hypovolemic shock definition

Hypovolemic Shock



Shock is a condition in which there is loss of effective circulating blood volume. Inadequate organ and tissue perfusion follows, ultimately resulting in cellular metabolic derangements. In any emergency situation, the onset of shock should be anticipated by assessing all injured people immediately. The underlying cause of shock (hypovolemic, cardiogenic, neurogenic, anaphylactic or septic) must be determined. Of these, hypovolemia is the most common cause .


Altered tissue perfusion related to failing circulation, impaired gas exchange related to a ventilation-perfusion imbalance, and decreased cardiac output related to decreased circulating blood volume are possible problems associated with hypovolemic shock. Therefore, the goals of treatment are to restore and maintain tissue perfusion and to correct physiologic abnormalities.

Management


For the patient experiencing hypovolemic shock, ensuring a patent airway and maintaining breathing are crucial. Additional ventilatory assistance is provided as required. A rapid physical examination is performed to determine the cause of shock.
Restoration of the circulating blood volume is accomplished with rapid fluid and blood replacement as prescribed based on the patient's response to therapy. Blood component therapy helps optimize cardiac preload, correct hypotension, and maintain tissue perfusion.
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Large-gauge IV catheters are inserted into peripheral veins. Two or more catheters are necessary for rapid fluid replacement and reversal of hemodynamic instability. The emphasis is on volume replacement. If it is suspected that a major vessel in the chest or abdomen has been disrupted, IV lines may be established in both upper and lower extremities.
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A central venous pressure (CVP) catheter also may be inserted (in or near the right atrium) to serve as a guide for fluid replacement. Continuous CVP readings give the direction and degree of change from baseline readings. The catheter is also a vehicle for emergency fluid volume replacement.


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IV fluids are infused at a rapid rate until systolic blood pressure or CVP increases to a satisfactory level above the baseline measurement or until there is improvement in the patient's clinical condition. Infusion of lactated Ringer's solution is useful initially because it approximates plasma electrolyte composition and osmolality, allows time for blood typing and screening, restores circulation, and serves as an adjunct to blood component therapy.
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Blood component therapy may also be prescribed, especially if blood loss has been severe or if the patient continues to hemorrhage. Measures to control hemorrhage are instituted because hemorrhage compounds the shock state. Serial hemoglobin and hematocrit values are obtained if continued bleeding is suspected. Also, the patient's legs are elevated slightly to improve cerebral circulation and promote venous return to the heart. However, this position is contraindicated for patients with head injuries. Unnecessary movement is also avoided.
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An indwelling urinary catheter is inserted to record urinary output every hour. Urine volume indicates the adequacy of kidney perfusion. However, fluid replacement should not be delayed while monitoring urine output.
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Ongoing nursing surveillance of the total patient is maintained. Blood pressure, heart and respiratory rates, skin temperature, color, pulse oximetry, neurologic status, CVP, arterial blood gases, ECG recordings, hematocrit, hemoglobin, coagulation profile, electrolytes, and urinary output are monitored serially to assess patient response to treatment. Commonly, a flow sheet is used to document these parameters, providing an analysis of trends rather than single values to reveal improvement or deterioration of the patient's condition.


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In addition, the body's defense mechanisms are supported. The patient should be reassured and comforted. Sedation may be necessary to relieve apprehension. Analgesics are used cautiously to relieve pain. Body temperature is maintained within normal limits to prevent increasing metabolic demands that the body may be unable to meet. Administration of large volumes of IV crystalloids, blood products, or both can result in hypothermia. Hypothermia may be prevented by warming the fluids administered.
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Resuscitation of the patient goes well beyond achieving a normal blood pressure and visual evidence of perfusion. Lactic acidosis is a common side effect of hemorrhage and injury. It is associated with poor cardiac performance and higher rates of morbidity and mortality. Base deficit and lactic acid are useful measures of successful and complete resuscitation. End points for resuscitation include a serum lactic acid level lower than 2.5 mmol/L within 24 hours after injury, normalization of vital signs and base deficit, and arrest of hemorrhage.


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