Fluid Management

Nigel White Consultant ICU

Royal Bournemouth Hospital

Advanced fluid management

Fluid management

• Normal distribution of fluids and electrolytes

• Composition of replacement fluids

• Daily requirements (including paeds)

• Abnormal losses

• Dehydration

Advanced fluid management

NICE Guidance

• https://www.nice.org.uk/guidance/cg174

Advanced fluid management

Distribution of total body water

Total body water42 L BWx0.6

Intracellular fluid28 L BWx0.4

Extracellular fluid14 L BWx0.2

Intravascular fluid3 L BWx0.05

Interstitial fluid11 L BWx0.15

Distribution of total body water

Total body water42 L BWx0.6

Intracellular fluid28 L BWx0.4

Extracellular fluid14 L BWx0.2

Intravascular fluid3 L BWx0.05

Interstitial fluid11 L BWx0.15

Colloid/Blood

CrystalloidDextrose

Composition of fluid compartments

plasma interstitial intracellular

CationsNa 140 146 12K 4 4 150Ca 5 3 10Mg 2 1 7

AnionsCl 103 104 3HCO 24 27 10SO4 1 1 -HPO4 2 2 116Protein 16 5 40

Contents of common iv fluidsSolution Electrolyte content Glucose

(mmol/L)

Saline 0.9% Na+ 154 Cl- 154 0

Glucose 4%/ Na+ 31 Cl- 31 40g/lsaline 0.18%

Glucose 5%/ Na+ 77 Cl- 77 50g/lSaline 0.45%

Glucose 5% Na+ Nil Cl- Nil 50g/l

Hartman’s Na+ 131 Cl- 112 0solution K+ 5 HCO3

- 29 Ca2+ 4 (as lactate)

Fluid types

• Crystalloid: aqueous solutions of mineral salts or other water-soluble molecules.

• For the purpose of fluid management we think of crystalloid as aqueous solutions of mineral salts

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Fluid types

• Colloid• Contains large molecule MW>30KDa• Remains in IV space (?)• Albumin mw 30,000

– 4.5% expensive,

• Gelatin mw 30,000– Short circulatory half life

• Starch mw 100-200,000.– Long circulatory half life

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Colloid

• No evidence for any benefit for gelatins or albumin

• Starch appears increasingly to be associated with renal failure and coagulopathy

• Evidence for increased mortality in sepsis • Have been withdrawn in RBH (and Poole)• You have to give more crystalloid to achieve

same resus goals but ratio seems to be about 1.4:1

How to use fluids

• Calculate fluids

• Calculate electrolyte requirements

• NICE suggest add dextrose to avoid ketosis

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Daily fluid requirements

• 4/2/1 ratio (Holliday Segar)

• 0-10kg 4mls/kg/hr (100mls/kg/day)

• 10-20kg 2mls/kg/hr (50mls/kg/day)

• >20kg 1ml/kg/hr (25mls.kg/day)

• Works for children as well (except neonates)

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Daily fluid requirments

• For adults 1-1.25mls/kg/hr

• NICE suggest 25-30mls/kg

• Ideal body weight is best if overweight

• There are many formulae for ibw

• Should seldom have more than 3l/day

• Consider 20-25ml/kg/day if frail or heart failure

Daily electrolyte requirements

Advanced fluid management

Weight Na mmol/kg/day

K mmol/kg/day

0-10 kg 2-4 1.5-2.5

10-20 kg 1-2 0.5-1.5

>20 kg 0.5-1 0.2-0.7

•For adults

•Na 1-2mmol/kg/day (NICE say 1mmol/kg/day)

•K 1mmol/kg/day

Glucose

• NICE suggest give 50-100g/day of iv glucose to limit starvation ketosis

Why do children need more fluid and electrolytes?

• Larger BSA so higher insensible losses

• Relatively immature kidneys so less able to concentrate urine and retain Na and K

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How to give maintenance fluids??

• I would suggest

• Calculate hourly rate

• In adults give this as 4%Dex/0.18%Saline with 40mmol/L KCL.

• In children use either 5%Dex/0.45%Saline with 40mmol/L KCL or 5%Dex/0.9%Saline

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Why the difference?

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RBH

• 0.18% Saline 4% dextrose is no longer available in places that treat children (A/E, eye unit.

• Replaced with 0.45%Saline/5% dextrose.• Guidelines on intranet (soon). Seek senior advice• Increasingly we think 0.45%Saline/5%dextrose

may be a better solution for adults as well.

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However

• These calculations are based on assumptions of normal fluid and electrolyte losses

• By definition hospital patients are not “normal” and may have abnormal losses whether apparent or not.

• Any patient receiving iv fluids should – have daily urea and electrolytes and their prescription altered

according to the results.

– have an accurate fluid balance chart

– Have twice weekly weightsThe

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Assessing volume status

• 2 concepts

• Shock – Refers to intravascular space

• Dehydration– Whole body fluid loss

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What is the difference

• Shock kills. – Loss of 20mls/kg from you intravascular space

is >25% loss of circulating fluid volume.

• Dehydration kills but slower– Loss of 20mls/kg from your total body water

represents about 3% of your total body water

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Shock

• Definition– Failure of delivery of oxygen (and nutrients) to

vital organs

• Effects– Rapid onset of tissue hypoxia and acidosis

• Outcome– Organ damage and death.

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What causes shock?

• Low cardiac output. Heart is either– Empty (hypovolaemic)– Failing (cardiogenic)

• Septic shock– Initially warm periphery (low SVR)– As shock develops periphery cool– Mostly hypovolaemic, rarely cardiogenic

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Diagnosis of hypovolaemic shock

• Clinical– Look pale/sweaty/cool peripheries/prolonged cap return

(vasoconstriction)– Organ perfusion– Pulse– Blood Pressure– Urine output

• Tests– Blood gas

• Lactate• Base excess

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Treatment of hypovolaemic shock

• Rapid expansion of intravascular volume

• Options– Crystalloid– Blood

• There is no place for dextrose containing solutions in shock resuscitation.

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Resuscitation of hypovolaemic shock

• Blood– Only if ongoing losses and Hb less than 100 or if

ongoing tissue ischamia, eg angina– Otherwise consider if Hb less than 80 1:1

• Colloid– NO!!– No convincing evidence better than crystalloid

• Crystalloid– Cheap, safe

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Resuscitation of shock

• CONTINUALLY REASSESS!!!!

• IF YOU HAVE GIVEN MORE THAN 40MLS/KG OF CRYSTALLOID OR COLLOID YOU MUST CALL HELP. THIS IS A SERIOUSY SHOCKED PATIENT WHO NEEDS ICU/HDU AND FURTHER Ix

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Diagnosis of cardiogenic shock

• Clinical– Look pale/sweaty/cool peripheries/prolonged cap return

(vasoconstriction)– Organ perfusion– Pulse– Blood Pressure– Urine output

• Tests– Blood gas

• Lactate• Base excess

• How to differentiate– Signs of failure (CVP, basal crackles)

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Management of cardiogenic shock

• Inotropes

• Mechanical aids

• Careful manipulation of volume status

• ICU/HDU or CCU

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Hypovolaemic shock is bad.So avoid it

• Assess losses and replace them

• Inpatients fluid balance charts– Often works of fiction– Use for rough guidance only– Losses from upper/lower GIT often missed– Assess patient.

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Avoiding hypovolaemia

• Replace losses with crystalloid

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Third space losses

• Third space is tissue oedema. It is unseen and occurs with any tissue damage be it trauma, elective surgery or serious illness

• It initially cannot be seen

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Third space losses

• Remember much third space loss is not lost but redistributed.

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How to avoid fluid overload

• Aggressive fluid loading in resuscitation with crystalloid

• After resuscitation give maintenance fluids

• Consider decreasing fluids to 80% if patient appears overloaded

• Diuretics may be necessary

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Dehydration

• Definition– Loss of total body water (and electrolytes)

• Effects– When severe patients become shocked

• Outcome– Rarely causes death in the absence of shock

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How to assess dehydration

• It is practically impossible

• The only reliable way is weight loss

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Dehydration

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Signs / Symptoms

Mild <5% Moderate 5-10%

Severe >10%

Urine output ↓ ↓↓ ↓↓↓

Dry mouth - + ++

Skin turgor normal ↓ ↓

Cardiac output

Normal Normal May be low

Ant fontanelle

Normal Sunken Sunken

Questions

?Advanced fluid management

Summary

• Fluids are drugs

• Know what and how you are prescribing

• There is no formula which accurately predicts requirements

• Do the nice on line learnign

• Regular review

• Daily u + e s

Advanced fluid management

Advanced fluid management