Nursing: A Concept-Based Approach to Learning Volume One, Fourth Edition

Nursing: A Concept-Based Approach to Learning Volume One, Fourth Edition

Module 16: Perfusion

Exemplar 16.L: Shock
Learning Outcomes

  • Analyze shock as it relates to perfusion.

  • Describe the pathophysiology of shock.

  • Describe the etiology of shock.

  • Compare the risk factors and prevention of shock.

  • Identify the clinical manifestations of shock.

  • Summarize diagnostic tests and therapies used by interprofessional teams in the collaborative care of an individual with shock.

  • Differentiate care of patients with shock across the lifespan.

  • Apply the nursing process in providing culturally competent care to an individual with shock.

Overview: Shock

  • Definition: Shock is a life-threatening condition characterized by decreased blood flow, leading to insufficient oxygenation, which results in cellular dysfunction.

  • Regulatory processes of the cardiovascular system maintain:

    • Adequate cardiac output (CO)

    • Intact vascular system

    • Sufficient blood volume

    • Functional tissue oxygen extraction processes

Pathophysiology of Shock

  • Condition: Characterization

    • Interrupted cardiovascular function cannot sustain normal cell metabolism, resulting in a clinical syndrome known as shock.

    • The body responds by shunting blood flow to the heart and brain.

  • Triggers:

    • Sustained drop in arterial blood pressure resulting in a decrease in cardiac output (CO).

    • Decreased blood volume activates peripheral vasodilation.

    • Cellular hypoxia and cell death may occur if shock is severe or prolonged.

Stages of Shock

  • Initial Stage:

    • Mean Arterial Pressure (MAP): < 10 mmHg

    • Sympathetic Nervous System (SNS) increases heart rate (HR) slightly and cardiac contractility.

    • Hormones like epinephrine and norepinephrine are secreted by the adrenal medulla.

  • Compensatory Stage:

    • MAP: 10-15 mmHg

    • Perfusion of cells, tissues, and organs is maintained through vasoconstriction of skin and abdominal vessels, while vessels in the heart and skeletal muscles dilate.

    • Hypothalamus and pituitary gland engage adaptive responses.

    • Ongoing vasoconstriction may affect organ systems negatively.

  • Progressive Stage:

    • MAP: >20 mmHg

    • Progressive signs: Increased HR, acidosis, hyperkalemia, organ dysfunction, generalized tissue anoxia, and widespread tissue death.

  • Refractory Stage:

    • The body becomes unresponsive to treatment; extensive cellular damage and death occur.

Effects of Shock on Different Systems
Respiratory System

  • Early signs: Increased respiratory rate, possible respiratory acidosis.

  • Potential Complication: Acute Respiratory Distress Syndrome (ARDS)

Urinary System

  • Changes: Decreased renal perfusion resulting in low glomerular filtration rate (GFR) and possible oliguria.

  • Potential Complication: Acute tubular necrosis or kidney failure.

Neurologic System

  • Early Signs: Decreased cognition, restlessness, and apathy.

  • Progressive Changes: Lethargy leading to coma in late stages.

Cardiovascular System

  • Early: No significant changes.

  • Progressive Signs: Slight elevation in blood pressure and HR, thready pulse.

  • Late Signs: MAP < 60 mmHg, imperceptible pulses.

Hepatic System

  • Progressive Changes: Decreased glucose production leading to hypoglycemia and lactic acid conversion resulting in metabolic acidosis.

  • Potential complication: Systemic bacterial infections due to destroyed Kupffer cells.

Gastrointestinal System

  • Early Signs: Increased gastrointestinal motility

  • Late Signs: Paralytic ileus and ulceration of GI mucosa with potential bowel necrosis.

Integumentary System

  • Responses: Pallor, cool and moist skin, late-stage edema, and changes in temperature and thirst.

Classifications (Etiology) of Shock

  • Hypovolemic Shock: Most common type characterized by a volume loss of 15% or more.

    • Causes include hemorrhage, burns, severe dehydration, renal fluid loss, and fluid shifts/third spacing.

  • Cardiogenic Shock: Pump failure where the heart cannot maintain CO and perfusion. Commonly caused by myocardial infarction (MI).

  • Obstructive Shock: Results from obstruction of the heart or great vessels, preventing effective cardiac pumping. Causes include pericardial tamponade and pulmonary embolism.

  • Distributive Shock: Characterized by vasodilation and decreased peripheral resistance, including septic, neurogenic, and anaphylactic shock.

Septic Shock

  • Known as septicemia, it's a leading cause of death for patients in ICUs, often resulting from gram-negative bacterial infections such as E. coli and Klebsiella.

Neurogenic Shock

  • Results from an imbalance of parasympathetic and sympathetic stimulation leading to sustained vasodilation and pooling of blood in veins and capillaries.

Anaphylactic Shock

  • Result of widespread hypersensitivity reaction characterized by vasodilation and pooling of blood, usually when a sensitized person comes into contact with allergens such as medications, blood products, latex, or food.

Risk Factors and Prevention of Shock

  • Vary according to type (e.g., cardiogenic shock associated with advancing cardiac disease).

  • Prevention strategies depend on the type: preventing heart disease lowers risk for cardiogenic shock, while safety measures can prevent trauma-induced shock.

Clinical Manifestations of Shock

  • Onset may vary (rapid or slow) influenced by the cause and severity.

  • Early signs may include tachycardia, increased respiratory effort, and decreased urine output. Severe cases can lead to cardiopulmonary failure and death if untreated.

Collaboration and Emergency Care

  • Involves treating the underlying cause, increasing arterial oxygenation, and improving tissue perfusion through therapies that include oxygen therapy, fluid replacement, and medications.

Diagnostic Tests

  • Laboratory Tests: Includes hemoglobin, hematocrit, white blood cell count, blood cultures, serum electrolytes, and renal function tests.

  • Central Venous Catheterization: Provides information about heart preload and monitors cardiac dynamics.

  • Other tests may include imaging studies (X-rays, CT scans, MRIs) and echocardiograms.

Pharmacologic Therapy

  • Vasoconstrictors: Norepinephrine, phenylephrine, epinephrine.

  • Inotropes: Dopamine, dobutamine, isoproterenol.

  • Vasodilators: Nitroglycerin, nitroprusside.

  • Colloid Solutions: Albumin, Hetastarch.

  • Others: Diuretics, sodium bicarbonate, calcium, broad-spectrum antibiotics, and morphine.

Oxygen and Fluid Replacement Therapy

  • All patients in shock require oxygen therapy, regardless of respiratory status.

  • IV fluids or blood represent the most effective treatment for hypovolemic shock and also used for septic, neurogenic, and anaphylactic shock.

Lifespan Considerations
Neonates and Infants

  • Small blood loss can be devastating.

    • Difficulty in monitoring blood pressure.

    • Risk factors include umbilical cord accidents and maternal infections.

  • Treatment includes vasopressor administration and airway management.

Children

  • Over 35% of pediatric ED patients may present in shock.

  • Common causes include gastroenteritis, burns, and trauma.

  • Septic shock may have different definitions; early treatment with antibiotics is crucial.

Pregnant Women

  • Unique causes include postpartum hemorrhage and trauma, necessitating careful management of both mother and fetus.

  • Treatment includes monitoring and supportive measures as both maternal and fetal health is interconnected.

Older Adults

  • More likely to progress to shock with poorer outcomes and higher mortality risks.

  • Considerations include monitoring for signs of sepsis, managing fluid statuses carefully, and considering age-related pharmacokinetics for medications.

Nursing Process

  • Assessment: Recognition of subtle symptoms to prevent deterioration. Assess for causes such as previous surgeries, traumatic injuries, and underlying health complexities.

  • Diagnosis: Identify nursing diagnoses including decreased cardiac output and potential for inadequate cerebral tissue perfusion.

  • Planning: Establish patient-centered goals focused on maintaining physiological stability and reducing anxiety.

  • Implementation: Include rapid fluid administration, monitoring physiologic responses, and promoting patient comfort and family involvement.

  • Evaluation: Expect outcomes like maintained airway and oxygenation, adequate urinary output, and coping strategies for the family regarding the patient's condition.