dehydrated Pyloric stenosis What is the extent of

1
Fluid compartments and IV Fluid therapy
Late Sciences lecture series Lecture 5

• Mahesh Nirmalan
• Critical Care Unit, Central Manchester Foundation
  Trust
• School of Bio Medicine
• University of Manchester, United Kingdom

2
Objectives

• Distribution of water within the body
• Distribution of electrolytes
• Principles of IV fluid therapy
• Common IV fluids

3
Fluid compartments
60-70 of total body weight is made up of water
4
Exchange of fluid between capillaries and tissues
COP20 mm
32 mm

• Oedema formation
• Definition of generalised oedema
• Definition of localised oedema

12 mm
5
Fluid spaces

• 1st Spacing Normal distribution within ECF and
  ICF
• 2nd spacing accumulation within the interstitial
  compartments oedema formation but available for
  physiological exchange between compartments
• 3rd spacing Accumulation in parts of the body
  where its not available for exchange between the
  different compartments Ascitis, tissue
  inflammation, oedema from burns/surgery

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Composition of body fluids

• Na, Cl-, HCO3- are predominantly in the ECF
• K, Mg2, PO43- are predominantly in the ICF
• The electrolyte composition of plasma and
  interstitial fluids are broadly similar
• The main difference between plasma and
  interstitial fluid is the high protein content in
  the plasma
• All compartments are electrically neutral
• More cations (gt2) in the plasma due to the
  Donnan effect ???
• Slightly more anions in the interstitial fluid
• Change in plasma proteins have important effects
  on cell functions that are poorly understood
• Malnutrition, Nephrotic syndrome,
• critical illness

Na,K ATPase
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The distribution of fluid between the ICF and ECF
compartments is mainly determined by the osmotic
effects of the small inorganic ions Na, Cl-
If the osmotic properties of the ECF is constant
there will be minimal fluid shifts between the
ICF and ECF
8
Distribution of free water

• General increase or decrease in total body water
  will involve all the 3 fluid compartments
• Most of the quantitative effects will be
  buffered by the ICF
• Hypotension is a very late sign of dehydration
• If free water is administered most of the
  administered volume will reach the ICF with very
  little change in plasma volume
• Distribution ratio of free water

ICF 70
In the absence of loss of ECF (vomiting diarrhoea
etc) changes in Na is usually the result of
changes in free water content
9
1 liter 5 Dextrose
Total body water1 liter
ECF1/3 350ml
ICF2/3 650ml
Intravascular 1/5 of ECF70ml
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Fluid distribution within the ECF

• The ECF has a uniform electrolyte composition
• Distribution of fluid between the interstitium
  and plasma is determined by plasma proteins and
  the COP
• Isotonic fluids will dilute plasma proteins and
  reduce COP
• Isotonic fluids will distribute between the
  interstitial fluid compartment and plasma
• Distribution ratio of a litre of isotonic fluid

Plasma 33
Interstitium 66
11
1 Litre 0.9 saline
Total body water
ICF0
ECF1 litre
Interstitial2/3 of ECF650ml
Intravascular 1/3 ECF350 ml
12
1 liter 5 Albumin
Intravascular1 liter
13
IV Fluids
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Current Deficits
Hypernatraemia is a very common feature of free
water loss
Mild C/O Thirst But no clinical signs of
dehydration Up to 5 deficit in TBW Will affect
all fluid compartments
Severe Cardiovascular signs Tachycardia
/hypotension Marked peripheral signs of
dehydration gt15 of TBW
Moderate Objective clinical signs of
dehydration Mucous membranes, skin turgor, mild
tachycardia Reduced UOP 5-15 of TBW
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IV Fluids

• 5 Dextrose Free water
• Dextrose saline
• Commonest cause for hyponatraemia in the surgical
  population
• The myth of 31
• Crystalloids 0.9 NaCl, RLS
• N.saline (150 mmol Na and 150 mMol Cl-)
• Not very physiological
• Hyperchloraemic acidosis.Why?
• Colloids Gelatin based, starch based, albumin
• Blood and blood products

16
Ringers Lactate solution

• Na 130mMol/l
• Cl- 109mMol/l
• Lactate 28mMol/l
• K 4mMol/l
• Ca2 3mEq/l

17
Case study

• Elderly male Height 5 feet 11 inches
• Weight 52Kg
• H/O duodenal ulcer
• Abdominal pain
• Severe vomiting of 3 weeks duration
• Unable to retain any food or drinks
• Wasted, dehydrated

DD??
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Pyloric stenosis

• What is the extent of dehydration would you
  expect in this patient?
• What would be the clinical signs?
• What electrolyte changes would you expect?
• How much fluid?
• What fluid?
• Over what period?

19
22 years old university student65 KgLife long
Lib Dem supporterFeels betrayed by the formation
of the new Libservative government72 hours of
hunger strike opposite the LibDem HQ

• What would the fluid deficit be?
• Serum electrolytes?
• What is the replacement fluid?
• Over how long?

20
72 years old female

• Radical hysterectomy in the morning
• 2 litres blood loss
• 2 litres blood transfused
• 5 dextrose infusion 75ml/hr
• Called at 2 AM to review as she has not passed
  urine for the past 5 hours
• Conscious, cold and clammy
• pH 7.31 BE -9 lactate 2.2 Hb 14.3
• Pulse 122/min BP 70/45 RR 18/min

21
??