Experts present new research using fibre optic sensing technology to obtain measurements of dissolved oxygen and microvascular blood perfusion in conscious animal models of acute kidney injury. The research aims to chronically measure tissue perfusion and oxygenation during disease progression without the confounding effects of anesthesia. Preliminary data is presented showing stable measurements can be obtained over multiple days from probes implanted in the renal cortex and medulla. Changes in intra-renal perfusion and oxygenation are observed in response to reductions in renal blood flow and in a ovine model of sepsis.

1. Measuring Tissue Perfusion
and PO2 in Conscious Animals
to Investigate Organ Failure
Sponsored by:
Experts present new, ground breaking research using
the latest in fibre optic sensing technology to obtain
dissolved oxygen and microvascular blood perfusion
in models of Acute Kidney Injury (AKI).

2. Measuring Tissue Perfusion
and PO2 in Conscious Animals
to Investigate Organ Failure
Sponsored by:
Clive May, Ph.D.
Professor
Pre-clinical Critical Care Unit
Florey Institute of Neuroscience
and Mental Health
Yugeesh Lankadeva, Ph.D.
Research Fellow
Pre-clinical Critical Care Unit
Florey Institute of Neuroscience
and Mental Health

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5. • The homeostatic control of tissue perfusion and oxygenation is essential for normal
organ function.
• There is increasing evidence that in many disease states there are heterogeneous
changes in perfusion of organs leading to areas of hypoxia and organ dysfunction.
• It is essential to monitor these changes if we are to determine the pathological
mechanisms causing tissue hypoxia and to develop therapies to prevent declines in
organ function.
• The challenge is to measure tissue perfusion and oxygenation chronically during the
course of a disease, and in conscious animals to avoid the confounding effects of
anaesthesia.
The Importance of Measuring Tissue Perfusion and PO2

6. Outline of Webinar
✓ Equipment
• Tissue perfusion and PO2
• Bladder urinary PO2
✓ Implantation of renal probes
✓ Validation studies
• Long-term stability
• Renal artery occlusion
✓ Preclinical studies
• Effect of sepsis on intra-renal
perfusion and oxygenation
• Changes during resuscitation
with noradrenaline and
angiotensin II
✓ Measurement of brain
perfusion and PO2
Click Here to Watch the Webinar

7. Fluorescence optode
Dual fiber
laser Doppler
probe
Thermistor
OxyLiteTM Pro and OxyFloTM Pro (Oxford Optronix, UK).
Enable simultaneous measurement of:
1. Tissue perfusion using the laser Doppler technique
2. Tissue oxygen partial pressure using a fluorescent quenching technique
3. Temperature
Standard probe
with luer lock
Probes for measurement of tissue perfusion and PO2

8. Custom made probes for chronic implantation

9. Renal vein catheter
Flow
probe
Calzavacca et al. Am J Physiol Regu Integr Comp Physiol, 308: R832-R839, 2015.
Medullary
probe
implanted
Cortical and
Medullary
probe
implanted
Implantation of probes in the renal cortex and medulla

10. Probes remain
securely fixed in
place after 10 days
implantation

11. Cortex Outer medulla
8 days post-implantation
There was no visible
haematoma around any of
the probe tips.
Around the optic fibre, there
was minimal observable
damage and little fibrosis in
either the cortex or the
medulla.
Histology at 8 days after implantation of fibre-optic probes
H & E
Masson’s
trichrome
Calzavacca et al. Am J Physiol 308: R832–R839, 2015.

12. Oxford Optronix Large Area Sensor
Measurement of urinary PO2
Oxford Optronix
LAS-1/O/E

13. Tuohy-Borst
Y Adapter
UrineBladder catheter with
LAS probe inserted
LAS probe
Measurement of
bladder urinary PO2

14. RenalBloodFlow
(mL/min)
2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4
1 0 0
1 5 0
2 0 0
2 5 0
TissuePO2
(mmHg)
2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4
0
1 0
2 0
3 0
4 0
5 0 M ed u lla
C o rte x
T im e o f d a y
(h o u r)
TissuePerfusion
(BPU)
2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4
0
5 0 0
1 0 0 0
1 5 0 0
In contrast to previous findings in anesthetized
animals, where medullary tissue PO2 was
significantly less than cortical tissue PO2, we found
that in conscious sheep the resting levels of PO2
were similar in both areas of the kidney.
Importantly, these levels were maintained for 5
days of measurement, providing confidence that
the chronically implanted probes provide stable
readings over a number of days.
Chronic measurement of tissue perfusion and PO2
Calzavacca et al. Am J Physiol 308: R832–R839, 2015.

15. -1 5 0 1 5 3 0 4 5
6 0
7 0
8 0
9 0
1 0 0
1 1 0
1 2 0
1 3 0
MeanArterialPressure
(mmHg)
-1 5 0 1 5 3 0 4 5
0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
RenalBLoodFlow
(mL/min)
2 0 % d e c re a s e in R B F
5 0 % d e c re a s e in R B F
-1 5 0 1 5 3 0 4 5
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
CorticalPerfusion
(bloodperfusionunits)
-1 5 0 1 5 3 0 4 5
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
MedullaryPerfusion
(bloodperfusionunits)
-1 5 0 1 5 3 0 4 5
0
1 0
2 0
3 0
4 0
5 0
T im e
(m in )
CorticaltPO2
(mmHg)
-1 5 0 1 5 3 0 4 5
0
1 0
2 0
3 0
4 0
5 0
T im e
(m in )
MedullarytPO2
(mmHg)
Reductions in renal blood
flow produce graded
decreases in cortical and
medullary tissue perfusion
and oxygenation
Effect of a 20% and 50
reduction in renal
blood flow on cortical
and medullary
perfusion and PO2
Calzavacca et al. Am J Physiol 308: R832–R839, 2015.

16. -24 -16 -8 0 8 16 24 32 40 48
40
50
60
70
80
90
100
110
120
* * * *
E. coli
MeanArterialPressure
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* *
E. coli
Time
(hours)
CorticalTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* * * * *
E. coli
Time
(hours)
MedullaryTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
50
100
150
200
250
300
350
400
* * * * *
E. coli
Time
(hours)
RenalBloodFlow
(mL/min)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
*
E. coli
CorticalTissuePerfusion
(bloodperfusionunits)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
* * * * *
E. coli
MedullaryTissuePerfusion
(bloodperfusionunits)
In ovine sepsis, hypotension develops, but renal blood flow
increases
Calzavacca et al. Critical Care Medicine 43: e431-9; 2015.

17. -24 -16 -8 0 8 16 24 32 40 48
40
50
60
70
80
90
100
110
120
* * * *
E. coli
MeanArterialPressure
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* *
E. coli
Time
(hours)
CorticalTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* * * * *
E. coli
Time
(hours)
MedullaryTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
50
100
150
200
250
300
350
400
* * * * *
E. coli
Time
(hours)
RenalBloodFlow
(mL/min)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
*
E. coli
CorticalTissuePerfusion
(bloodperfusionunits)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
* * * * *
E. coli
MedullaryTissuePerfusion
(bloodperfusionunits)
In sepsis, cortical perfusion and oxygenation were maintained
Calzavacca et al. Critical Care Medicine 43: e431-9; 2015.

18. -24 -16 -8 0 8 16 24 32 40 48
40
50
60
70
80
90
100
110
120
* * * *
E. coli
MeanArterialPressure
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* *
E. coli
Time
(hours)
CorticalTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
10
20
30
40
50
60
* * * * *
E. coli
Time
(hours)
MedullaryTissuepO2
(mmHg)
-24 -16 -8 0 8 16 24 32 40 48
0
50
100
150
200
250
300
350
400
* * * * *
E. coli
Time
(hours)
RenalBloodFlow
(mL/min)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
*
E. coli
CorticalTissuePerfusion
(bloodperfusionunits)
-24 -16 -8 0 8 16 24 32 40 48
0
250
500
750
1000
1250
1500
1750
2000
* * * * *
E. coli
MedullaryTissuePerfusion
(bloodperfusionunits)
But, medullary perfusion and oxygenation were reduced
Calzavacca et al. Critical Care Medicine 43: e431-9; 2015.

19. ✓ Noradrenaline is the main
vasopressor used to restore
blood pressure and maintain
renal function in septic patients
Dellinger et al 2013
✓ We propose that angiotensin II
should also be used as a primary
vasopressor in sepsis
Do vasopressors used for
resuscitation in sepsis improve
or worsen renal hypoxia?
Critical Care 2009, 13:R190
Crit Care Med. 2018 Jan;46(1):e41-e48.

20. BUT, the effects of
resuscitation with
noradrenaline, or angiotensin
II, on intra-renal perfusion
and oxygenation during septic
AKI are unknown…
CONCLUSIONS
Angiotensin II effectively increased blood pressure in
patients with vasodilatory shock that did not respond
to high doses of conventional vasopressors.
N Engl J Med. 2017 377(5):419-430

21. Thank you to our webinar sponsors
Click below to learn more about solutions presented in this webinar

22. Renal vein catheter
Flow probe
Oxygen/perfusion
probes
Fibre optic probes for measurement intra-renal perfusion and oxygenation

23. Renal vein catheter
Flow probe
Oxygen probes
Baseline
24 h
Sepsis
24 h 1 h 2 h 3 h 4 h 5 h 6 h 7h 8 h
Escherichia coli (2.8 x 109 CFU bolus + 1.26 x 109 CFU, i.v)
Noradrenaline /Angiotensin II / Saline
Arterial, renal venous and urine samples collected at baseline, 24, 26, 28, 30 and 32 h sepsis for blood gas and creatinine measurements
Investigation of the effects of noradrenaline or angiotensin II on intra-renal
perfusion and oxygenation during septic AKI
Click Here to Watch the Webinar

24. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
5 0
6 0
7 0
8 0
9 0
1 0 0
M ean
A rterial
P re s s u re
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
5 0
1 0 0
1 5 0
2 0 0
H e a rt
R a te
(b p m )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
T im e (h )
R e n al
B lo od
F lo w
(m l/m in)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2
4
6
8
T im e (h )
R e n al
V a s c u la r
C o n d u c ta n c e
(m l/m in /m m H g )
E .c o li
N A /A n g II/S a lin e
Saline (Vehicle); n=8
Sepsis is characterised by hypotension, tachycardia and renal hyper-perfusion
Characteristics of ovine sepsis:
Hypotension
Tachycardia
Renal vasodilatation
Increased renal blood flow
Lankadeva et al 2016 Kidney Int, 90: 100-108
Lankadeva et al 2018 Crit Care Med, 46:e41-48

25. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
5 0
6 0
7 0
8 0
9 0
1 0 0
M ean
A rterial
P re s s u re
(m m H g )
E .c o li
N E /A n g II/S a lin e
*#
*#
*#
*# *#
*#
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
5 0
1 0 0
1 5 0
2 0 0
H e a rt
R a te
(b p m )
E .c o li
N E /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2 0 0
4 0 0
6 0 0
T im e (h )
R e n al
B lo od
F lo w
(m l/m in)
E .c o li
N E /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2
4
6
8
T im e (h )
R e n al
V a s c u la r
C o n d u c ta n c e
(m l/m in /m m H g )
E .c o li
N E /A n g II/S a lin e
*#
*#
*
# *
#
*
#*
#
Saline (Vehicle); n=8
Noradrenaline (NA); n=8
Angiotensin II (Ang II); n=8
Treatment with noradrenaline and angiotensin II reversed sepsis-induced hypotension
Noradrenaline and angiotensin II
were titrated to produce similar
increases in blood pressure
Lankadeva et al 2016 Kidney Int, 90: 100-108
Lankadeva et al 2018 Crit Care Med, 46:e41-48

26. Saline (Vehicle); n=8
Lankadeva et al 2016 Kidney Int, 90: 100-108;
Septic AKI was characterized oliguria, reduced function and increased plasma creatinine
0 2 4 2 6 2 8 3 0 3 2
0 .0
0 .2
0 .4
0 .6
0 .8
U rine
F lo w
(m L /m in)
E .c o li
N A /A n g II
/S a line
T im e (h )
0 2 4 2 6 2 8 3 0 3 2
0
5 0
1 0 0
1 5 0
G lo m erular
Filtration
R a te
(m L /m in)
E .c o li
N A /A n g II
/S a line
T im e (h )
0 2 4 2 6 2 8 3 0 3 2
0
5 0
1 0 0
1 5 0
2 0 0
P la s m a
C reatin ine
(m ol/L)
E .c o li
N A /A n g II
/S a line
T im e (h )
Lankadeva et al 2018 Crit Care Med, 46:e41-48

27. Saline (Vehicle); n=8 Noradrenaline (NA); n=8 Angiotensin II (Ang II); n=8
0 2 4 2 6 2 8 3 0 3 2
0 .0
0 .5
1 .0
1 .5
2 .0
U rine
F lo w
(m L /m in)
E .c o li
N A /A n g II
/S a line
*
#
T im e (h )
0 2 4 2 6 2 8 3 0 3 2
0
5 0
1 0 0
1 5 0
G lo m erular
Filtration
R a te
(m L /m in)
E .c o li
N A /A n g II
/S a line
T im e (h )
*
#
0 2 4 2 6 2 8 3 0 3 2
0
5 0
1 0 0
1 5 0
2 0 0
P la s m a
C reatin ine
(m ol/L)
E .c o li
N A /A n g II
/S a line
*
#
Noradrenaline and angiotensin II increased renal function in ovine sepsis
Lankadeva et al 2016 Kidney Int, 90: 100-108; Lankadeva et al 2018 Crit Care Med, 46:e41-48

28. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
Saline (Vehicle); n=7
Renal cortical tissue
perfusion and
oxygenation was
preserved during
septic AKI
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
Lankadeva et al 2016 Kidney Int, 90: 100-108
Lankadeva et al 2018 Crit Care Med, 46:e41-48

29. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
Saline (Vehicle); n=7
BUT, sepsis caused
selective reductions
in renal medullary
tissue perfusion and
oxygenation
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
Lankadeva et al 2016 Kidney Int, 90: 100-108

30. 0 4 8 1 2 1 6 2 0 2 4
0
1 0
2 0
3 0
4 0
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
M e du llary
T is s u e
p O 2
(m m H g )
U rin e F low
(m L /m in)
E .c o li
T im e (h )
U rin e F lo w (n = 1 4 )
M e d u lla ry p O 2 (n = 1 4 )
Reductions in renal
medullary
oxygenation occur
very early in sepsis
and several hours
before the
development of
acute kidney injury
Lankadeva et al 2016 Kidney Int, 90: 100-108

31. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2 0
4 0
6 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
* *
*
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
*
*
Saline (Vehicle); n=7
Noradrenaline (NA); n=7
Resuscitation with
noradrenaline
exacerbated renal
medullary ischemia
and hypoxia in
septic AKI
Lankadeva et al 2016 Kidney Int, 90: 100-108

32. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2 0
4 0
6 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
* *
*
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
*
*
Saline (Vehicle); n=7
Noradrenaline (NA); n=7
Angiotensin II (Ang II); n=7
Angiotensin II caused
a similar increase in
blood pressure to
noradrenaline, but
did not reduce
medullary perfusion
and oxygenation
Lankadeva et al 2016 Kidney Int, 90: 100-108
Lankadeva et al 2018 Crit Care Med, 46:e41-48

33. ↑↑↑ Risk of
AKI
Renal tubular
Injury
Reduced GFR
= AKI
Kidney Failure
SEPSIS
Traditional Biomarker
Serum Creatinine
Biomarker to assess
Kidney oxygenation
Emerging Biomakers
Urinary NGAL and
Plasma Cystatin C
AKI – acute kidney injury
GFR – glomerular filtration rate
NGAL – neutrophil gelatinase-associated
lipocalin
Pathogenesis
Kidney Hypoxia??
Limitations in current clinical biomarkers for detecting septic acute kidney injury

34. 30μm
(Modified from Pannabecker & Dantzler 2006)
Collecting ducts
Descending vasa recta
Ascending vasa recta
✓ Anatomically, the renal medullary
vasa recta run close and parallel to
collecting ducts
✓ Does urinary oxygen tension
equilibrate with renal medullary
tissue oxygen tension during
development of septic acute
kidney injury?
Rational for measuring bladder urinary PO2

35. Oxygen probe
Bladder
catheter
Oxygen
probes
The effects sepsis and vasopressors on intra-renal and urinary
oxygenation

36. During the development of sepsis medullary
and urinary PO2 fall in parallel.
The fall in urinary PO2 precedes the development of AKI
Correlation between urinary and medullary
PO2 in conscious sheep
0 6 1 2 1 8 2 4
0
1 0
2 0
3 0
4 0
0 .0 0
0 .0 5
0 .1 0
0 .1 5
T im e (h )
pO2(mmHg)
UrineFlow(mL/min/kg)
E . C o li
U rin e F lo w (n = 1 4 )
U rin a ry p O 2 (n = 1 4 )
M e d u lla ry p O 2 (n = 1 4 )
(Lankadeva et al 2016 Kidney Int, 90: 100-108)
Urinary PO2 as a real-time, non-invasive biomarker of medullary PO2
0 6 1 2 1 8 2 4
0
1 0
2 0
3 0
4 0
0 .0 0
0 .0 5
0 .1 0
0 .1 5
T im e (h )
pO2(mmHg)
UrineFlow(mL/min/kg)
E . C o li
U rin e F lo w (n = 1 4 )
U rin a ry p O 2 (n = 1 4 )
M e d u lla ry p O 2 (n = 1 4 )

37. 0 1 2 4 8 2 4
0
1 0
2 0
3 0
4 0
5 0
0
1 0
2 0
3 0
4 0
5 0
MedullaTissuepO2
(mmHg)
UrinarypO2
(mmHg)
*
*
M edullary pO 2 (n=8)
U rinary pO 2 (n=8)
T im e fro m E .co li infusion (h)
0 1 2 4 8 2 4
0
4 0
8 0
1 2 0
1 6 0
7 0
8 0
9 0
1 0 0
1 1 0
T im e fro m E .co li infusion (h)
SerumCreatinine
(mol/L)
UrinaryNGAL
(ng/ml)
*
*
U rinary N G A L (n=8)
S erum C reatinine (n=8)
Urinary
NGAL 8 h
Serum
creatinine 24 h
Medullary
PO2 1 h
Urinary
PO2 1 h
Urinary PO2 is a
diagnostic marker
that detects risk of
septic AKI earlier
than traditional
(creatinine) and
emerging (NGAL)
biomarkers
Lankadeva et al 2018 Crit Care Med, 46:e41-48

38. 0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
2 0
4 0
6 0
T im e (h )
C ortical
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
C ortical
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
M edulla
T is s u e
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
* *
*
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
3 0 0
6 0 0
9 0 0
1 2 0 0
1 5 0 0
1 8 0 0
M edullary
T is s u e
P erfu s io n
(blood
p erfu sion
u nits)
E .c o li
N A /A n g II/S a lin e
*
*
0 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2
0
1 0
2 0
3 0
4 0
5 0
T im e (h )
U rinary
p O 2
(m m H g )
E .c o li
N A /A n g II/S a lin e
*
Medullary PO2 (mmHg)
0 20 40 60
UrinaryPO2
(mmHg)
0
20
40
60
r = 0.67
Changes in bladder urinary PO2 parallel the changes in
medullary tissue PO2
Saline (Vehicle); n=7 Noradrenaline (NA); n=7 Angiotensin II (Ang II); n=7
Lankadeva et al 2016 Kidney Int, 90: 100-108; Lankadeva et al 2018 Crit Care Med, 46:e41-48

39. Noradrenaline reduces urinary PO2 in both ovine and human septic
AKI, reflecting reduced medullary tissue PO2
-2 0 -1 0 0 1 0 2 0 3 0 4 0 5 0 6 0
0
1 0
2 0
3 0
pO2
(mmHg)
U rinary pO 2 (n = 6)
M e d u lla ry p O 2 (n = 6 )
N o ra d re n a lin e in fu sio n
(1 .0 -6 .0 ) g /m in
T im e (m in u te s )
O v in e S e p tic A K I
-2 0 -1 0 0 1 0 2 0 3 0 4 0 5 0 6 0
0
1 0
2 0
3 0
UrinarypO2
(mmHg)
T im e (m in u te s )
P a tie n t 1
P a tie n t 2
P a tie n t 3
N o ra d re n a lin e in fu sio n
(1 .0 -8 .0 ) g /m in
H u m a n S e p tic A K I
Urinary PO2 - Novel biomarker - ‘Bench to Bedside’

40. ↑↑↑ Risk of
AKI
Renal tubular
dysfunction
Reduced GFR
= AKI
Kidney Failure
SEPSIS
Traditional Biomarker
Serum Creatinine
Bladder urinary
oxygenation
Emerging Biomakers
Urinary NGAL
AKI – acute kidney injury
GFR – glomerular filtration rate
NGAL – neutrophil gelatinase-associated
lipocalin
Pathogenesis
Medullary hypoxia
Urinary oxygenation:
a non-invasive, real-time biomarker to aid in early diagnosis of AKI in patients?

41. Measurement of brain perfusion and oxygenation
We have also used the Oxford Optronix probes in
experiments to determine brain perfusion following a
cardiac arrest.
Two small craniotomies were drilled in the skull
over the left and right cerebral cortex. Probes
were inserted about 15 mm and the outer
sheath of the probe was fixed to the skull with
dental cement.
Readings were unstable immediately after
insertion, but stabilised after 2 days implantation.

42. Validity of the measurements of brain
perfusion and PO2 are:
✓ The large decreases post-cardiac arrest and
improvement with cardiac massage
✓ The similar changes in the two probes in
different hemispheres of the brain
✓ Similar changes in brain perfusion and
carotid blood flow
✓ A similar lack of perfusion during cardiac
massage measured by perfusion weighted
imaging in a MRI scanner
Brain perfusion and oxygenation after a cardiac arrest
MeanArterialPressure
(mmHg)
0
2 0
4 0
6 0
8 0
C a rd ia c M a s s a g e
(1 0 m in )
C a rd ia c
A rre s t
T im e (m in )
TissuePerfusion
(BPU)
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
T im e (m in )
TissuePO2
(mmHg)
0
2 0
4 0
6 0
8 0
CarotidBloodFlow
(mL/min)
0
1 0 0
2 0 0
3 0 0
C a rd ia c
A rre s t
C a rd ia c M a s s a g e
(1 0 m in )

43. ✓ We have developed a method to chronically implant fibre optic probes in the
kidney for the measurement of tissue perfusion and PO2 and temperature
✓ These probes cause minimal tissue damage, remain fixed in place and provide
stable measurements for at least 10 days
✓ It is also possible to measure bladder urinary PO2 using a probe inserted into
the tip of a bladder catheter
✓ These techniques enable long-term monitoring of microvascular changes and
alterations in tissue oxygenation during the development of disease and the
effects of treatments.
Summary 1

44. ✓ In sepsis, there is redistribution of intra-renal blood flow as indicated by reduced
medullary perfusion and the development of hypoxia, while cortical perfusion and
oxygenation is preserved
✓ Changes in bladder urinary PO2 closely follow changes in medullary PO2, suggesting
that urinary PO2 may be a useful non-invasive, real-time biomarker to predict the
development of AKI
✓ Noradrenaline, the primary vasopressor used to maintain arterial pressure in
septic patients, enhanced the level of medullary hypoxia. It is unknown if this
hypoxia enhances the progression of AKI
✓ Angiotensin II restored arterial pressure in sepsis without causing further hypoxia
in the renal medulla or cortex. Angiotensin II should be considered as a primary
vasopressor drug in septic AKI.
Summary 2

45. Thank You
Sponsored by:
Clive May, Ph.D.
Professor
Pre-clinical Critical Care Unit
Florey Institute of Neuroscience
and Mental Health
Yugeesh Lankadeva, Ph.D.
Research Fellow
Pre-clinical Critical Care Unit
Florey Institute of Neuroscience
and Mental Health
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