Nursing: A Concept-Based Approach to Learning Volume One, Fourth Edition - Module 16: Perfusion

Nursing: A Concept-Based Approach to Learning Volume One, Fourth Edition - Module 16: Perfusion

Exemplar Learning Outcomes 16.L

  • 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 a decrease in blood flow, leading to insufficient oxygenation and resulting in cellular dysfunction.
  • Ongoing Physiological Processes: Steady oxygen delivery and metabolic waste removal are maintained through the regulatory processes of the cardiovascular system, depending on:
    • Adequate cardiac output (CO)
    • Intact vascular system
    • Sufficient blood volume
    • Functional tissue oxygen extraction processes

Pathophysiology of Shock

  • Impact of Cardiovascular Function:
    • Interrupted cardiovascular function cannot sustain normal cell metabolism, leading to shock.
    • In response to shock, the body shunts blood flow primarily to the heart and brain.
  • Triggering Factors:
    • Sustained drop in arterial blood pressure causing a decrease in CO.
    • Leads to decreased blood volume and peripheral vasodilation.
    • Severe or long-lasting shock results in cellular hypoxia and potential cell death.

Stages of Shock

  • Initial Stage:
    • Mean Arterial Pressure (MAP) < 10 mmHg.
    • Responses include:
    • Slight increase in HR and cardiac contractility.
    • Release of epinephrine and norepinephrine by adrenal medulla.
  • Compensatory Stage:
    • MAP 10-15 mmHg, body attempts to maintain perfusion.
    • Vasoconstriction occurs, along with interstitial cellular shifts. Limited O2 leads to anaerobic metabolism; ongoing vasoconstriction affects organ systems.
  • Progressive Stage:
    • MAP > 20 mmHg.
    • Compensatory systems can no longer maintain MAP. Symptoms evolve to include:
    • Increased HR, acidosis, hyperkalemia, organ dysfunction, generalized tissue anoxia, and widespread tissue death.
  • Refractory Stage:
    • Not responsive to treatment; irreversible.

Effects of Shock (1 of 2)

Respiratory:

  • Increased respiratory rate leading to respiratory acidosis; ARDS is a potential complication.

Urinary:

  • Decreased renal perfusion with decreased GFR; late signs include oliguria and risk of acute tubular necrosis.

Neurologic:

  • Decreased cognition; early signs include restlessness and apathy, progressing to lethargy and potentially coma.

Cardiovascular:

  • Changes range from no initial change, slight increases in BP and HR, to late signs of MAP < 60 mmHg and imperceptible pulses.

Effects of Shock (2 of 2)

Hepatic:

  • Early decreased glucose production; progressive hypoglycemia and metabolic acidosis with potential for systemic bacterial infections due to destroyed Kupffer cells.

Gastrointestinal:

  • Early increased GI motility and late signs of paralytic ileus; risks include bowel necrosis.

Integumentary:

  • Signs include pallor, cool, moist skin, and late edema; metabolic processes also shift towards decreased temperature and increased thirst due to acidosis.

Classifications of Shock (Etiology)

  • General Overview:
    • Classifications are determined by the underlying cause with all categories experiencing similar stages and body system effects.
  • Hypovolemic Shock:
    • Most common type, characterized by a volume loss of 15% or more, possibly due to hemorrhage, burns, severe dehydration, renal fluid loss, or fluid shift.
  • Cardiogenic Shock:
    • Caused by pump failure where the heart cannot maintain CO and perfusion, often due to myocardial infarction (MI), dysrhythmias, or pathologic changes.
    • Results in further tissue ischemia and necrosis, with cyanosis and potential pulmonary edema.
  • Obstructive Shock:
    • Caused by obstruction of the heart or great vessels, resulting in impaired venous return or ineffective pumping, due to factors like pericardial tamponade or pulmonary embolism.
  • Distributive Shock:
    • Characterized by vasodilation and reduced peripheral resistance without significant changes in blood volume. Types include septic, neurogenic, and anaphylactic shock.

Septic Shock

  • Definition: Often termed septicemia, it is a leading cause of death in ICUs and results from a systemic inflammatory response often due to gram-negative bacteria.
  • Common Pathogens: E. coli, Klebsiella, also gram-positive Staphylococcus, Streptococcus.

Neurogenic Shock

  • Mechanism: An imbalance of parasympathetic and sympathetic stimulation leading to sustained vasodilation, blood pooling, and impaired capillary pressure.
  • Symptoms: Bradycardia and warm, pink extremities early, progressing to tachycardia and cool skin as compensatory mechanisms fail.
  • Causes: Include head injuries, spinal cord trauma, heat exposure, and severe pain.

Anaphylactic Shock

  • Mechanism: Result of widespread hypersensitivity, leading to vasodilation, blood pooling, and hypovolemia with altered cellular metabolism.
  • Triggers: Common allergens include medications, blood products, latex, foods, and insect stings.

Risk Factors and Prevention

  • Risk Factors:
    • Variable by shock type; includes conditions like advancing cardiac disease, high-risk behaviors for trauma, or diseases impeding clotting.
  • Prevention: Risk mitigation approaches depend on shock type including heart disease prevention and infection control.

Clinical Manifestations

  • Onset: Can be rapid or slow based on underlying cause and severity.
  • Signs of Early Shock: May be nonspecific; include tachycardia, increased respiratory effort, decreased urine output, and diaphoresis.
  • Progression Symptoms: If untreated, symptoms evolve to include significant drops in blood pressure, narrowing pulse pressure, reduced cerebral blood flow with decreased level of consciousness, potentially leading to cardiopulmonary failure and death.

Collaboration in Treatment

  • Goals: Treat underlying causes, increase arterial oxygenation, and improve tissue perfusion.
  • Emergency Interventions: May include oxygen therapy, fluid replacement, and medication administration.

Diagnostic Tests (1 of 2)

  • Goals: Often centered around determining the type of shock and assessing the patient’s physical condition.
  • Laboratory Tests: Include hemoglobin, hematocrit, WBC, blood cultures, serum electrolytes, BUN, creatinine, cardiac enzymes, ABGs, urine specific gravity, and osmolality.
  • Central Venous Catheterization: Used to provide preload data, cardiac dynamics monitoring, fluid balance, and vasopressor effects.

Diagnostic Tests (2 of 2)

  • Additional Tests: Depending on condition, may include imaging tests like X-rays, CT scans, MRIs, endoscopic exams, echocardiograms, and gastric tonometry.

Pharmacologic Therapy (1 of 2)

  • Vasoconstrictors (Vasopressors): Include norepinephrine, phenylephrine, and epinephrine.
  • Inotropes: Such as dopamine, dobutamine, and isoproterenol.
  • Vasodilators: Include nitroglycerin and nitroprusside.

Pharmacologic Therapy (2 of 2)

  • Colloid Solutions: Such as albumin, Extran, Hetastarch, and plasma protein fraction.
  • Other Medications: Include diuretics, sodium bicarbonate, calcium, antidysrhythmic agents, broad-spectrum antibiotics, epinephrine, antihistamines, and morphine.

Oxygen Therapy

  • Requirement: All patients experiencing shock must receive oxygen therapy, regardless of their respiratory status.
  • Management: Oxygen should be maintained during the first 4-6 hours of care; ventilatory assistance may be necessary.

Fluid Replacement Therapy

  • Treatment Regimen: IV fluids or blood are most effective for hypovolemic shock, with fluids also applicable for septic, neurogenic, and anaphylactic shocks.
  • Types of Fluids: Include crystalloid solutions, colloid solutions, and blood products administered through large-bore peripheral lines or central lines.

Lifespan Considerations (1 of 9) - Neonates and Infants

  • Risks: Small blood losses can have devastating impacts, particularly for low-birthweight and very low-birthweight neonates.
  • Monitoring Difficulties: Blood pressure monitoring is challenging, and heart rate extremes can indicate compromised cardiac output.
  • Common Risk Factors: Involve umbilical cord accidents, neonatal hemolysis, maternal infections, or asphyxia.

Lifespan Considerations (2 of 9) - Treatment

  • Clinical Significance: Neonates represent a major morbidity and mortality risk, with treatment ranging from vasopressors to blood volume expansion.
  • Supportive Measures: Secure the airway, provide oxygen, achieve IV access, and infuse fluids or whole blood.
  • Delayed Treatment Consequences: Can lead to severe neurodevelopmental outcomes; parents may be prepared for these possibilities.

Lifespan Considerations (3 of 9) - Children

  • Statistics: More than 35% of children in pediatric emergency departments present in shock; early Pediatric Advanced Life Support (PALS) is crucial for outcomes.
  • Common Causes of Hypovolemic Shock: Include gastroenteritis, burns, diabetes insipidus, heatstroke, trauma, and surgery.
  • Common Causes of Distributive Shock: Encompass anaphylaxis, head injury, and sepsis.
  • Common Causes of Cardiogenic Shock: Include dysrhythmias, congenital heart disease, and cardiomyopathies.

Lifespan Considerations (4 of 9) - Septic Shock in Children

  • Definition Distinction: In children, septic shock includes cardiovascular dysfunction but not necessarily hypotension.
  • Clinical Signs: Altered mental status, temperature instability, tachypnea, tachycardia, reduced urine output, delayed capillary refill, and metabolic acidosis; hypotension is a late sign.

Lifespan Considerations (5 of 9) - Pregnant Women

  • Common Causes: Can result from trauma, postpartum hemorrhage, infections, or valvular diseases.
  • Impact on Normal Pregnancy: Shock can affect physiological adaptations associated with pregnancy, threatening maternal and fetal health.

Lifespan Considerations (6 of 9) - Management

  • Ventilation Needs: Crucial for maintaining oxygen status; prevent complications of respiratory alkalosis.
  • Position During CPR: If needed, place patients in left lateral tilt.
  • Medications: Ephedrine is first-line for pregnant women in shock; oxytocin for postpartum hemorrhage.

Lifespan Considerations (7 of 9) - Fetal Monitoring

  • Continuous Monitoring: During maternal treatment for shock, continuous fetal heart rate monitoring is essential to detect potential hypoxia.

Lifespan Considerations (8 of 9) - Older Adults

  • Progression Risks: Older adults are more at risk for progressing to shock with poorer overall outcomes.
  • Increased Mortality: Age-related changes make older adults particularly vulnerable.

Lifespan Considerations (9 of 9) - Assessment

  • Functional Status Monitoring: Assessing pre-shock functional status can be critical for outcomes.
  • Fluid Management Cautions: Be vigilant of fluid overload, especially regarding diastolic dysfunction; adjust treatments based on age-specific pharmacokinetics.

Nursing Process

  • Rapid Assessment: Importance of immediate response to subtle symptoms to prevent decompensation.
  • Preventive Measures: Early identification of shock risks promotes rapid intervention and care, ensuring better outcomes.

Assessment of Shock Types

  • Hypovolemic Shock: Check for recent surgeries, traumatic injuries, or burns.
  • Cardiogenic Shock: Suspected if there is a recent left anterior wall MI.
  • Neurogenic Shock: Consider spinal cord injuries or related anesthesia.
  • Anaphylactic Shock: Be aware of allergies or previous drug reactions.
  • Septic Shock: Recognize in hospitalized, chronically ill, or invasively treated patients.

Diagnosis and Planning

  • Nursing Diagnoses: Potential diagnoses may include decreased CO and inadequate tissue perfusion.
  • Planning Goals: Focus on maintaining perfusion, understanding procedures, verbalizing feelings, and reducing cardiac workload.

Implementation in Nursing Care (1 of 4)

  • ED/ICU Protocols: Follow protocols for hypovolemic shock involving fluid administration and patient monitoring.
  • Patient Assistance: Facilitate IV access and ensure proper fluid preparation and administration using pressure bags or IV push methods.

Implementation in Nursing Care (2 of 4)

  • Cardiovascular Monitoring: Assess BP, heart rate and rhythm, and monitor peripheral pulses for hemodynamic stability.
  • Baseline Observations: Establish patient's initial condition to track changes throughout treatment.

Implementation in Nursing Care (3 of 4)

  • Tissue Perfusion Monitoring: Regular checks of skin color, temperature, turgor, moisture levels, as well as overall cardiopulmonary functioning.

Implementation in Nursing Care (4 of 4)

  • Anxiety Relief Measures: Maintain a calm environment, reduce anxiety through pain relief and by providing emotional support for patients and families.

Evaluation of Patient Outcomes

  • Expected Outcomes: Patient should maintain an adequate airway and oxygenation, manage urinary output, and avoid progression to uncompensated shock.
  • Family Support: Families should adequately cope with the stress of the patient's condition and treatment.