FLUIDS AND ELECTROLYTE IMBALANCE

Water, Electrolyte, and Acid-Base Balance

Help maintain body temperature and cell shape Help transport nutrients, gasses and wastes Fluids

Fluid Is used to indicate that other substances are also found in these compartments and that they influence the water balance in and between compartments.

Fluids 60% of an adult’s body weight * 70 Kg adult male: 60% X 70= 42 Liters Infants = more water Elderly = less water More fat = ↓water More muscle = ↑water Infants and elderly - prone to fluid imbalance

FLUID BALANCE 40% 50% OVER 60 40-50% 50-60% 40-60 50% 60% 18-40 55% 65% UNDER 18 FEMALE MALE AGE TOTAL BODY WATER (AS PERCENTAGE OF BODY WEIGHT) IN RELATION TO AGE AND SEX

60 % Intracellular Fluid 40% or 2/3 Intravascular 5% or 1/4 Transcellular fluid 1-2% ie csf, pericardial, synovial, intraocular, sweat Arterial Fluid 2% Extracellular Fluid 20% or 1/3 Interstitial 15% or 3/4 Venous Fluid 3% Total Body Water

Function of Water : Most of cellular activities are performed in water solutions.

Intracellular Fluid Compartment Includes all the water and electrolytes inside the cells of the body. Contains high concentrations of: potassium, phosphate, magnesium and sulfate ions, along with most of the proteins in the body.

Extracellular Fluid Compartment Includes all the fluid outside the cells : interstitial fluid, plasma, lymph, secretions of glands, fluid within subcompartments separated by epithelial membranes. Contains high concentrations of : sodium, chloride and bicarbonate. One-third of the ECF is in plasma.

Extracellular Fluid Osmolality Osmolality Adding or removing water from a solution changes this Increased osmolality Triggers thirst and ADH secretion Decreased osmolality Inhibits thirst and ADH secretion

Transcellular Exchange Mechanisms: ACTIVE TRANSPORT PASSIVE TRANSPORT Diffusion Osmosis Filtration Facilitated diffusion

Movement of Water Between Body Fluid Compartments: HYDROSTATIC PRESSURE- pressure in the blood vessels resulting from the weight of the water and cardiac contraction OSMOTIC PRESSURE- pressure exerted by proteins in plasma which pulls water into the circulatory system

16% TBW 40% TBW 4% TBW - makes up ~60% of total body weight (TBW) - distributed in three fluid compartments. Body Fluid

16% TBW 40% TBW 4% TBW Fluid is continually exchanged between the three compartments.

16% TBW 40% TBW 4% TBW Exchange between Blood & Tissue Fluid - determined by four factors: capillary blood pressure plasma colloid osmotic pressure interstitium Hydrostatic Pressure Interstitium colloid osmotic pressure

16% TBW 40% TBW 4% TBW - not affected by electrolyte concentrations - Edema = water accumulation in tissue fluid Exchange between Blood & Tissue Fluid

16% TBW 40% TBW 4% TBW Exchange between Tissue Fluid & Intracellular Fluid - determined by two: 1) intracellular osmotic pressure electrolytes 2) interstitial osmotic pressure electrolytes

Water Gain Water is gained from three sources. 1) food (~700 ml/day) 2) drink – voluntarily controlled 3) metabolic water (200 ml/day) --- produced as a byproduct of aerobic respiration

Routes of water loss 1) Urine – obligatory (unavoidable) and physiologically regulated, minimum 400 ml/day 2) Feces -- obligatory water loss, ~200 ml/day 3) Breath – obligatory water loss, ~300 ml/day 4) Cutaneous evaporation -- obligatory water loss, ~400 ml/day 5) Sweat – for releasing heat, varies significantly

Regulation of Water Intake - governed by thirst.  blood volume and  osmolarity  peripheral volume sensors central osmoreceptors  hypothalamus  thirst felt

Regulation of Urine Concentration and Volume Volume and composition depends on the condition of the body. blood concentration = kidney produce urine. To eliminate solutes and conserve water – help to lower blood concentration Blood concentration = kidney produce urine Water is lost, solutes are conserved, blood concentration increases.

Regulation of Water Output - The only physiological control is through variations in urine volume. - urine volume regulated by hormones

Water Content Regulation Content regulated so total volume of water in body remains constant Kidneys primary regulator of water excretion Regulation processes Osmosis Osmolality Baroreceptors Learned behavior Sources of water Ingestion Cellular metabolism Routes of water loss Urine Evaporation Perspiration Respiratory passages Feces

HORMONAL MECHANISMS Helps to regulate blood composition and blood volume.

1. ANTIDIURETIC HORMONE (ADH) Secreted by posterior pituitary gland into circulation to the kidney Function: to regulate the amount of water reabsorbed RETAINS WATER BLOOD VOL BLOOD PRESSURE CONC. URINE

ADH permeability to water of the kidney = more water is reabsorbed = CONCENTRATED URINE ADH Kidney is less permeable to water = DILUTED URINE 1. ANTIDIURETIC HORMONE (ADH)

1) ADH dehydration   blood volume and/or  osmolality  hypothalamic receptors / peripheral volume sensors  posterior pituitary to release ADH   H 2 O reabsorption  Water retention

2. ATRIAL NATRIURETIC FACTOR Secreted by the cells in the RIGHT ATRIUM when the BP in the RA is Function: Reduces the ability of the kidney to concentrate urine PRODUCTION OF LARGE VOLUME OF URINE BLOOD VOLUME CAUSES BP

2) Atrial Natriuretic Factor  blood volume =↑ BP  atrial volume sensors  atria to release ANF  inhibits Na + and H 2 O reabsorption   water output = ↓ BP

3. ALDOSTERONE Secreted by ADRENAL GLAND Function: regulates the rate of active transport in the kidney REABSORPTION OF NaCl

3. ALDOSTERONE ABSENCE of aldosterone = Na + and Cl - remain in nephron = part of the urine

4. RENIN AND ANGIOTENSIN FUNCTION: regulate aldosterone secretion RENIN secreted by the cells in the juxtaglomerular apparatus in the kidney. An enzyme that acts on proteins produce by liver

Liver: In the protein, certain amino acids are removed leaving ANGIOTENSIN I. ANGIOTENSIN I is rapidly converted into smaller peptide called ANGIOTENSIN II. ANGIOTENSIN II acts on the adrenal gland causing it to secrete ALDOSTERONE!!! RENIN AND ANGIOTENSIN

BP Na + K + BP = RENIN IS RELEASED Na + reabsorbed by nephron H 2 O is reabsorbed CONSERVE WATER = PREVENT IN BP RENIN production

Dehydration - decrease in body fluid Causes the lack of drinking water 2) excessive loss of body fluid due to: overheat diabetes overuse of diuretics diarrhea

Edema - the accumulation of fluid in the interstitial spaces caused by: increased capillary filtration, or 2) reduced capillary reabsorption, or 3) obstructed lymphatic drainage

HORMONE REGULATION: Insulin and Epinephrine = cause K+ and phosphate to move from extracellular fluid into cells Parathyroid hormone = cause Ca++ and phosphate to move from bone to extracellular fluid Calcitonin = moves calcium to bones ELECTROLYTE BALANCE

Electrolytes = small ions that carry charges

Na + K + Ca ++ Cl - PO 4 --- Distribution of Electrolytes Cell Extracellular space

Ions Factors which influence the concentration of water and solutes inside the cells: Transport mechanisms Permeability of the cell membrane Concentration of water and solutes in the extracellular fluid

Ions - 285 – 295 mosm/kg Osmolality 24 mg = 1 mmol 1.8 – 3.0 mg/dL Magnesium (Mg 2+ ) 31 mg = 1 mmol 2.5 – 4.5 mg/dL Phosphorus 40 mg = 1 mmol 8.5 – 10.5 mg/dL Calcium (Ca 2+ ) 61 mg = 1 meq 22 – 26 meq/L Bicarbonate (HCO 3 - ) 35 mg = 1 meq 98 – 107 meq/L Chloride (Cl - ) 39 mg = 1 meq 3.5 – 5.0 meq/L Potassium (K + ) 23 mg = 1 meq 135 – 145 meq/L Sodium (Na + ) Mass Conversion Normal Plasma Values NORMAL VALUES AND MASS CONVERSION FACTORS

Sodium Dominant extracellular ion. About 90 to 95% of the osmotic pressure of the extracellular fluid results from sodium ions and the negative ions associated with them. Recommended dietary intake is less than 2.5 grams per day. Kidneys provide the major route by which the excess sodium ions are excreted.

SODIUM (Na) MOST ABUNDANT cation in the ECF 135-145 mEq/L Aldosterone  increases sodium reabsorption ANP  increases sodium excretion Cl accompanies Na FUNCTIONS: 1. assists in nerve transmission and muscle contraction 2. Major determinant of ECF osmolality 3. Primary regulator of ECF volume

Sodium Primary mechanisms that regulate the sodium ion concentration in the extracellular fluid: Changes in the blood pressure Changes in the osmolality of the extracellular fluid

Regulation of plasma Na + Aldosterone plasma Na +   aldosterone  renal Na + excretion   plasma Na + Na + plasma

Renin-angiotensin-II renin  angiotensin-II   aldosterone   renal Na + excretion   plasma Na + Na + plasma

3) ADH increases water reabsorption in kidneys  water retention  dilute plasma Na + plasma Na + H 2 O

Atrial Natriuretic Factor inhibits renal reabsorption of Na + and H 2 O and the excretion of renin and ADH  eliminate more sodium and water   plasma Na + Na + plasma Na +

Sodium imbalance hypernatremia plasma sodium > 145 mEq/L, hyponatremia plasma sodium < 130 mEq/L

HYPERNATREMIA Na > 145 mEq/L Assoc w/ water loss or sodium gain Etiology: inadequate water intake , excessive salt ingestion / hypertonic feedings w/o water supplements, near drowning in sea water, diuretics

HYPERNATREMIA S/SX: Polyuria Anorexia Nausea/vomiting, Thirst Dry and swollen tongue Fever Dry and flushed skin Altered LOC Seizure Muscle weakness Crackles Dyspnea Cardiac manifestations dependent on type of hypernatremia Dx: inc serum sodium and Cl level, inc serum osmolality, inc urine sp.gravity, inc urine osmolality

Mgt: sodium restriction, water restriction, diuretics, isotonic non saline soln. (D5W) or hypotonic soln, Desmopressin Acetate for Diabetes Insipidus Nsg considerations History – diet, medication Monitor VS, LOC, I and O, weight, lung sounds Monitor Na levels Oral care Initiate gastric feedings slowly Seizure precaution

HYPONATREMIA Na < 135 mEq/L Etiology: diuretics , excessive sweating, vomiting, diarrhea, SIADH, aldosterone deficiency, cardiac, renal, liver disease

HYPONATREMIA s/sx: headache, apprehension , restlessness, altered LOC, seizures(<115meq/l), coma, poor skin turgor, dry mucosa, orthostatic hypotension, crackles, nausea/vomiting, abdominal cramping Dx: dec serum and urine sodium and osmolality, dec Cl

Mgt: sodium replacement, water restriction, isotonic soln for moderate hyponatremia, hypertonic saline soln for neurologic manifestations, diuretic for SIADH Nsg. Consideration Monitor I and O, LOC, VS, serum Na Seizure precaution diet

Potassium (K) MOST ABUNDANT cation in the ICF 3.5-5.5 mEq/L Major electrolyte maintaining ICF balance maintains ICF Osmolality Aldosterone promotes renal excretion of K+ Mg accompanies K FUNCTIONS: 1. nerve conduction and muscle contraction 2. metabolism of carbohydrates, fats and proteins 3. Fosters acid-base balance

Potassium Electrically excitable tissue such as muscle and nerves are highly sensitive to slight changes in extracellular potassium concentration. concentration of potassium must be maintained within a narrow range for tissues to function normally.

Potassium CONDITIONS THAT MAKE K+ BECOME MORE CONC Circulatory system shock resulting from plasma loss dehydration tissue damage In response, aldosterone secretion increases and causes potassium secretion to increase.

Regulation of Potassium by aldosterone Aldosterone  stimulates K + secretion by the kidneys   Plasma K + K + plasma K +

Potassium Imbalance hyperkalemia (> 5.5 mEq/L) hypokalemia (< 3.5 mEq/L)

Abnormal Concentration of Potassium Ions

a. HYPERKALEMIA K+ > 5.0 mEq/L Etiology: IVF with K+, acidosis, hyper-alimentation excess K+ replacement, decreased renal excretion, Diuretics s/sx: nerve and muscle irritability Tachycardia Diarrhea ECG changes ventricular dysrythmia and cardiac arrest skeletal muscle weakness, paralysis Dx: inc serum K level ECG: peaked T waves and wide QRS ABGs – metabolic acidosis

Mgmt: K restriction (coffee, cocoa, tea, dried fruits, beans, whole grain breads, milk, eggs) diuretics Polystyrene Sulfonate (Kayexalate) IV insulin Beta 2 agonist IV Calcium gluconate IV NaHCo3 – alkalinize plasma Dialysis Nsg consideration: Monitor VS, urine output, lung sounds, Crea, BUN monitor K levels and ECG observe for muscle weakness and dysrythmia, paresthesia and GI symptoms

b. HYPOKALEMIA K+ < 3.5 mEq/L Etiology: use of diuretic, corticosteroids and penicillin, vomiting and diarrhea, ileostomy, villous adenoma, alkalosis, hyperinsulinism, hyperaldosteronism s/sx: anorexia, Nausea/vomiting, decreased bowel motility, fatigue, muscle weakness, leg cramps, paresthesias, shallow respiration, SOB dysrhythmias and increased sensitivity to digitalis, hypotension, weak pulse, dilute urine, glucose intolerance

Dx: dec serum K level ECG - flattened , depressed T waves, presence of “U” waves ABGs - metabolic alkalosis Medical Mgmt : diet ( fruits, fruit juices, vegetables, fish, whole grains, nuts, milk, meats) oral or IV replacement Nsg mgmt : monitor cardiac function, pulses, renal function monitor serum potassium concentration IV K diluted in saline monitor IV sites for phlebitis

Normal ECG Hypokalemia Hyperkalemia

CALCIUM (Ca) Majority of calcium - bones and teeth Normal serum range 8.5-10.5 mg/dL Ca ++ has an inverse relationship with PO 4 FUNCTIONS 1. formation and mineralization of bones/teeth 2. muscular contraction and relaxation 3. cardiac function 4. blood coagulation 5. Promotes absorption and utilization of Vit B12

Functions of Ca ++ - lends strength to the skeleton - activates muscle contraction Excitation Contraction [ Ca ++ ] i (Action Potentials) (shortening)

Functions of Ca ++ - lends strength to the skeleton - activates muscle contraction - serves as a second messenger for some hormones and neurotransmitters

Functions of Ca ++ - lends strength to the skeleton - activates muscle contraction - serves as a second messenger for some hormones and neurotransmitters - activates exocytosis of neurotransmitters and other cellular secretions

Functions of Ca ++ - lends strength to the skeleton - activates muscle contraction - serves as a second messenger for some hormones and neurotransmitters - activates exocytosis of neurotransmitters and other cellular secretions - essential factor in blood clotting. Ca ++

Functions of Ca ++ - lends strength to the skeleton - activates muscle contraction - serves as a second messenger for some hormones and neurotransmitters - activates exocytosis of neurotransmitters and other cellular secretions - essential factor in blood clotting. - activates many cellular enzymes

Dynamics of Calcium Ca ++ plasma Ca ++ Ca ++ Ca ++

Regulation of calcium 1) parathyroid hormone (PTH): dissolving Ca ++ in bones Respond ↓blood Ca++ -> ↑ PTH production = ↑ blood Ca++ - reducing renal excretion of Ca ++ plasma Ca ++ Ca ++ PTH increases Vit. D synthesis in the kidney which increases Ca2+ absorption in the small intestine. PTH decreases urinary Ca2+ excretion and increases urinary phosphate excretion.

2) calcitonin (secreted by C cells in thyroid gland):

2) calcitonin (secreted by C cells in thyroid gland): depositing Ca ++ in bones Respond when high Ca ++ in the blood plasma Ca ++ Ca ++

3) calcitrol ( derivative of vitamin D): - enhancing intestinal absorption of Ca ++ from food plasma Ca ++ Ca ++ Ca ++

Calcium imbalances hypocalcemia (< 4.5 mEq/L) hypercalcemia (> 5.8 mEq/L).

Regulation: GIT  absorbs Ca+ in the intestine with the help of Vitamin D Kidney  Ca+ is filtered in the glomerulus and reabsorbed in the tubules PTH  increases Ca+ by bone resorption, increase intestinal and renal Ca+ reabsorption and activation of Vitamin D Calcitonin  reduces bone resorption, increase Ca and Phosphorus deposition in bones and secretion in urine

a. HYPERCALCEMIA Serum calcium > 10.5 mg/dL Etiology: Overuse of calcium supplements and antacids, excessive Vitamin A and D, malignancy, hyperparathyroidism, prolonged immobilization, thiazide diuretic s/sx: anorexia, Nausea/vomiting, polyuria, muscle weakness, fatigue, lethargy Dx: inc serum Ca ECG: Shortened QT interval, ST segments inc PTH levels xrays - osteoporosis

Mgmt: 0.9% NaCl IV Phosphate Diuretics – Furosemide IM Calcitonin corticosteroids dietary restriction (cheese, ice cream, milk, yogurt, oatmeal, tofu) Nsg Mgmt: Assess VS, apical pulses and ECG, bowel sounds, renal function, hydration status safety precautions in unconscious patients inc mobility inc fluid intake monitor cardiac rate and rhythm

b. HYPOCALCEMIA Calcium < 8.5 mg/dL Etiology: removal of parathyroid gland during thyroid surgery, Vit. D and Mg deficiency, Furosemide, infusion of citrated blood, inflammation of pancreas, renal failure, thyroid CA, low albumin, alkalosis, alcohol abuse, osteoporosis (total body Ca deficit) s/sx: Tetany, (+) Chovstek’s (+) Trousseaus’s, seizures, depression, impaired memory, confusion, delirium, hallucinations, hypotension, dysrythmia

(+) Chovstek’s Trousseaus Sign

Dx: dec Ca level ECG: prolonged QT interval Mgmt: Calcium salts Vit D diet (milk, cheese, yogurt, green leafy vegetables) Nsg mgmt monitor cardiac status, bleeding monitor IV sites for phlebitis seizure precautions reduce smoking

Magnesium Mg Second to K+ in the ICF Normal range is 1.3-2.1 mEq/L FUNCTIONS 1. intracellular production and utilization of ATP 2. protein and DNA synthesis 3. neuromuscular irritability 4, produce vasodilation of peripheral arteries

a. HYPERMAGNESEMIA M > 2.1 mEq/L Etiology: use of Mg antacids, K sparing diuretics, Renal failure, Mg medications, DKA, adrenocortical insufficiency s/sx: hypotension, nausea, vomiting, flushing, lethargy, difficulty speaking, drowsiness, dec LOC, coma, muscle weakness, paralysis, depressed tendon reflexes, oliguria, ↓RR

Mgmt: discontinue Mg supplements Loop diuretics IV Ca gluconate Hemodialysis Nsg mgmt: monitor VS observe DTR’s and changes in LOC seizure precautions

b. HYPOMAGNESEMIA Mg < 1.5 mEq/l Etiology : alcohol w/drawal, tube feedings, diarrhea, fistula, GIT suctioning, drugs ie antacid, aminoglycosides, insulin therapy, sepsis, burns, hypothermia s/sx: hyperexcitability w/ muscle weakness, tremors, tetany, seizures, stridor, Chvostek and Trousseau’s signs, ECG changes, mood changes

Dx: serum Mg level ECG – prolonged PR and QT interval, ST depression, Widened QRS, flat T waves low albumin level Mgmt: diet (green leafy vegetables, nuts, legumes, whole grains, seafood, peanut butter, chocolate) IV Mg Sulfate via infusion pump Nsg Mgmt: seizure precautions Test ability to swallow, DTR’s Monitor I and O, VS during Mg administration

The Anions CHLORIDE PHOSPHATES BICARBONATES

Chloride (Cl) The MAJOR Anion in the ECF Normal range is 95-108 mEq/L Inc Na reabsorption causes increased Cl reabsorption FUNCTIONS 1. major component of gastric juice aside from H+ 2. together with Na+, regulates plasma osmolality 3. participates in the chloride shift – inverse relationship with Bicarbonate 4. acts as chemical buffer

Regulation of Cl – No direct regulation indirectly regulated as an effect of Na + homeostasis. As sodium is retained or excreted, Cl – passively follows. Chloride Imbalance hyperchloremia (> 105 mEq/L) hypochloremia (< 95 mEq/L).

a. HYPERCHLOREMIA Serum Cl > 108 mEq/L Etiology: sodium excess, loss of bicarbonate ions s/sx: tachypnea, weakness, lethargy, deep rapid respirations, diminished cognitive ability and hypertension, dysrhytmia, coma

Dx: inc serum Cl dec serum bicarbonate Mgmt: Lactated Ringers soln IV Na Bicarbonate Diuretics Nsg mgmt: monitor VS, ABGs, I and O, neurologic, cardiac and respiratory changes

b. HYPOCHLOREMIA Cl < 96 mEq/l Etiology: Cl deficient formula, salt restricted diets, severe vomiting and diarrhea s/sx: hyperexcitability of muscles, tetany, hyperactive DTR’s, weakness, twitching, muscle cramps, dysrhytmias, seizures, coma

Dx: dec serum Cl level ABG’s – metabolic alkalosis Mgmt: Normal saline/half strength saline diet ( tomato juice, salty broth, canned vegetables, processed meats and fruits avoid free/bottled water) Nsg mgmt: monitor I and O, ABG’s, VS, LOC, muscle strength and movement

Phosphates (PO4) The MAJOR Anion in the ICF Normal range is 2.5-4.5 mg/L Reciprocal relationship w/ Ca PTH  inc bone resorption, inc PO4 absorption from GIT, inhibit PO4 excretion from kidney Calcitonin  increases renal excretion of PO4 FUNCTIONS 1. component of bones 2. needed to generate ATP 3. components of DNA and RNA

Phosphates needed for the synthesis of: ATP, GTP DNA, RNA phospholipids

Regulation of Phosphate by parathyroid hormone PTH  increases renal excretion of phosphate  decrease plasma phosphate - no real phosphate imbalances PO 4 --- plasma PO 4 ---

a. HYPERPHOSPHATEMIA Serum PO4 > 4.5 mg/dL Etiology: excess vit D , renal failure, tissue trauma, chemotherapy, PO4 containing medications, hypoparathyroidism s/sx: tetany, tachycardia, palpitations, anorexia, vomiting, muscle weakness, hyperreflexia, tachycardia, soft tissue calcification

Dx: inc serum phosphorus level dec Ca level xray – skeletal changes Mgmt: diet – limit milk, ice cream, cheese, meat, fish, carbonated beverages, nuts, dried food, sardines Dialysis Nsg mgmt: dietary restrictions monitor signs of impending hypocalcemia and changes in urine output

b. HYPOPHOSPHATEMIA Serum PO4 < 2.5 mg/dl Etiology: administration of calories in severe CHON-Calorie malnutrition (iatrogenic), chronic alcoholism, prolonged hyperventilation, poor dietary intake, DKA, thermal burns, respiratory alkalosis, antacids w/c bind with PO4, Vit D deficiency s/sx: irritability, fatigue, apprehension, weakness, hyperglycemia, numbness, paresthesias, confusion, seizure, coma

Dx: dec serum PO4 level Mgmt: oral or IV Phosphorus correction diet (milk, organ meat, nuts, fish, poultry, whole grains) Nsg mgmt: introduce TPN solution gradually prevent infection

Acid An acid is any chemical that releases H + in solution. Base A base is any chemical that accepts H + .

pH is the negative logarithm of H + concentration, and an indicator of acidity. pH = - log [H + ] Example: [H + ] = 0.1  M = 10 –7 M

Normal functions of proteins (especially enzymes) heavily depend on an optimal pH. pH7.35-pH7.45

Regulation of acid-base balance 1) Chemical Buffers 2) Respiratory Control of pH 3) Renal Control of pH

Buffer is any mechanism that resists changes in pH. substance that can accept or donate hydrogen prevent excessive changes in pH

Dynamics of Acid Base Balance Acids and bases are constantly produced in the body They must be constantly regulated CO2 and HCO3 are crucial in the balance Respiratory and renal system are active in regulation

Kidney - Regulate bicarbonate level in ECF 1. RESPIRATORY/METABOLIC ACIDOSIS - kidney excrete H and reabsorbs/generates Bicarbonate 2. RESPIRATORY/METABOLIC ALKALOSIS - kidney retains H ion and excrete Bicarbonate

Lung Control CO2 and Carbonic acid content of ECF 1. METABOLIC ACIDOSIS - increased RR to eliminate CO2 2. METABOLIC ALKALOSIS - decreased RR to retain CO2

3) The Protein Buffer There are three major buffers in body fluid. 1) The Bicarbonate (HCO 3 - ) Buffer 2) The Phosphate Buffer Chemical Buffers

Properties of Chemical Buffers - respond to pH changes within a fraction of a second. - Bind to H  but can not remove H  out of the body - Limited ability to correct pH changes

 pH  stimulate peripheral/central chemoreceptors   pulmonary ventilation  removal of CO 2 and  pH H 2 CO 3 H  + HCO 3 - H 2 O + CO 2

Limit to respiratory control of pH The respiratory regulatory mechanism cannot remove H + out of the body. Its efficiency depends on the availability of HCO 3 - . H  + HCO 3 - H 2 CO 3 H 2 O + CO 2

Renal Control of pH The kidneys can neutralize more acid or base than both the respiratory system and chemical buffers. a. Renal tubules secrete hydrogen ions into the tubular fluid, where most of it combines with bicarbonate, ammonia, and phosphate buffers. b. Bound and free H + are then excreted in urine.

The kidneys are the only organs that actually expel H + from the body. Other buffering systems only reduce its concentration by binding it to another chemical. 3. Tubular secretion of H + continues as long as a sufficient concentration gradient exists between the tubule cells and the tubular fluid.

Disorders of Acid-Base Balance Acidosis : < pH 7.35 , Alkalosis : > pH 7.45 Mild acidosis depresses CNS, causing confusion , disorientation , and coma . Mild alkalosis CNS becomes hyperexcitable. Nerves fire spontaneously and overstimulate skeletal muscles. - Severe acidosis or alkalosis is lethal.

Respiratory vs Metabolic Cause Respiratory acidosis / alkalosis - caused by hypoventilation or hyperventilation H  + HCO - H 2 CO 3 H 2 O + CO 2 Initial change Emphysema

Respiratory acidosis / alkalosis - caused by hypoventilation or hyperventilation Metabolic acidosis or alkalosis - result from any causes but respiratory problems Diabetes   production of organic acids  metabolic acidosis Chronic vomiting  loss of stomach acid  metabolic alkalosis

FLUIDS AND ELECTROLYTE IMBALANCE

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