Fluid and Electrolyte Imbalances

1. Fluid and Electrolyte Imbalances

3. Body Fluid Compartments • 2/3 (65%) of TBW is intracellular (ICF) • 1/3 extracellular water • 25 % interstitial fluid (ISF) • 5- 8 % in plasma (IVF intravascular fluid) • 1- 2 % in transcellular fluids – CSF, intraocular fluids, serous membranes, and in GI, respiratory and urinary tracts (third space)

6. Fluid compartments are separated by membranes that are freely permeable to water. • Movement of fluids due to: • hydrostatic pressure • osmotic pressure • Capillary filtration (hydrostatic) pressure • Capillary colloid osmotic pressure • Interstitial hydrostatic pressure • Tissue colloid osmotic pressure

8. Balance • Fluid and electrolyte homeostasis is maintained in the body • Neutral balance: input = output • Positive balance: input > output • Negative balance: input < output

10. Solutes – dissolved particles • Electrolytes – charged particles • Cations – positively charged ions • Na+, K+ , Ca++, H+ • Anions – negatively charged ions • Cl-, HCO3- , PO43- • Non-electrolytes - Uncharged • Proteins, urea, glucose, O2, CO2

11. Body fluids are: • Electrically neutral • Osmotically maintained • Specific number of particles per volume of fluid

12. Homeostasis maintained by: • Ion transport • Water movement • Kidney function

13. MW (Molecular Weight) = sum of the weights of atoms in a molecule mEq (milliequivalents) = MW (in mg)/ valence mOsm (milliosmoles) = number of particles in a solution

14. Tonicity Isotonic Hypertonic Hypotonic

16. Cell in a hypertonic solution

17. Cell in a hypotonic solution

18. Movement of body fluids “ Where sodium goes, water follows.” Diffusion – movement of particles down a concentration gradient.Osmosis – diffusion of water across a selectively permeable membraneActive transport – movement of particles up a concentration gradient ; requires energy

20. Regulation of body water • ADH – antidiuretic hormone + thirst • Triggered by • Decreased amount of water in body • Increased amount of Na+ in the body • Increased blood osmolality • Decreased circulating blood volume • Stimulate osmoreceptors in hypothalamusADH released from posterior pituitaryIncreased thirst

22. Result: increased water consumption increased water conservation Increased water in body, increased volume and decreased Na+ concentration

23. Dysfunction or trauma can cause: • Decreased amount of water in body • Increased amount of Na+ in the body • Increased blood osmolality • Decreased circulating blood volume

24. Edema is the accumulation of fluid within the interstitial spaces. Causes: increased hydrostatic pressure lowered plasma osmotic pressure increased capillary membrane permeability lymphatic channel obstruction

25. Hydrostatic pressure increases due to: Venous obstruction: thrombophlebitis (inflammation of veins) hepatic obstruction tight clothing on extremities prolonged standing Salt or water retention congestive heart failure renal failure

26. Decreased plasma osmotic pressure: ↓ plasma albumin (liver disease or protein malnutrition) plasma proteins lost in : glomerular diseases of kidney hemorrhage, burns, open wounds and cirrhosis of liver

27. Increased capillary permeability: Inflammation immune responses (allergic reactions) Lymphatic channels blocked: surgical removal infection involving lymphatics lymphedema

28. Fluid accumulation: increases distance for diffusion may impair blood flow = slower healing increased risk of infection pressure sores over bony prominences Psychological effects

29. Edema of specific organs can be life threatening (larynx, brain, lung) Water is trapped, unavailable for metabolic processes. Can result in dehydration and shock. (severe burns)

30. Electrolyte balance • Na + (Sodium) • 90 % of total ECF cations • 136 -145 mEq / L • Pairs with Cl- , HCO3- to neutralize charge • Low in ICF • Most important ion in regulating water balance • Important in nerve and muscle function

32. Regulation of Sodium • Renal tubule reabsorption affected by hormones: • Aldosterone • Renin/angiotensin • Atrial Natriuretic Peptide (ANP) • Increased secretion of Na, decreased lood volume

33. Potassium • Major intracellular cation • ICF conc. = 150- 160 mEq/ L • Resting membrane potential • Regulates fluid, ion balance inside cell • pH balance

34. Regulation of Potassium • Through kidney • Aldosterone • Insulin

35. Isotonic alterations in water balance • Loses plasma or ECF • Isotonic fluid loss • ↓ECF volume, weight loss, dry skin and mucous membranes, ↓ urine output, and hypovolemia ( rapid heart rate, flattened neck veins, and normal or ↓ B.P. – shock)

36. Isotonic fluid excess • Excess IV fluids • Hypersecretion of aldosterone • Effect of drugs – cortisone Hypervolemia – weight gain, decreased hematocrit, diluted plasma proteins, distended neck veins, ↑ B.P. Can lead to edema (↑ capillary hydrostatic pressure) pulmonary edema and heart failure

37. Electrolyte imbalances: Sodium • Hypernatremia (high levels of sodium) • Plasma Na+ > 145 mEq / L • Due to ↑ Na + or ↓ water • Water moves from ICF → ECF • Cells dehydrate

39. Hypernatremia Due to: • Hypertonic IV soln. • Oversecretion of aldosterone • Loss of pure water • Long term sweating with chronic fever • Respiratory infection → water vapor loss • Diabetes – polyuria • Insufficient intake of water (hypodipsia)

40. Clinical manifestationsof Hypernatremia • Thirst • Lethargy • Neurological dysfunction due to dehydration of brain cells • Decreased vascular volume

41. Treatment of Hypernatremia • Lower serum Na+ • Isotonic salt-free IV fluid • Oral solutions preferable

42. Hyponatremia • Overall decrease in Na+ in ECF • Two types: depletional and dilutional • DepletionalHyponatremia Na+ loss: • diuretics, chronic vomiting • Chronic diarrhea • Decreased aldosterone • Decreased Na+ intake

43. DilutionalHyponatremia: • Renal dysfunction with ↑ intake of hypotonic fluids • Excessive sweating→ increased thirst → intake of excessive amounts of pure water • Syndrome of Inappropriate ADH (SIADH) or oliguric renal failure, severe congestive heart failure, cirrhosis all lead to: • Impaired renal excretion of water • Hyperglycemia – attracts water

44. Clinical manifestations of Hyponatremia • Neurological symptoms • Lethargy, headache, confusion, apprehension, depressed reflexes, seizures and coma • Muscle symptoms • Cramps, weakness, fatigue • Gastrointestinal symptoms • Nausea, vomiting, abdominal cramps, and diarrhea

45. Hypokalemia • Serum K+ < 3.5 mEq /L • Beware if diabetic • Insulin gets K+ into cell • Ketoacidosis – H+ replaces K+, which is lost in urine • β – adrenergic drugs or epinephrine

46. Causes of Hypokalemia • Decreased intake of K+ • Increased K+ loss • Chronic diuretics • Acid/base imbalance • Trauma and stress • Increased aldosterone • Redistribution between ICF and ECF

47. Clinical manifestations of Hypokalemia • Neuromuscular disorders • Weakness, flaccid paralysis, respiratory arrest, constipation • Dysrhythmias, appearance of U wave • Postural hypotension • Cardiac arrest • Treatment- • Increase K+ intake, but slowly, preferably by foods

48. Hyperkalemia • Serum K+ > 5.5 mEq / L • Check for renal disease • Massive cellular trauma • Insulin deficiency • Addison’s disease • Potassium sparing diuretics • Decreased blood pH • Exercise causes K+ to move out of cells

49. Clinical manifestations of Hyperkalemia • Early – hyperactive muscles , paresthesia • Late - Muscle weakness, flaccid paralysis • Change in ECG pattern • Dysrhythmias • Bradycardia , heart block, cardiac arrest

50. Treatment of Hyperkalemia • Decrease intake and increase renal excretion • Insulin + glucose • Bicarbonate • Ca++ counters effect on heart