Cardiac output

Heart rate x stroke volume = 70mls/kg/min (approximately 5l/min)

Cardiac Index

Cardiac output / Body surface area = 2.2-2.5l/min/m2

Cardiac Cycle

Duration 0.8 - 0.9s

1. Closure of mitral valve (systole)
2. Opening aortic vavle
3. Closure aortic valve (forms "dichrotic notch" - outward momentum)
4. Opening mitral valve (ventricular filling)

EVD = 120mls, ESV = 40mls : Ejection fraction = 80/120 (67%)

In exercise

1. Phases of cycle shorten
2. Ventricular diastole disproportionately shorter - reduced filling time
3. VFT offset by "atrial kick" for more filling 

Heart sounds

1. Mitral / Tricuspid valve closure
2. Aortic / Pulmonary valve closure
3. Rapid ventricular filling
4. Atrial contraction against stiff ventricle 

Determinants of Cardiac output

1. Non-invasive
   • Pulse, HR, BP, urine output
   • ECG
   • Echo
2. Invasive
   • Oseophageal doppler

   • PiCCO - Thermodilution
   • Swann-Ganz Pulmonary artery catheter

     
     Multi-lumen balloon-tipped flow-directed catheter; passed through right heart into pulmonary artery
     Reflects Left heart function: - "Wedge" forms continousc column of blood from left atrium (via lungs)
     Indications: (1) inotropic support (2) LV monitoring (3) Multi-organ failure

     Parameters

     • Direct
       1. Mean arterial pressure
       2. Mean pulmonary artery pressure
       3. Pulmonary artery occlusion pressure
       4. Ejection fraction
       5. Cardiac output - measured using indicator dilution / thermodilution technique (volume₁-temp₁ vs volume₂-temp₂)
       6. Heart rate
       7. Mixed venous oxygen saturation
     • Derived
       1. Cardiac index
       2. Stroke volume
       3. Systemic vascular resistance
       4. Pulmonary vascular resistance
       5. Oxygen delivery

       Systemic Vascular resistance

       (MAP - CVP)/CO X 80 = 900-1400 dyn/s/cm^-5

       Pulmonary vascular resistance

       (MPAP - PAOP)/CO x 80 = 150-250dyn/s/cm^-5

     • Complications of insertion:
       1. Any of the central line complications
       2. Cardiac arrythmias
       3. Valve injury: incompetence of TV or PV
       4. Pulmonary artery rupture
       5. Pulmonary infarction (if balloon kept wedged too long)
       6. Catheter knotting
       7. Sepsis