Heart Anatomy and Physiology

1. Gross Anatomy

• Endocardium - inner smooth lining
• Myocardium - the contractile muscle bulk
• Epicardium - outer visceral pericardial layer

Chambers

Valves

2. Conduction System

SA Node → Atrial muscle → AV Node → Bundle of His
    → Right & Left Bundle Branches → Purkinje Fibers → Ventricular myocardium

1. Sinoatrial (SA) node - the primary pacemaker, located at the junction of the superior vena cava and right atrium (crista terminalis). Discharges spontaneously at 60-100 bpm.
2. Atrioventricular (AV) node - near the opening of the coronary sinus, close to the septal cusp of the tricuspid valve. Introduces a delay (~0.12 s) allowing atrial contraction to complete before ventricular activation.
3. Bundle of His - direct continuation of the AV node, travels along the lower border of the membranous interventricular septum before splitting into right and left bundle branches.
4. Right and left bundle branches - travel down respective sides of the interventricular septum toward the apex.
5. Purkinje fibers - subendocardial plexus with the most functional contacts to working myocardium. Ensure rapid, near-simultaneous activation of ventricular muscle from apex to base.

3. Cardiac Action Potentials

• Phase 0 - rapid upstroke; fast Na+ channels open
• Phase 1 - early rapid repolarization; transient K+ outflow
• Phase 2 - plateau; slow L-type Ca2+ channels open (balanced by K+ outflow) - unique to cardiac muscle, prevents tetanic contraction
• Phase 3 - rapid repolarization; K+ channels open
• Phase 4 - resting potential (-85 to -90 mV)

4. Excitation-Contraction Coupling

1. Action potential spreads into T tubules (5x wider in cardiac vs. skeletal muscle - hold large calcium stores)
2. L-type Ca2+ channels (LTCC/dihydropyridine receptors) in T tubule membrane open - small Ca2+ influx
3. This triggers ryanodine receptors (RyR2) in the sarcoplasmic reticulum (SR) to release a far larger Ca2+ store - "calcium-induced calcium release"
4. Cytosolic Ca2+ rises, binds troponin C on thin filaments
5. Troponin C-Ca2+ binding causes tropomyosin to shift, exposing myosin-binding sites on actin
6. Cross-bridge cycling: myosin heads bind actin, ATPase activity causes power stroke (sliding filaments) → contraction
7. Relaxation: Ca2+ pumped back into SR by SERCA2 (ATP-dependent), and out of cell via Na+/Ca2+ exchanger (NCX) and Ca2+-ATPase

5. The Cardiac Cycle

• LV systolic pressure: ~120 mmHg
• LV diastolic pressure: ~0-12 mmHg
• Aortic pressure: ~120/80 mmHg

6. Determinants of Cardiac Performance

Preload (end-diastolic volume / venous return)

Afterload (aortic pressure / peripheral vascular resistance)

Contractility (inotropy)

• Positive inotropes (digoxin, catecholamines, Ca2+): shift the Frank-Starling curve upward - greater SV at any given EDV; increased ejection fraction
• Negative inotropes (beta-blockers, Ca2+ channel blockers, heart failure): shift curve downward

7. Coronary Blood Flow

• Left coronary artery (LCA): divides into left anterior descending (LAD - supplies anterior LV, septum) and left circumflex (supplies lateral LV)
• Right coronary artery (RCA): supplies right ventricle, inferior LV, SA node, AV node in most individuals

• Subepicardial flow: during both systole and diastole
• Subendocardial flow: predominantly during diastole (compressed by intramyocardial pressure during systole)

Summary Table: Key Numbers

Nursing Diagnosis: Jaundice (Hyperbilirubinemia)

Pathophysiology Overview

Nursing Assessment

Subjective Data (History)

• Onset and duration of yellow discoloration
• Color of urine (dark/tea-colored = conjugated bilirubin spilling into urine)
• Color of stool (pale/clay-colored = obstructive jaundice)
• Pruritus (itching) - from bile salt deposition in skin
• Fatigue, malaise, anorexia, nausea
• Abdominal pain (RUQ pain suggests biliary/hepatic cause)
• Fever, chills (suggest cholangitis - a surgical emergency)
• Alcohol use, drug history, recent blood transfusions, travel history
• Family history (Gilbert's syndrome affects 4-7% of population)

Objective Data (Physical Examination)

• Skin and sclerae: yellow discoloration (scleral icterus is often the first visible sign)
• Skin integrity: scratch marks, excoriations from pruritus
• Abdomen: hepatomegaly, splenomegaly, tenderness, Murphy's sign (cholecystitis), palpable gallbladder (Courvoisier's sign in malignant obstruction)
• Neurological: confusion, asterixis (hepatic encephalopathy in advanced liver disease)
• Vital signs: fever (infection/cholangitis), hypotension (sepsis)
• Nutritional status: muscle wasting, cachexia, ascites

Laboratory Investigations (to guide diagnosis and monitor)

NANDA-I Nursing Diagnoses

1. Impaired Liver Function / Impaired Metabolic Function

• Monitor serum bilirubin (total, direct, indirect), LFTs, PT/INR, albumin daily or per orders
• Assess and document degree of jaundice (skin, sclera, mucous membranes) at each shift
• Monitor urine color and output; test urine for bilirubin and urobilinogen
• Observe stool color (pale/acholic = biliary obstruction)
• Administer prescribed medications (ursodeoxycholic acid, corticosteroids, antivirals) as ordered
• Avoid hepatotoxic drugs (acetaminophen in excess, NSAIDs, certain antibiotics) and report any new medications to the medical team
• Prepare patient for procedures (ERCP, biliary stenting, cholecystectomy) if indicated

• Serum bilirubin trending toward normal range
• Patient verbalizes understanding of underlying cause and treatment plan

2. Impaired Skin Integrity / Risk for Impaired Skin Integrity

• Assess skin condition every shift; document any abrasions, excoriations, or breaks
• Keep fingernails short and clean to minimize skin damage from scratching
• Apply cool, damp cloths or cool compresses to pruritic areas for relief
• Use mild, pH-balanced soaps; pat skin dry (do not rub)
• Apply emollients/moisturizers regularly; avoid alcohol-based lotions
• Maintain cool, low-humidity room environment (reduces pruritus intensity)
• Administer antipruritic medications as prescribed:
  • H1 antihistamines (diphenhydramine, hydroxyzine)
  • Bile acid resins (cholestyramine) - bind bile salts in gut
  • Opioid antagonists (naltrexone) - for refractory pruritus
  • Rifampicin (second-line; monitor for hepatotoxicity)
• Dress patient in soft, loose-fitting, non-irritating cotton clothing
• Educate patient to avoid scratching; suggest gentle patting instead

• Patient reports reduced severity of pruritus (numeric scale)
• No new skin breakdown or infection

3. Imbalanced Nutrition: Less Than Body Requirements

• Assess nutritional status: weight, BMI, albumin, pre-albumin, dietary intake
• Provide small, frequent meals rather than large meals
• Offer high-carbohydrate, moderate-protein, low-fat diet (in obstructive jaundice where fat digestion is impaired due to lack of bile)
• Administer fat-soluble vitamin supplements (A, D, E, K) as prescribed - especially in obstructive jaundice where bile is absent from gut
• Monitor for signs of Vitamin K deficiency (prolonged PT/INR, easy bruising, bleeding)
• Administer IV Vitamin K or FFP if coagulopathy is present
• Consult dietitian for individualized nutritional support
• Encourage oral fluid intake; monitor for dehydration
• Administer antiemetics before meals if nausea is present
• Provide oral care before meals to improve appetite

• Patient maintains or regains stable weight
• Adequate caloric and protein intake documented
• Vitamin K-dependent coagulation factors normalize

4. Acute/Chronic Pain

• Assess pain location, quality, severity (0-10 scale), radiation, onset, and aggravating/relieving factors
• Administer analgesics as prescribed; evaluate and document effectiveness
• Position patient for comfort (semi-Fowler's or side-lying may reduce pain)
• Apply warmth to abdomen (if not contraindicated) for biliary colic
• Note: Pain with fever, rigors, and jaundice = Charcot's triad (cholangitis) - escalate immediately
• Monitor for peritoneal signs (rigid abdomen, rebound tenderness) suggesting perforation

• Patient reports pain controlled at acceptable level
• Patient demonstrates non-pharmacologic pain management strategies

5. Risk for Deficient Fluid Volume

• Monitor intake and output strictly (including ascites drainage if applicable)
• Monitor vital signs for signs of dehydration or hypovolemia (tachycardia, hypotension)
• Assess skin turgor, mucous membrane moisture, daily weight
• Administer IV fluids as ordered
• Monitor electrolytes (Na+, K+, Mg2+) - cirrhotic patients prone to hyponatremia, hypokalemia
• Administer diuretics (spironolactone, furosemide) for ascites if prescribed; monitor response

• Balanced fluid intake and output
• Stable hemodynamic parameters

6. Risk for Disturbed Thought Processes (Hepatic Encephalopathy)

• Assess neurological status and orientation at each shift using a structured scale (West Haven criteria)
• Test for asterixis (ask patient to dorsiflex wrists with arms outstretched)
• Monitor serum ammonia levels
• Administer lactulose as prescribed (goal: 2-3 soft stools/day to reduce ammonia absorption)
• Administer rifaximin if prescribed (non-absorbed antibiotic reducing gut bacteria ammonia production)
• Restrict dietary protein only if encephalopathy is present (not routine - patients need adequate nutrition)
• Maintain safety: bed rails up, call light within reach, fall prevention measures
• Minimize sedating medications; avoid benzodiazepines if possible (worsen encephalopathy)
• Orient patient frequently; involve family in monitoring changes

• Patient remains oriented to person, place, time
• No asterixis; stable serum ammonia

7. Deficient Knowledge

• Assess current level of knowledge and learning readiness
• Teach about the cause of jaundice and expected course of illness
• Explain all diagnostic tests and procedures in plain language
• Instruct on dietary modifications (low-fat diet, avoid alcohol, adequate hydration)
• Educate about medications: purpose, dose, side effects, adherence
• Warn against hepatotoxic substances: alcohol, herbal supplements, excess paracetamol
• Teach warning signs requiring immediate medical attention: sudden worsening of jaundice, high fever with rigors (cholangitis), confusion, black tarry stools (GI bleeding), severe abdominal pain
• Provide written discharge instructions; reinforce with verbal teaching
• Arrange follow-up appointments and explain the importance of repeat labs

• Patient correctly states the cause and treatment plan
• Patient identifies warning signs that require emergency care
• Patient demonstrates medication compliance

8. Anxiety / Fear

• Establish therapeutic relationship; use active listening techniques
• Provide clear, honest information about diagnosis and what to expect
• Allow patient and family to express fears and concerns
• Facilitate access to chaplain, social worker, or psychologist if appropriate
• Involve patient in care planning to restore sense of control
• Explain all procedures before performing them

• Patient reports reduced anxiety
• Patient demonstrates coping strategies

Summary: Priority Nursing Diagnoses at a Glance

Special Considerations