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Introduction to Shock

In medical terms, “shock” is a life-threatening condition where blood is being pumped throughout the body at an insufficient level, starving the body of oxygen and nutrients. Shock is actually a result of the body attempting to protect itself from harmful stimuli, such as injury. During this defense response heart rate increases, blood vessels narrow, and the kidney retains water to help maintain blood volume; all in an attempt to maintain appropriate blood supply to the vital organs.

Unfortunately these compensatory measures eventually fail, causing blood pressure to drop to a dangerous level. When this happens, cells become starved for oxygen and enter an anaerobic metabolism stage where high levels of carbon dioxide and lactate is produced. These substances lower the pH of the blood, leading to even more complications. As the condition continues to deteriorate, cell death escalates to cause irreversible damage and even death.

Causes of Shock

Shock is a condition that can be caused by a number of factors that ultimately lead to the same problem; reduced tissue perfusion. Shock can generally be divided into the following classification.

Hypovolemic Shock

Hypovolemic shock is a type of shock that occurs when there is not enough blood volume in the body to adequately perfuse the tissues. Probably the most common type of hypovolemic shock is also called hemorrhagic shock, and results from excessive bleeding as a result of trauma, ulcers, or other conditions that cause blood loss. Hypovolemic shock may also be caused by severe dehydration, where there is not enough water present in the body to maintain blood pressure despite no blood being lost.

Obstructive Shock

Another type of shock is obstructed shock, where tissues are unable to be perfused because of an obstruction that is blocking blood flow, such as a blood clot.

Distributive Shock

In distributive shock, blood simply does not reach where it needs to go due to an abnormal distributive pattern. This unusual occurrence can be caused by a number of factors, including other types of shock.

Cardiogenic Shock

The heart is a critical organ responsible for pumping oxygenated blood throughout the body. During Cardiogenic shock, however, the heart is unable to pump adequate amounts of blood to support tissue function. Cardiogenic shock is most often a result of a heart condition or damage to the heart, such as in the case of a heart attack.

Neurogenic Shock

This type of shock is caused by a loss of communication between the sympathetic nervous system and the blood vessels it controls. Ordinarily the nervous system plays a major role in adjusting the tone of blood vessels in order to control blood pressure. When this connection is lost, the vessels relax and dilate, leading to a dangerous drop in blood pressure. Neurogenic shock is most commonly caused by damage to the spinal cord.

Anaphylactic Shock

Anaphylactic shock is the result of a severe allergic reaction that caused blood vessels to dilate and blood pressure to fall. Additionally, the allergens may also cause excess fluid to be taken up into the tissues, leading to swelling and even lower blood pressure and volume.

Septic Shock

Caused by widespread infection, septic shock can be life threatening if not treated quickly. This infection can result in many small blood clots which block the perfusion to the tissues.

 Signs and Symptoms of Shock

The signs and symptoms of shock become progressively more noticeable as the condition worsen, making detection of early signs important for early intervention.

Early Signs

  • Elevated heart rate
  • Minimal drop in mean arterial pressure (MAP) ~ 10mmHg

Compensatory Signs

  • Further drop in MAP ~ 10 – 15mmHg
  • Increased elevated heart rate
  • Weak and rapid pulse
  • Restlessness
  • Fatigue
  • Cool, clammy skin

Progressive Signs

  • MAP drops ~ 20mmHg from baseline
  • Reduced urine output
  • Extreme fatigue
  • Pale skin
  • Bluish discoloration of the nail beds and lips
  • Dizziness
  • Altered mental status

Refractory Signs

  • Unconsciousness
  • Cell and organ damage

Clinical Manifestations

The clinical manifestations of shock include a range of signs, symptoms, and tests that can be observed or performed to help identify the condition. Examples of these manifestations include the following.

Physical manifestations

  • Reduced alertness
  • Heart rate > 100 beats per min
  • Respiratory rate > 22 breaths per min
  • Systolic Blood pressure <90mmHg, or a ≥30mmHg drop from baseline
  • Urine output < 0.5mL/kg/hour

Laboratory manifestations

  • Lactate > 3mmol/L, or 27 mg/dL
  • PaCO2 < 32mmHg
  • Base deficit < −4 mEq/L

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Treatment

Pharmacology of Shock

Treatment of shock generally consists of three categories; Supportive care, IV fluids, and additional treatment needed depending on the specific type of shock.

Supportive care

Supportive care begins by turning the client’s head to the side to avoid aspiration of any vomit that may occur. Warm blankets are placed and oxygen is supplied either a face mask, or intubation if necessary. Catheters are placed to allow access to venous system. Additional monitoring tools are placed in order to monitor blood pressure, heart rate, oxygen saturation, urine output, and more. These tools help the medical team to assess and monitor the condition of the client, allowing them to make more educated decisions on treatment strategy.

Vasopressors (phenylephrine, norepinephrine, epinephrine, and vasopressin, and dopamine) and inotropes (dobutamine and milrinone) are drugs that can be used to rapidly increase blood pressure by way of vasoconstriction. Doses of these drugs may be required during the initial treatment phases of shock. It should be noted that these medications are not a cure, they only allow for a temporarily increase in blood pressure to buy the client time. The ultimate goal when treating shock is to treat the cause and allow the body to restore and maintain blood pressure and tissue perfusion on its own.

IV Fluids

Another hallmark treatment for shock is the administration of IV fluids which are used to restore vascular volume. The typical initial treatment approach is 1L of normal saline infused over a period of 15 minutes. If parameters do not return to normal, additional fluid may be administered.

Additional Treatments

Supportive care and IV fluids are the mainstays of shock treatment, but additional measures may need to be taken depending on the specific type of shock being treated. These additional treatments typically deal with dealing with the source of the shock which varies between types. Perhaps the most obvious example of a necessary additional treatment is in the case of hemorrhagic shock, which results from severe blood loss. In this case, the bleeding event would also need to be promptly addressed alongside the other two measures in order for the shock to be treated. In the case of septic shock caused by widespread infection, broad spectrum antibiotics would also be administered to begin infection treatment.

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Nursing Interventions

Nursing interventions play a critical role in the success or failure of treating clients with shock. In fact, nurses are often the one who initially identify the condition due to their close client contact. It is for this reason that nurses must remain vigilant and well trained to recognize the early signs of shock.

Additionally, many of the methods used to treat shock fall directly to the responsibility of nurses, including fluid administration, monitoring vital signs, catheter placement, oxygen administration, and providing supportive care.

Conclusion

“Shock” is an umbrella term which can be broken down into a number of different subtypes. While each of these subtypes arises from different causes, they share important similarities such as hypotension and inadequate tissue perfusion. Likewise, the treatment of these subtypes also possesses many similarities in addition to a few differences. Whichever type of shock is being treated, however, nurses will undoubtedly be on the front lines.

References

Quick and dirty guide to shock. Medic Tests.
https://legacy.medictests.com/quick-dirty-guide-shock/. Accessed May 25, 2020.

Shock. Merck Manuals. https://www.merckmanuals.com/professional/critical-care-medicine/shock-and-fluid-resuscitation/shock. Accessed May 25, 2020.

Shock. Better Health. https://www.betterhealth.vic.gov.au/health/ConditionsAndTreatments/shock. Accessed May 25, 2020.

Inotropes and Vasopressors. NCBI. https://www.ncbi.nlm.nih.gov/books/NBK482411/. Accessed May 25, 2020.