Cardiac and noncardiac shock (circulatory failure)

17 Cardiac and noncardiac shock (circulatory failure)

Overview/pathophysiology

A shock state exists when tissue perfusion decreases to the point of cellular metabolic dysfunction. Shock is classified according to the causative event.

Hypovolemic shock:

Occurs when volume in the intravascular space is inadequate and cannot meet the metabolic needs of tissues, as with severe hemorrhage or dehydration.

Cardiogenic shock:

Occurs when cardiac failure results in decreased tissue perfusion, as in severe myocardial infarction (MI) in which more than 40% of heart muscle has been affected.

Distributive shock conditions:

Characterized by displacement of a significant amount of vascular volume. The three types are neurogenic shock, anaphylactic shock, and septic shock.

Neurogenic shock:

Occurs when a neurologic event (e.g., spinal cord injury) causes loss of sympathetic tone, resulting in massive vasodilation and decreased perfusion pressures.

Anaphylactic shock:

Caused by a severe systemic response to an allergen (foreign protein), resulting in massive vasodilation, increased capillary permeability, decreased perfusion, decreased venous return, and subsequent decreased cardiac output.

Septic shock:

Occurs when bacterial toxins cause an overwhelming systemic infection.

Regardless of the cause, shock results in cellular hypoxia secondary to decreased perfusion and ultimately in cellular, tissue, and organ dysfunction. A prolonged shock state can result in death; therefore, early recognition and intervention are essential.

Health care setting

Critical care unit (e.g., cardiogenic shock in coronary care unit; distributive shock in medical intensive care unit [ICU])

Diagnostic tests

Diagnosis is usually based on presenting symptoms and clinical signs.

For septic shock

Cultures of blood, sputum, wound, and urine:

To identify causative organism.

White blood cell (WBC) count:

Elevated in the presence of infection.

For anaphylactic shock

WBC count:

Will reveal increased eosinophils, a type of granulocyte that appears in the presence of allergic reaction.

Nursing diagnoses:

Ineffective tissue perfusion

Risk for electrolyte imbalance

related to decreased circulating blood volume occurring with shock

Desired Outcome: Within 1-2 hr of treatment, patient has adequate perfusion as evidenced by peripheral pulse amplitude more than 2+ on a 0-4+ scale; brisk capillary refill (less than 2 sec); SBP greater than 90 mm Hg; Sao₂ greater than 92%; mean arterial pressure (MAP) 70-100 mm Hg; CVP at least 5 cm H₂O; HR regular and 100 bpm or less; no significant change in mental status; orientation to person, place, and time; and urine output at least 30 mL/hr (0.5 mL/kg/hr).

ASSESSMENT/INTERVENTIONS	RATIONALES
Assess and document peripheral perfusion status. Report significant findings.	Decreased peripheral perfusion is an early sign of decreased cardiac output and shock. Significant findings include coolness and pallor of the extremities, decreased amplitude of pulses, and delayed capillary refill.
Assess BP at frequent intervals; be alert to readings more than 20 mm Hg below patient’s normal range or to other indicators of hypotension, such as dizziness, altered mentation, or decreased urinary output.	Decreased SBP of greater than 20 mm Hg below patient’s normal range necessitates immediate intervention to avoid irreversible organ damage due to poor perfusion.
If severe hypotension is present, place patient in a supine position.	This position promotes venous return. BP must be at least 80/60 mm Hg for adequate coronary and renal artery perfusion.
Monitor CVP (if line is inserted).	CVP will show adequacy of venous return and blood volume; 5-10 cm H₂O usually is considered an adequate range. Values near zero can indicate hypovolemia, especially when associated with decreased urinary output, vasoconstriction, and increased HR.
Assess for restlessness, confusion, mental status changes, and decreased level of consciousness (LOC). Intervene to keep patient safe, and reorient as indicated.	These are indicators of decreased cerebral perfusion, which could result in cerebral hypoxia.
Monitor for the presence of chest pain and an irregular HR. Report significant findings.	These are indicators of decreased coronary artery perfusion and require prompt intervention.
Monitor urinary output hourly. Notify health care provider if it is less than 30 mL/hr (0.5 mL/kg/hr) in the presence of adequate intake. Check weight daily for evidence of gain.	Decreased urinary output is a sign of decreased cardiac output and decreased renal perfusion. Weight gain may be a signal of fluid retention, which can occur with decreased renal perfusion.
Monitor laboratory results for elevated BUN and creatinine levels; report increases.	BUN more than 20 mg/dL and creatinine more than 1.5 mg/dL are signals of decreased renal perfusion.
Monitor serum electrolyte values for evidence of imbalances, particularly of Na⁺ and K⁺. Assess for clinical signs of hyperkalemia, such as muscle weakness, hyporeflexia, and irregular HR, and to clinical signs of hypernatremia, such as fluid retention and edema.	Hypernatremia (Na⁺ level greater than 147 mEq/L) and hyperkalemia (K⁺ level greater than 5.0 mEq/L) may be signs of renal and metabolic complications of shock as a result of decreased renal perfusion and the kidneys’ inability to regulate electrolytes.
Avoid use of sedatives or tranquilizers.	LOC can be altered by these medications, and tissue hypoperfusion makes absorption unpredictable.
Administer fluids and medications as prescribed and according to type of shock, patient’s clinical situation, and hemodynamic interventions as follows:	Interventions are determined by clinical presentation and severity of the shock state. Patients are transferred to ICU for invasive hemodynamic monitoring with pulmonary artery catheter and use of vasoactive intravenous (IV) drips to improve tissue perfusion.
For Cardiogenic Shock
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