When the heart is unable to meet the needs of the body, then the heart has failed. Whether the cause is due to myocardial infarction, valvular disease or arrhythmia. Heart failure is inadequate maintenance of blood pressure and or blood flow. Potential Energy (PE) is blood pressure and Kinetic Energy (KE) is blood flow. SMII is a measure of the heart’s energy or power.

1. The Measure of Lifewww.uscom.com.au
Fluid Responsiveness
and SMII
Pediatric Septic Shock

2. The Measure of Lifewww.uscom.com.au
Smith Madigan Inotropy Index
(SMII)
• When the heart is unable to meet the demands of
the body then the heart has failed
• Whether the cause is myocardial infarction,
valvular disease or arrhythmia
• Heart failure is inadequate blood pressure and or
blood flow - CI < 2.4 l/min/m2
• Potential Energy (PE) is blood pressure and
Kinetic Energy (KE) is blood flow.
• PE + KE = SMI ; SMI / BSA = SMII
• SMII is a measure of the heart’s energy or power

3. The Measure of Lifewww.uscom.com.au
Causes of a Low Stroke Volume
• Low SV, and consequently low CI, may be due to:
• Hypovolemia - inadequate preload in response to a
volume challenge
• Hypovolemia and hypocontractility - low preload and
myocardial depression which may not respond to fluid
alone
• The non-responders are on a lower, flatter Frank-Starling curve
• Inotropes are needed to increase SV in the face of cardiac
failure, when there is enough preload
• Hypocontractility – Myocardial depression with
normovolemia

4. The Measure of Lifewww.uscom.com.au
Fluid Responders
• Stroke volume (SV ml) and SMII (W/m2) after 40ml/kg
volume resuscitation show clinical or hemodynamic
improvement

5. The Measure of Lifewww.uscom.com.au
Fluid Non Responders
• Stroke volume (SV ml) and SMII (W/m2) after 40ml/kg
volume resuscitation showing clear evidence of heart
failure

6. The Measure of Lifewww.uscom.com.au
Case 1
• After 30 ml/kg of fluid, no increase in SV
• SMII was 0.94W/m2, CI 2.35 l/min
• Dobutamine was started at 10mcg/kg/min
• At 40 ml/kg, SMII was 1.34
• At 60 ml/kg, SMII was 1.66
and CI 4.4 l/min/m2

7. The Measure of Lifewww.uscom.com.au
Case 2
• No increase in SV after 20 or 30 ml/kg
• After 20 ml/kg, SMII was 0.88 W/m2, CI 2.15 l/min and
dobutamine was started at 15mcg/kg/min
• At 40 ml/kg, SMII was 1.36
• At 60 ml/kg, SMII was 1.73
and CI 4.7 l/min/m2

8. The Measure of Lifewww.uscom.com.au
Which Inotrope?
• Both of the non-responders had very high SVRI
values of 3,300 d.s.cm-5 and 3,450 d.s.cm-5
• A vaso-dilating inotrope, dobutamine, was
chosen
• A vasoconstricting inotrope would be more
appropriate for a low SVR/high CI

9. The Measure of Lifewww.uscom.com.au
Which Inotrope?
• A rational choice of inotrope can be made on the
basis of the CI, SMII and SVRI
• We should ask three questions:
1). Is the CI high, low or normal?
2). Is the SVRI high, low or normal.
3). Is the SMII normal or low?
• Is there a need to increase inotropy?
• Is vasodilation or vasoconstriction necessary?

10. The Measure of Lifewww.uscom.com.au
Conclusion
USCOM
• Measures the energy of the heart
• Identifies patients who need an inotrope to
optimise SVI and CI
• Identifies which inotrope to use
• Measurement of SVI, SMII and SVRI
guides appropriate, effective and rapid
management