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Aina Meducci 2012

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Hypovolemic shock (haemorrhagic)


In this week, shock has becoming our main topic in every class. So, here's the thing about it

**********************************************************


What is shock??
A serious condition that occurs when the cardiovascular system is unable to supply enough blood flow to the body, causing inadequate tissue perfussion.

Major classes of shock include:

  • Cardiogenic Shock (associated with heart problems)
  • Hypovolemic Shock (caused by inadequate fluid volume)
  • Anaphylactic Shock (caused by allergic reaction)
  • Toxic Shock (associated with infections)
  • Neurogenic Shock (caused by damage to the nervous system)

Shock is a life-threatening condition that requires immediate medical treatment. Some degree of shock can accompany any medical emergency. Shock can get worse very rapidly.

Recognition of shock

Depending on the specific cause and type of shock, symptoms may include:

  • Anxiety or agitation
  • Bluish lips and fingernails
  • Chest pain
  • Confusion
  • Cool, clammy skin
  • Decreased or no urine output
  • Dizziness or light-headedness
  • Faintness
  • Low blood pressure (Hypotension)
  • Paleness (pallor)
  • Profuse sweating, moist skin
  • Rapid pulse
  • Shallow breathing
  • Unconsciousness
  • Weakness
  • Hyperventilating
  • Extended capillary refill time >2secs

**ONLY HYPOVOLEMIC SHOCK WILL BE DISCUSSED**


Hypovolemic shock


Hypovolemic shock refers to a medical or surgical condition in which rapid fluid loss results in multiple organ failure due to inadequate circulating volume and subsequent inadequate perfusion. Most often, hypovolemic shock is secondary to rapid blood loss. (Hemorrhagic shock)



Example of severe blood loss
(sorry couldn't found nice pic)


Acute external blood loss secondary to penetrating trauma and severe GI bleeding disorders are 2 common causes of hemorrhagic shock. Hemorrhagic shock can also result from significant acute internal blood loss into the thoracic and abdominal cavities.

Two common causes of rapid internal blood loss are solid organ injury and rupture of an abdominal aortic aneurysm. Hypovolemic shock can result from significant fluid (other than blood) loss. Two examples of hypovolemic shock secondary to fluid loss include refractory gastroenteritis and extensive burns.

**Losing about 1/5 or more of the normal amount of blood in the body causes hypovolemic shock.


Pathophysiology of hypovolemic shock (you may read the summary ^^ )


The hematologic system responds to an acute severe blood loss by activating the coagulation cascade and contracting the bleeding vessels (by means of local thromboxane A2 release). In addition, platelets are activated (also by means of local thromboxane A2 release) and form an immature clot on the bleeding source. The damaged vessel exposes collagen, which subsequently causes fibrin deposition and stabilization of the clot. Approximately 24 hours are needed for
complete clot fibrination and mature formation.

The cardiovascular system initially responds to hypovolemic shock by;

  • increasing the heart rate
  • increasing myocardial contractility
  • and constricting peripheral blood vessels.

This response occurs secondary to an increased release of norepinephrine and decreased baseline vagal tone (regulated by the baroreceptors in the carotid arch, aortic arch, left atrium, and pulmonary vessels). The cardiovascular system also responds by redistributing blood to the
brain, heart, and kidneys and away from skin, muscle, and GI tract.


The pathophysiology of hypovolemic shock is that when fluid volume goes down a decrease in the circulating volume of blood is seen. When the circulating volume of blood occurs the preload to the heart is decreased. A decrease in preload causes a decrease in stroke volume which will cause a decrease in the cardiac output. With reduced cardiac output you will see decreased cellular oxygen perfusion. When cells don’t receive enough oxygen they die. In addition to hypovolemic shock there is cardiogenic shock.

The renal system responds to hemorrhagic shock by stimulating an increase in renin secretion from the juxtaglomerular apparatus. Renin converts angiotensinogen to angiotensin I, which subsequently is converted to angiotensin II by the lungs and liver. Angiotensin II has 2 main effects, both of which help to reverse hemorrhagic shock, vasoconstriction of arteriolar smooth muscle, and stimulation of aldosterone secretion by the adrenal cortex. Aldosterone is responsible for active sodium reabsorption and subsequent water conservation.


The neuroendocrine system responds to hemorrhagic shock by causing an increase in circulating antidiuretic hormone (ADH). ADH is released from the posterior pituitary gland in response to a decrease in BP (as detected by baroreceptors) and a decrease in the sodium concentration (as detected by osmoreceptors). ADH indirectly leads to an increased reabsorption of water and salt (NaCl) by the distal tubule, the collecting ducts, and the loop of Henle.


Some of the complication associated with hypovolemic shock include;

  • Kidney damage
  • Brain damage
  • Gangrene of arms or legs, sometimes leading to amputation
  • Heart attack

**The pathophysiology of hypovolemic shock is much more involved than what was just listed. To explore the pathophysiology in more detail, references for further reading are suggested. These intricate mechanisms list above are effective in maintaining vital organ perfusion in severe blood loss. Without fluid and blood resuscitation and/or correction of the underlying pathology causing the hemorrhage, cardiac perfusion eventually diminishes, and multiple organ failure soon follows.






Summary of hypovolemic shock



Animals at hypovolemic RISK

  • Traumatic causes can result from penetrating and blunt trauma. Common traumatic injuries that can result in hemorrhagic shock include the following: myocardial laceration and rupture, major vessel laceration, solid abdominal organ injury, pelvic and femoral fractures, and scalp lacerations.Vascular disorders that can result in significant blood loss include aneurysms, dissections, and arteriovenous malformations.

  • GI disorders that can result in hemorrhagic shock include the following: bleeding esophageal varices, bleeding peptic ulcers, Mallory-Weiss tears, and aortointestinal fistulas.

  • Pregnancy-related disorders include ruptured ectopic pregnancy,placenta previa, and abruption of the placenta. Hypovolemic shock secondary to an ectopic pregnancy is common. Hypovolemic shock secondary to an ectopic pregnancy in a patient with a negative urine pregnancy test is rare but has been reported.

Treatment

Don't be too panic when you see people or animal in hypovolemic shock (particularly if you knew it) This is what you can do;


Before medical arrive;

  • Keep the person/animal comfortable and warm (to avoid hypothermia).
  • Have them lie flat with the feet lifted about 12 inches to increase circulation. However, if the person has a head, neck, back, or leg injury, do not change the person's position unless he or she is in immediate danger.
  • Do not give fluids by mouth. (it may cause heart to stop immediately-die)
  • If person/animal is having an allergic reaction, treat the allergic reaction, if you know how.
  • If the person/animal must be carried, try to keep him or her flat, with the head down and feet lifted. Stabilize the head and neck before moving a person with a suspected spinal injury.


Do like this



After medical arrived;

The goal of hospital treatment is to replace blood and fluids. An intravenous (IV) line will be put into the person's arm to allow blood or blood products to be given.

Fluid administration can increase cardiac pre-load as well as help with overall perfusion. There are two types of fluids.

  • Crystalloids such as normal saline, D5W, and lactated ringers.
  • Colloids such as whole blood, plasma and hetastarch.

While colloids might be preferred in some situations because of affinity to intravascular restoration, the down side is cost, potential for allergic reaction and speed or lack of speed in type and cross matching in an emergency.

Medicines such as dopamine, dobutamine, epinephrine, and norepinephrine may be needed to increase blood pressure and the amount of blood pumped out of the heart (cardiac output). One of the method to monitor the status of the patient is to do heart monitoring as well as urinary cathether (to collect and monitor how much urine is produced)


Sources: Hypovolemic shock; PubMed health, Shock; AricRn, Hypovolemic shock; emedicine.medscape.com, Shock; ambulancetechnicianstudy.co.uk




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