Antidiuretic Hormone ADH

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Antidiuretic HormoneADH
Collecting Duct
Hypertonic Interstitial Fluid
Urine
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Calcitonin
Calcium
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Estrogen
Calcium
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Parathormone
Calcium
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Blood pH 7.4(7.35-7.45)

• Blood pH regulated by
• 1. Kidneys
• 2. Lungs
• 3. Buffers in blood

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H Secreted HCO3- Resorbed
Blood
H
Kidney Nephron
Urine
HCO3-
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Kidneys Regulate pH

• Excreting excess hydrogen ions, retain
  bicarbonate
• if pH is too low
• Retaining hydrogen ions, excrete bicarbonate
• if pH is too high

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Lungs Regulate pH

• Breathe faster to get rid of excess carbon
  dioxide if pH is too low
• Carbon dioxide forms carbonic acid in the blood
• Breathe slower to retain carbon dioxide if pH is
  too high

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Carbon Dioxide and Acid
CO2 H2O H2CO3 H HCO3-
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More Carbon Dioxide More Acid Lower pH

• Breathing slower will retain CO2 , pH will
• decrease (more acid)
• Breathing faster will eliminate more CO2 pH will
• increase (less acid)

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Blood pH Drops to 7.3How does the body
compensate?

• Breathe faster to get rid of carbon dioxide
• eliminates acid

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Blood pH Increases to 7.45How does the body
compensate?

• Breathe slower to retain more carbon dioxide
• retains more acid

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The role of ADH

• ADH urinary concentration
• ADH secreted in response to ?
  osmolality
• secreted in response to ? vol
• ADH acts on DCT / CD to reabsorb water
• Acts via V2 receptors aquaporin 2
• Acts only on WATER

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Calculation of osmolality

• Difficult measure add all active osmoles
• Easy sodium x 2 urea glucose
• Normal 280 - 290 mosm / kg

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Fluid shifts in disease

• Fluid loss
• GI diarrhoea, vomiting, etc.
• Renal diuresis
• Vascular haemorrhage
• Skin burns,sweat
• Fluid gain
• Iatrogenic
• Heart / liver / kidney failure

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Prescribing fluids

• Crystalloids
• 0.9 saline - not normal !
• 5 dextrose
• 0.18 saline 0.45 dextrose
• Others
• Colloids
• Blood
• Plasma / albumin
• Synthetics eg gelofusion

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The rules of fluid replacement

• Replace blood with blood
• Replace plasma with colloid
• Resuscitate with crystalloid or colloid
• Replace ECF depletion with saline
• Rehydrate with dextrose

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How much fluid to give ?

• What is your starting point ?
• Euvolaemia ? ( normal )
• Hypovolaemia ? ( dry )
• Hypervolaemia ? ( wet )
• What are the expected losses ?
• What are the expected gains ?

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Signs of hypo / hypervolaemia

• Signs of
• Volume depletion Volume overload
• Postural hypotension
  Hypertension
• Tachycardia Tachycardia
• Absence of JVP _at_ 45o
  Raised JVP / gallop rhythm
• Decreased skin turgor Oedema
• Dry mucosae Pleural effusions
• Supine hypotension Pulmonary oedema
• Oliguria Ascites
• Organ failure Organ failure

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What are the expected losses ?

• Measurable
• urine ( measure hourly if necessary )
• GI ( stool, stoma, drains, tubes )
• Insensible
• sweat
• exhaled

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• Electrolyte (Na, K, Ca) Steady State
• Amount Ingested Amount Excreted.
• Normal entry Mainly ingestion in food.
• Clinical entry Can include parenteral
  administration.

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Case 1

• A 62 year old man is 2 days post-colectomy. He is
  euvolaemic, and is allowed to drink 500ml. His
  urine output is 63 ml/hour
• 1. How much IV fluid does he need today ?
• 2. What type of IV fluid does he need ?

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Case 2

• 3 days after her admission, a 43 year old woman
  with diabetic ketoacidosis has a blood pressure
  of 88/46 mmHg pulse of 110 bpm. Her charts show
  that her urine output over the last 3 days was
  26.5 litres, whilst her total intake was 18
  litres
• 1. How much fluid does she need to regain a
  normal BP ?
• 2. What fluids would you use ?

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Case 3

• An 85 year old man receives IV fluids for 3 days
  following a stroke he is not allowed to eat. He
  has ankle oedema and a JVP of 5 cms his charts
  reveal a total input of 9 l and a urine output of
  6 litres over these 3 days.
• 1. How much excess fluid does he carry ?
• 2. What would you do with his IV fluids ?

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Case 4

• 5 days after a liver transplant, a 48 year old
  man has a pyrexia of 40.8oC. His charts for the
  last 24 hours reveal
• urine output 2.7 litres
• drain output 525 ml
• nasogastric output 1.475 litres
• blood transfusion 2 units (350 ml each)
• IV crystalloid 2.5 litres
• oral fluids 500 ml

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Case 4 cont

• On examination he is tachycardic his supine BP
  is OK, but you cant sit him up to check his
  erect BP. His serum Na is 140 mmol/l.
• How much IV fluid does he need ?
• What fluid would you use ?

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Case 5

• 30yo girl
• SOB, moist cough, chest pain
• ESKD
• Very little urine output
• Has missed dialysis last 3 sessions

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Case 5

• What next?
• Current weight 78kg
• IBW 68kg
• JVP twitching her ear
• No peripheral oedema
• Coarse crackles to mid zones
• BP 240/110
• P 100
• Gallop rhythm
• 4cm of liver in RUQ

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Case 5

• Assessment
• Acute significant overload
• Probably about 10kg

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Case 6

• 55yo lady
• Presents to dialysis for her routine session
• BP 78/30
• History of dizziness for the last 6 hours
• Current weight 58kg
• IBW 59kg

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Case 6

• P 120
• Chest clear
• HS dual
• No oedema
• Admits to 24hours of diarrhoea
• Thirsty
• No JVP visible

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Case 6

• Dehydrated
• Volume constricted
• Hypotensive due to decreased circulating fluid
  volume
• Resuscitation?

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The End
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Acknowledgements

• Paddy Gibson 4th year teaching ppt 2009
• Robert Harris Fluid Balance ppt 2009
• Heather Laird-Fick Fluid and electrolyte
  disorders ppt 2009
• JXZhang Lecture 14 ppt 2009
• Dennis Wormington fundamentals of fluid
  assessment ppt 2009