Does fluid responsiveness imply fluid need?...Does fluid responsiveness imply fluid need? S Magder...

Does fluid responsiveness imply fluid need?

S MagderDivision of Critical Care,

McGill University Health Centre

What is the importance of fluid for

• Water is the primary solvent for all the bodies chemicals:

• Water is the primary solvent for all the bodies chemicals: – Allows convective and diffusional transport

• Water is the primary solvent for all the bodies chemicals: – Allows convective and diffusional transport– Allows proteins to form their tertiary structures that

are essential for their function

Water is 60% of total weight

Extra-cellularWater 18%

Water is 60% of total weight

Extra-cellularWater 18%

Plasma water 5%

Inter-stitial

40% 60%

General Schema

Inter-stitial

40% 60%

General Schema

Inter-stitial

40% 60%

General SchemaPlasma vol ~ 3.5 l

Inter-stitial

40% 60%

General SchemaPlasma vol ~ 3.5 l

~ 12 l

When “volume resuscitating” consider-----

• Hydration• Extracellular volume• Intravascular volume

What is hydration?

• The state of hydration refers to the amount of water relative to the amount of solute particles–Dehydration -- not enough water for the solute

( ie osmolality is above normal)–Excess hydration -- too much water for the

solute ( ie osmolality is below normal)• Hydration is assessed by examining the solutes

– Primarily Na+

– Also glucose, urea, alcohol, ketones etc

Assessment of extracelluar

• Excess volume

• Excess volume– Peripheral edema

• Excess volume– Peripheral edema– Acites

• Excess volume– Peripheral edema– Acites– Pulmonary edema and pleural effusions

• Decreased volume

• Decreased volume– Loss of skin turgor

• Decreased volume– Loss of skin turgor– Loss of sweat

Fluid status is not really about water balance but rather “salt solution balance”

Assessment of vascular volume

• Excess volume

• Excess volume– Elevated jugular veins

• Excess volume– Elevated jugular veins– S3

• Excess volume– Elevated jugular veins– S3 – Pulmonary venous congestion

• Decreased volume

• Decreased volume– Postural hypotension

• Decreased volume– Postural hypotension– Flat neck veins

• Decreased volume– Postural hypotension– Flat neck veins– Tachycardia (not a strong sign)

Increasing evidence of harmful effects of excess fluid

• Adesanya A et al Vasc Endovascular Surg 2008; 42:531-536.• Vincent JL et al. Crit Care Med 2006; 34:344-353.• Joshi GP et al Anesth Analg 2005; 101:601-605• Wiedemann HP et al N Engl J Med 2006; 354:2564-2575.• Boyd et al (VASST trial). CCM 2011;39:259-265Durairaj L & Schmidt.

Chest 2008;133:252-263

Increasing evidence of harmful effects of excess fluid

• Adesanya A et al Vasc Endovascular Surg 2008; 42:531-536.• Vincent JL et al. Crit Care Med 2006; 34:344-353.• Joshi GP et al Anesth Analg 2005; 101:601-605• Wiedemann HP et al N Engl J Med 2006; 354:2564-2575.• Boyd et al (VASST trial). CCM 2011;39:259-265Durairaj L & Schmidt.

Chest 2008;133:252-263

- therefore try to avoid excess volume - Key is to identify likelyhood of lack of volume responsiveness- tests are useful in the negative

Patient has low urine output and is thought to be “pre-renal”

How does volume increase the flow of urine?

1. Increase renal blood flow

1. Increase renal blood flow2. By increasing blood pressure

1. Increase renal blood flow2. By increasing blood pressure3. By increasing cardiac output

What determines flow?

Review of cardiovascular basics

Volume stretches the veins and creates the “recoil” pressure that drives flow back to the heart

Heart has a “permissive”

function. It lowers the outflow

pressure and allows veins to

Determinants of flow

Stressed VolumeCv x RvQ =

Heart has a “restorative”

function

which refills the veins

MCFPStressed volume

Unstressed volume

MCFPStressed volume

Unstressed volume

Cardiac function

Frank-Starling’s Law“the greater the preload the greater the Q--

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

-- up to a maximum”

Pra (mmHg)

Q (l/min)

plateau

-- up to a maximum”

MCFPStressed volume

Unstressed volume

Cardiac function

MCFPStressed volume

Unstressed volume

Cardiac function

Return Function

MCFPStressed volume

Unstressed volume

Cardiac function

Return Function

Pra/CVP

Cardiac output

Pra/CVP

Cardiac output

PraCardiacPreload

Pra/CVP

Cardiac output

PraCardiacPreload

Pra/CVP

Gradient for VR

Cardiac output

PraCardiacPreload

Cardiac limited“Wasted preload”

Pra/CVP

Gradient for VR

Cardiac output

If cardiac function becomes limited the volume infusion will not increase cardiac output

“Plateau”Q

Volume does not increase cardiac output

“Plateau”Q

Volume does not increase cardiac output

= ‘wasted preload” (excess volume)

Pra/CVP

Cardiac output

Maximal return“Cardiac independent”

Pra/CVP

Cardiac output

Lowering Pra further will not increase Q

VR = -Pra

RvMCFP

VR = -Pra

RvMCFP

VR = -Pra

RvMCFP

VR = -Pra

RvMCFP

VR = -Pra

RvMCFP

Stressed volume must increase to increase Q

Version 1

Version 11. Is this pt volume responsive?

Version 11. Is this pt volume responsive?2. Does this pt need volume?

Version 2

Version 21. Does this pt need volume?2. Is this pt volume responsive?

ie is the patient on the flat part of the cardiac function curve?

Crit Care Med 2010 Vol. 38, No. 11

Fluid Protocol

CI < 4 and CVP < 12 ?

Chest tube drainage > 200mL/hror Hb < 80 mg/dL ?

Protocol Fluid Bolus

Check CI and

PRBC’s+ Platelets

CVP incr. > 2 and

CI incr. < 0.3

CVP incr. < 2 and

CI incr. > 0.3

CI < 2.2 or

MAP < 70 or

SBP < Target or

CVP < 3

Total Protocol

Fluid >1L/24hr?

Bleeding Corrected?

Exclude

250 mL NS Bolus until 24

CatecholamineProtocol

Weaning Protocol

Patient on Catecholamines

Yes Yes

Observe

Patient on Catecholamines?

Observe

CI < 2.2or

MAP < Targetor

SBP < Targetor

CVP < 3

CatecholamineProtocol

Weaning Protocol

CVP incr. < 2 and

CI incr. < 0.3

CVP incr. > 2 and

CI incr. > 0.3

Exclude bleeders

Limit Q&

Inadequatechallenge

Cardiac response ok

Limit HES to 1 l

Pt not volume responsive

Targets

Triggers for considering fluids

• Decreased Q• Decreased BP• Decreased urine output• Decreased CVP• ? Increased lactate• ? Decreased ScVO2

Estimate of CVP is readily available from Jugular Venous Pressure

SternalAngle

5 cm8 cm

SternalAngle

5 cm8 cm 13

cm H2O

It is often argued that CVP is of no value

It is true!!

It is true!!• CVP must be used in the context of

the hemodynamics (especially Q) and the changes over time

• Think of use of PCO2 – it must always be in the context of the pH

Consider the following:

In the sitting position the CVP of a normal person is < 0 mmHg,

yet cardiac output (Q) and blood volume are normal

&There is no need for fluid infusion

What does CVP tell you?

• Is the CVP high and therefore it is unlikely that volume loading will help?– There is no “optimal” CVP – Concept should be “high” vs “low” CVP

• What happened to the CVP in relation to a change in hemodynamics (especially cardiac output)

Approach

Approach• Although not perfect, CVP is a reasonable

start– Should be used in the “negative”

start– Should be used in the “negative”– a “high” CVP means that fluids are unlikely to

help– The pattern helps, especially relationship of

CVP to Q• fall in Q with rise in CVP indicates “pump

problem” - give inotropes• Fall in Q with a fall in CVP indicates return

function - give fluid

Large overlap between responders and non responders

Bafaqeeh & Magder JICM 2007

Responders

Non-responders

Responders

Non-responders

Some Patients at all values of CVP fail to respond to fluids

totalresnon res

25% 45%

totalresnon res

25% 45% 82%

totalresnon res

25% 45% 82% 100%

Fluids in pt with high CVP

• Systemic capillaries are upstream from the CVP

• Therefore – if CVP is high, capillary pressure must be even higher

• The consequence is that raising the cap pressure further will increase capillary leak

• This could further compress the heart and create the need for even higher levels of CVP

Gold standard of responsiveness is a volume challenge

• To test Starling’s law the fluid needs to be given quickly – the faster it is given the less that is needed– It makes no sense to test “preload” responses

over long periods of time (eg Kumar et al 2004)

• The type of fluid is not critical if given quickly enough

Gold standard of responsiveness is a volume challenge

• To test Starling’s law the fluid needs to be given quickly – the faster it is given the less that is needed– It makes no sense to test “preload” responses

over long periods of time (eg Kumar et al 2004)

• The type of fluid is not critical if given quickly enough

• There needs to be a change in CVP to know that Starling’s Law has been tested

Fluid Challenge with Q measurement

1 Assess the value of Pra ( NOT the wedge).

2 Give sufficient fluid to raise Pra by ~2mmHg and observe Q.

2 Give sufficient fluid to raise Pra by ~2mmHg and observe Q. Pra

2 Give sufficient fluid to raise Pra by ~2mmHg and observe Q.

Type of fluid is not of importance if given fast enough

Change in CVP of even 1 mmHg should be sufficient to test the Starling response

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

Pra (mmHg)

Q (l/min)

plateau

Pra (mmHg)

Q (l/min)

plateau

Pra (mmHg)

Q (l/min)

Slope = 500 ml/min/mmHg

plateau

Inspiratory fall in Pra

↓ Ppl

Inspiratory fall in Pra

↓ Ppl

Inspiratory fall in Pra No Inspiratory fall in Pra

↓ Ppl

↓ Ppl Q

↓ Ppl

↓ Ppl Q

↓ Ppl

‘a’0-‘c’

‘y’

‘v’

Prominent ‘y’

13 mmHg

Unlikely to respond to fluids when ‘y’ ≥ 4 mmHg

Systolic or Pulse Pressure Variation

Insp Insp Insp

mmHgBaseline(“apnea”)

Insp Insp Insp

Baseline(“apnea”)

Insp Insp Insp

dDown SPV

Insp Insp Insp

dDown SPV

Insp Insp Insp

Raising the pressure with fluids vs NE

Aorta Ra

Baseline

Aorta Ra

BaselineFluid

Aorta Ra

BaselineFluid

Norepinephrine

Aorta RaCapillaries

BaselineFluid

Norepinephrine

Aorta RaCapillaries

BaselineFluid

Norepinephrine

Aorta RaCapillaries

BaselineFluid

Norepinephrine

Aorta RaCapillaries

BaselineFluid

Norepinephrine

Use fluids judiciously

Avoid the Michelin Man syndrome

Normal Saline in Patient with Large Extra-cellular Volume

Inter-stitialPl

The rule that saline distribution is 1/3 vascular 2/3 interstitial is no longer true

Determinants of Fluid Filtration(Starling Forces)

Jv = Kf,c [(Pc-Pt)-σd(πc –πt)]

where: Jv = vol flow across the wall Kf,c = filtration coefficient Pc = Capillary pressure Pt = tissue pressure πc =capillary oncotic pressure πt = tissue oncotic pressure σd = reflection coefficient

Out In

Inter-stitial

Effect of Normal Saline

Plasma & Interstitial spaces are expanded

Inter-stitial

Inter-stitialPl

Inter-stitial

Inter-stitialPl

The rule that saline distribution is 1/3 vascular 2/3 interstitial is no longer true

Inter-stitial

35% 65%

General Schema

Vascular Capacitance

• Cannot be measured clinically

• Cannot be measured clinically• Increased by vasodilators, α-adrenergic

blockers, and sedation

blockers, and sedation• Reserves can be determined from the

“volume history of the patient”

blockers, and sedation• Reserves can be determined from the

“volume history of the patient”Beware of narcotics or vasodilators in

patients with increased sympathetic tone

Change in Volume

PMCFP ↑

Change in Volume

PMCFP ↑

Change in Volume

PMCFP ↑

PraCardiacPreload

Cardiac limited“Wasted preload”

Pra/CVP

Gradient for VR

Cardiac output

Distinguish fluid challenge and

fluid infusion

• “Challenge” is a small amount of fluid given rapidly while you observe a clinical effect

• Infusion of fluids are to maintain normal physiological status

Importance of

volume

Importance of

volume

Increase the initial

volume

Importance of

volume

Importance of

volume

Importance of

volume

Importance of

volume

Stressed volume

Importance of

volume

volume Greater flow

Stressed volume

Importance of

volume

Greater flow

Stressed volume

Importance of

volume

Greater flow

Stressed volume

Importance of

volume

Greater flow

Stressed volume

Importance of

volume

Greater flow

Stressed volume

Importance of

volume

Greater flow

Stressed volume

Importance of

volume

What CVP is a “high CVP”?i.e. at what value does Q plateau?

Bafaqeeh & Magder JCCM 2007

• 66 ICU patients – variety of disorders

• 66 ICU patients – variety of disorders• 135 measurements

• 66 ICU patients – variety of disorders• 135 measurements• Fluid challenges ordered by treating clinician

based on presumed clinical need

based on presumed clinical need• “Successful” fluid challenge = increase in

CVP ≥ 2 mmHg ( n = 118)

based on presumed clinical need• “Successful” fluid challenge = increase in

CVP ≥ 2 mmHg ( n = 118)• Increase in CI ≥ 0.3 L/min/m2 considered

“responders” & < 0.3 “non-responders”

PraCardiacPreload

Pra/CVP

Cardiac output

PraCardiacPreload

Pra/CVP

Cardiac output

Non-flow indications for fluids

• Correct hydration (ie high Na+)• Replete interstitial reserves• Replete unstressed volume reserves

Change in Capacitance(can change by 10-15 ml /kg)

What about a low CVP?

Does fluid responsiveness imply fluid need?...Does fluid responsiveness imply fluid need? S Magder...

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