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CHAPTE R 40 

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Water in the body functions primarily to: o Transport nutrients to cells and wastes from cells o Transport hormones, enzymes, blood platelets, and RBCs and WBCs o Act as a solvent for electrolytes and nonelectrolytes o Help maintain normal body temperature o Facilitate digestion and promote elimination o Act as a tissue lubricant Total body water or fluid = total amount of water, approximately 50-60% of body weight in a healthy person Intracellular fluid is the fluid w/in cells, about 70% of total body water or 40% of the adult’s body weight Extracellular fluid is all the fluid outside the cells, account for 30% of total body water or 20% of the adult’s body weight o Intravascular fluid, or plasma is the liquid component of the blood (fluid found within the vascular system) o Interstitial fluid is the fluid that surrounds tissue cells and includes lymph. o Transcellular fluids include cerebrospinal, pericardial, synovial, intraocular, and pleural fluids, as well as digestive secretions. o Capillary walls and cell membranes separate the intracellular and extracellular compartments. Infants have more total body fluid and ECF than adults o Infants at increased risk for fluid volume deficits Higher adipose tissue = lower total body water Fluid intake is regulated primarily by the thirst mechanism o Located in the hypothalamus, the thirst control center is stimulated by Intracellular dehydration and decreased blood volume. Ingested liquids = largest water intake Water from food = second largest source of water Water is an end product in oxidation that occurs during the metabolism of food substances, specifically carbs, fats, and protein Fluid intake averages 2600mL per day, 1500mL as urine form kidneys, 600mL fluid loss from skin, 300mL from lungs, and 200mL in feces via the GI tract. Desirable amount of fluid intake and loss in adults ranges from 1500-3500 mL each 24 hours. Most people average 25000-2600 mL per day. In a healthy adult, intake and output should be nearly equal Electrolytes: substances that are capable of breaking into particles called ions o Ion: an atom or molecule carrying an electrical charge.  Positive = cation  Major cations: sodium, potassium, calcium, hydrogen, and magnesium  Negative = anion  Major anions: chloride, bicarbonate, and phosphate

CHAPTE R 40

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o Molecules in the body that remain intact, without a charge, are called nonelectrolytes o Major electrolytes in the ECF:  Sodium  Chloride  Calcium  Bicarbonate o Major electrolytes in the ICF:  Potassium  Phosphorus  Magnesium o Electrolytes are measure in terms of their chemical combining power, or chemical activity Regulation of homeostatic mechanisms o Solvents: liquids that hold a substance in solution  Water is primary solvent in the body o Solutes: substances that are dissolved in a solution  Electrolytes and nonelectrolytes Osmosis: o Water (the solvent) passes form an area of lesser solute concentration (i.e. more water) to an area of greater solute concentration and less water until equilibrium is established.  Volume of more concentrated solution increases, volume of weaker solution decreases o Water and gases move by osmosis o The greater the difference in the concentration of the two solutions on each side of a semipermeable membrane the greater the osmotic pressure or drawing power of water. o Concentration of particles in a solution, pulling power, is the osmolarity of a solution  Isotonic solutions: have the same osmolarity as plasma (between 275 and 295 mOsm/L)  Isotonic fluid remains in the intravascular compartment w/o any et flow across the semipermeable membrane  Hypertonic solutions: have greater osmolarity than plasma (>295)  Water moves out of the cells and is drawn into the intravascular compartment, causing cells to shrink  Hypotonic solutions: have less osmolarity than plasma (26 mEq/L (compensatory)

Treatment is directed at improving ventilation Pharmacologic measures Pulmonary hygiene measures Adequate hydration Supplemental oxygen Mechanical ventilation may be necessary to correct disorder but must be used cautiously to decrease PaCO2 slowly.

Respiratory Acidosis Acute respiratory disease Pulmonary edema Aspiration of a foreign body Atelectasis Overdose of sedative or anesthetic Cardiac arrest Chronic respiratory disease Emphysema Bronchial asthma Cystic fibrosis Inadequate mechanical ventilation CNS depression Neuromuscular disease

Respiratory Alkalosis Hyperventilation Lightheadedness Extreme anxiety (most Inability to common cause) concentrate

If anxiety is the cause, encourage the patient to breathe more slowly (causes accumulation of CO2) or breathe into a closed system (paper bag). Sedative may also be necessary in extreme

CHAPTE R 40 Hypoxemia High fever Early sepsis Excessive ventilation by mechanical ventilator CNS lesion involving the respiratory center

anxiety. Hyperventilation Treatment of other causes is directed at correcting the underlying syndrome problem. Tinnitus Palpitations Sweating Dry mouth Tremulousness Convulsions and loss of consciousness ABGs pH >7.45 PaCO2...