Cardiovascular Support

• Overall cardiac function (cardiac output)

  1. Preload

  2. Afterload

  3. Contractility

  4. Heart rate
• Preload


  The amount that the heart muscle is stretched when filled with blood just before a contraction
• Afterload


  The resistance that the heart must overcome to eject blood from the left ventricle, through the aortic valve and into the aorta
• Common causes of raised afterload

  • Hypertension
  • Aortic stenosis
• Contractility


  The strength of the heart muscle contraction
• Heart rate


  The number of heartbeats per minute
• Systemic vascular resistance


  The resistance in the systemic circulation that the heart must overcome to pump blood around the body
• Stroke volume


  The volume of blood ejected during each beat
• Cardiac output


  The volume of blood ejected by the heart per minute
• Formula for Cardiac output: Cardiac output = stroke volume x heart rate
• Mean arterial pressure (MAP)

  The average blood pressure throughout the entire cardiac cycle, including both systole and diastole
• Mean arterial pressure is a product of

  Cardiac output and systemic vascular resistance
• Low arterial pressure may result from

  Low cardiac output or low systemic vascular resistance
• An adequate mean arterial pressure is essential for tissue perfusion throughout the body
• Low mean arterial pressure results in tissue hypoperfusion, leading to hypoxia, anaerobic respiration, lactate production, and damage to the tissue
• Monitoring Cardiac function


  Can be monitored closely
• Mean arterial pressure


  Essential for tissue perfusion throughout the body
• Low mean arterial pressure


  Results in tissue hypoperfusion, leading to hypoxia, anaerobic respiration, lactate production, and damage to the tissue
• Monitoring cardiac function


  Can be monitored closely in the intensive care unit. The extent of monitoring depends on the individual patient and clinical problems
• Basic non-invasive monitoring involves

  • Heart rate
  • Peripheral blood pressure
  • Pulse oximetry (oxygen saturations)
  • Continuous ECG monitoring
• More intense monitoring can involve

  • Invasive blood pressure monitoring via an arterial line
  • Arterial blood gas analysis taken from an arterial line
  • Central venous pressure via a central venous catheter in the vena cava/right atrium
  • Central venous oxygen saturation measured using blood samples from a central venous catheter
  • Pulmonary wedge pressure via a pulmonary artery catheter (rarely done)
  • Pulmonary artery oxygen saturation via a pulmonary artery catheter (rarely done)
  • Echocardiogram (transoesophageal or transthoracic)
• Cardiac output monitoring can involve

  • Pulse contour cardiac output (PiCCO) monitors cardiac output via a central venous catheter and thermodilution arterial line
  • Oesophageal Doppler monitor assesses the blood flow through the thoracic aorta to estimate stroke volume and cardiac output
• Fluid status


  An important part of maintaining cardiac function is optimising the fluid status. This is the first step before considering inotrope and vasopressor medications
• Central venous pressure


  Is often used as an estimate of preload. It helps guide fluid resuscitation
• Too much fluid


  Can lead to fluid overload, creating congestion in the circulation, resulting in congestive heart failure, pulmonary oedema, and increased mortality
• Inotropes

  • Medications that alter the contractility of the heart
• Positive inotropes


  • Act to increase the contractility of the heart, increasing cardiac output (CO) and mean arterial pressure (MAP). They are used in patients with low cardiac output
• Examples of positive inotropes

  • Adrenaline
  • Dobutamine
  • Isoprenaline
  • Noradrenaline (weak inotrope and mostly a vasopressor)
  • Dopamine (not an inotrope at lower infusion rates)
  • Milrinone
  • Levosimendan
• Negative inotropes


  • Act to reduce the contractility of the heart. Examples are Beta-blockers, Calcium channel blockers, Flecainide
• Vasopressors


  • Medications that cause vasoconstriction
• Negative inotropes


  • Reduce the contractility of the heart
• Vasopressors


  • Cause vasoconstriction, increasing systemic vascular resistance and mean arterial pressure (MAP)
• Use of Vasopressors


  Commonly used by anaesthetists as a bolus dose or in ICU as an infusion to improve patient’s blood pressure and tissue perfusion, especially in conditions like severe sepsis
• Common Vasopressors


  • Noradrenaline (given as an infusion via a central line)
  • Vasopressin (given as an infusion via a central line)
  • Adrenaline (given as an infusion via a central line or as a bolus in an emergency)
  • Metaraminol (given as a bolus or an infusion)
  • Ephedrine (given as a bolus)
  • Phenylephrine (given as a bolus or an infusion)
• Vasopressin


  • Acts as antidiuretic hormone (ADH), causes contraction of smooth muscle in blood vessels, and stimulates water reabsorption from the collecting ducts in the kidneys
• Antimuscarinic Medication


  • Used to treat bradycardia by blocking acetylcholine receptors
• Antimuscarinic Medication


  • Glycopyronium
  • Atropine
• Intra-Aortic Balloon Pump


  • Device used in cardiac conditions like cardiogenic shock, acute coronary syndrome, and post-heart surgery, inserted via the femoral artery to the descending thoracic aorta, inflates during diastole to improve coronary perfusion and deflates during systole to reduce afterload and increase cardiac output
• An intra-aortic balloon pump increases coronary blood flow, reduces afterload, and increases cardiac output
• Last updated


  August 2021