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Cardiovascular support

Cardiac Assessment

  1. Non-invasive
    • Pulse
    • Blood pressure
    • ECG
    • Echocardiography: systolic function, cardiac filling, valve function, general morphology
    • Indicators of cardiac index: Consciousness, CRT, urine output
  2. Invasive
    1. ABGs
    2. Serum lactate: rising levels indicate poor cardiac index
    3. Gastric tonometry - adequacy of splanchnic perfusion is estimated from gastric intramucosal pH using gastric probe. ("belief" that gut is first oran system to reflect poor peripheral perfusion)
    4. Mixed venous sats - SvO2 shows oxygen extraction
    • Arterial line
    • CVP monitoring - absolute with response to fluid challenges
    • Pulmonary artery catheterisation
    • TOE: more detailed picture of left heart + thoracic aorta
    • Indicators if cardiac index:

 

Cardiac Output

Heart rate x Stroke volume

 

 

Determinants of Stroke volume:

Preload:  Contractility Afterload:

Degree of stretch of cardiac myocytes in diastole

  • Volume of blood present in a ventricle of the heart

Determined by Frank-Starling curve

Increased by

  • Intrinsic: ANS stimulation
  • Extrinsic: catecholamines 

Ventricular wall tension

  • Analagous to arterial pressure

Hypovolaemia
Tamponade
PEEP/Ventilation (reduces venous return)

 

 Stunning, infarction
Hypoxia
Acidosis

Tachyarrythmias
Bradyarrythmias
Flutter/fibrillation

  

 

Pharmacological support

  1. Inotropic drugs
    • Adrenergic agonists: Adrenaline, noradrenaline
    • Dopaminergic agonists (with some adrenergic activity): Dopamine, dobutamine, dopexamine
    • Phosphodiesterase inhibitors: Milrinone, enoximone - inhibits degradation of intracellular cAMP; causes increase in intracellular concentration of calcium ions leading to enhanced contractility
    • Calcium chloride
  2. Vasoconstrictors
  3. Vasodilators

 

Drug Alpha-1 Beta-1 Beta-2 DA1 Notes
  Vasoconstriction HR+
FOC+		 Bronchodilation Increased splanchnic / renal blood flow  
Adrenaline
 +++ +++ ++    
Noradrenaline
 +++ +     Vasopressor
Dopamine
 + + + +++ Dose dependent effects
No evidence of renoprotective benefit
Dobutamine
   +++ ++   Inodilator
Useful in low output/high resistance
Salbutamol   + +++   Acute severe asthma

Problems with inotropes

  • Arrhythmias
  • Increased myocardial oxygen consumption and demand

 

Electrical support

  • Cardiac pacemaker (chronotropic support)

Mechanical support

  • Intra-aortic balloon pump (for myocardium capable of recovery): - reduces afterload "sucking" effect on deflation, increases coronary blood flow
  1. Inserted percutaneously/direct vision into femoral artery.
  2. Passed until tip lies distal to arch vessel
  3. Balloon triggered by ECG to deflate during systole (reduces arterload) and inflate during diastole (displaces blood to coronary arteries retrogradely)

    Complications: femoral artery damage, ischaemia, haemolysis

  • Ventricular assist device
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