Fluids and Electrolytes

1. 18 Fluids and Electrolytes

2. LEARNING OBJECTIVE 1 • Explain the normal composition of fluids and electrolytes in the body.

3. Body Fluid Composition • Compartments • ICF • Cell cytoplasm and nucleus • ECF • Serum and interstitial fluid • Cerebral spinal fluid • GI fluids

4. Functions of Body Fluids • Salivary enzymes • Transport to body tissues: • Electrolytes • Oxygen • Nutrient • Hormones • Immune Cells

5. Functions of Body Fluids • Elimination of waste products • Bowel • Bladder • Movement of electrolytes between ICF/ECF • Temperature regulation • Perspiration • Capillary dilatation

6. LEARNING OBJECTIVE 2 • Describe the normal osmolality of the blood and urine.

7. Osmolality • Number of solutes per kilogram of water • Isotonic • Hypertonic • Hypotonic

8. Regulation of Body Fluids • Osmosis • Movement of water • Diffusion • Movement of molecules

9. Osmosis & Diffusion

10. Diffusion • Molecule size • Electrical charges • Pressure gradient • Active diffusion • Passive diffusion

11. Filtration • Movement is result of hydrostatic pressure • Pressure of water on surrounding tissues • Created by heart action • Arterial pressure is greater than venous pressure • Filtration is opposed by oncotic pressure • Plasma proteins produce oncotic pressure

12. LEARNING OBJECTIVE 3 • Evaluate fluid status of an adult according to normal fluid and electrolyte values.

13. Evaluation of Fluid Status • Osmolality • Normal is 275 – 295 mOsm/kg • Water deficit – >295 mOsm/kg • Water excess – <275 mOsm/kg • Multiply sodium x2

14. Evaluation of Fluid Status • Normal serum hematocrit • 40 – 50% • Dilute serum • Low hematocrit and electrolyte levels • Concentrated serum • Elevated hematocrit and electrolyte levels

15. Distribution of Body Fluids • Overhydration: osmosis shifts water from blood to ICF and ECF • ECF: lower extremity/sacral edema • ICF: cellular edema • Causes • Decreased renal excretion • Cirrhosis • Congestive heart failure

16. Fluid Accumulation • Can also occur in lung capillaries, alveoli • Crackles heard on auscultation • Decrease in gas exchange • Respiratory acidosis • Accumulation in heart atria • S3 heart sound

17. Dehydration • Causes • Excessive urinary water loss • Hyperglycemia • Inadequate fluid intake • Diuretic overuse

18. Dehydration and the Elderly • Increased risks for dehydration • Decrease in thirst • Lack of fluid replacement • Use of diuretic medications for high BP • Susceptibility to contagious diseases

19. Manifestations of Dehydration • Thirst; dry mouth and tongue • Tenting of skin • Elevated temperature • Orthostatic hypotension • Tachycardia and weak pulse • Mottled skin

20. LEARNING OBJECTIVE 4 • Define the normal ranges of electrolytes in the body.

21. Electrolytes • Sodium • Chloride • Potassium • Calcium • Phosphorus • Magnesium

22. Sodium • Most abundant cation in ECF • Functions • ECF volume • Acid-base balance • Nerve impulse control • Normal serum values • 135-145 mEq/L

23. Sodium Regulation • Aldosterone • Sodium retention • Antidiuretic hormone (ADH) • Water reabsorption • Atrial natriuretic peptide (ANP) • Sodium excretion

24. Potassium • Intracellular cation • Normal serum levels: 3.5 – 5.0 mEq/L • Functions • Cellular integrity • Neuromuscular impulse transmission • Acid-base balance • Conversion of carbohydrate to energy • Formation of proteins

25. Potassium • Food sources include bananas, meat, potatoes • Anabolic states • Stored in cells • Catabolic states • Moves into blood • Excreted via kidney and GI tract

26. Calcium • Cation found in both ICF and ECF but > in ECF. • Normal serum levels: 8.5 – 10.5 mg/dL • Neuromuscular transmission; muscle contraction • Blood clotting; cell membrane function • Found mainly in bones and teeth • Exists in ionized and non-ionized forms • Acidosis and alkalosis

27. Calcium Regulation • Vitamin D • Calcium absorption • Calcitonin • Inhibits resorption in bone • Inhibits renal excretion • Parathyroid hormone • Mobilizes calcium from bone • Increases kidney reabsorption

28. Magnesium • Intracellular Cation • Normal serum levels: 1.4 – 2.1 mg/dL • Co-factor of enzymatic reactions • Neuromuscular interactions • Cardiac contractility • Food sources

29. Phosphorus • Intracellular anion • Normal serum levels: 1.5 – 2.5 mg/dL • Needed for metabolism, nerve and muscle function • Part of energy units • Component of phospholipids • Regulated by calcitonin, parathyroid hormone and Vitamin D

30. Chloride • Primary extracellular anion • Normal serum levels: 95 – 108 mEq/L • Creates electrical neutrality when combined with sodium • Hydrochloric acid • Buffers carbonic acid • Anion gap - calculated AG = (Na + K) – (Cl + HC03 (metabolic acidosis)

31. LEARNING OBJECTIVE 4 • Discuss various circumstances that place the patient at risk for fluid and electrolyte imbalances.

32. Causes of Hypernatremia • Deficit of water relative to sodium • Causes • Excessive water losses • Sweating • Diabetes insipidus • Sodium retention • Cushing's syndrome

33. Manifestations of Hypernatremia • Thirst • Low grade fever • Edema • Altered mental status • Hypertension • Weight gain • Coma and seizures

34. Causes of Hyponatremia • Water retention • Inadequate sodium intake • Loss of sodium-rich fluid • Excess use of 5% dextrose solution • Syndrome of Inappropriate Anti-diuretic Hormone (SIADH)

35. Manifestations of Hyponatremia • Depolarization and repolarization of cells • Neurological symptoms • Lethargy • Headache • Personality changes • Seizures • Permanent brain damage below 115 mEq/L

36. Manifestations of Hyponatremia • Fluid overload causes dilutional hyponatremia • Symptoms: • Hypertension • Bounding pulse • Fluid retention • Weight gain

37. Causes of Hyperkalemia • Increased potassium intake • Inappropriate potassium supplementation • Decreased urinary excretion of potassium • Acute and chronic renal failure • Potassium-sparing diuretic • Cellular release of potassium

38. Manifestation of Hyperkalemia • Muscle weakness and cramping • ECG changes – peaked T waves • Irregular pulse • Irritability • Abdominal distention and cramping • Muscle weakness • Paresthesia • Diarrhea

39. Hyperkalemia in Cardiac rhythm

40. Causes of Hypokalemia • Sweat, urinary and GI losses • Diarrhea • Decreased intake • Increased insulin levels • Cushing’s disease • Stress • Hypomagnesemia

41. Manifestations of Hypokalemia • Muscle weakness • Cramps • Nausea • Vomiting • Decreased bowel sounds • Paresthesias • ECG changes

42. ECG changes in hypokalemia

43. Causes of Hypercalcemia • Primary hyperparathyroidism • Calcium mobilization from bones • Bone malignancy • Calcium liberation from bones • Drug toxicity • Thiazide diuretics • Vitamin A and D

44. Manifestations of Hypercalcemia • Neuromuscular • Renal • Gastrointestinal • Cardiovascular • Musculoskeletal • Eye and skin

45. Causes of Hypocalcemia • Reduced calcium intake or absorption • Low parathyroid hormone • Increased phosphorus • Decreased magnesium • Hypoalbuminemia • Alkalosis

46. Manifestations of Hypocalcemia • Decreased cardiac contractility • Neuromuscular symptoms • Mental changes • Pathological fractures • Trousseau’s sign https://www.youtube.com/watch?v=H13yn9AwtPY&feature=relmfu • Chvostek sign https://www.youtube.com/watch?v=ep6IEqnyxJU

47. Causes and Manifestation of Hypermagnesemia • Causes • Renal failure • Treatment for pregnancy-induced HTN • Manifestations • Decreased neuromuscular activity • Respiratory depression and cardiac arrest • Nausea, vomiting, drowsiness

48. Causes of Hypomagnesemia • Decrease in GI absorption • Excessive calcium absorption • Malnutrition • Intake of phytates, oxalates and fat • Increased kidney excretion • Diuresis • Alcoholism

49. Manifestations of Hypomagnesemia • More evident at serum levels <1 mg/dL • Confusion • Lethargy • Nausea and vomiting • Seizures and hyperactive reflexes • Cardiac symptoms – Torsades de Pointes