Understanding Electrolytes and Fluid Balance in the Body

1. 9 Nutrients Involved in Fluid and Electrolyte Balance

2. Body Fluids • Body fluid is the liquid portion of cells and tissues • Characterized by its ability to move freely and changeably, adapting to the shape of the container that holds it • About 50−70% of healthy adult body weight

3. Body Fluids • Intracelluar fluid: within the cell • 2/3 of body fluid • Extracellular fluid: outside the cell • 1/3 of body fluid • Interstitial fluid flows between cells that make up a particular tissue or organ (muscle, liver) • Intravascular fluid is the water in the blood and lymph • Plasma transports blood cells within arteries, veins, and capillaries Intracellular and Extracellular Fluid

5. Body Fluids • Fluid composition of tissue varies by: • Tissue type: lean tissues have higher fluid content than fat tissues • Gender: males have more lean tissue and therefore more body fluid than females • Age: decrease in body water results partly from loss of lean tissue as people age

6. Electrolytes • Dissolved substances that disassociate in solution into electrically charged particles called ions • Positive charge: sodium, potassium • Negative charge: chloride, phosphorus • Predominant electrolytes • Extracellular fluid: potassium, phosphorus • Intracellular fluid: sodium, chloride Role of Electrolytes in Water Balance

7. Functions of Body Fluids • Fluids dissolve and transport substances • Water is an excellent solvent because it dissolves a variety of substances • Water-soluble substances are readily transported in the bloodstream: amino acids, glucose, vitamins, minerals, medications • Fatty substances must be attached to or surrounded by water-soluble proteins

8. Functions of Body Fluids • Fluids account for blood volume • Appropriate body fluid levels are essential for maintaining healthful blood volume • Blood pressure increases when blood volume rises • High blood pressure (hypertension) is a risk factor for heart disease and stroke • Low blood pressure can cause people to feel tired, confused, or dizzy • Kidneys help to regulate blood volume and blood pressure

9. Functions of Body Fluids • Fluids account for blood volume • Antidiuretic hormone (ADH) stimulates the kidneys to reabsorb water, reducing urine • Renin responds to decreased blood pressure • Angiotensin II (vasoconstrictor) increases blood pressure • Aldosterone signals the kidneys to retain sodium and chloride, thereby retaining water, increasing blood pressure, and decreasing urine output

11. Functions of Body Fluids • Fluids help maintain body temperature • Body temperature must be within a safe range • Water has a high capacity for heat, which means that only sustained high heat can increase body temperature • Sweating releases heat as the evaporation of water from the skin cools the skin and blood

13. Functions of Body Fluids • Protect and lubricate tissues • Cerebrospinal fluid protects the brain and spinal cord • Amniotic fluid protects the fetus • Synovial fluid lubricates joints • Tears cleanse and lubricate eyes • Saliva moistens food for swallowing

14. Functions of Electrolytes • Electrolytes help regulate fluid balance • Cell membranes are permeable to water, but not freely permeable to electrolytes • Water moves by osmosis to areas where the concentration of solute is high • This action provides a means to control movement of water into and out of the cells • Osmotic pressure keeps electrolytes in solution from drawing liquid toward them across a semipermeable membrane

17. Functions of Electrolytes • Electrolytes enable nerves to respond to stimuli • Nerve impulses are initiated at nerve cell membranes in response to a change in electrical charge across the membrane • Depolarization—Action Potential—Repolarization • Sodium and potassium ensure that nerve impulses are generated, transmitted, and completed

19. Functions of Electrolytes • Electrolytes signal muscles to contract • Muscles are stimulated to contract in response to stimulation of nerve cells • Influx of calcium into the muscle from the extracellular space stimulates contraction • Muscles can relax after contraction once the electrical signal is complete and calcium is pumped out of the muscle cell

20. Fluid Balance • Thirst mechanism (hypothalamus) prompts us to drink when it is stimulated by • Increased concentration of salt and other dissolved substances in the blood • A reduction in blood volume and blood pressure, such as during profuse sweating, vomiting, diarrhea, or low fluid intake • Dry mouth and throat from reduced saliva • ADH signals the kidneys to retain water

21. Fluid Balance • Body gains fluids • Water enters the body through beverages • Some foods have very high water content • Water from metabolic reactions contributes 10−14% of daily water need

23. Fluid Balance • Sensible water loss • Kidneys excrete water as urine • Sweat during exercise or in hot environment • Insensible water loss • Skin (not sweating) or lungs during exhalation • Significant loss • Illness, injury, exercise, high altitude, pregnancy, breastfeeding, diuretics

24. Water • Water • Essential for life • Amount needed varies with gender, age, body size, health status, physical activity level, environment • Sources of drinking water: carbonated, mineral, distilled, purified, tap, bottled ABC Video Bottled Water

27. Water • What happens if we drink too much water? • Becoming overhydrated is rare • Dilution of blood sodium concentration • What happens if we don’t drink enough water? • Dehydration • Leading cause of death around the world Water Balance

28. Sodium • Sodium • Major positively charged electrolyte in the extracellular fluid • Blood pressure and acid−base balance • Nerve impulse transmission • Muscle contraction and relaxation • Assists in glucose absorption from the small intestine

29. Sodium • Sodium • AI: 1,500 mg, most recommend < 2,300 mg/day • Processed foods are high in sodium • High blood pressure more common from high-sodium diets • Excessive intake may increase urinary calcium excretion in some people, which in turn may increase the risk for bone loss

31. Sodium • What if you consume too much sodium? • Hypernatremia is an abnormally high blood sodium concentration • Patients with congestive heart failure or kidney disease cannot effectively excrete sodium • Causes high blood volume, edema (swelling), and high blood pressure

32. Sodium • What if you don’t consume enough sodium? • Hyponatremia is an abnormally low blood sodium level • From prolonged sweating, vomiting, diarrhea • Symptoms: headaches, dizziness, fatigue, nausea, vomiting, and muscle cramps • If untreated: seizures, coma, and death

33. Potassium • Potassium • Major positively charged electrolyte in the intracellular fluid • Together with sodium, maintains fluid balance and regulates the contraction of muscles and transmission of nerve impulses • High potassium intake helps maintain a lower blood pressure

34. Potassium • Recommended intake • 4,700 mg/day • Sources of potassium • Good sources: fresh fruits, vegetables, legumes, and whole grains • Processing foods increases sodium and decreases potassium content

36. Potassium • What happens if you consume too much potassium? • Hyperkalemia: high blood potassium levels • Can alter normal heart rhythm, resulting in heart attack and death • People with kidney disease are unable to regulate their blood potassium levels and should avoid consuming potassium-containing salt substitutes

37. Potassium • What happens if you don’t consume enough potassium? • Hypokalemia: low blood potassium levels • Seen in people with kidney disease or diabetic ketoacidosis • Can occur when taking certain diuretics and with extreme dehydration, vomiting, diarrhea, alcohol abuse, long-term consumption of natural licorice (glycyrrhizic acid or GZA), or eating disorder (abnormal heart rhythms)

38. Chloride • Functions of chloride • In extracellular fluid • Aids digestion: hydrochloric acid (HCl) in the stomach • Assists the immune system and in the transmission of nerve impulses • Recommended intake • AI: 2,300 mg/day

39. Chloride • What happens if you consume too much chloride? • Primary dietary source: table salt • Hypertension in salt-sensitive individuals • What happens if you don’t consume enough chloride? • This is rare but can occur in people with severe dehydration, frequent vomiting, and eating disorders

40. Phosphorus • Functions of phosphorus: • Major intracellular negatively charged electrolyte • Required for fluid balance • Critical role in bone formation • Regulates biochemical reactions by activating or deactivating enzymes (phosphorylation) • Found in ATP, DNA, RNA, cell membranes (phospholipids), and lipoproteins

41. Phosphorus • Recommended intake • RDA for phosphorus is 700 mg/day • Sources of phosphorus • Widespread in many foods • High in protein foods (meat, milk, eggs) • More readily absorbed from animal sources • Phytic acid: plant storage form • Soft drinks

43. Phosphorus • What happens if you consume too much phosphorus? • High blood phosphorus can occur among people with kidney disease or when taking too many vitamin D supplements • Causes muscle spasms, convulsions • What if you don’t consume enough phosphorus? • Deficiencies of phosphorus are rare

44. Medical Disorders • Disorders related to fluid and electrolyte imbalance include: • Dehydration • Heatstroke • Water intoxication • Hypertension • Neuromuscular disorders • Obesity

46. Dehydration • Dehydration occurs when fluid loss exceeds fluid intake • Commonly due to heavy exercise or high environmental temperatures • Elderly and infants are at increased risk

48. Heatstroke • Heatstroke occurs from failure in the body’s heat-regulating mechanisms • Hot, humid environments • Symptoms: rapid pulse, hot and dry skin, high body temperature, loss of consciousness • Fatal during exercise in extreme heat • Stop exercising when feeling dizzy, light-headed, disoriented, or nauseated

49. Water Intoxication • Overhydration can occur but it is rare • Kidneys retain too much water, causing overhydration and hyponatremia • Documented cases of deaths among college students (hazing rituals)

50. Hypertension • Hypertension: major chronic disease characterized by high blood pressure • Often without symptoms • Increases a person’s risk of heart disease, stroke, kidney disease • Can reduce brain function, impair physical mobility, and cause death • Systolic pressure over 140 mm Hg • Diastolic pressure over 90 mm Hg