NCLEX-RN: Medical–Surgical Nursing

Medical–Surgical Nursing: Cardiovascular System

Focus topic: Medical–Surgical Nursing

The heart and the circulatory system, both systemic and pulmonary, constitute one of the most essential systems of the body; failure to function results in death of the organism. The heart is a hollow muscular organ that, by contracting rhythmically, effectively pumps the blood through the circulatory system to nourish all of the body tissues.

Medical–Surgical Nursing: Anatomy

Focus topic: Medical–Surgical Nursing

Medical–Surgical Nursing: Gross Structure of the Heart

Focus topic: Medical–Surgical Nursing

Layers
A. Pericardium—protective covering.

  • Fibrous pericardium—fibrous sac.
  • Serous pericardium—allows for free cardiac motion.

B. Epicardium—covers surface of heart, extends onto great vessels, and becomes continuous with inner lining of pericardium.
C. Myocardium—muscular portion of heart that pumps blood and is responsible for the contractile force of the heart.
D. Endocardium—thin, delicate layer of tissue that lines cardiac chambers and covers surface of heart valves.

Chambers of the Heart
Definition: The heart is a four-chambered muscular organ. It is divided by a thick, muscular wall into right and left halves. Each half is divided into upper and lower chambers; upper chambers are called atria and lower chambers are called ventricles.
A. Right atrium (RA)—(receiving chamber) is a thin walled, distensible, low-pressure collecting chamber that receives deoxygenated blood from the systemic venous system and sends most blood to the right ventricle during ventricular diastole or filling. The venous blood remaining in right atrium is propelled forward into the right ventricle during atrial systole or contraction.

  • Inlets: superior vena cava, inferior vena cava, coronary sinus, thebesian veins.
  • Outlet: tricuspid valve.

B. Right ventricle (RV)—(ejecting chamber) is a thin-walled, low-pressure crescent-shaped pump for propelling blood into the low-resistance pulmonary circuit.

  • Normal thickness: 0.5 cm.
  • Inlet: right atrium, tricuspid valve.
  • Outlet: pulmonic valve into pulmonary artery.
  • Generates pressure of 25 mm Hg, which is enough to close tricuspid valve and open pulmonic valve—propelling blood into pulmonary artery and lungs.
  • Work load of right ventricle is less than that of left ventricle because pulmonary system is normally low pressure; therefore there is less resistance to blood flow.

C. Left atrium (LA)—(receiving chamber) is a thin walled, medium-pressure collecting chamber that receives oxygenated blood from the pulmonary venous system.

  • Inlets: four pulmonary veins.
  • Outlet: mitral valve.

D. Left ventricle (LV)—(ejecting chamber) is a thick-walled, high-pressure, cone-shaped pump for propelling blood into the high-resistance systemic circuit.

  • Normal thickness: 1.5 cm (about two to three times the thickness of the right ventricle).
  • Inlet: left atrium, mitral valve.
  • Outlet: aortic valve into aorta.
  • Must generate a higher pressure than right ventricle because it is contracting against the high-pressure systemic circulation where there is a much greater resistance to blood flow.

Valves
Definition: Valves are strong membranous openings responsible for maintaining the forward flow of blood through the chamber. These valves open and close passively in response to pressure and volume changes within chambers of the heart.
A. Atrioventricular valves prevent back-flow of blood from the ventricles to the atria during systole.

  • Tricuspid—right heart valve; between right atrium and right ventricle.
    a. Three cusps or leaflets.
    b. Open during ventricular diastole.
    c. Free edges anchored to papillary muscles in right ventricle by chordae tendineae, which contract when the ventricular walls contract (systole).
  • Mitral—left heart valve; between left atrium and left ventricle.
    a. Two cusps or leaflets.

b. Open during ventricular diastole.
c. Free edges anchored to papillary muscles in the left ventricle by chordae tendineae, which contract when the ventricular walls contract (systole).

B. Semilunar valves prevent backflow from the aorta and pulmonary artery into the ventricles during diastole.

  • Pulmonic—three cusps or leaflets; opens from the right ventricle into the pulmonary artery.
  • Aortic—three cusps or leaflets; opens from the left ventricle into the aorta; orifices for coronary arteries arise from wall of aorta above two of the three cusps.

C. Valves function passively.

  • Close when backward pressure pushes blood backward.
  • Open when forward pressure forces blood in a forward direction.

Conduction System
Definition: Conduction system is composed of specialized tissue that allows rapid transmission of electrical impulses through the myocardium.
A. Sinoatrial (SA) node—main pacemaker of heart in which normal rhythmic self-excitatory impulse is generated.

  • Located at the junction of right atrium and superior vena cava.
  • Activates myocardial cells, initiates process of depolarization.
  • 60–100 electrical impulses/min.
  • External control is through autonomic nervous system.
    a. Sympathetic—increases rate.
    b. Parasympathetic—slows rate.
  • Nerves affect cardiac pumping in two ways.
    a. Change heart rate.
    b. Change strength of contraction of the heart.
  • Intrinsic automaticity—initiates electrical impulses automatically.

B. Internodal tracts—transmission of electrical impulses through atria from sinoatrial node to atrioventricular node.
C. Atrioventricular (AV) node—contains delay tissue that delays impulse transmission, allowing atrial contraction to eject blood into ventricle before ventricular contraction (“atrial kick”).

D. Bundle of His.

  • Conducts electrical impulse from AV node into ventricles.
  • Divides into right bundle branch and left bundle branch.

E. Purkinje fibers—conduct electrical impulse from right and left bundle branches to all parts of the ventricles.

Medical–Surgical Nursing: Coronary Blood Supply

Focus topic: Medical–Surgical Nursing

Definition: Oxygen and other nutrients are supplied to the cells of the heart by vessels of the coronary circulation. Coronary circulation consists of coronary arteries and coronary veins. Coronary artery blood flow to the myocardium occurs primarily during diastole, when coronary vascular resistance is lower. To maintain adequate blood supply through coronary arteries to nourish the myocardium, mean arterial pressure (MAP) must be at least 60 mm Hg. A MAP between 60 and 70 mm Hg is necessary to maintain vital body organs (e.g., brain and kidneys).
A. Coronary arteries—transport oxygen-rich blood from the heart, under high pressure, to the body tissues.

  • Right coronary artery (RCA)—in most people supplies
    a. AV node.
    b. Right ventricle.
    c. Inferior and posterior walls of left ventricle.
  • Posterior descending coronary artery (PDA) supplies posterior wall of left ventricle.
  • Left coronary artery—left main (LM) and left anterior descending (LAD) supply
    a. Intraventricular septum.
    b. Bundle branches.
    c. Anterior wall and apex of left ventricle.
  • Left circumflex coronary artery (LCX) supplies
    a. Left atrium.
    b. Lateral and posterior surfaces of left ventricle.
    c. Sometimes portions of intraventricular septum.
    d. Sinoatrial (SA) node in about 45% of people.
    e. AV node in about 10% of people.
    f. Peripheral branches arise from both LCX and LAD and form a network of vessels throughout myocardium.

B. Veins—generally parallel arterial system.

  • Coronary sinus veins empty into right atrium.
  • Thebesian veins empty into right atrium.

Medical–Surgical Nursing: Gross Structure of Vasculature

Focus topic: Medical–Surgical Nursing

Arteries
A. The function of the arteries is to transport blood under high pressure to the body tissues.

  • Arteries have thick, elastic walls.
  • Move blood forward through the circulatory system.

B. Arterioles.

  • Small arteries with little elastic tissue and more smooth muscle.
  • Serve as major control of blood pressure and flow.
  • Respond to O2 and CO2 levels by constricting or dilating.

Capillaries
Definition: Microcirculation between arterioles and venules. The exchange of fluid, cellular nutrients, and metabolic waste products takes place through thin-walled vessels.
A. Capillary walls are thin and permeable to fluid and small substances.
B. Blood flow is slowest in capillaries.

Veins
Definition: Primary function is to act as conduits for transport of the blood from tissues back to the heart.
A. Venous system.

  • Low-pressure, high-volume system.
  • Walls are thin but muscular.
  • Walls are able to contract or expand, thereby storing a small or large amount of blood.
  • Larger veins have valves to maintain forward blood flow and prevent backflow.

B. Factors influencing venous return.

  • Muscle contraction (e.g., walking, leg exercises).
  • Gravity (e.g., elevating legs).
  • Competent valves.
  • Respiration.
    a. Inspiration increases venous return.
    b. Expiration decreases venous return.
  • Compliancy of right heart (central venous pressure [CVP]).

C. Venules: small vessels made up of muscle and connective tissue. Collect blood from capillary beds and direct it to larger veins.

Medical–Surgical Nursing: Physiology

Focus topic: Medical–Surgical Nursing

Medical–Surgical Nursing: Regulation of Cardiac Function

Focus topic: Medical–Surgical Nursing

Contraction
Definition: The heart muscle utilizes chemical energy to do the work of contraction—a shortening or increase in tension.
A. The sarcomere is the unit of contraction and contains the proteins actin and myosin.
B. Sliding theory of contraction.

  • Actin slides inward on myosin causing shortening of sarcomere, resulting in systole.
  •  When calcium is used up, actin and myosin slide apart, resulting in systole.

C. Each cardiac cell is composed of many sarcomeres.

Cardiac Muscle Principles
A. Frank–Starling law: the greater the heart is filled during diastole, within physiological limits, the greater the quantity of blood pumped into the aorta and pulmonary artery.

  • The heart can pump a large amount of blood or a small amount depending on the amount that flows into it from the veins.
  • It automatically adapts to whatever the load or volume may be (within physiological limits of the total amount the heart can pump).

B. All-or-none principle: Cardiac muscle either contracts or does not contract when stimulated.

C. Two phases of contractility.

  • Isometric—increasing tension while maintaining length of muscle fiber.
  • Isotonic—shortening muscle fiber while tension remains constant.

D. Cardiac output (CO)—the amount of blood pumped out by the heart in one minute.

  • Calculation: CO = SV (stroke volume) × HR (heart rate).
    a. Cardiac output is 4–7 L/min.
    b. Varies according to body size; cardiac index is used to adjust for differences in body size.
  • Stroke volume—amount of blood ejected from the ventricle with each contraction.
  • Factors affecting cardiac output.
    a. Heart rate.
    b. Stroke volume.
    (1) Preload—volume of blood in the ventricles before contraction.
    (2) Afterload—peripheral vascular resistance that the left ventricle must pump against.
    (3) Contractility.

E. Cardiac reserve—ability of heart to respond to increased demands by increasing cardiac output. CO is increased by increasing heart rate or increasing stroke volume, by increasing either preload or contractility. Increased demands on cardiovascular system may be due to many conditions, such as exercise, stress, hypovolemia, etc.

Properties of Cardiac Cells
A. Automaticity: ability to initiate an electrical impulse without external stimuli; spontaneously and repetitively.

  • Although all cells of the heart can initiate an electrical impulse, certain areas of the heart will initiate impulses within the following ranges:
    a. SA node: 60–100.
    b. Junctional node: 40–60.
    c. Bundle branch Purkinje system: 20–40.
  • Causes depolarization and repolarization.

B. Conductivity: ability to transmit electrical impulse.
C. Contractility: ability of muscle to shorten in response to electrical impulse.
D. Excitability: ability to be stimulated by an impulse (depolarization).
E. Refractoriness: inability to respond to a stimulus until the cells return to a resting state (repolarized).

  • Absolute refractory period—no amount of electrical stimulation will cause contraction.
  • Relative refractory period—a strong enough electrical stimulation will cause contraction.

F. Electrical and mechanical properties determine system function.

Pulse
Definition: The rhythmic dilation of an artery caused by the contraction of the heart.
A. Number of times the “ventricles” contract.
B. Rate—extrinsically controlled by the ANS, which adjusts rapidly to regulate CO.
C. Increased heart rate = increased myocardial O2 demand.
D. Pulse deficit—difference between apical and radial pulse, due to weakened or ineffective contraction of heart.
E. Pulse pressure—difference between systolic and diastolic pressure.

Blood Pressure
A. A measure of pressure exerted on walls of arterial systems.

  • Systolic BP is the maximum amount of pressure exerted on the walls of the arterial system when the heart contracts.
  • Diastolic BP is pressure within the arterial system following contraction during the “relaxation” phase.

B. Factors influencing blood pressure.

  • CO (cardiac output).
  • SVR (systemic vascular resistance—resistance created in the small arteries and arterioles).
  • Volume of fluid: hypovolemia (decreased blood pressure) such as hemorrhage.
  • Diameter and elasticity of blood vessels; for example, arteriosclerosis (increased blood pressure).

Medical–Surgical Nursing: Autonomic Nervous System Influence

Focus topic: Medical–Surgical Nursing

Cardiac Muscle
A. Sympathetic nervous system (adrenergic)—innervates all cardiac muscle.

  • Secretes epinephrine and norepinephrine.
  • Response stimulates beta1 receptors.
    a. Increases SA node rate of discharge.
    b. Increases conductivity.
    c. Increases contractility of cardiac muscle.
    d. Increases cell irritability.

B. Parasympathetic nervous system (cholinergic)—innervates primarily atrial tissue.

  • Mediated via vagus nerve.
  • Secretes acetylcholine.
  • Maintenance of homeostasis—“brake of heart.”
    a. Decreases SA node rate of discharge.
    b. Decreases conductivity, especially of AV node.
    c. Decreases atrial contractility.

Systemic Blood Vessels
A. Sympathetic nervous system.

  • Vasoconstriction of blood vessels through action mainly on alpha1 receptors of precapillary sphincter (one exception: vasodilation of coronary arteries).
  • Causes vasodilation of selected blood vessels via beta2 receptor stimulation.

B. Parasympathetic nervous system.

  • Usually predominates so that blood vessels are not vasoconstricted.
  • Effect is vasodilation in certain areas such as cerebrum, salivary glands, and lower colon.

Baroreceptor Reflex
A. Most important circulatory reflex is called baroreceptor reflex.

  • Initiated by baroreceptors (also called pressoreceptors) located in arch of the aorta and at beginning of internal carotid arteries.
  • Rise in pressure results in baroreceptors transmitting signals to CNS to inhibit sympathetic action.
  • Other signals, in turn, sent to circulatory system reduce pressure back toward normal.
  • Result is decreased heart rate, vasodilation and decreased blood pressure.

B. Effect of decreased pressure on baroreceptors.

  • Sympathetic stimulation overrides vagal response.
  • Result is increased heart rate, vasoconstriction, and increased blood pressure.

Other Chemical Controls of Blood Pressure
A. Kidney.

  • Juxtaglomerular apparatus releases renin, which causes vasoconstriction to increase blood pressure.
  • Adrenal cortex releases aldosterone, causing sodium and water to be reabsorbed. This increases blood volume and blood pressure.

B. Antidiuretic hormone (vasopressin)—acts on kidney tubules to reabsorb water, thereby increasing blood volume and blood pressure.
C. Histamine release from mast cells’ response to antigen.

  • Arterioles dilate.
  • Venules constrict.

D. Capillary fluid shift mechanisms (balance of hydrostatic/oncotic forces); for example, decreased blood pressure or an increase in oncotic pressure allows capillaries to reabsorb interstitial fluid.

System Assessment
A. Assess client’s cardiac history.

  • Pain—onset, character, location, radiation, duration, intensity, precipitating or aggravating factors, relieving factors, and intensity/severity on a scale of 0–10.
    a. Ischemic pain of angina.
    (1) Substernal, neck, jaw, arms/shoulders; vague pressure, radiates; confused with “indigestion.”
    (2) Precipitated by emotional or physical activity, relieved by rest or Tridil (nitroglycerin).
    b. Pain of myocardial infarction.
    (1) Similar location of angina, more intense.
    (2) Accompanied by dyspnea, diaphoresis, nausea/vomiting; not precipitated.
    (3) Not relieved by rest or nitroglycerin.
  • Dyspnea—subjective feeling of inability to get enough air.
    a. Dyspnea on exertion (DOE) occurs with activity.
    b. Orthopnea occurs while in a reclining position—client sits up or uses several pillows to sleep.
    c. Paroxysmal nocturnal dyspnea (PND) interrupts client’s sleep—gets up to relieve.
  • Respiratory rate and depth.
    a. Tachypnea: increase in rate of breathing.
    b. Hyperpnea: increase in depth of breathing (causes decrease in PCO2).
  • Cough—dry or productive of mucoid foamy sputum with heart failure; pink tinged with acute pulmonary edema.
  • Cyanosis—bluish mucous membranes or skin color due to significant deficiency of oxygen in the blood (O2 saturation less than 85%).
  • Fatigue—result of decreased cardiac output.
  • Palpitations—awareness of rapid or irregular heartbeat.
  • Syncope—transient loss of consciousness due to inadequate cerebral blood flow (e.g., bradycardia).
  • Edema.
    a. Bilateral, dependent (ankles or sacrum) due to accumulation of interstitial fluid secondary to increased venous pressure (e.g., volume overload)—accompanied by weight gain.
    b. Unilateral due to venous insufficiency.
  • Skin—color, temperature, dry or moist, hair
    growth, nails, capillary refill.

B. Evaluate pressure through inspection and palpation of venous and arterial systems.

  • Internal jugular veins—located deep in sternocleidomastoid muscle.
  • Venous pulsations.
    a. Observe venous pulsation in neck to assess central venous pressure (CVP) and adequacy of circulating blood volume.
    b. Assessment of jugular venous pressure (JVP) done to estimate volume and pressure on right side of heart. Increased JVP causes increased jugular vein distention.
    c. Normal JVP 3–10 cm H2O. Increase caused by
    (1) Right ventricular failure.
    (2) Tricuspid stenosis or regurgitation.
    (3) Pulmonary hypertension.
    (4) Cardiac tamponade.
    (5) Constrictive pericarditis.
    (6) Hypervolemia.
    (7) Superior vena cava obstruction.
  • Arterial system.
    a. Neck—carotid artery.
    b. Upper extremities—radial, brachial, and ulnar.
    c. Lower extremities—femoral, popliteal, posterior tibial, dorsalis pedis, pedal.
  • Grading peripheral pulses.
    a. 0 = absent.
    b. 1+ = weak.
    c. 2+ = diminished.
    d. 3+ = strong.
    e. 4+ = full/bounding.
  • Pulsus paradoxus: systolic blood pressure drop greater than 10 mm Hg during inspiration (cardiac tamponade).

Medical–Surgical Nursing

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C. Assess heart sounds by auscultation.

  • Auscultatory areas.
    a. Aortic: second intercostal space right of sternum.
    b. Pulmonic: second intercostal space left of sternum.
    c. Tricuspid: fifth intercostal space left, close to sternum.
    d. Mitral: fifth intercostal space mid-clavicular line at the apex of the heart.
    e. PMI: point of maximal impulse.
  • Heart sounds—frequency, pitch, intensity, duration.
    a. S1 (“lub”)—closure of mitral and tricuspid valve.
    b. S2 (“dub”)—closure of aortic and pulmonic valve.
    c. S3 and S4—diastolic filling sounds.
    (1) S3—rapid filling of ventricle in early diastole; heard after S2; sign of heart failure in client over age 40.
    (2) S4—coincides with atrial contraction due to poorly compliant ventricle; prior to S1; normal in older adult.
  • Murmurs: turbulence of blood flow through valve; classified by their timing and heard between heart sounds.
    a. Systolic: occurring between S1 and S2.
    (1) Mitral and tricuspid insufficiency.
    (2) Aortic and pulmonic stenosis.
    (3) Patent foramen ovale.
    (4) Ventricular septal defect.
    b. Diastolic: occurring between S2 and S1.
    (1) Mitral and tricuspid stenosis.
    (2) Aortic and pulmonic insufficiency.
    c. Location: point where murmur is loudest.
    d. Radiation: transmission from point of maximal intensity to surrounding areas.
    e. Quality: blowing, harsh, musical, or rumbling.
    f. Pitch: high, medium, or low.
    g. Pattern: determined by intensity over time.
    (1) Crescendo: soft to loud.
    (2) Decrescendo: loud to soft.
    (3) Crescendo–decrescendo: soft to loud to soft.
    (4) Plateau: same throughout.
    h. Intensity (loudness): Grade 1–6.
    (1) Grade 1 = barely audible through stethoscope.
    (2) Grade 6 = audible with the stethoscope just off the client’s skin.
  • Pericardial friction rub due to inflammation—“squeak” timed with heart sounds.

D. Evaluate arterial pressure.

  • Measurement of blood pressure—indirect via cuff.
    a. Both arms.
    b. Lying, standing.
  • Presence of bruits (sound of abnormal turbulence of blood flow usually around obstruction).

E. Evaluate chest x-ray to determine abnormalities of lung fluids and cardiac silhouette.
F. Assess lungs for adventitious sounds.

  • Rales: fine, medium, coarse.
  • Rhonchi: sibilant, sonorous.

G. Assess client’s readiness for a cardiac rehabilitation program.

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