Effective, non-invasive cardiac output with good comparison and concordance with ODM. In Pre-op setting allows advanced cardiac assessment, Inotropy appears to correlate with AT and enables effective use of CVS medication.

1. Pre-operative, non-invasive
cardiac output measurement
H.G. WAKELING
Department of Anaesthesia
Western Sussex Hospitals NHS Trust
Chair
Cancer Enhanced Survival Clinical Advisory Group
SE Coast Strategic Network and Clinical Senate
NHS England
howard.wakeling@nhs.net

2. Conflict of Interest
Honoraria
Financial help with
travel to attend
scientific meetings
From
 Deltex Medical
 Intavent
 Astratech

3. The USCOM Device
Describe the USCOM Device
What it does
How to use it
Learning curve identification
Correlation with Oesophageal Doppler
Case Histories
Bedside Inotropy and CPET

4. The USCOM Device
Continuous wave US
Aortic and pulmonary
valves
Trans-cutaneous
Completely non-invasive
Neonates to Geriatrics

5. How does it work?
Fd= 2Ft x V x cosθ
C
Fd Doppler frequency
Ft Transmitted frequency
V Velocity of blood
θ Angle between beam
and blood flow
C Velocity of sound in soft
tissue (constant)

6. USCOM looks at
flow through valves
Different waveform
from desc. aorta
Velocity-time integral
VTi

7. Aortic valve outflow
Fibrous Annulus
Rigid
 Little systolic change
Constant size in
adulthood
Linear relationship
with height

8. Outflow Tract Diameter:
Linearly related to
height in adults
Linearly related to
height in children
Neonates <50cm
weight is used

9. 1 Start of systole
2 Valve opening
3 Peak velocity
4 End of blood flow
valve closes
5 VTi
6 Diastolic flow
 Early diastolic filling
 Atrial contraction

13. Pulmonary Valve

14. Learning Curve?
4 novice operators
1 experienced operator
SV measurements
Before Passive leg raise (PLR)
After PLR
In 25 healthy volunteers
One ‘novice’ vs expert compared in 24
patients

15. First 10 measurements Median(IQR)
PrePLR PostPLR
Experienced 71(59 – 85) 87(76 – 93)
Novice 66(53 – 76) 77(67 – 86)
Measurements 20 – 25
Experienced 64(57 – 75) 79(74 – 87)
Novice 65(56 – 71) 78(73 – 86)

17. Inter-rater correlation between assessors
A: during training, pre leg raise (R2
= 0.71) B: during training, post leg raise (R2
= 0.59)
C: post-training, pre leg raise (R2
= 0.94) D: post training, post leg raise (R2
= 0.95)

18. Comparison with ODM
135 paired observations in theatre

19. Bland–Altman plot
All 135 paired readings
Mean Bias 5.9ml,
95%CI -20-+32,
% error 30%

20. Testing for Concordance
77 paired readings pre/post fluid
45% of challenges SVODM ↑≥10%
94% SVUSCOM also ↑
5 cases SVUSCOM ≥10% when no ΔSVODM
Sensitivity was 94%, Specificity 88%
Positive predictive value (PPV) 87%
Negative predictive value (NPV) of 95%.

21. Testing for Concordance

22. Bedside Inotropy
Acknowledgement Prof. B.Smith and Veronica Madigan, Bathurst Base Hospital and
Charles Sturt University.
USCOM allows for Inotropy assessment

23. Inotropy – heart power
External cardiac work
Kinetic energy – flow of the blood
Potential energy – generation of BP
Power is work per unit time

24. Kinetic energy
½.mass.velocity2
Mass = SV x Density
Density is dependant on Hb
Mean velocity
Velocity sampled every 10 milliseconds
If flow time 360ms – 36 readings to
average

25. Potential Energy
Δ Pressure x Δ Volume
Δ Pressure
Pressure leaving the heart (MAP) minus
pressure of blood entering heart (CVP)
Δ Volume
Stroke Volume

26. Work = KE + PE
Power is work per unit time
Time for heart to work is the flow time
Measured in Watts
Power = Kinetic energy + Potential energy
Flow time Flow time
Indexed by dividing by BSA
Smith-Madigan Inotropy Index (SMII) W.m-2

27. Application of Inotropy Index
Normal heart SMII 1.6 – 2.2 W.m-2
LVF patients SMII 0.4 – 1.0 W.m-2
Failing heart 33% normal inotropy

28. Ratio of Potential to Kinetic energy
PKR
Normally 30:1
Sepsis much lower – possibly only 3:1
Flow but little Pressure
Arterial hypertension - vasoconstriction
May be over 150:1
Very little flow
Very high SVR

29. Comparison with CPET data
USCOM measurements pre and
immediately post CPET
23 patients so far
Preliminary data shows good
correlation between SMII and
Anaerobic Threshold
Both pre and post CPET

30. SMII Pre CPET vs AT

31. SMII Post CPET vs AT
Correlation Coefficient 0.56

32. SMII vs AT
In addition 3 patients with low SMII
failed to reach AT!
So preliminary data suggests SMII may
be useful as correlates well with AT
Important - independent of exercise

33. Case history
Specialist Pre-assessment Anaesthesia and Medicine Clinic (SPAM)
Mr PH
88 years 80.6Kg 173.5cm
Extended right hemicolectomy
Poor exercise tolerance
Orthopnoea, swollen ankles, PND+
No Angina

34. Medications and PMH
Atenolol 50mg od
Frusemide 40mg od
ISMN 60mg pd
Iron
GTN
Ca Bladder
TURP
Ischaemic heart
disease
Pleural effusions
2012
‘normal’ echo

36. PH
CI 1.1 l/min/m2
FT 303ms
SVRI 6384 ds.cm-5
m2
DO2 300 ml/min
INO 0.68 W/m2
PKR 132

37. PH
Symptoms and Signs of LVF
Low CI
Very high SVR and PKR
Low Inotropy
Plan
Stop Atenolol and ISMN
Additional diuretic (Co-Amilofruse)

38. PH 4 weeks later

39. PH
Before and After
CI 1.1
FT 303
SVRI 6384
DO2 300
INO 0.68
PKR 132
2.1 l/min/m2
268 ms
3679 ds.cm-5
m2
572 ml/min
0.93 W/m2
107

40. PH
Successful surgery
Stroke Volume optimisation ODM
No crystalloid
Low dose dobutamine 24 hours
2 days level HDU
Troponin rise
Echo confirmed diastolic heart failure
Aspirin, ramipril clopidogrel started
2 days level 1

41. PH
3 days level 1 bed
Home day 11
Echo 8 weeks later
Dilated and severely impaired LV
EF 35%
6/12
Remains well

42. USCOM Summary
Effective, non-invasive cardiac output
4 hour or 50 uses learning curve
Good comparison with ODM
Good concordance with ODM
In Pre-op setting:
Allows advanced cardiac assessment
Inotropy appears to correlate with AT
Enables effective use of CVS medication