the most common type of shock, with very young children and older adults being the most susceptible.

Hypovolemic shock results from significant and sudden blood or fluid losses within your body. Blood loss of this magnitude can occur because of:

  • bleeding from serious cuts or wounds
  • bleeding from blunt traumatic injuries due to accidents
  • internal bleeding from abdominal organs or ruptured ectopic pregnancy
  • bleeding from the digestive tract
  • significant vaginal bleeding

In addition to actual blood loss, the loss of body fluids can cause a decrease in blood volume. This can occur in cases of:

  • excessive or prolonged diarrhea
  • severe burns
  • protracted and excessive vomiting
  • excessive sweating

Blood carries oxygen and other essential substances to your organs and tissues. When heavy bleeding occurs, there is not enough blood in circulation for the heart to be an effective pump. Once your body loses these substances faster than it can replace them, organs in your body begin to shut down and the symptoms of shock occur. Blood pressure plummets, which can be life-threatening.

Distributive shock is a distribution problem. The blood vessels make up the network responsible for distributing blood to the body. When these vessels leak or become too large or dilated, blood pressure will go down resulting in shock. Common causes of distributive shock are anaphylaxis, sepsis and trauma to the spinal cord.

Obstructive shock occurs when a physical obstruction alters the body’s ability to maintain perfusion. Causes include pulmonary embolism, tension pneumothorax and pericardial tamponade.

 

neurogenic-shock

 

Neurogenic shock occurs after an injury to the spinal cord. sympathetic output is disrupted resulting in unopposed vagal tone. Major clinical signs are hypotension and bradycardia. Acute spinal cord injury is most commonly seen with blunt trauma accounting for approximately 85 to 90 percent of cases. The most commonly affected area is the cervical region, followed by the thoracolumbar junction, the thoracic region, and the lumbar region.Neurogenic shock must be differentiated from “spinal” shock. Spinal shock is defined as temporary loss of spinal reflex activity occurring below a total or near-total spinal cord injury.

Patients are generally hypotensive with warm, dry skin. The loss of sympathetic tone may impair the ability to redirect blood flow from the periphery to the core circulation leading to excessive heat loss and hypothermia. Bradycardia is a characteristic finding of neurogenic shock; however, it is not universally present. These symptoms can be expected to last from one to three weeks.
The anatomic level of the injury to the spinal cord impacts the likelihood and severity of neurogenic shock. Injuries above the T1 level have the capability of disrupting the spinal cord tracts that control the entire sympathetic system. Injuries occurring in the levels from T1 to L3 may only partially interrupt the sympathetic outflow. The higher the level of injury the more likely it is for the patient to exhibit severe symptoms.
Neurogenic shock may be present with both complete and incomplete spinal cord lesions. The initial presentation represents the acute traumatic injury to the cord. However, a secondary cord injury may evolve over the first few days to weeks following the initial injury. The secondary cord injury is thought to be a result of ischemia to the spinal cord and may lead to a higher level of dysfunction than originally present or to an incomplete injury becoming a complete lesion.

The diagnosis of neurogenic shock should be one of exclusion. Neurogenic shock must be differentiated from other types of shock, particularly hypovolemic. When dealing with a trauma patient, one must always assume that any hypotension is a result of ongoing blood loss. A patient suffering from neurogenic shock may also have concomitant injuries which may contribute to hemodynamic instability. Clinical clues such as hypotension, bradycardia, neurologic dysfunction, and warm, dry skin may lead the clinician to suspect neurogenic shock; however, only after other injuries have been identified and treated can the diagnosis of neurogenic shock safely be made.

anashock

Anaphylactic shock
A sudden, life-threatening allergic reaction, characterized by dilation ofblood vessels with a sharp drop in blood pressure and bronchial spasm withshortness of breath. Anaphylactic shock is caused by exposure to a foreignsubstance, such as a drug or bee venom, to which the individual has beenpreviously exposed. The substances act as antigens, provoking apreliminary immune response during the first exposure that results in a full-blown, immediate response during secondary exposure, called animmediate hypersensitivity reaction. Emergency treatment, includingepinephrine injections, must be administered to prevent death. Also calledanaphylaxis.

Anaphylaxis symptoms occur suddenly and can progress quickly. The early symptoms may be mild, such as a runny nose, a skin rash or a “strange feeling.” These symptoms can quickly lead to more serious problems, including:

  • Trouble breathing
  • Hives or swelling
  • Tightness of the throat
  • Hoarse voice
  • Nausea
  • Vomiting
  • Abdominal pain
  • Diarrhea
  • Dizziness
  • Fainting
  • Low blood pressure
  • Rapid heart beat
  • Feeling of doom
  • Cardiac arrest

People who have had a severe allergic reaction are at risk for future reactions. Even if your first reaction is mild, future reactions might be more severe. That’s why it’s important to carry self-injectable epinephrine if you are at risk, and 911 should be dialed in the event of a very serious reaction.

systemic-inflammatory-response-syndrome-sepsis-pathway

 

Sepsis is the result of an infection, and causes drastic changes in the body. It can be very dangerous and potentially life-threatening.It occurs when chemicals that fight infection by triggering inflammatory reactions are released into the bloodstream.

Doctors have identified three stages of sepsis:

  • Sepsis is when the infection reaches the bloodstream and causes inflammation in the body.
  • Severe sepsis is when the infection is severe enough to affect the function of your organs, such as the heart, brain, and kidneys.
  • Septic shock is when you experience a significant drop in blood pressure that can lead to respiratory or heart failure, stroke, failure of other organs, and death.

It is thought that the inflammation resulting from sepsis causes tiny blood clots to form. This can block oxygen and nutrients from reaching vital organs.

The inflammation occurs most often in older adults or those with a weakened immune system. But both sepsis and septic shock can happen to anyone.

Septic shock is the most common cause of death in intensive care units in the United States.

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typesofshock

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