Lecture+12++Fluids+and+electrolytes-2011

Lecture+12++Fluids+and+electrolytes-2011 - Lecture 12:...

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Unformatted text preview: Lecture 12: Fluids and Electrolytes Lecture Electrolytes Outline • Overview of fluids and electrolytes in the body • Distribution of body fluids • Roles of body fluids, electrolytes Roles • Thirst mechanism • Water intake/losses • Disorder due to imbalance of body fluids & Disorder electrolytes electrolytes Fluids, electrolytes Fluids, Fluids – move freely and change form Fluids according to the shape of container according Body fluids – water plus dissolved substances Body (solutes) = liquid portion of cells and tissues (solutes) some of the solutes are minerals (sodium, some potassium, chloride, phosphorus, calcium) which are called electrolytes which Electrolytes become dissociated into + and – Electrolytes ions when dissolved in water ions Our body is mostly water (earth’s surface is 75% water!) Our Body fluids and electrolytes Body Big picture: • The body is mostly made of water (~60-70% in children, The ~50-60% in adults) ~50-60% • Cells are mostly made of water (>70%): “life occurs Cells under water”= “biological reactions happen in water” under • Basics of Body Fluids and Electrolytes Body fluid = liquid portion of cells and tissues = Body water + electrolytes water Cells have electrolytes (positively or negatively Cells charged elements called ions) that serve many functions functions The major ions inside of cells are potassium The (K) and chloride (Cl) (K) The major ions outside of cells are sodium The (Na) and chloride (Cl) (Na) Distribution of body fluids • 2/3 body fluid is within the cells = intracellular fluid • 1/3 body fluid is outside the cells = extracellular fluid – Extracellular fluid in the tissues/organs = interstitial fluid – flows between the cells that make up a particular tissue/organ – Extracellular fluid in the liquid portion of the blood or lymph = intravascular fluid • Blood is ~1/3 of extracellular fluid Distribution of body fluids Distribution Intravascular fluid Body fluids play important roles Body • • • • Fluids dissolve and transport substances - water is excellent Fluids solvent for amino acids, glucose, vitamins, minerals, medications – transported in the blood stream transported Fluids account for blood volume – blood volume is amount of fluid Fluids in the blood – Blood volumes increases blood pressure increases Blood – Blood volume decreases blood pressure decreases Blood – Kidney plays a central role in regulating blood volume & Kidney pressure pressure Fluids maintain body temperature – water has high heat capacity Fluids the ability to take in or release heat without significant temp change, our body water protects us from extreme temperatures change, – Sweating cools the body down – heat transported from body to Sweating skin surface through blood – water evaporates cooling effect Fluids protect and lubricate tissues – cerebrospinal fluid in brain Fluids and spinal column protects against damage, fluid in mucus linings of stomach and intestines facilitate food movement of Electrolytes in body fluid play important roles Electrolytes regulate fluid balance Electrolytes in body fluid play important roles • Electrolytes enable nerves to respond to stimuli – Na+ and K+ play critical roles propagating nerve impulses along nerve and muscle cells • Electrolytes signal muscles to contract – Ca++ - increase flow from extracellular fluid into muscle cell contraction pump out of cell relaxation Common sources of some electrolytes in diet • Na – Dill pickle (4 in) 1731 mg – Cured ham (3 oz) 1177 – Tomato juice (1 cup) 654 •K – – – – Potato (1 med serving) Yogurt (8-oz container) Banana (large) Tomato juice (1 cup) 1081 mg 579 554 556 •P – Cheddar cheese (3 oz) – Lentils (1 cup) 435 mg 356 Maintaining fluid balance is essential • IN We drink and retain fluid when dehydrated • OUT Excrete fluid (urinate) when we consume more than we need Thirst mechanism • Controlled in hypothalamus of the brain by group of cells called “thirst mechanism” • Stimulated by: – Increased concentration of salt and other dissolved substances in blood – eating potato chips, crackers, sandwich – salty – Reduction in blood volume and blood pressure – sweating, blood loss, vomiting, diarrhea, low fluid intake – Dryness in mouth and throat – indicates low amount of fluid in the blood lower production of saliva Thirst mechanism • Hypothalamus detects changes stimulates release of anti-diuretic hormone (ADH) – – Signals kidney to reduce urine flow and return more water to bloodstream – Kidney releases angiotensin II constriction of blood vessels retains more water – Water is drawn out of salivary glands in mouth to further dilute substances in blood makes mouth & throat dry Thirst mechanism • Thirst mechanism not always sufficient • People stop drinking when no more thirsty – but fluid intake may not be enough to restore fluid balance – Happens during intense exercise in the heat or high humidity – Lesson: drink regularly during the day and not wait till you’re thirsty – carry bottled water Balancing water intake/losses Balancing Intake: • beverages beverages • foods foods • metabolic water (water from body’s metabolic reactions) reactions) Losses: • urine, sweat (sensible water loss - noticeable by urine, the person) the • skin evaporation, exhalation (insensible water loss) skin water • faeces Balance between the two is important for a healthy fluid Balance level level Intake • Beverages – 90-100% water: water, tea, coffee, cola, clear broth – 60-89% water: fruit juices, milk Fruits >90%: watermelon, tomato, cantaloupe 60-89%: apple, peach, banana, pineapple, grapes Dried grapes = raisins (1-19% water) How much water do we need? • Depends on age, body size, health status, physical activity, environmental conditions • DRI (Daily Recommended Intake) – Adult men 19-50 yrs old 3.7 L (3.0 L water, ~0.6 L from beverages & foods) – Adult women 19-50 yrs old 2.7 L(2.2 L water, ~0.5 L from beverages & food) Water intake & loss: woman expending 2500kcal/day Water Drinking water • Carbonated – natural or added CO2 • Mineral – contains 250-500 ppm of minerals • Distilled – all dissolved minerals are removed • Purified - all dissolved minerals and contaminants are removed • Bottled – comes from different sources – Rapid popularity in last 20 yrs – 3B gallons of bottled water/yr in US – Traveling in another country/ unsure of water source – drink bottled water Disorders due to fluid & electrolyte imbalance • Dehydration – fluid excretion > fluid intake Disorders due to fluid & electrolyte imbalance • Heat stroke – potentially fatal response to high temp where heat regulating mechanism of the body fails – Symptoms: rapid pulse, hot-dry skin, high temperature, dizziness, loss of consciousness – Could happen during intense physical activity under high heat and high humidity Disorders due to fluid & electrolyte imbalance • Water intoxication – Can occur but rare – Kidney disease where too much water is retained overhydration and hyponatremia (low Na+ levels) – Excessive amounts of water forced on students during fraternity hazing rituals – Lesson: anything taken in excess can be toxic Disorders due to fluid & electrolyte imbalance • Hypertension – blood pressure > 140/90 mm Hg (systolic/diastolic) – 90-95% of cases – called primary or essential hypertension – causes unknown – may be due to salt sensitivity – Other 5% - due to kidney disease, apnea (sleep disorder affecting breathing), chronic alcohol abuse Incidence of hypertension increases with age Reducing hypertension • Lose weight – decrease of 6-7 points for every 17 lbs lost • Increase physical activity – easily achievable for most people – light intensity exercise 30-60 min or intense exercise for 20 – 30 min • Reduce alcohol intake – abstain or no more than 2 drinks/day • Reduce salt intake – AI (Allowable Intake) for Na+ 1500 mg/day, do not exceed 2500 mg/day • Eat whole grains, fruits, vegetables, low fat protein sources • (Take anti-high BP pills) ...
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