Antidiuretic Hormone ADH ADH Hypertonic Interstitial Fluid Collecting Duct H2OH2O Urine

Calcitonin Calcium

Estrogen Calcium

Parathormone Calcium

Blood pH = 7.4 ( ) Blood pH regulated by 1. Kidneys 2. Lungs 3. Buffers in blood

H + Secreted HCO 3 - Resorbed Blood Kidney Nephron HCO 3 - H+H+ Urine

Kidneys Regulate pH Excreting excess hydrogen ions, retain bicarbonate –if pH is too low Retaining hydrogen ions, excrete bicarbonate –if pH is too high

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

Carbon Dioxide and Acid CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - Carbonic Acid

More Carbon Dioxide = More Acid = Lower pH Breathing slower will retain CO 2, pH will –decrease (more acid) Breathing faster will eliminate more CO 2 pH will –increase (less acid)

Blood pH Drops to 7.3 How does the body compensate? Breathe faster to get rid of carbon dioxide –eliminates acid

Blood pH Increases to 7.45 How does the body compensate? Breathe slower to retain more carbon dioxide –retains more acid

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 PGPG

Calculation of osmolality Difficult: measure & add all active osmoles Easy = [ sodium x 2 ] + urea + glucose Normal = mosm / kg PGPG

Fluid shifts in disease Fluid loss: –GI: diarrhoea, vomiting, etc. –Renal: diuresis –Vascular: haemorrhage –Skin: burns,sweat Fluid gain: –Iatrogenic: –Heart / liver / kidney failure: PG

Prescribing fluids: Crystalloids: –0.9% saline - not “normal” ! –5% dextrose –0.18% saline % dextrose –Others Colloids: –Blood –Plasma / albumin –Synthetics eg gelofusion PG

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 PGPG

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 ? PG

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

What are the expected losses ? Measurable: –urine ( measure hourly if necessary ) –GI ( stool, stoma, drains, tubes ) Insensible: –sweat –exhaled PGPG

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

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 ? PG

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 ? PG

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 ? PGPG

Case 4: 5 days after a liver transplant, a 48 year old man has a pyrexia of 40.8 o C. 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 PG

Case 4 cont: On examination he is tachycardic; his supine BP is OK, but you can’t 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 ? PG

Case 5 30yo girl SOB, moist cough, chest pain ESKD Very little urine output Has missed dialysis last 3 sessions

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

Case 5 Assessment –Acute significant overload –Probably about 10kg

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

Case 6 P 120 Chest clear HS dual No oedema Admits to 24hours of diarrhoea Thirsty No JVP visible

Case 6 Dehydrated Volume constricted Hypotensive due to decreased circulating fluid volume Resuscitation?

The End

Acknowledgements Paddy Gibson – 4 th 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