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1. A clinical syndrome marked by inadequate perfusion and oxygenation of cells, tissues, and organs, usually due to marginal or markedly lowered blood pressure.
SYN: SEE: circulatory collapse

Shock may be caused by dehydration, hemorrhage, sepsis, myocardial infarction, valvular heart disease, cardiac tamponade, adrenal failure, burns, trauma, spinal cord injury, hypoxia, anaphylaxis, poisoning, and other major insults to the body.

Patients at risk for shock include, but are not limited to, those with severe injuries, external or suspected internal hemorrhage, profound fluid loss or sequestration (severe vomiting, diarrhea, burns), allergen exposures, sepsis, impaired left ventricular function, electrical and thermal injuries (including lightning strikes), and diabetes (if receiving supplemental insulin).

Shock results in failure of multiple organ systems, including the brain, heart, kidneys, lungs, skin, and gastrointestinal tract. Common consequences of shock are confusion, agitation, anxiety, or coma; syncope or presyncope; increased work of breathing; respiratory distress; pulmonary edema; decreased urinary output; and/or acute renal failure. Signs of shock include tachycardia, tachypnea, hypotension, and cool, clammy, or cyanotic skin.

Attempts to restore normal blood pressure and tissue perfusion include fluid resuscitation (in hypovolemic shock); control of hemorrhage (in shock caused by trauma or bleeding); administration of corticosteroids (in adrenal failure); pressor support (in cardiogenic or septic shock); the administration of epinephrine (in anaphylaxis); antibiotic administration with the drainage of infected foci (in sepsis); pericardiocentesis (in cardiac tamponade); transfusion; and oxygenation. Oral or parenterally administered sugars (typically glucose) can treat hypoglycemia caused by insulin, oral hypoglycemic drugs, or insulinomas.

Shock syndrome is a life-threatening medical emergency and requires very careful therapy and monitoring. If the patient does not respond at once, treatment and monitoring in the best facility available (such as intensive care unit) are essential. It is important that the electrocardiographic, arterial and central venous blood pressures, blood gases, core and skin temperatures, pulse rate, blood volume, blood glucose, hematocrit, cardiac output, urine flow rate, and neurological status be monitored frequently and regularly, e.g., hourly.

One or more large-bore intravenous catheters are inserted, and prescribed fluid therapy is initiated. External monitoring of vital signs is instituted; an arterial catheter may be placed for precise hemodynamic monitoring; and an indwelling urinary catheter is inserted to track urine output hourly. Prescribed oxygen therapy is provided; SaO2 (oxygen saturation), arterial blood gas levels, and ventilatory function are monitored to determine the need for ventilatory support. If occult bleeding is suspected, stools and gastric fluids are tested, and injured tissues and spaces are carefully assessed or imaged. Routine measures are taken to reduce the risk of decubitus ulcers, muscular atrophy, deep venous thrombosis, delirium, and contractures. The patient is maintained in a normothermic environment for comfort. Radiant warmers are useful in preventing hypothermia in patients who cannot be kept clothed or covered during assessment and treatment. The environment is kept as calm and controlled as possible. Procedures and treatments are explained to the patient in a simple, clear, easily understandable manner.

Positioning is based on the type of shock. Hypovolemic shock states respond best to supine positioning, or even elevation of the feet and lower legs; cardiac and anaphylactic shock states require head elevation to ease ventilatory effort. Correct body alignment should be maintained, whatever the necessary position. Oral fluids are often withheld to prevent vomiting and aspiration. Oral care and misting are provided frequently to prevent dryness, stomatitis, sordes, and salivary obstructions. The patient's sensorium is closely assessed, and sensory overload is prevented as much as possible. Regular assessments are conducted for acute organ dysfunction, e.g., urine output below 0.5 mL/kg/hr, hypotension, hypoxemia, lactic acidosis, and low platelet count. While providing comfort measures and emotional support, the health care professional acts as a liaison to family members or significant others, providing them with information on the patient's status and the treatment regimen. If shock is irreversible, the family must prepare for the patient's death; family members are encouraged to be with, talk to, and touch the patient, and social work and mental health consultations or spiritual measures may be obtained for the patient and family as determined by their beliefs and desires.

2. An electrical shock, e.g., a discharge of electricity from a cardioverter or defibrillator.

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