FLUIDS AND ELECTROLYTES in surgical patient

1. FLUIDS AND ELECTROLYTESin surgical patient Miklosh Bala, MD

2. Fluid = Drug!!!

3. Too wet

4. Too dry

5. IT’S COMPLICATED! Please don’t write up fluids on patients you know nothing about without looking at various parameters (to be explained below)

6. Fluid Prescribing • Left to the most junior member of the team • Wide variability in prescribing practices • About 26% prescribed > 2L 0.9% saline/day Fluid therapy is often poorly taught, poorly understood and poorly done

7. Objectives • Review physiology controlling fluid/elec balance • Appreciate differences in surgical patients • Be able to order fluid regime for surgical patients

8. Total Body Water body wt% Total body water% total 60 100 intracellular 40 67 extracellular 20 33 intravas 5 8 interstitial 15 25

9. Distribution of Body Fluids • Does total body water, as a percentage of body weight vary with: • Age? • Gender?

10. Distribution of Body Fluids • A decrease in the percent of body weight that is water is noted with increasing age. • Men have a slightly higher percentage of body weight as water than women. • Why?

11. Total Body Water • How much volume is Total Body Water in a typical 70-kg man?

12. Total Body Water • 70 kg x 1 L/kg x 60% = 42 L

13. Fluid Compartments Intracellular Intravascular Interstitial 66% 25% 8%

14. Extracellular Fluid Volume • What are 3 clinical conditions where the ratio of interstital/intravascular volume is increased?

15. Extracellular Fluid Volume • Congestive heart failure • Hypoalbuminemia • Inflammation

16. Osmotic Activity • The total osmotic activity in a solution is the sum of the individual osmotic activities of all the solute particles in the solution. • What is the osmolarity of • 0.9% NaCl?

17. Osmotic Activity • 0.9% NaCl = 154 mEq/L Na + 154 mEq/L Cl • = 154 mOsm/L Na + 154 mOsm/L Cl • = 308 mOsm/L • What is normal plasma osmolarity?

18. Osmolarity • Normal plasma osmolarity = 280 - 290 mOsm/L

19. Electrolytes • What are the primary electrolytes? • Extracellular • Intracellular

20. Electrolytes • Extracellular • Cation - Sodium • Anion - Chloride • Intracellular • Cation - Potassium • Anion - Bicarbonate

21. Maintenance • Where is water lost normally? • How much water is lost normally? • What is the ideal maintenance fluid?

22. Normal Water Exchange Avg daily ml Min daily ml Sensibleurine 800-1500 300intestinal 0-250 0sweat 0 0 Insensiblelungs/skin 600-900 600-900 8-10 mls/kg/D -  10%/ o rise in Temp

23. Normal Intake of Water 2000mls - 1300 free water 700 bound to food additional water comes from catabolism

24. Maintenance • Diuretics • Diarrhea • Fever • Open wound • Artificial airway

25. Fluid and Electrolyte Therapy Surgical patients have • Maintenance volume requirements • On going losses • Volume excess/deficits • Maintenance electrolyte requirements • Electrolyte excess/deficits

26. Maintenance • In the nonstressed, fasting state, 150 g/day dextrose provides enough calories to limit proteolysis. • This protein-sparing effect is not sufficient in the stressed, catabolic patient. • What are the daily requirements for sodium and potassium?

27. Maintenance • 70 kg man average needs • Sodium 140 meq/day • Potassium 50 meq/day • What is the ideal maintenance fluid for the nonstressed, fasting, 70 kg man?

28. 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

29. Maintenance • D5 + 1/2NS + 20meq/L KCl • 100 mL/hour • Provides total • 2.4 L water • 120 g dextrose • 185 meq sodium • 48 meq potassium

30. On Going Losses • NG • drains • fistulae • third space losses Concentration is similar to plasma Replace with isotonic fluids

31. Insensible Losses • An extra 500 mL of fluid a day is required for every degree of fever above 37C.

32. Resuscitation • What is “Third Space?”

33. Third Space • Fluid compartments that are not freely mobilized by normal homeostatic mechanisms.

34. GI Losses

35. GI Losses

36. GI Losses

37. GI Losses

38. GI Losses

39. GI Losses

40. Questions to ask before prescribing fluid Why? What? How much?

41. Why does he need fluid? • Maintenance • Replacement • Resuscitation

42. Fluid and Electrolyte Therapy Goal • normal hemodynamic parameters • normal electrolyte concentration Method replace normal maintenance requirements ongoing losses deficits

43. Fluid and Electrolyte Therapy The best estimate of the volume required is the patients response After therapy started observe • vital signs • Urine output (0.5mls/Kg/hr) • Central venous pressure

44. Normal Capillary Homeostasis

45. Preload Third-space Edema Fluid Compartments in Shock Intracellular Interstitial Intravascular

46. Capillary Leak in Shock

47. Restoration of Intravascular Space

48. What fluids does he need?

49. Crystalloids • Advantages • readily available • cheap • resuscitate intravascular and interstitial space • promote urinary output • Disadvantages • does not stay intravascular • larger volumes are needed • may result in edema formation

50. Non-Protein Colloids • Advantages • readily available • equivalent to protein colloids • Disadvantages • expensive • dose related coagulopathy • long tissue half-life (starches) • short intravascular dwell time (dextrans) • anaphylaxis (dextrans >> starches) • difficulty with blood cross-matching