Assessment of Cardiac Output: hemodynamic monitoring

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Martia
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257969
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Assessment of Cardiac Output: hemodynamic monitoring
Updated:
2014-01-28 16:38:28
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nursing
Folders:
N303Critical Care,Test 1
Description:
nursing school
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  1. heart pressures
    • atrial systole - pressure in 2 atria exceeds resistance of ventricles and tricuspid and mitral valves open
    • ventricular systole - pressure in 2 ventricles exceeds resistance of outflow vessels, tricuspid and mitral close, pulmonic and aortic valves open
  2. preload
    • volume of blood filling the ventricles at end of diastole
    • measured by:
    • 1. RV - central venous pressure (CVP)
    • 2. LV - pulmonary artery end diastole pressure (PCWP) or Wedge
  3. assessment of right heart preload
    • increased right heart preload (fluid overload):
    • 1. jugular vein distention
    • 2. ascites
    • 3. hepatic engorgement
    • 4. peripheral edema

    • decreased right heart preload (dehydration):
    • 1. poor skin turgor (immediate sign)
    • 2. dry mucous membranes
    • 3. orthostatic hypotension
    • 4. flat jugular veins
  4. assessment of left heart preload
    • increased left heart preload (mostly pulmonary symptoms):
    • 1. dyspnea
    • 2. cough
    • 3. third and fourth heart sounds
  5. starling's law
    • force of contraction of cardiac muscles is dependent on stretch of cardiac muscle fibers
    • increased preload=increased contractility
  6. factors affecting preload
    • blood volume
    • 1. hypo/hypervolemia
    • atrial contractions
    • 1. atrial kick - 25-30% of cardiac output
    • 2. loss of atrial kick in atrial fibrillation
    • venous return to heart
    • 1. physical, physiological, and medication factors
    • cardiac muscle fibers
    • 1. heart failure
  7. afterload
    • resistance to ejection of blood from the ventricle  or  the pressure the ventricle must generate to overcome resistance created by arteries
    • measured by systemic vascular resistance (SVR) normal=800 to 1200
    • increased afterload=increased workload on heart
    • increased workload=increased O2 demand
    • dilated vessels=low SVR
    • constricted vessels=high SVR
  8. factors affecting afterload
    • outflow obstructions
    • 1. aortic stenosis
    • vascular tone
    • 1. vasodilation (septic shock)
    • 2. vasoconstriction (HTN)
    • medications
    • 1. vasodilators
    • 2. vasoconstrictors
  9. contractility
    • ability of cardiac muscle fibers to shorten in length
    • increased muscle fiber shortening=increased contractility=increased cardiac squeeze
    • inotropy - meds that affect contractility
    • 1. positive inotrope - increase contractility (digoxin, epi, milronone)
    • 2. negative inotrope - decrease contractility (beta blocker & CCB)
  10. factors affecting contractility
    • autonomic nervous system stimulation
    • 1. increased stimulation=fight or flight= catecholamines=increased contractility
    • medication - positive and negative inotropes
    • electrolytes - imbalances=decreased contractility
    • oxygenation - hypoxia=decreased contractility
    • acid base balance (7.35-7.45) - acidosis= decreased contractility
    • preload (fluid balance) - increased preload
    • =increased contractility (starling's law)
    • muscle fiber condition - CHF/cardiomegaly= decreased contractility
  11. diagnostic testing
    • creatinine phosphokinase (CPK) - onset 4 to 12 hrs post damage
    • troponin - found in cardiac muscle; onset 3 to 4 hrs post myocardial damage
    • b type natriuretic peptide (BNP) - for heart failure; released from ventricles when preload is increased; normal=100
  12. diagnostic procedures to assess CO
    • CXR
    • ECG and stress ECG
    • echo and TEE
    • cardiac cath
    • electrophysiology study
    • nuclear perfusion imaging
  13. pulmonary artery catheter
    • Swan-Ganz or right heart catheter
    • measures pulmonary artery systolic and diastolic pressures
    • wedge pressure (pulmonary artery occlusion)
    • cardiac output
    • central venous pressure
  14. central venous pressure (CVP)
    • measures filling pressures of right heart and measures fluid status
    • normal CVP : 2-6
    • low CVP : hypovolemia, dehydration, bleeding, vasodilation, diuresis
    • high CVP : fluid overload, CHF, acute MI, renal failure
  15. PA Pressures
    • normal : 20-30/8-15
    • measures systolic and diastolic pressures of pulmonary artery
    • reflects state of right ventricle and lung
    • low PA : hypovolemia
    • high PA : fluid overload/CHF, mitral stenosis, lung disease/COPD, pulmonary embolus, idiopathic pulmonary hypertension
  16. pulmonary artery wedge pressure
    • normal: 4-12
    • reflects blood pressure in the left ventricle at end diastole
    • low wedge : hypovolemia
    • high wedge : fluid overload, MI/cardiogenic shock, CHF
  17. Cardiac output (CO)
    • amount of blood ejected by the heart per minute
    • normal : 4-8L/min
    • CO= HR x stroke volume
    • stroke volume - amount of blood ejected by heart per beat
    • normal stroke volume : 50-100mL
  18. Cardiac Index (CI)
    • normal : 2.4 to 4
    • CI < 2 indicates shock state
    • CI=CO/ body surface area
  19. septic shock
    • bacterial endotoxins produce massive arterial vasodilation
    • severe decrease of BP
    • decreased SVR
    • increased HR, contractility, CO
  20. Cardiogenic shock
    • nonfunctioning ventricular wall and heart loses pumping ability
    • severe decrease in BP
    • decreased CO
    • increased SVR
    • vasoconstriction
  21. complications of swan-ganz catheter
    • pneumothorax
    • infection
    • balloon rupture
    • pulmonary infarction
    • pulmonary artery rupture
    • v tach

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