NOTE: At around 08:20 Jon says PVR is peripheral vascular resistance, but it should be pulmonary vascular resistance. This is correct in the outline and transcript.

Overview of Preload and Afterload

Preload, Afterload, and Contractility play a role in determining stroke volume, which determines Cardiac Output.

Nursing Points

General

1. CO = SV x HR.
2. Stroke Volume = Preload, Afterload, Contractility
3. Preload
   1. Stretch during filling
   2. Impacted by blood volume
   3. End Diastolic Volume
   4. Central Venous Pressure (CVP)
      1. 2-6 mmHg
4. Afterload
   1. Resistance against contraction
   2. Vascular constriction
   3. Pulmonary Vascular Resistance (PVR)
   4. Systemic Vascular Resistance (SVR)
      1. 800-1400 dynes/sec/cm-5
5. Contractility
   1. Force of contraction

Assessment

1. Preload
   1. Too Low
      1. Causes
         1. Massive Peripheral Vasodilation (Shock)
         2. Hemorrhage
         3. Dehydration
      2. Symptoms
         1. ↓ cardiac output
         2. ↓ blood pressure
         3. ↓ peripheral perfusion
   2. Too High Causes
      1. Causes
         1. Heart Failure
         2. Kidney Failure
         3. Volume Overload
      2. Symptoms
         1. Pulmonary congestion
         2. Vascular congestion
         3. ↑ blood pressure
2. Afterload
   1. Too Low
      1. Causes
         1. Massive Peripheral Vasodilation (Shock)
         2. Hypotension
      2. Symptoms
         1. Venous pooling (redness, edema)
         2. Hypotension
   2. Too High
      1. Causes
         1. Vasoconstriction
         2. Hypertension
         3. Blood Clots
      2. Symptoms
         1. s/s blood clot- lungs, legs
         2. Hypertension
         3. Chest pain
         4. Palpitations
3. Contractility
   1. Too Low
      1. Causes
         1. Cardiomyopathy
         2. Arrhythmias
         3. Electrolyte abnormalities
      2. Symptoms
         1. Bradycardia
         2. Hypotension
   2. Too High
      1. Causes
         1. Hypertension
         2. Electrolyte abnormalities
      2. Symptoms
         1. Myocardial ischemia
         2. Chest Pain

Therapeutic Management for Preload and Afterload

1. Preload
   1. Too Low
      1. Treat Cause
      2. Isotonic fluids
      3. Blood Products
   2. Too High
      1. Treat Cause
      2. Diuretics
         1. Furosemide
         2. Bumetanide
      3. ACE inhibitors
         1. Captoril
         2. Lisinopril
2. Afterload
   1. Too Low
      1. Treat Cause
      2. Vasopressors
         1. Norepinephrine
         2. Epinephrine
         3. Vasopressin
         4. Neosynephrine
   2. Too High
      1. Treat Cause
      2. Vasodilators
         1. Nitroprusside
      3. Antihypertensives
3. Contractility
   1. Too Low
      1. Treat Cause
      2. Cardiac Glycosides
         1. Digoxin
      3. Sympathomimetics
         1. Epinephrine
   2. Too High
      1. Treat Cause
      2. Beta Blockers
         1. Metoprolol
         2. Carvedilol
      3. Calcium Channel Blockers
         1. Amlodipine
         2. Nicardipine