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FLUID THERAPY

FLUID THERAPY. Body Fluid Compartments :. ICF: 55%~75%. Male (55%) > female (45%) Most concentrated in skeletal muscle TBW=0.6xBW ICF=0.4xBW ECF=0.2xBW. 2/3. X 50~70% lean body weight. TBW. Extravascular  Interstitial fluid. 3/4. 1/3. ECF. Intravascular plasma. 1/4.

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FLUID THERAPY

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  1. FLUID THERAPY

  2. Body Fluid Compartments: ICF: 55%~75% • Male (55%) > female (45%) • Most concentrated in skeletal muscle • TBW=0.6xBW • ICF=0.4xBW • ECF=0.2xBW 2/3 X 50~70% lean body weight TBW Extravascular Interstitial fluid 3/4 1/3 ECF Intravascular plasma 1/4

  3. Total body water (TBW) • TBW varies with age ,gender and body habitus • In adult males= 55% of body weight • In adult female=45% of body weight • In infant = 80% of body weight • Obese patients have less TBW per Kg than lean body adult.

  4. Body compartment fluid 1= Intracellular fluid (ICF)=55% TBW or 30%-40% BW 2= Extracellular fluid (ECF) =45%TBW or 20% BW • Interstitial fluid =15% of body weight • Intravascular fluid or plasma volume = 5% of body weight

  5. Fluid compartments ICF

  6. Fluid compartments ICF Plasma Interstitial ECF

  7. Fluid compartments ICF Plasma Interstitial ECF

  8. Fluid compartments Capillary Membrane ICF Plasma Interstitial ECF

  9. Fluid compartments Capillary Membrane ICF Plasma Interstitial ECF

  10. Fluid compartments Capillary Membrane Cell Membrane ICF Plasma Interstitial ECF

  11. Colloid osmotic pressure Capillary Membrane Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin). Plasma Interstitial ECF

  12. Colloid osmotic pressure Capillary Membrane Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin). Plasma Interstitial ECF

  13. Colloid osmotic pressure Capillary Membrane Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin). The albumin on the plasma side gives rise to a colloid osmotic pressure gradient favouring movement of water into the plasma H2O Plasma Interstitial H2O ECF

  14. Colloid osmotic pressure Capillary Membrane Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin). The albumin on the plasma side gives rise to a colloid osmotic pressure gradient favouring movement of water into the plasma This is balanced out by the hydrostatic pressure difference H2O H2O Plasma Interstitial H2O 120/80 H2O ECF

  15. Starling equation Q=Pc-Posm

  16. Cell Membrane Cell Membrane H2O ICF H2O Interstitial Cell membrane is freely permeable to H20 but

  17. Cell Membrane Cell Membrane H2O ICF H2O Interstitial Na+ K+ Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!

  18. Cell Membrane Cell Membrane H2O ICF H2O Interstitial Na- K+ [K+] =4 Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!

  19. Cell Membrane Cell Membrane H2O ICF H2O Interstitial Na- K+ [K+] =150 [K+] =4 Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!

  20. Cell Membrane Cell Membrane H2O Na+= 144 ICF H2O Interstitial Na- K+ [K+] =150 [K+] =4 Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!

  21. Cell Membrane Cell Membrane H2O Na+= 10 Na+= 144 ICF H2O Interstitial Na- K+ [K+] =150 [K+] =4 Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!

  22. Cations Anions 150 Na+ 100 Cl- ECF 50 HCO3- 0 K+ Protein Ca 2+ Mg 2+ PO43- Organic anion 50 ICF 100 150 Composition of Body Fluids: Osmolarity = solute/(solute+solvent) Osmolality = solute/solvent (290~310mOsm/L) Tonicity = effective osmolality Plasma osmolility = 2 x (Na) + (Glucose/18) + (Urea/2.8) Plasma tonicity = 2 x (Na) + (Glucose/18)

  23. Composition body fluid compartments

  24. Composition of GI Secretions * Average concentration: mmol/L

  25. Sweat:Na 10-70 mEq/LCl 5-60 mEq/LK 1-15 mEq/LMg 0.2-5 mEq/LUrine:Na 50-250 mEq/24hK 30-120 mEq/24hCl 100-250 mEq/24h

  26. Questions to ask before prescribing fluid • Does my patient need intravenous fluid? • Why does my patient need intravenous fluid? • How much and which fluid does he need?

  27. Does he need fluid? • May be drinking • May be on NG feed/TPN – both of these contain fluid which counts as maintenance • May be receiving many drug infusions e.g. antibiotics/paracetamol – can amount to 1+ litre/day • He may only need a bit of maintenance fluid • This calculation should be done for each patient

  28. Why does he need fluid? • Maintenance –water and electrolytes • To supply the daily needs – (e.g. 4% dextrose/0.18%saline/KCl) • Replacement To replace ongoing losses • know the content of the fluid! (usually crystalloid) • Resuscitation - e.g.colloid/blood • To correct an intravascular or extracellular volume deficit

  29. Fluid balance charts Always calculate the balance between inputs and outputs

  30. Sources of daily water loss • Urine 1200-1500 ml/d (30ml/hr) • Sweat 200-400 ml/d • Lungs 500ml/d • Feces 100-200 ml/d

  31. Daily Electrolyte loss Na+ 100 mEq K+ 100 mEq Cl- 150 mEq

  32. Daily Requirements • Water 25-35 ml/kg (30) • Sodium approx 1mmol/kg • Potassium approx 1mmol/kg • Calories minimum 400 Calories (i.e. 100 g dextrose) (calories help to deal with electrolytes normally)

  33. Average Daily Requirements • 70 kg man needs: 2100 ml H2O 70 mmol Na+ 70 mmol K+ 70 mmolCl- • 50kg man needs 1500 ml H2O 50 mmol Na+ 50 mmol K+ 50 mmolCl-

  34. Properties of Commonly Used Crystalloid Solutions

  35. MAINTENANCE If you were on a desert island, would you drink from the sea or a stream? 0.9% saline is not a maintenance fluid

  36. MAINTENANCE • Prescribe maintenance if not drinking >6hrs • 4%/0.18% dextrose/saline with 20mmol potassium in 500ml, or 40mmol in 1 litre (1 litre is cheaper). Or no potassium • Prescribe in ml/hrvia a pump. • The correct volume of this by weight per day for maintenance will provide roughly the correct amount of sodium and potassium for each patient. Maximum 100ml/hr to avoid hyponatraemia.

  37. Potassium • A normal serum potassium is not an indication that the patient does not need potassium – it just means that their stores haven’t run out yet. • A low potassium means that losses are high and body stores very low. • A high potassium may be drug related but commonly is due to acute renal failure – monitor U&Es and do not give extra K. • Remember that TPN, NG feed and food contain K

  38. Sodium • We all need some. However most drugs contain sodium so we don’t need to give a lot in fluids unless the patient is losing it. • Causes of a low Na – too much fluid (commonest cause in hospital!) – fluid restrict • SIADH inappropriate antidiuretic hormone secretion– pneumonia, brain pathology • High Na loss – usually upper GI losses – tend to be obvious

  39. 4 – 2 – 1 Rule • 100 – 50 – 20 Rule for daily fluid requirements • 4 mL/kg for 1st 10 kg • 2 mL/kg for 2nd 10 kg • 1 mL/kg for each additional kg

  40. Maintenance Fluids: Example • 60 kg female • 1st 10 kg: 4 mL/kg x 10 kg = 40 mL • 2nd 10 kg: 2 mL/kg x 10 kg = 20 mL • Remaining: 60 kg – 20 kg = 40 kg 1 mL/kg x 40 kg = 40 mL • Maintenance Rate = 120 mL/hr

  41. REPLACEMENT • Losses should be accounted for with replacement fluid: balanced solution( Hartmanns – Ringers Lactate) • Work out how much patient is losing and replace this with Hartmanns or RL – better to calculate retrospectively and replace. • Fluid prescriptions for losses must be reviewed regularly and updated.

  42. Fluid Deficits • Fasting • Bowel Loss (Bowel Prep, vomiting, diarrhea) • Blood Loss • Trauma • Fractures • Burns • Sepsis • Pancreatitis

  43. LOSSES • Upper GI loss: stomach, small bowel ileostomy/fistula/bile leak: high Na and Cl content – may become hypochloraemic and alkalotic – appropriate to use 0.9%NaCl • Lower GI loss: diarrhoea - lose lots of water and potassium: Hartmanns or RL is appropriate to replace + extra potassium

  44. Insensible Fluid Loss • Evaporative • Exudative • Tissue Edema (surgical manipulation) • Fluid Sequestration (bowel, lung) • Extent of fluid loss or redistribution (the “Third Space”) dependent on type of surgical procedure • Mobilization of Third Space Fluid POD#3

  45. Insensible Fluid Loss • 4 – 6 – 8 Rule • Replace with Crystalloid (NS, LR, Plasmalyte) • Minor: 4 mL/kg/hr • Moderate: 6 mL/kg/hr • Major: 8 mL/kg/h

  46. Replacement Strategies • Sweat: D5¼NS + 5 mEq KCl/L • Gastric: D5½NS + 20 mEq KCl/L • Biliary/pancreatic: LR • Small Bowel: LR • Colon: LR • 3rd space losses: LR

  47. Example • 68 kg female for laparoscopic cholecystectomy • Fasted since midnight, OR start at 8am • Maintenance = 40 + 20 + 48 = 108 mL/hr • Deficit = 108 mL/hr x 8hr = 864 mL • 3rd Space (4mL/kg/hr) = 272 mL/hr

  48. Example • Intra-operative Fluid Replacement of: • Fluid Deficit 864 mL • Maintenance Fluid 108 mL/hr • 3rd Space Loss 272 mL/hr • Ongoing blood loss (crystalloid vs. colloid)

  49. How much fluid does he need? • Weight for maintenance 30-35 ml/kg/24hrs • History, fasting, losses, sepsis, fluid balance charts • Clinical status, current losses, fluid intake, urine output • Electrolytes, Hb (may be raised in dehydration)

  50. Shock • Circulatory failure leading to inadequate perfusion and delivery of oxygen to vital organs • Blood Pressure is often used as an indirect estimator of tissue perfusion • Oxygen delivery is an interaction of Cardiac Output, Blood Volume, Systemic Vascular Resistance

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