176 Week 7 notes Day 1

Perfusion

• Perfusion is the circulation of blood throughout the body.
• Key rule: Air goes in and out, blood goes round and round.

Factors Affecting Perfusion

• Perfusion issues can be:
  • Temporary: e.g., acute myocardial infarction (MI) causing a drop in blood pressure.
  • Long term: e.g., chronic hypertension.
  • Permanent: e.g., heart failure.

Cardiac Anatomy

• Blood flow:
  • Superior vena cava to right atrium.
  • Right atrium squeezes to right ventricle.
  • Right ventricle squeezes through pulmonary arteries to lungs (to pick up oxygen, drop off CO2).
  • Pulmonary veins back to left atrium.
  • Left atrium squeezes to left ventricle.
  • Left ventricle squeezes to the body through the aorta.
• Heart has four chambers and four valves.
• Heart muscle gets blood during diastole (coronary arteries fill).
• Central perfusion involves the heart and lungs.

Cardiac Output

• Cardiac output (CO) is the amount of blood the heart pumps in one minute.
• Cardiac Output = Heart Rate * Stroke Volume
  • Heart rate (HR): number of beats per minute.
  • Stroke volume (SV): amount of blood ejected with each beat.
• Changes in heart rate affect cardiac output.

Factors Affecting Heart Rate

• Cardiac arrhythmias.
• Blood volume: Insufficient blood volume reduces cardiac output.
• Heart's ability to squeeze (contractility): Issues arise in heart failure.
• Heart attacks: Damage from heart attacks affects the heart's ability to pump.
• Medications: Can improve heart function.
• Heart disease.

Preload vs. Afterload

• Preload: Volume or stretch in the ventricles as they fill with blood.
• Afterload: Pressure required to open the aortic valve.
  • Cardiac output is determined by stroke volume and heart rate: CO = SV * HR
  • Stroke volume is impacted by preload, afterload, and contractility.

Preload Explained

• Preload is the stretch on the ventricles during diastole as they fill with blood, think of it like filling a balloon.
• Measured by central venous pressure (CVP).
• Factors decreasing preload:
  • Decreased blood volume (e.g., hemorrhage).
• Factors increasing preload:
  • Heart failure.
  • Renal failure.

Afterload Explained

• Afterload is the resistance the ventricle must overcome to open the aortic valve during systole.
• Measured by systemic vascular resistance (SVR).
• Factors decreasing afterload:
  • Low blood pressure.
• Factors increasing afterload:
  • Hypertension.
  • Vasoconstriction.

Treatment Strategies

• Low preload: Administer blood products or fluids to increase volume and stretch.
• High preload: Administer diuretics or ACE inhibitors to decrease volume and stretch.
• High afterload: Administer vasodilators to reduce resistance.
• Low afterload: Administer vasoconstrictors to increase resistance.

Cardiac Medications

• Diuretics (e.g., Lasix, spironolactone): Reduce preload by decreasing fluid volume.
• ACE inhibitors, ARBs, and nitrates: Reduce afterload by vasodilation.
• Inotropes (e.g., milrinone, dopamine, dobutamine, digoxin): Improve contractility, making the heart squeeze better.
• Chronotropes:
  • Beta blockers (olol):
    • Rate control.
  • Calcium channel blockers (pines):
    • Rate control.
  • Digoxin: Slows heart rate; watch for toxicity (visual disturbances, bradycardia, GI upset).
    • Rate control.
• Antiarrhythmics (e.g., amiodarone): Control rhythm.

Signs of Low Cardiac Output

• Decreased level of consciousness.
• Chest pain.
• Wet, crackly lung sounds.
• Cold, clammy skin.
• Decreased urine output.
• Weak peripheral pulses.

Dangerous Arrhythmias with No Cardiac Output

• Pulseless ventricular tachycardia.
• Ventricular fibrillation.
• Asystole.

Risk Factors for Perfusion Issues

• Age: Connective tissues and heart muscle stiffen with age.
• Social and economic factors: Low income, low education, healthcare disparities.
• Noncompliance with treatment.
• Stress.
• Poor eating habits (high sodium, fat, cholesterol).

Age-Related Changes

• Connective tissue becomes denser and less stretchy.
• SA node has fewer cells.
• Fewer bundle of His and Purkinje fibers.
• Blood vessels develop atherosclerosis and stiffen.
• Increased risk of arrhythmias.
• Heart valves thicken and stiffen, leading to stenosis or regurgitation (murmurs).
• Peripheral vessels stiffen, impairing vasoconstriction and vasodilation.

Impaired Central Perfusion

• Leads to hypoxia due to poor blood flow and oxygenation.
• Can result in tissue death if unmanaged.

Diagnostic Tests

Lab Tests

• Cardiac enzymes:
  • Troponin (gold standard): Elevates with heart muscle damage; monitored in series.
  • Creatinine kinase: Released with muscle damage.
  • Myoglobin: Positive indicates heart attack.
• Serum lipids: High cholesterol contributes to plaque formation.
• Complete blood count (CBC):
  • Checks red blood cell count.
  • Hemoglobin levels.
• Blood coagulability:
  • Platelets.
  • PT/INR.
  • PTT.
  • D-dimer: Positive indicates a clot is present.
• Bone marrow biopsy: Assesses red blood cell production (if H&H is abnormal).

Electrocardiogram (ECG/EKG)

• Assesses electrical activity of the heart.

Stress Tests

• Treadmill/stationary bike with heart monitoring.
• Pharmacological stress test: Uses drugs to simulate exercise.

Radiograph Studies

• Chest X-ray: Assesses heart size.

Ultrasound

• 2D echocardiogram: Assesses chamber size, wall thickness, valve function, and blood flow (Doppler studies).

Arteriogram and Mammograms

• Imaging of vessels with dye.

Cardiac Interventions

Pacemaker Placement

• Used when the SA or AV node is not functioning correctly.
• Typically placed in the upper left chest.
• Can be temporary or permanent.

Diet Therapy

• Low sodium, low fat, low cholesterol.
• Monitor potassium levels (3.5-5 mEq/L).

Immediate Actions for Chest Pain

• Prioritize over almost everything except lack of breathing.
• Administer oxygen to maximize hemoglobin saturation.
• CPR: Essential skill.

Temporary Pacemakers

• Transvenous: Inserted through the subclavian vein.
• External: Applied through the skin (painful, requires sedation).

Pacemaker Purpose

• Restore regular heart rhythm.
• Improve cardiac output.

Basic Cardiac Rhythms

Five Steps for EKG Interpretation

1. Rate: Count R peaks, multiply by 10 (normal: 60-100 bpm).
2. Rhythm: Check if R peaks are evenly spaced (regular).
3. P Wave: Present with every QRS complex.
4. PR Interval: Should be five mini boxes or less (0.10-0.20 seconds).
5. QRS: Present, upright, and not wide (three little boxes or 0.12 seconds).

Normal Sinus Rhythm

• Has PQRST for every beat.
• Regular.
• Rate between 60-100 bpm.

Sinus Bradycardia

• Regular, has all parts (PQRST).
• Rate below 60 bpm.
• Symptoms: Asymptomatic or low confusion.
• Causes: Drug-induced (digoxin, beta blockers).
• Treatment: Atropine, pacemaker.

Sinus Tachycardia

• Has all parts (PQRST).
• Regular.
• Rate: 100-150 bpm.
• Symptoms: Similar to bradycardia.
• Causes: Dehydration, stress, fever, caffeine toxicity.
• Treatment: Address the primary cause, minimize caffeine, manage anxiety, beta blockers.

Dysrhythmias

• Atrial: Originates in the SA node or atria.
• Junctional: Originates at the AV node.
• Ventricular: Originates below the AV node.

Atrial Fibrillation (A-Fib)

• Irregular rhythm (only irregular rhythm in this class).
• No visible P waves.
• Increased risk of clot formation due to quivering atria.
• Complications: Clots can travel to the lungs, brain, or other areas.
• Treatment:
  • Control rate (new onset: 100-150 bpm).
  • Anticoagulate to prevent clots.
  • Cardioversion (synchronized).

Ventricular Tachycardia (V-Tach)

• Check for a pulse.
• Wide, bizarre QRS complexes.
• Fast rate (up to 250 bpm).
• Treatment:
  • No pulse: CPR, defibrillation.
  • Pulse and unstable: Cardioversion.
  • Pulse and stable: Amiodarone and cardioversion.

Ventricular Fibrillation (V-Fib)

• Ventricles quiver (no contraction).
• No cardiac output.
• Disorganized electrical activity.
• Treatment: CPR, defibrillation.

Asystole

• No electrical or mechanical activity.
• No pulse or respiration.
• Treatment: CPR, epinephrine, atropine, transcutaneous pacing (not guaranteed to work).