Surgery 6th year, Tutorial (Dr. AbdulWahid)

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Oct. 26th, 2011

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  • Fluid deficits may occur across all compartments, or may occur in any one of them: Water loss (dehydration) depletes all compartments equally. This leads to hypernatremic dehydration. Common examples include diabetes insipidus, osmotic diuresis (e.g. uncontrolled hyperglycemia), osmotic diarrheas. A tendency towards hypernatremia is usually followed by intense thirst and rapid restoration of the fluid deficit. However, when access to free water is restricted (demented or ventilated patients), hypernatremic dehydration develops. 2. Salt and water loss (isotonic loss) may lead to depletion of extracellular fluid. Examples include burns, ascites, secretory diarrheas (cholera), diuretic therapy and third spacing. 3. Intravascular fluid loss is seen with acute hemorrhage
  • Surgery 6th year, Tutorial (Dr. AbdulWahid)

    1. 1. Fluid & Electrolytes Management <ul><li>Component & composition of body </li></ul><ul><li>fluid </li></ul><ul><li>Mechanisms of fluid homeostasis </li></ul><ul><li>Parenteral fluid therapy </li></ul>
    2. 2. Fluid and electrolyte balance is an extremely complicated thing.
    3. 4.
    4. 5.
    5. 6.
    6. 7.
    7. 8. Solutes – dissolved particles <ul><li>Electrolytes – charged particles </li></ul><ul><ul><li>Cations – positively charged ions </li></ul></ul><ul><ul><ul><li>Na + , K + , Ca ++ , H + </li></ul></ul></ul><ul><ul><li>Anions – negatively charged ions </li></ul></ul><ul><ul><ul><li>Cl - , HCO 3 - , PO 4 3- </li></ul></ul></ul><ul><li>Non-electrolytes - Uncharged </li></ul><ul><ul><ul><li>Proteins, urea, glucose, O 2 , CO 2 </li></ul></ul></ul>
    8. 9. Composition of Body Fluids: <ul><li>Osmolarity = solute/(solute+solvent) </li></ul><ul><li>Osmolality = solute/solvent (290~310mOsm/L) </li></ul><ul><li>Tonicity = effective osmolality </li></ul><ul><li>Plasma osmolility = 2 x (Na) + (Glucose/18) + (Urea/2.8) </li></ul><ul><li>Plasma tonicity = 2 x (Na) + (Glucose/18) </li></ul>Ca 2+ Mg 2+ K + Na + Cl - PO 4 3- Organic anion HCO 3 - Protein 0 50 50 100 150 100 150 Cations Anions ECF ICF
    9. 10.
    10. 12.
    11. 14. Regulation of Fluids: <ul><li>Renal sympathetic nerves </li></ul><ul><li>Renin-angiotensin- </li></ul><ul><li>aldosterone system </li></ul><ul><li>Atrial natriuretic peptide (ANP) </li></ul>
    12. 16. GI secretions Volume (ml) per day <ul><li>Saliva 1500 </li></ul><ul><li>Gastric 2500 </li></ul><ul><li>Bile 500 </li></ul><ul><li>Pancreatic 700 </li></ul><ul><li>Intestinal 3000 </li></ul><ul><li>TOTAL 8000 </li></ul>
    13. 17. Composition of GI Secretions: * Average concentration: mmol/L 0 40 30 60 100-9000 Colon 115 75 (54~95) 5 (3~7) 140 (113~185) 100-800 Pancreas 35 100 (89~180) 5 (3~12) 145 (131~164) 50-800 Bile 30 104 (43~137) 5 (2~8) 140 (80~150) 3000 Ileum 0 80 5 140 100~2000 Duodenum 0 130 (8~154) 10 (0~32) 60 (9~116) 1500 (100~4000) Stomach 30 10 (8~18) 26 (20~30) 10 (2~10) 1500 (500~2000) Salivary HCO 3 - Cl - K + Na +* Volume (ml/24h) Source
    14. 19. <ul><li>Crystalloid solutions – </li></ul><ul><li>clear fluids made up of water and electrolyte solutions; Will cross a semi-permeable membrane e.g Normal, hypo and hypertonic saline solutions; Dextrose solutions; Ringer’s lactate and Hartmann’s solution. </li></ul>
    15. 20. <ul><li>Colloid solutions – </li></ul><ul><li>Gelatinous solutions containing particles suspended in solution. These particles will not form a sediment under the influence of gravity and are largely unable to cross a semi-permeable membrane. e.g. Albumin, Dextrans, Hydroxyethyl starch [HES]; Haemaccel and Gelofusine </li></ul>
    16. 21. Saline Solutions <ul><li>(1) 0.9% Normal Saline – Think of it as ‘Salt and water’ </li></ul><ul><li>Principal fluid used for intravascular resuscitation and replacement of salt loss e.g diarrhoea and vomiting </li></ul><ul><li>Contains: Na+ 154 mmol/l, K+ - Nil, Cl - - 154 mmol/l; But K+ is often added </li></ul><ul><li>IsoOsmolar compared to normal plasma </li></ul><ul><li>Distribution: Stays almost entirely in the Extracellular space </li></ul><ul><li> Of 1 litre – 750ml Extra cellular fluid; 250ml intravacular fluid </li></ul><ul><li>So for 100ml blood loss – need to give 400ml N.saline [only 25% remains intravascular] </li></ul><ul><li>(2) 0.45% Normal saline = ‘Half’ Normal Saline = HYPOtonic saline </li></ul><ul><li>Reserved for severe hyperosmolar states E.g. severe dehydration </li></ul><ul><li>Leads to HYPOnatraemia if plasma sodium is normal </li></ul><ul><li>May cause rapid reduction in serum sodium if used in excess or infused too rapidly. This may lead to cerebral oedema and rarely, central pontine demyelinosis ; Use with caution! </li></ul><ul><li>(3) 1.8, 3.0, 7.0, 7.5 and 10% Saline = HYPERtonic saline </li></ul><ul><li>Reserved for plasma expansion with colloids </li></ul><ul><li>In practice rarely used in general wards; Reserved for high dependency, specialist areas </li></ul><ul><li>Distributed almost entirely in the ECF and intravascular space. This leads to an osmotic gradient between the ECF and ICF, causing passage of fluid into the EC space. This fluid distributes itself evenly across the ECF and intravascualr space, in turn leading to intravascular repletion. </li></ul><ul><li>Large volumes will cause HYPERnatraemia and IC dehydration. </li></ul>
    17. 22. Dextrose solutions <ul><li>(1) 5% Dextrose (often written D5W) – Think of it as ‘Sugar and Water’ </li></ul><ul><li>Primarily used to maintain water balance in patients who are not able to take anything by mouth; Commonly used post-operatively in conjuction with salt retaining fluids ie saline; Often prescribed as 2L D5W: 1L N.Saline [‘Physiological replacement’ of water and Na+ losses] </li></ul><ul><li>Provides some calories [ approximately 10% of daily requirements] </li></ul><ul><li>Regarded as ‘electrolyte free’ – contains NO Sodium, Potassium, Chloride or Calcium </li></ul><ul><li>Distribution: <10% Intravascular; > 66% intracellular </li></ul><ul><li>When infused is rapidly redistributed into the intracellular space; Less than 10% stays in the intravascular space therefore it is of limited use in fluid resuscitation. </li></ul><ul><li>For every 100ml blood loss – need 1000ml dextrose replacement [10% retained in intravascular space </li></ul><ul><li>Common cause of iatrogenic hyponatraemia in surgical patient </li></ul><ul><li>(2) Dextrose saline – Think of it as ‘a bit of salt and sugar’ </li></ul><ul><li>Similar indications to 5% dextrose; Provides Na+ 30mmol/l and Cl - 30mmol/l Ie a sprinkling of salt and sugar! </li></ul><ul><li>Primarily used to replace water losses post-operatively </li></ul><ul><li>Limited indications outside of post-operative replacement – ‘Neither really saline or dextrose’; Advantage – doesn’t commonly cause water or salt overload. </li></ul>
    18. 23. Colloid solutions <ul><li>The colloid solutions </li></ul><ul><li>contain particles which do not readily cross semi-permeable membranes such as the capillary membrane </li></ul><ul><li>Thus the volume infused stays (initially) almost entirely within the intravascular space </li></ul><ul><li>Stay intravascular for a prolonged period compared to crystalloids </li></ul><ul><li>However they leak out of the intravascular space when the capillary permeability significantly changes e.g. Severe trauma or sepsis </li></ul><ul><li>Until recently they were regarded as the gold standard for intravascular resuscitation (see next slide) </li></ul><ul><li>Because of their gelatinous properties they cause platelet dysfunction and interfere with fibrinolysis and coagulation factors (factor VIII) – thus they can cause significant coagulopathy in large volumes. </li></ul>
    19. 24. Fluid & electrolyte balance <ul><li>Fluid replacement </li></ul><ul><ul><li>Maintenance requirement </li></ul></ul><ul><ul><li>Replacement of losses </li></ul></ul><ul><ul><li>Ongoing losses </li></ul></ul>
    20. 25. Volume Deficit-Clinical Types <ul><li>Total body water: </li></ul><ul><ul><li>Water loss (diabetes insipidus, osmotic diarrhea) </li></ul></ul><ul><li>Extracellular: </li></ul><ul><ul><li>Salt and water loss ( ascites, edema) </li></ul></ul><ul><ul><li>Third spacing </li></ul></ul><ul><li>Intravascular: </li></ul><ul><ul><li>Acute hemorrhage </li></ul></ul>
    21. 26. Replacement of losses <ul><li>Actual losses </li></ul><ul><ul><li>Bleeding </li></ul></ul><ul><ul><li>Vomiting/diarrhoea </li></ul></ul><ul><li>Ongoing losses </li></ul><ul><ul><li>Stoma </li></ul></ul><ul><ul><li>Drains </li></ul></ul><ul><ul><li>Fistulae </li></ul></ul><ul><ul><li>NGT </li></ul></ul><ul><ul><li>U/O </li></ul></ul>
    22. 27. Parenteral Fluid Therapy: <ul><li>Crystalloids: </li></ul><ul><li>- contain Na as the main osmotically </li></ul><ul><li>active particle </li></ul><ul><li>- useful for volume expansion (mainly </li></ul><ul><li>interstitial space) </li></ul><ul><li>- for maintenance infusion </li></ul><ul><li>- correction of electrolyte abnormality </li></ul>
    23. 28. Crystalloids: <ul><li>Isotonic crystalloids </li></ul><ul><li>- Lactated Ringer’s, 0.9% NaCl </li></ul><ul><li>- only 25% remain intravascularly </li></ul><ul><li>Hypertonic saline solutions </li></ul><ul><li>- 3% NaCl </li></ul><ul><li>Hypotonic solutions </li></ul><ul><li>- D5W, 0.45% NaCl </li></ul><ul><li>- less than 10% remain intra- </li></ul><ul><li>vascularly, inadequate for fluid </li></ul><ul><li>resuscitation </li></ul>
    24. 29. Colloid Solutions: <ul><li>Contain high molecular weight </li></ul><ul><li>substances  do not readily migrate across </li></ul><ul><li>capillary walls </li></ul><ul><li>Preparations </li></ul><ul><li>- Albumin: 5%, 25% </li></ul><ul><li>- Dextran </li></ul><ul><li>- Gelifundol </li></ul><ul><li>- Haes-steril 10% </li></ul>
    25. 30. Common parenteral fluid therapy D5W 310 154 154 500 6% Hetastarch 330 130-160 <2.5 130-160 250,500 5% Albumin 273 28 109 3 4 130 Lactated Ringer’s 308 154 154 0.9% NaCl 154 77 77 0.45% NaCl 406 278 77 77 D5/0.45% NaCl 1026 513 513 3% NaCl 280-310 27 103 5 4 142 ECF 330 130-160 <2.5 130-160 20,50,100 25% Albumin mOsm/L Dextrose HCO 3 - Cl - Mg 2+ Ca 2+ K + Na + Volumes Solutions
    26. 31. The Influence of Colloid & Crystalloid on Blood Volume: 1000cc 500cc 500cc 500cc 200 600 1000 Lactated Ringers 5% Albumin 6% Hetastarch Whole blood Blood volume Infusion volume
    27. 32. Example of IVF order <ul><li>Maintenance (patient of average weight): </li></ul><ul><ul><li>1L N/S + 20mmol KCl </li></ul></ul><ul><ul><li>1L 4% Dex N/5 + 20mmol KCl </li></ul></ul><ul><ul><li>1L 4% Dex N/5 + 20mmol KCl </li></ul></ul><ul><li>Note: </li></ul><ul><ul><li>Gastric outlet obstruction – N/S + KCl </li></ul></ul><ul><ul><li>SBO – Hartmann’s solution </li></ul></ul><ul><ul><li>Most of ongoing “surgical” losses are rich in Na </li></ul></ul>
    28. 33. Your fluid chart should look something like this. (I have written it out twice as I was unconvinced of my first attempt)
    29. 34. Maintenance <ul><li>Variable </li></ul><ul><li>Usually 2.5-3L/day </li></ul><ul><li>Rough guide: </li></ul><ul><ul><li>2-3mmol NaCl/kg/day </li></ul></ul><ul><ul><li>1-2mmol K/kg/day </li></ul></ul><ul><li>Volume </li></ul><ul><li>Electrolytes </li></ul>
    30. 35. Fluid Management: <ul><li>Goal: </li></ul><ul><li>- to maintain urine output of </li></ul><ul><li>0.5~1.0ml/kg/h </li></ul><ul><li>Electrolytes require: </li></ul><ul><li>- Na + : 1-2mmol/kg/day </li></ul><ul><li>- K + : 0.5~1.0mmol/kg/day </li></ul><ul><li>Avoid fluid overload, especially in malnutrition, </li></ul><ul><li>heart failure and renal insufficiency patient </li></ul>
    31. 36. Fluid Management: <ul><li>For acute blood loss </li></ul><ul><li>- Begin with 2-3L isotonic crystalloid to </li></ul><ul><li>restore blood pressure and peripheral </li></ul><ul><li>perfusion </li></ul><ul><li>- Early use of colloid </li></ul><ul><li>- Crystalloid + 5% albumin in a ratio of 4:1 </li></ul><ul><li>- Blood transfusion </li></ul><ul><li>- Large borne IV line </li></ul>

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