circulation

Chapter 50: Circulation

Objectives

• Understand the structure and function of the cardiovascular system.
• Identify major risk factors for cardiovascular disease according to Healthy People 2020.
• Describe three main alterations in cardiovascular function.
• Outline nursing management of clients with cardiovascular disease.
• Explain the importance of cardiopulmonary resuscitation (CPR).
• Describe the procedure for applying a sequential compression device (SCD).

Physiology of the Cardiovascular System

• The cardiovascular system transports:
  • Oxygen
  • Fluids
  • Electrolytes
  • Metabolic products
• The cardiovascular system works closely with the respiratory system, and their functions are interlinked.

Heart Wall Anatomy

• Heart size: Approximately the size of a fist.
• Enclosed by the pericardium:
  • Outer (parietal) pericardium anchors and protects the heart.
  • Inner (visceral) pericardium adheres to the heart's surface, forming the epicardium.
• Layers of the heart wall:
  • Epicardium: Outermost layer.
  • Myocardium: Cardiac muscle responsible for contractions.
  • Endocardium: Lines heart chambers and great vessels.
• Chambers of the heart:
  • Four hollow chambers:
  • Two atria (upper chambers)
  • Two ventricles (lower chambers)
  • Valves:
  • Atrioventricular Valves (AV Valves):
    • Tricuspid Valve: Right atrium to right ventricle.
    • Bicuspid (Mitral) Valve: Left atrium to left ventricle.
  • Semilunar Valves:
    • Pulmonary Valve: Right ventricle to pulmonary artery.
    • Aortic Valve: Left ventricle to aorta.
• Function of the valves: Prevent backflow of blood.

Blood Flow Through the Heart

• Review the textbook (page 1324) for the flow of blood.
• Deoxygenated blood: Enters the right side of the heart, moves to the lungs for oxygenation, returns to the left side, and is pumped to the body.
• Cardiac Cycle:
  • Systole: Blood is ejected from the ventricles.
  • Diastole: Ventricles fill with blood.

Cardiac Output

• Definition: Amount of blood pumped by ventricles per minute.
• Formula:
  $ext{Cardiac Output} = ext{Heart Rate} imes ext{Stroke Volume}$
• Stroke Volume: Amount of blood ejected with each contraction, measured in milliliters.
• Factors impacting heart rate:
  • Nervous system (sympathetic nervous system)
  • Hormones
• Poor cardiac output: Leads to insufficient oxygen and nutrient delivery to tissues, impairing perfusion.
• Increased heart rate: Can raise cardiac output but rates above 150 bpm decrease output due to insufficient ventricular filling.

Blood Vessels in the Cardiovascular System

• Pulmonary System: Low-pressure system with veins carrying deoxygenated blood.
• Systemic System: Higher pressure system with arteries carrying oxygenated blood to tissues.

Functions of Blood

• Delivers:
  • Oxygen
  • Nutrients
  • Hormones
• Removes waste products.
• Regulates:
  • Body temperature
  • pH levels
  • Fluid volume
• Functions to prevent infection and blood loss.

Lifespan Considerations

• Heart rate in newborns: 100-170 bpm; average ~120 bpm.
• Heart rate at ages 2-10: 80-130 bpm; average for adults is 60-100 bpm.
• Blood pressure: Gradually increases to about 110/65 mmHg by age 16.

Risk Factors for Cardiovascular Disease

• Atherosclerosis: Fatty plaque buildup in arteries leading to cardiovascular disease (CVD) and is a primary cause of death in North America.
• Non-modifiable Risk Factors:
  • Genetic predisposition
  • Age (affects those over 65)
  • Gender (estrogen protective until menopause)
• Modifiable Risk Factors: Can be altered or reduced, such as:
  • Elevated serum lipid levels (trans fats raise LDL, polyunsaturated fats raise HDL)
  • Hypertension and high sodium intake
  • Cigarette smoking (increases heart rate and blood pressure)
  • Diabetes (accelerates atherosclerosis)
  • Obesity and sedentary lifestyle
• Other risk factors include stress, alcohol intake, and poor diet.
• Metabolic Syndrome: Cluster of symptoms including increased blood pressure, diabetes, obesity, and elevated cholesterol.
• C-reactive protein: Indicative of chronic inflammation, produced by the liver.
• Homocysteine Levels: Elevated due to B vitamin deficiencies, kidney disease, and smoking, and can damage endothelium.

Alterations in Cardiovascular Function

• Conditions affecting heart function, blood flow to organs/tissues, and blood composition can alter cardiovascular function.
• Decreased Cardiac Output:
  • Caused by occlusions from atherosclerosis or blood clots, leading to necrotic tissue and potential myocardial infarction (MI).
  • Signs of MI: Chest pain (radiating to left arm/jaw), nausea, shortness of breath, diaphoresis.
  • Symptoms in Women: Fatigue, nausea, shoulder blade pain.
• Heart Failure: Inability to meet body's oxygen and nutrient demands, often stemming from MI, chronic hypertension, or atherosclerosis.
• Types of Heart Failure:
  • Left-sided heart failure: Leads to pulmonary congestion (cough, crackles, restlessness).
  • Right-sided heart failure: Symptoms include fluid retention (dependence edema, ascites), fatigue, and weight gain.

Case Study - Heart Failure Assessment

• Patient with increasing shortness of breath and bilateral ankle swelling.
• Nursing Action: Elevate head of the bed and assess lung sounds.
• Assessment Symptoms: Increasing shortness of breath while lying flat (orthopnea) indicates worsening heart failure.

Impaired Tissue Perfusion

• Causes: Atherosclerosis leads to ischemia; signs include decreased peripheral pulses and cool extremities.
• Thrombus Formation: Occurs due to inflamed veins; if loose, it can become an embolus affecting smaller vessels, especially in pulmonary circulation (causing pulmonary embolism).

Blood Alterations

• Oxygen Transport: Blood carries oxygen bound to hemoglobin.
• Anemia: Caused by loss of RBCs, low hemoglobin, or inadequate RBC production.
• Signs of Anemia: Chronic fatigue, pallor, shortness of breath, hypotension.

Assessment of Anemia

• Patient with anemia presents fatigue when ambulating.
• Explanation: Decreased oxygen-carrying capacity due to anemia.

Patient Assessment

• Components:
  • Comprehensive history: current and past cardiovascular issues, family history, lifestyle factors.
  • Physical Assessment: Obtain blood pressure in both arms (should be within 10 mmHg), assess peripheral pulses, apical pulse, listen for bruits, and auscultate lung sounds.
  • Assess for skin color, temperature, lesions, and edema.
• Diagnostic Studies:
  • Blood tests (evaluate hemoglobin, hematocrit, electrolyte levels, creatinine kinase).
  • Hemodynamic studies to measure heart pressures and fluid status (via arterial or venous catheters).

Nursing Interventions for Cardiac and Vascular Function

• Vascular Integrity: Elevation of legs, leg exercises, and frequent position changes.
• Medication Management:
  • Nitrates, calcium channel blockers, and ACE inhibitors to decrease workload.
  • Monitor for orthostatic hypotension with beta blockers.
  • Positive inotropic medications (like digoxin) to improve contractility and require careful monitoring.

Prevention of Venous Stasis

• Risk for Thrombus: Promote venous return with sequential compression devices (SCDs).
• Contraindications for SCD: Arterial insufficiency, cellulitis, active DVT, or preexisting venous thrombosis.
• Nurse's Responsibility: Application, maintenance, and monitoring of SCD therapy.

Cardiopulmonary Resuscitation (CPR)

• Signs of Cardiac Arrest: Apnea, absence of carotid/femoral pulse, dilated pupils.
• Skin Indicators: Pale or cool, cyanosis may indicate respiratory failure preceding cardiac failure.
• DNR Orders: Only apply when indicated; no partial or slow codes exist.

Quiz Review Questions

• Example scenario of saturation at 95% with confusion and cyanosis.
  • question: Likely indicates tissue hypoxia despite normal saturation.
• Low pulse oximeter reading (84%) requires prompt administration of oxygen.
• Prioritize patients in distress (e.g., heart failure with increasing shortness of breath and crackles).
• Patient weight gain of 4 pounds in 2 days indicates fluid retention and worsening condition.