So we can use science to treat septic shock instead of dogma ... The scientific approach to septic shock…[r]
(1)Septic Shock – Time to Use Science?
HR SVR Hb
SV DO2 CVP
CO SpO2 BP
Professor Brendan Smith
School of Biomedical Science, Charles Sturt University, Medical School, University of Notre Dame, Australia,
(2)Vasopressors And
(3)Definition of shock:
“Any haemodynamic disturbance leading to inadequate perfusion and oxygenation
of the tissues.”
(4)(5)BP Low
Low SVR
(6)High SVR
BP High
(7)BP = CO x SVR
(8)CO SVR
Vasopressors and DO2
CO
SVR
BP can only rise if inotropy is good and CO is maintained
Otherwise CO & DO2 fall with vasoconstriction.
(9)The heart must have sufficient
inotropy (contractility) to overcome the increase in afterload produced
by vasoconstriction or
(10)90% of septic shock patients have depressed inotropy.
Increasing SVR with vasopressors
reduces SV, CO and DO2!!
We have been fooled by the
“Blood Flow depends on Blood Pressure”
(11)Pure vasopressors in septic shock
Three types of clinicians use them… - The ignorant
- The lazy
-The ignorant and lazy!!
(John Hinds 2016)
(12)(13)Inotropy.
Inotropy (myocardial contractility) as a
concept is well known to all clinicians
but not as a discrete quantity.
Depressed inotropy is an important feature of many ICU presentations –
1o Cardiac Conditions –
AMI, LVF, Cardiomyopathy
(14)2o Myocardial Depression –
Septic shock, Pancreatitis, Pneumonia, DKA, Burns, Hypoxia, Crush Injury,
Hypovolaemia, Anaemia, Thyroid Disorders, Hyperthermia, Hypothermia, Poisoning,
Evenomation,
Iatrogenic Antihypertensives, chemotherapy, electrolyte disorders, sedation, steroids,
anaesthetics…
(15)How we assess inotropy?
- We use surrogates of global cardiac function
- BP, HR, urine output, skin perfusion, capillary refill, skin temperature, bowel sounds, Ejection Fraction, sweating, … ??
- All of these are totally unreliable indicators of cardiac function even in the hands of senior clinicians
(16)How we titrate inotropes?
Noradrenaline - ↑BP but ↓Flow
Dobutamine - ↓BP but ↑Flow
Adrenaline - ↓BP and ↑Flow (Low dose)
Adrenaline - ↑BP and ↓Flow (High dose)
How can you titrate inotropes
(17)Even more illogical…
How we juggle powerful inotropes
without measuring inotropy!
Was it low before?
Is it normal now?
(18)When should we use inotropes?
In >95% of cases this is done by clinical judgment alone!
Which inotrope and how much? What are our therapeutic targets?
How we know we’ve reached them? If only we could measure inotropy!!
(19)(20)Total Inotropy = PE + KE
( = blood pressure + blood flow)
Inotropy = BPm x SV x 10-3 + x SV x 10-6 x ρ x Vm2
7.5 x FT 2 x FT
The Smith-Madigan Formula
The unit of inotropy is the Watt
British Journal of Anaesthesia – 2013
(doi: 10.1093 / bja / aet118)
(21)(22)(23)(24)U-S-C-O-M
(25)Preload Inotropy Afterload
Why is inotropy so important?
BP = SVR x HR x SV : SV x HR = CO
Fluid loading
www.learnhemodynamics.com
(26)Starling Curves and Inotropy Index (SMII)
+inotropy
Left ventricular end diastolic volume Stroke Volume Index 50 25 SV
SMII = 2.0
SMII = 1.8
SMII =1.4 SMII = 1.1
(27)SMII %Δ
(28)(29)SV
LVEDV
ΔSV
~75ml/m2l
(30)(31)But what’s normal?
We have data from ~ 3,500 normal patients from birth to 88 years
(32)Now we know what’s normal
we can start to treat the abnormal.
That’s the scientific way!
(33)The Bathurst Universal
Haemodynamic Protocol
(BUSH)
(34)(35)(36)The scientific approach to septic shock…
Measure the variable(s)
Compare to normal reference values Administer the treatment
Remeasure the variable(s)
Compare to normal reference values
When the value of the variable(s) is within normal limits, then we can say
(37)So much for the theory –
what about the patient data?
(38)We treated 45 septic shock patients according to the BUSH Protocol
and
64 septic shock patients treated with “usual care” – SSC Guidelines
We analysed for 8 possible outcomes which were not mutually exclusive:
(39)Translator: You don’t need to translate all this,
but this is so you know what the abbreviations mean in the next few slides…
the variables we analysed for were:
Time taken to achieve haemodynamic stability – TTHS Morbidity (death)
Acute Heart Failure (AHF) Acute Renal Failure (ARF)
Acute Respiratory Failure (need for positive pressure ventilation – PPV) Time to completion of first round of antibiotics
Total fluid used in first 24 hours and first 48 hours Need to transfer patients to tertiary hospital (Sydney)
(40)Outcomes…
Parameter BUSH Control P = Odds Ratio
n = 45 64 -
-TTHS
(hours) 1.25 19.9 <0.001
-Mortality 3 (6.7%) 25 (39%) <0.001 13.7
AHF 2 (4.4%) 31 (48.4%) <0.001 20.0
ARF 4 (8.9%) 47 (73.4%) <0.001 28.6
PPV 9 (20%) 27 (42.1%) 0.017 2.92
(41)Parameter BUSH Control P = Odds Ratio
n = 45 64 -
-TTAB
(hours) 0.63 4.28 <0.001
-Total Fluid
24 hours 4.44 L 7.32 L <0.001
-Total Fluid
48 Hours 7.57 L 11.49 L <0.001
-Tertiary
Transfer 2 (4.4%) 16 (25%) <0.001 7.1
RRT 0 (0%) 6 (9.5%) 0.033
(42)Take Home Messages…
(43)Fluid Resuscitation…
If the first 20ml/kg doesn’t work, (i.e produce a sustained increase in BP)
why waste time giving further
fluid boluses?
Go to Plan B…
(44)Measure Haemodynamics ASAP
Especially Inotropy Index…
(45)In patients with septic shock
(46)CVP measurement (and IVC imaging) are not reliable measures of preload.
Saline does not carry oxygen.
Vasopressors do not increase
CO and DO2
Inotropy can be measured easily.
(47)(48)(49)If we use science, then treating septic shock should be like clockwork
Logical, integrated and smooth.
(50)(51)HR SVR Hb
SV DO2 CVP
CO SpO2 BP
Thank you for listening.