Cardiac Output

  • The most recent advance in noninvasive cardiac output monitoring is use of Electrical impedance cardiography technology.
  • Mean stroke volume is the amount of blood pumped out of each ventricle per beat. It is calculated as the cardiac output in L/min divided by the heart rate..
  • Cardiac Output (CO) = Stroke Volume x Heart Rate
  • Normal SV is 70 mL and hence in a supine, resting man CO is 5.0 L/ min. (70 mLX 72 beats/min.)
  • Cardiac Index (CI) = CO/ Body Surface Area (BSA) = SV x HR/BSA. CI averages 3.2L.
  • The cardiac output starts to increase from 5th week of pregnancy and reaches its peak 40-50% at about 30-34 weeks. Cardiac output increase further during labour (+50%) and immediately following delivery (+70%) It returns to pre-pregnancy level by 4 weeks time after labour.
  • Cardiac output is increased in conditions which cause decrease in peripheral vascular resistance :-
  1. AV fistula or shunt
  2. Severe anemia
  3. Thyrotoxicosis
  4. Wet beri-beri.
  • Sympathomimietic causing increase in mean blood pressure, heart rate and cardiac output on intravenous infusion is Adrenaline.
  • Stewart-Hamilton equation scientific principle is the basis for thermodilu負ion method used in measurement of cardiac output by pulmonary catheter.
  • The highest volume overload in a parturient due to maximum cardiac output is seen immediately after delivery.
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