Week 9: Perfusion and Cardiac Physiology

• Perfusion Overview

  • Refers to the delivery of deoxygenated blood (high CO2, low oxygen) to the right side of the heart and subsequently to the lungs.

  • Oxygenation occurs in the lungs, resulting in oxygenated blood (high O2, low CO2) entering the left side of the heart.

  • The cardiac system's role includes:

    • Delivery of oxygen, nutrients, and other substances to tissues.

    • Removal of metabolic waste products from cellular metabolism.

• Blood Flow Through the Heart

  • The heart consists of four chambers and valves.

  • Cycle of blood flow:

    • Oxygenated blood enters the right atrium → moves to right ventricle → pumped to lungs for oxygenation → returns to left atrium → moves to left ventricle → pumped out through aorta to the body.

• Heart Nourishment

  • Supplied through the coronary arteries that branch from the aorta, delivering oxygen-rich blood to the heart muscle.

Cardiac Cycle

• Blood Vessel Functionality

  • Arterial: Carries blood away from the heart, delivering oxygen and nutrients.

  • Venous: Returns blood to the heart; aided by valves, gravity, and muscle contractions. Venous blood is typically deoxygenated (except for pulmonary circulation).

• Cardiac Cycle Events:

  • One complete heartbeat comprises:

    • Systole: Ventricles contract, atrioventricular (AV) valves close, producing the "lub" sound (S1).

    • Diastole: Ventricles relax, semilunar (SL) valves close, producing the "dub" sound (S2).

Cardiac Output

• Definition: Amount of blood pumped from the left ventricle per minute; normal range is 4 to 8 L/min.

• Key Components:

  • Stroke Volume (SV): Amount of blood ejected with each contraction (normal 50 to 75 mL).

  • Heart Rate (HR): Number of heartbeats per minute.

    • Formula: CO = SV x HR

• Factors Influencing Cardiac Output:

  • Preload: Volume of blood in left ventricle at end of diastole.

  • Afterload: Resistance the left ventricle must overcome to eject blood.

  • Myocardial Contractility: Strength of cardiac muscle contraction.

Conduction System

• Overview: Responsible for rhythmic contraction and relaxation of heart chambers through electrical impulses.

• Key Components of Conduction:

  • SA Node: Initiates electrical impulses at a rate of 60-100 beats per minute.

  • Electrocardiogram (ECG): Measures electrical activity of the heart, detecting normal sinus rhythm (NSR).

Pulse Characteristics

• Definition: The wave of blood created by heart contractions, assessed for:

  • Rate: Number of beats.

  • Rhythm: Regularity of intervals.

  • Strength/Volume/Amplitude: Force of the pulse.

  • Symmetry: Comparing both sides of the body.

Alterations in Cardiac Function

• Factors Affecting Cardiac Function:

  • Diseases affecting heart rhythm, strength of contraction, and blood flow.

  • Compliance: Ability of arteries to stretch and contract.

• Blood Pressure:

  • Definition: Force exerted by blood against arterial walls, an indicator of cardiac health.

  • Systolic: Maximum pressure during ventricular contraction.

  • Diastolic: Minimum pressure during heart relaxation.

• Pulse Pressure:

  • Difference between systolic and diastolic pressures, example 120/80 mmHg (PP = 40 mmHg).

Hypertension and Hypotension

• Hypertension:

  • Defined as consistent readings above baseline (e.g., 140/90 mmHg is stage one).

  • Risk factors include obesity, smoking, high sodium intake.

• Hypotension:

  • Defined as blood pressure less than 90/60 mmHg.

  • Symptoms may include dizziness, nausea, syncope.

BP Assessment

• Individualized Monitoring: Assess blood pressure regularly, especially during shifts in patient condition or complaints.

• Two-Step Method: Used to accurately estimate systolic BP, considering factors affecting BP like age, gender, weight.

Nursing Process for Cardiac Care

• Assessments: Patient history, risk factors, lifestyle impact on health.

• Diagnosis: Includes decreased cardiac output, activity tolerance, risk of falls.

• Planning: Define SMART goals to improve perfusion and cardiac output outcomes.

• Interventions: Health education, lifestyle changes, medications, monitoring vital signs, skin care management.

• Evaluation: Assess effectiveness of interventions and modify care plans accordingly.

Pain Management Overview

• Nature of Pain:

  • Subjective experience with physiological and psychological components; requires recognition and management that considers individual patient perspectives.

• Types of Pain:

  • Acute/Transient: Protective, identifiable cause, short duration (post-injury).

  • Chronic: Prolonged, may be less identifiable, can persist beyond expected healing time.

• Assessment Tools: Use numerical and descriptive scales for measuring pain severity.