1. Limitations of assessing fluid responsiveness in the perioperative period
Simon Tilma Vistisen
Associate Professor
Department of Anesthesiology and Intensive Care, Aarhus University Hospitals, Denmark

2. Conflicts of interest
None to declare

3. Agenda
The (relevant) physiologic limitations to pulse pressure variation (PPV) and stroke volume variation (SVV)
Briefly: What to do when encountering limitations?
The mini-fluid challenge and its limitations
What are the more “clinical” limitations?
What can fluid responsiveness prediction not predict?
Does fluid responsiveness prediction matter for patients?

4. Definition: Fluid responsiveness prediction
Answering the question:
Will flow (stroke volume and/or cardiac output) increase with volume expansion?

5. All the limitations Background PPV prediction
Crit Care Med Sep;37(9):2642-7

6. LIMITS

7. HR/RR ratio – the explanation
Destructive interference between the “low RVSV” and the “purge effect” towards the LV

8. HR/RR ratio

9. HR/RR ratio Single study, small cohort – BUT convincing!
Not confirmed – particularly not in GA

10. Increased abdominal pressure (laparoscopic procedures)
Rationale for this limitation: Increased abdominal pressure impedes venous return (filling)
Some experimental and clinical studies…

11. Increased abdominal pressure (laparoscopic procedures)
PPV and SVV did not change with pneumoperitoneum

12. Increased abdominal pressure (laparoscopic procedures)

13. Increased abdominal pressure (laparoscopic procedures)

14. Increased abdominal pressure (laparoscopic procedures)
For now, SVV appears useful to predict fluid responsiveness Perhaps at a slightly higher threshold (12-14%) We need more studies in this area to settle thresholds.

15. The tidal volume limitation
Some issues…
De backer et al. ICM 2005
n=15
Sens
n=12
Spec 15
100 12 14
93.3 11
91.7 13
86.7 10
83.3

16. The tidal volume limitation

17. PPV proportional to tidal volume
Liu et al. BMC Anesthesiology
(2016) 16:75

18. Indexing PPV to tidal volume or driving pressure

19. On the other hand…

20. What is it with this tidal volume?!?
Are we looking at the “right” data?
Changes in pleural pressure changes could be the key?

21. Liu et al. CCM 2016,

22. What is your tidal volume during surgery?6? 8?
10?

23. LIMITS
REMEMBER:
PPV is not perfect!

24. What to use when limitations are present?
Manipulate ventilator settings
Tidal volume challenge (6  8 ml/kg)
(and maybe reduce RR at he same time)
End-expiratory occlusion test
Recruitment maneuver
(Extrasystoles)
Mini-fluid challenge – to be continued…
Fluid challenge
Vistisen et al. Curr Opin Cit Care, 2017,

25. The mini-fluid challenge…

26. What is the mini-fluid challenge?
Consists of 100 ml infusion in 1 (few) minute(s)
- Muller et al., Anesthesiology Mallat et al, BJA Guinot et al, EJA Jacquet-Legrèze et al. AIC Biais, Anesthesiology, Smorenberg, j Clin Anest, 2018
Vistisen et al. Curr Opin Cit Care, 2017

27. How is it evaluated? MFC induced changes in hemodynamic variables
Jacquet-Legrèze et al. AIC 2016
MFC induced changes in hemodynamic variables
VTI (Muller et al.)
PPV (Mallat et al.)
SV (Guinot et al., Biais et al.)
CO (Smorenberg et al.)
EtCO2 (Jacquet-Legrèze et al.)
Meant to predict fluid responsiveness:
Hemodynamic response of the entire “normal” FC ( ml)

28. Does it predict fluid responsiveness?
MFC variable
AUC
Sens.
Spec.
Threshold
Muller et al., 2011
VTI
0.92 95 78
10%
Guinot et al., 2015 SV
0.93 89 7%
Mallat et al., 2015
PPV 86 85 2%
Jacquet-Legrèze et al, 2016
EtCO2
0.74 33
100 3%
Biais et al., 2017
0.95 93 6%
Smorenberg et al, 2018 CO 1 5%

29. Ready to endorse the mini-fluid challenge!
Design issues…
A self-fulfilling prophecy design?
BL MFC
BL2 FC
Design
MFC var
FR var
Muller
BL-MFC-FC
VTI
Guinot
BL1-MFC-BL2-FC SV
Mallat
PPV CO
Jacquet-Legrèze
EtCO2
Biais
Smorenberg

30. A self-fulfilling prophecy design?
∆VTI500
∆VTI400 ???
∆VTI100
Discard the mini-fluid challenge!
∆VTI400 ~ 15%
Sensitivity: 63% (95%)
Specificity: 37% (78%)
AUC: ???

31. Regression to the mean! Have I fooled you twice?
∆VTI500
∆VTI100
∆VTI400
VTI0
VTI100
VTI500
Measurement error and physiologic variation
Regression to the mean!
∆VTI100 = VTI100 - VTI0
∆VTI100 = VTI100 - VTI0
∆VTI500 = VTI500 - VTI0
∆VTI400 = VTI500 - VTI100
Sensitivity: 70% - 95%
Specificity: 39% - 78%

32. To conclude on the mini-fluid challenge
It’s an interesting approach! May limit fluid infusion
There is one study with optimal design – two baselines
Guinot et al., AUC: 0.93
There are two studies with suboptimal/questionable design Changes in PPV or EtCO2 (not the outcome variable)
Mallat et al., AUC: 0.91 and 0.92
Jacquet-Lagrèze et al., AUC: 0.74
There are three studies that are inconclusive due to the study design (in my opinion!)

33. “Clinical” limitations …
Fluid responsiveness prediction is answering the question:
Will stroke volume increase with increased intravascular volume?
It is NOT:
Assessing the risk of fluid side effects
Coagulation?
Dilution?
(Congestion?)
(Edema formation?)
Advising on choice of fluid type

34. Fluid responsiveness prediction – beneficial for patients?
Hear-say evidence: “You’re drowning the patients with that monitor”

35. High risk surgery – GDT coupled with valid fluid responsiveness monitoring
Perioperative goal-directed therapy with uncalibrated pulse contour methods: impact on fluid management and postoperative outcome, BJA,119 (1): 22–30 (2017) – with comments

36. High risk surgery – GDT coupled with valid fluid responsiveness monitoring
Results: Post-operative morbidity
Michard F et al, BJA, 2017, 22–30

37. High risk surgery – GDT coupled with valid fluid responsiveness monitoring
Results: Colloid infusion
Michard F et al, BJA, 2017, 22–30

38. High risk surgery – GDT coupled with valid fluid responsiveness monitoring
Results: Crystalloid infusion
Michard F et al, BJA, 2017, 22–30

39. High risk surgery – GDT coupled with valid fluid responsiveness monitoring
Results: Total volume infusion
Michard F et al, BJA, 2017, 22–30

40. Drowning patients? Perhaps some overload – if you SV MAXimize
NO! If you use valid fluid responsiveness monitoring

41. OPTIMISE II trial – the fluid protocol
accessed 7/

42. Sepsis:%
GA: OK
Monnet and Teboul Ann. Intensive Care (2018) 8:54

43. Take home…
PPV and SVV are good-excellent predictors of fluid responsiveness in most GA settings
In laparoscopic surgery, PPV and SVV work well but perhaps not excellently and perhaps thresholds needs adjustment
Tidal volume can be set at approx. 8 ml/kg (temporarily)
Be aware of the HR/RR ratio limitation…
A SV increase after a mini-fluid challenge of 100 ml may not merit additional ml infusion
PPV and SVV have a central role to play in the GDT framework  Prevents fluid overload!
ICU and GA are not the same settings!