Fluid balance
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Fluid Balance. Outline of Talk. Fluid compartments What can go wrong Calculating fluid requirements Principles of fluid replacement Scenarios. Where is the Fluid?. Where is the Fluid?. 60% of body weight is fluid 2/3 is intracellular and 1/3 extracellular

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Fluid balance

Fluid Balance


Outline of talk

Outline of Talk

  • Fluid compartments

  • What can go wrong

  • Calculating fluid requirements

  • Principles of fluid replacement

  • Scenarios


Where is the fluid

Where is the Fluid?


Fluid balance

Where is the Fluid?

  • 60% of body weight is fluid

  • 2/3 is intracellular and 1/3 extracellular

  • 2/3 of extracellular is interstitial and 1/3 intravascular


Fluid balance

So for a 75kg person…

Intravascular

5 litres

  • 60% of body weight is fluid

  • 2/3 is intracellular and 1/3 extracellular

  • 2/3 of extracellular is interstitial and 1/3 intravascular

Interstitial

10 litres

Intracellular

30 litres


What is normal fluid intake and output

What is normal fluid intake and output?


What is normal fluid intake and output1

What is normal fluid intake and output?

Renal losses

1500ml/day

Insensible losses

500ml/day

Intravascular

5 litres

Normal intake

2000ml/day

Interstitial

10 litres

Intracellular

30 litres


What can go wrong

What can go Wrong?


What can go wrong 1 imbalance between input and output

What can go wrong? 1. Imbalance between input and output

XS losses

Vomiting

Diarrhoea

Drains

Fever

Intravascular

5 litres

Inadequate or

overhydration

Interstitial

10 litres

Poor Output

Oliguria

Intracellular

30 litres


What can go wrong 2 redistribution

What can go wrong? 2. Redistribution

Intravascular

Intravascular

pressure

Capillary

leakage

Plasma oncotic pressure

(hypoalbiminaemia)

Peripheral +/- pulmonary oedema

Interstitial


What can go wrong 3 osmolar problems

What can go wrong? 3. Osmolar problems

Interstitial

Hypotonic fluid causes

water to move into

intracellular space

Hypertonic fluid causes

water to move out

of intracellular space

Intracellular

Water move in and out of intracellular space

with changes in extracellular osmolarity


Purpose of fluid replacement

Purpose of Fluid Replacement


Purpose of fluid replacement1

Purpose of Fluid Replacement

To maintain tissue perfusion by:

1) Maintaining intravascular fluid volume of about 5 litres

2) Correcting any deficits

3) Allowing for ongoing losses


How to calculate daily fluid requirements

How to Calculate Daily Fluid Requirements?


Fluid balance

How to Calculate Daily Fluid Requirements

Requirement =

Deficit +

Maintenance +

Ongoing Losses


Assessment of the deficit volume status

Assessment of the Deficit (Volume Status)


Assessment of volume status are they dry wet or euvolaemic

Assessment of Volume Status – are they dry, wet or euvolaemic?

  • History

  • Pulse

  • BP incl Postural BP

  • Skin Turgor

  • Mouth Dryness

  • Capillary Refill

  • JVP

  • Third sound and MR


Assessment of volume status are they dry wet or euvolaemic1

Assessment of Volume Status – are they dry, wet or euvolaemic?

  • Lung bases

  • SpO2

  • Body Weight

  • Urine Output

  • Fluid Balance Chart

  • Serum Biochem

  • Urine Biochem


Assessment of volume status are they dry wet or euvolaemic2

Assessment of Volume Status – are they dry, wet or euvolaemic?

  • Lung bases

  • SpO2

  • Body Weight

  • Urine Output

  • Fluid Balance Chart

  • Serum Biochem

  • Urine Biochem


Serum biochem the urea creatinine ratio

Serum Biochem- The Urea:Creatinine Ratio

  • Normal Blood Urea =

  • Normal Serum Creatinine =

  • Normal Urea:Creatinine Ratio =


Urea creatinine ratio

Urea:Creatinine Ratio

  • Normal Blood Urea = 2-7mmol/l

  • Normal Serum Creatinine = 40- 120umol/l

  • Normal Urea:Creatinine Ratio = 60-80:1

  • Raised Ratio >100:1 suggests patient dehydrated. Why?


Why u c ratio 100 1 suggests dry

Why U:C Ratio >100:1 suggests Dry

  • Both urea and creatinine freely filtered by glomerulus

  • Urea reabsorbed passively with Na and water by PCT when dehydrated

  • No such mechanism exists for creatinine which instead is secretedby PCT

  • This leads to U:C ratio >100:1 when dry


Urine biochemistry

Urine Biochemistry

Pre-Renal

Established ATN

>40mmol/l

<350mmol/l

<20mmol/l

>500mmol/

Urine Na

Urine Osm

In practice we hardly ever request urine biochem


Assessment of volume status

Assessment of volume status

Hypovolaemic

(dehydrated)

Hypervolaemic

(overloaded)


Assessment of volume status1

Assessment of volume status

Hypovolaemic

(dehydrated)

Hypervolaemic

(overloaded)

Raised JVP

S3 with functional MR

Bibasal crackles

Periph/sacral oedema

Hypertension

  • Reduced skin turgor

  • Dry mouth

  • Tachycardia

  • Postural fall BP

  • Poor cap refill


Fluid balance

How to Calculate Daily Fluid Requirements

Requirement =

Deficit +

Maintenance +

Ongoing Losses


Maintenance requirements day in healthy adult

Maintenance Requirements/day in Healthy Adult?

Water =

Sodium =

Potassium =


Maintenance requirements day in healthy adult1

Maintenance Requirements/day in Healthy Adult

Water 1.5 - 2.5 litres

Sodium 50 - 100mmol

Potassium 40 - 80mmol


Fluid balance

How to Calculate Daily Fluid Requirements

Requirement =

Deficit +

Maintenance +

Ongoing Losses


Measuring losses

Measuring Losses

  • Fluid balance charts notoriously inaccurate

  • Insensible losses can increase significantly with exercise, fever, raised ambient temperature

  • Interstitial (third space) losses difficult to quantify


Composition of losses

Composition of Losses

  • Vomit is mostly HCl – contains very little K and a lot of chloride (hypokalaemia is due to renal K wasting)

  • Diarrhoea is more alkaline – contains quite a lot of K and no chloride


Two other things it helps to know when judging fluid requirements

Two Other Things it Helps to Know when Judging Fluid Requirements?

Deficit

Maintenance

Ongoing Losses +


Two other things it helps to know when judging fluid requirements1

Two Other Things it Helps to Know when Judging Fluid Requirements

Deficit

Maintenance

Ongoing Losses

Cardiac Status

Kidney Function


What replacement fluids are available

What Replacement Fluids are Available?


What replacement fluids are available1

What Replacement Fluids are Available?

Crystalloid Colloid Blood


What replacement fluids are available2

What Replacement Fluids are Available?

Crystalloid

  • Saline 0.9%

  • Hartmanns

  • Dextrose 5%


So what s in the fluid

So What’s in the Fluid?


So what s in the fluid1

So What’s in the Fluid?

Sodium

mmol/l

Potassium

mmol/l

Chloride

mmol/l

Osmolarity

mosm/l

Other

per litre

Plasma

Saline 0.9%

Dextrose 5%

Hartmann’s

Gelofusin

136-145

154

0

131

154

98-105

154

0

111

125

280-300

308

278

275

290

3.5-5.2

0

0

5

<0.4

Dextrose 50g

Lactate 29mmol

Gelatin 40g


Where does the fluid go volume of distribution

Where does the Fluid Go? (Volume of Distribution)


Where does the fluid go volume of distribution1

Where does the Fluid Go? (Volume of Distribution)

Saline

Hartmanns

Gelofusine

Dextrose 5%

Intravascular

5 litres

Interstitial

10 litres

Intracellular

30 litres


Principles of fluid replacement

Principles of Fluid Replacement

  • Saline v Dextrose

  • Saline v Hartmanns

  • Crystalloid v Colloid

  • Blood

  • Fast v Slow


Saline v dextrose

Saline v Dextrose


Saline v dextrose1

Saline v Dextrose

  • Saline more effective than dextrose for fluid resuscitation because sodium content restricts distribution to extracellular space. Dextrose loses osmotic effect of glucose as it is metabolised and so moves into intracellular sace


Saline v hartmanns

Saline v Hartmanns


Saline v hartmanns1

Saline v Hartmanns

  • Both used to expand the intravascular space and both distributed throughout the interstitial space

  • Saline preferred if hypochloraemic. Large volumes may cause hyperchloraemic acidosis

  • Hartmanns is the more physiological of the two. Only clear contraindications are tight brains (risk of cerebral oedema) and hyponatraemia (because not enough sodium). Risks of lactic acidosis and hyperkalaemia are probably exaggerated


Crystalloid v colloid

Crystalloid v Colloid


Crystalloid v colloid1

Crystalloid v Colloid

  • Colloid better at expanding intravascular space (1 litre gelofusine equiv 2 litres saline) and probably preferred as initial volume expander in haemorrhagic shock while waiting for blood. Otherwise no clear indication to give one over the other.


Blood

Blood


Blood1

Blood

  • Indicated to correct hypovolaemia due to blood loss

  • NB Aggressive correction of anemia in critically ill patients does not improve outcome – target Hb 70-90g/l gives same outcomes as target Hb 100-120g/l


Fast v slow

Fast v Slow


Fast v slow1

Fast v Slow

  • Aim is to give as much as required in order to restore circulating blood volume, and by implication tissue perfusion, as quickly as possible

  • NB 4 hourly bags usually run 5 hourly and then only deliver 100ml/hr, ie < 1/3 of a can of coke per hour.

  • Remember to choose the correct venflon


Choose the correct venflon

Choose the Correct Venflon


Scenarios

Scenarios

  • Maintenance IV Fluid

  • Pre-op fluids

  • Septic shock

  • Massive blood loss from trauma

  • AKI but not shocked

  • Post obstructive diuresis/recovery from ATN

  • Cardiorenal Failure

  • Diagnosis of hypovolaemia in doubt

  • XS losses from vomiting

  • XS losses from diarrhoea


Fluid balance

Prescribe Maintenance IV Fluid for a healthy adult to give 1.5-2.5 litres water, 50-100mmol sodium and 40mmol potassium


Maintenance iv fluid for a healthy adult

Maintenance IV Fluid for a Healthy Adult

  • Dextrose 5% + 20mmol K

  • Dextrose 5%

  • Saline N + 20mmol K

  • Dextrose 5%

Rx 6 hourly to give 2 litres water,

how much sodium and 40mmol K?


Maintenance iv fluid for a healthy adult1

Maintenance IV Fluid for a Healthy Adult

  • Dextrose 5% + 20mmol K

  • Dextrose 5%

  • Saline N + 20mmol K

  • Dextrose 5%

Rx 6 hourly to give 2 litres water,

77mmol sodium and 40mmol K


Pre op fluids

Pre-Op Fluids


Pre op fluids1

Pre-Op Fluids

Clear fluids and calorific drinks can safely be given until 2 hours before GA

If bowel prep given (and it isnt always) then fluid replacement will be required

People with diabetes will require variable rate insulin infusion (previously known as sliding scale)


Septic shock

Septic Shock


Septic shock1

Septic Shock

  • Rx Saline, Hartmann’s or Gelofusine (probably doesn’t matter which) 20ml/kg as quickly as possible

  • Vasoconstrictor inotropes such as Noradrenaline also often required

  • NB Fluids are an important part of a package of measures (the Sepsis Six) required to treat septic shock effectively


Massive blood loss from trauma

Massive Blood Loss from Trauma


Massive blood loss from trauma1

Massive Blood Loss from Trauma

  • Rx Gelofusine 20ml/kg fast until blood products arrive. Use O neg blood if delay rather than more gelofusin

  • NB there is no absolute indication to give Gelofusine here though it will expand the intravascular space for longer than an equivalent volume of saline


Minimum volume resuscitation

Minimum Volume Resuscitation

  • Better to restore a recordable BP than a normal BP. For example in AAA where unable to control bleeding if you fill to achieve a normal intravascular volume then patient more likely to continue bleeding. Also no clotting factors in gelofusine or crystalloid. So Rx gelofusine 20ml/kg then O neg blood if cross match blood still unavailable


Aki but not shocked

AKI but not shocked


Aki but not shocked1

AKI but not shocked

  • Rx Saline or Hartmann’s

    - in the absence of any signs of fluid overload the default should be 1 litre in one hour, 1 litre in 2 hours, 1 litre in 4 hours then review

  • Decision on whether Saline or Hartmann’s will be determined to an extent by the serum K and the likelihood it might rise further


Post obstructive diuresis recovery from atn

Post Obstructive Diuresis/ Recovery from ATN


Post obstructive diuresis recovery from atn1

Post Obstructive Diuresis/ Recovery from ATN

  • Recovery from obstruction/ATN usually characterised by polyuria of up to 5 litres poor quality urine daily, preceding the fall in urea and creatinine

  • ‘500mls plus previous days output’ doesn’t work because patients will start mobilising the XS interstitial fluid they have accumulated during acute illness

  • eg if passing 5 litres/day try 4.5 litres intake while checking U&E daily. If both U and C falling proportionately then prescription probably ok.


Cardiorenal failure

Cardiorenal Failure


Cardiorenal failure1

Cardiorenal Failure

  • Rx trial of frusemide IV with salt and water restriction if cardiac failure predominates, recognising that worsening kidney function may be the price you have to pay in order to keep lungs free of fluid

  • Rx cautious trial of fluid if renal failure predominates, recognising that peripheral oedema may be an acceptable compromise in the trade off between heart and kidneys

  • This is usually tricky requiring senior help and sometimes dialysis


Diagnosis of hypovolaemia in doubt

Diagnosis of Hypovolaemia in Doubt


Diagnosis of hypovolaemia in doubt1

Diagnosis of Hypovolaemia in Doubt

  • Rx bolus of 250mls N Saline or Gelofusin over 5-10 mins (ie squeezed in) with measurement of HR, BP, Cap Refill, CVP if monitored, before and 15 mins after infusion. If vital signs improve then further bolus likely to be required


Xs losses from vomiting

XS losses from Vomiting


Xs losses from vomiting1

XS losses from Vomiting

  • Rx Saline 0.9% or Hartmann’s and appropriate K supps with maintenance Dextrose 5%

  • Vomit contains mainly HCl so patients likely to be hypochloraemic. If so then Hartmann’s doesn’t contain enough chloride


Xs losses from diarrhoea

XS losses from Diarrhoea


Xs losses from diarrhoea1

XS losses from Diarrhoea

  • Rx Hartmann’s and appropriate K supps with maintenance Dextrose 5%

  • Diarrhoea doesn’t contain chloride so risk of hyperchloraemia with Saline

  • Same advice applies for ileostomy, small bowel fistula, ileus, bowel obstruction


Summary

Summary

  • To be written!


Question 1

Question 1

You are called to the receiving ward to write up more iv fluids for Mrs S age 65. She is currently nil by mouth and is now awaiting a second day for (delayed) endoscopy after a small nonhaemodynamically significant haematemesis.

Well with no other PMH; MEWS 0

Hb unchanged at 12.5. U+E all n range


Fluid balance

What will you prescribe?


Typical maintenance fluids

Typical Maintenance Fluids

How much and how fast?

2L

6 hourly 500 ml bags

2:1 dextrose:saline 40-60 mmol K


Example typical maintenance fluids

Example Typical Maintenance Fluids

500 ml 5% dextrose 6 hours 20 mmol KCl

500 ml 5% dextrose 6 hours

500 ml N saline 6 hours 20 mmol KCl

500 mls 5% dextrose


Who gets maintenance fluids

Who gets maintenance fluids?

Patient with normal renal function with upset in normal water intake eg pre-operatively

Do not already have upset in water or electrolyte balance

Special circumstances need greater individualised care


Question 2

Question 2

  • You are asked to write up fluids for a 60 year old man who has diarrhoea. Nurses concerned “looks a bit dry.” U+E checked previous day were N.

  • Weight is 70 kg

    • BP 120/70 mmHg

    • PR 80/min

    • Mucous Membranes dry. Skin turgor seems normal and CRT 2 secs. Chest Clear.

    • Oral intake minimal with faecal output of 1000 ml a day

    • Urine output 100 ml in the last 3 hours. Managed 1200 yesterday


Fluid balance

What will you prescribe?


Prescription suggestion

Prescription-suggestion

1 L NaCL 0.9% - 4hrs

500 ml Dextrose 5 % - 4 hrs + 20mmol KCL

500 ml Dextrose 5 % - 4hrs

500 ml NaCL 0.9% - 4hrs + 20 mmol KCL

500 ml Dextrose 5% - 4hrs

500ml Dextrose 5 % + 20 mmol KCL -4hrs

Total in 24 hours = 3. 5 L

CHECK U/Es and Reassess


Question 3

Question 3

You are with your senior assessing a new admission. Mrs D aged 50 has Crohns Disease and has not been very well for 5 days.

She has been passing large volumes of liquid stool into her colostomy bag and has had a very poor oral intake of fluids.

Poor urine volumes


Question 3 cont

Question 3 cont

Mucous membranes dry, reduced skin turgour eyes sunken

CRT 4 secs

P 86 BP 105/70

Urea 17 creat 128

Senior says she is severely dehydrated and wants you to write up appropriate fluid


What would be an appropriate regime for the severely dehydrated patient

What would be an appropriate regime for the severely dehydrated patient?

  • 1L saline 1 hour

  • 1L 2 hours

  • 1L 4 hours


Question 4

Question 4

You are asked to see a 60 year old male who is 2 days post laparotomy who has stopped passing urine


Fluid balance

Let’s consider if it was oliguria?


Question 5

Question 5

SEVERE SEPSIS

  • A 30 year old lady attends AMU with a 3 day history of cough, breathlessness and temp 39. On arrival she has

    • BP 80/40mmHg

    • PR 120/min

    • Resp Rate 35

    • Clinically dry

    • L Basal Bronchial Breathing

    • Urea 15.0 with Creatinine 150

    • Platelets 98 and abnormal clotting


Scenario

Scenario

Mrs N 85 y resident nursing home

Less well for 1 week

Poor oral intake and intermittant diarrhoea

This morning, staff of nursing home difficulty waking her

Sleepy and confused

PMH angina

osteoporosis

R # NOF 2008 hemi-arthroplasty

DH aspirin 75 mg

alendronate 70 mg weekly

paracetamol prn


Fluid balance

GCS E3 M6 V4 looks very dry p 80 BP 120/70 T 37 O2 sats

Reduced skin turgor

No JVP

No localising signs, no neck stiffness

Little else to find despite full examination of CVS, RS, GIS and CNS


Fluid balance

Differential?

Vascular event? Head injury?

Infection – respiratory, UTI, GI source ?

meningitis??

Bowel infarction?

Investigations – Na 165 mmol/L

HYPERNATRAEMIA


Scenario1

scenario


Fluid balance

Mr P 70 y day 2 post TURP

Previously well

Increasingly confused and agitated

Called to see him

What goes through your mind?

Drug effect – new or withdrawal?

Infection?

Hypoxic – PTE, pneumonia

“Silent” MI

Glucose?


Fluid balance

Na 121 mmol/L

previous U+E pre-op N 141mmol/L


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