Shock is a life-threatening condition with a variety of underlying causes. It is characterized by inadequate tissue perfusion that, if untreated, results in cell death. The nurse caring for the patient with shock or at risk for shock must understand the underlying mechanisms of shock and recognize its subtle as well as more obvious signs. Rapid assessment and response are essential to the patient’s recovery.
Shock a condition in which systemic blood pressure is inadequate to deliver oxygen and nutrients to support vital organs and cellular function. Adequate blood flow to the tissues and cells requires the following components: adequate cardiac pump, effective vasculature or circulatory system, and sufficient blood volume. When one component is impaired, blood flow to the tissues is threatened or compromised. Without treatment, inadequate blood flow to the tissues results in poor delivery of oxygen and nutrients to the cells, cellular starvation, cell death, organ dysfunction progressing to organ failure, and eventual death.
3 Common Types of Shock:
It can be classified by etiology and may be described as:
(1) Hypovolemic: Hypovolemic shock occurs when there is a decrease in the intravascular volume.
(2) Cardiogenic: Cardiogenic shock occurs when the heart has an impaired pumping ability; it may be of coronary or noncoronary origin.
(3) Circulatory or distributive : Circulatory shock results from a maldistribution or mismatch of blood flow to the cells.
Some authors identify a fourth category, obstructive, that results from disorders that cause mechanical obstruction to blood flow through the central circulatory system despite normal myocardial function and intravascular volume.
Some think of the shock syndrome as a continuum along which the patient struggles to survive. A convenient way to understand the physiologic responses and subsequent clinical signs and symptoms is to divide the continuum into separate stages: compensatory, progressive, and irreversible.
In the compensatory stage of shock, the patient’s blood pressure remains within normal limits. Vasoconstriction, increased heart rate, and increased contractility of the heart contribute to maintaining adequate cardiac output. This results from stimulation of the sympathetic nervous system and subsequent release of catecholamines (epinephrine and norepinephrine).
The patient displays the often-described “fight or flight” response. The body shunts blood from organs such as the skin, kidneys, and gastrointestinal tract to the brain and heart to ensure adequate blood supply to these vital organs. As a result, the patient’s skin is cold and clammy, bowel sounds are hypoactive, and urine output decreases in response to the release of aldosterone and ADH.
In the progressive stage of shock, the mechanisms that regulate blood pressure can no longer compensate and the MAP falls below normal limits, with an average systolic blood pressure of less than 90 mm Hg.
The irreversible (or refractory) stage of shock represents the point along the shock continuum at which organ damage is so severe that the patient does not respond to treatment and cannot survive. Despite treatment, blood pressure remains low. Complete renal and liver failure, compounded by the release of necrotic tissue toxins, creates an overwhelming metabolic acidosis.