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Fluid, electro, acid
fluid, electrolytes, and acid-base balance
| Question | Answer |
|---|---|
| Body Fluids pg996 | Relative amount of fluid in infants 73% |
| Relative amount of fluid in old age | 45% |
| Relative amount of fluid in young men, young women | 60%, 50% |
| Least hydrated tissue containing 20% water | adipose |
| Skeletal muscle is about what % water | 75% |
| Two main fluid compartments | Intracellular fluid (ICF) compartment, Extracellular fluid (ECF) compartment |
| (ICF) accounts for what amount of water in adult males | 25L of the 40L of body water |
| Remaining 1/3 of body water is outside cells, (ECF) | the bodies "internal environment" and the "external environment" of each cell |
| EFC has 2 subcompartments | Plasma, interstitial fluid (IF) |
| Fluid portion of the blood | plasma |
| (IF) Interstitial fluid | the fluid in the microscopic space between the tissue cells |
| A number of other examples of ECF that are distinct from both plasma and interstitial fluid, but are still considered part of IF | lymph, cerebrospinal fluid, humors of the eye, synovial fluid, serous fluid, secretions of the GI tract |
| Universal solvent | water |
| solutes may be classified broadly as | electrolytes and nonelectrolytes |
| pg996 Nonelectrolytes | have bonds(usually covalent) that prevent them from dissociating in solution. NO electrically charged species are created when non electrolytes dissolve in water. Most are organic molecules (glucose, lipids, creatine, urea) |
| pg996 Electrolytes | chemical compounds, DO dissociate into ions in H20. Ions are charged, they conduct electrical current, so named "electrolyte". Include inorganic salts, inorganic& organic acids and bases, some proteins |
| Electrolyes have greater osmotic power because | each electrolyte molecule dissociates into at least two ions |
| molecule of NaCl contributes twice as many solute particles as | glucose (which remains undissociated) |
| MgCl contributes 3 times as many | NaCl Na +Cl (electrolyte; two particles) MgCl Mg +2Cl (electrolyte; three particles) glucose glucose (nonelectrolyte; one particle) |
| greatest ability to cause fluid shifts | electrolytes |
| Electrolyte concentrations of body fluids are usually expressed in | milliequivalents per liter (mEq/L) |
| Equation for measuring concentration | pg 997 |
| to compute the mEq/L | 1)determine the normal concentration of these ions in plasma 2) look up their atomic weights in the periodic table 3) plug these values into the equation |
| Ions w/ a single charge, lmEq is = to 1mmol, which, when dissolved in 1kg of water, produces 1 mOsm pg997 | true |
| each fluid compartment has a distinctive pattern of electrolytes. except for the relatively high protein content in plasma, however, the extracellular fluids are very similar. | Their chief cation is Na, major anion is Cl |
| Plasma contains somewhat fewer chloride ions than interstitial fluid, | because the non penetrating plasma proteins are normally anions and plasma is electrical neutral. |
| ICFs contain small amounts of Na and Cl. | MOST ABUNDANT cation is K, major anion is HPO. |
| cells also contain substantial quantities of soluble proteins | (about 3 times the amount found in plasma) |
| Na and K ion concentrations in ECF and ICF are nearly opposite | true |
| activity of cellular ATP-dependent sodium-potassium pumps, which keep intracellular Na concentrations low, K concentrations high | ICF and ECF opposite in Na and K ion concentrations |
| Renal mechanisms can reinforce these ion distributions | by secreting K into the filtrate as Na is reabsorbed from the filtrate |
| Electrolytes most abundant solutes in body fluids pg998 | and determine most of their chemical and physical reaction,BUT do not make up the build of dissolved solutes in these fluids |
| Proteins and some of the non electrolytes (phospholipids, cholesterol, and triglycerides) found in the ECF are late molecules. | true |
| They account for about 90% of the mass of dissolved solutes in plasma, 60% in the IF, and 97% in the ICF pg998 | true |
| Fluid movement among compartments pg 998 | osmotic and hydrostatic pressures regulates continuous exchange and mixing of body fluids |
| water moves freely between compartments along osmotic gradients, | solutes are unequally distributed because of their size, electrical charge, or dependence on transport proteins. |
| Anything that changes the solute concentration in any compartment | leads to net water flows |
| Substances must pass through both the plasma and IF in order to reach the ICF | true |
| In the lungs, GI tract, and kidneys, | exchanges between the "outside world" and plasma occur almost continuously |
| these exchanges alter plasma composition and volume, | w/ plasma serving s the "highway" for delivering substances throughout the body. |
| exchanges between plasma and IF occur across capillary membranes pg998 | true |
| Exchanges between the IF and ICF occur across plasma membranes and | depend on the membranes" complex permeability properties |
| As a general rule, 2-way osmotic flow of water is substantial. But, pg998 | ion fluxes are restricted and, in most cases, ions move selectively by active transport or through channels. |
| Movements of nutrients, respiratory gases, and wastes are typically unidirectional. | example: glucose and oxygen move into the cells and metabolic wastes move out |
| Osmolalities of all body fluids are equal (except during the first few minutes after a change in one of the fluids occurs) | true, though many factors can change volumes of ICF and ECF |
| Increasing the ECF solute content (mainly the NaCl concentration) can be expected to cause osmotic and volume changes in the ICF- namely, | a shift of water out of the cells |
| Conversely, decreasing ECF osmolality causes water to move into the cells,. Thus, the ICF volume is determined by the ECF solute concentration. | these concepts underlie all events that control fluid balance in the body and should be understood thoroughly |
| Water Balance and ECF Osmolality Pg 998 | Water intake is typically 2500ml a day in adults |
| Body water produced by cellular metabolism is called | metabolic water or water of oxidation |
| Water output occurs by several routes | true |
| Insensible water loss | water that vaporizes out of the lungs in expired ari or diffuses directly through the skin |
| 60% of water output is excreted by the kidneys | true |
| healthy people have a remarkable ability to maintain the tonicity of their body fluids with very narrow limits (280-300 mOsm/kg | true |
| Rise in plasma osmolality triggers pg999 | thirst causes us to drink, release of antidiuretic hormone (ADH) which cause kidneys to conserve water and excrete concentrated urine, |
| Decline in osmolality | inhibits both thurst and ADH release, the latter followed by output of large volumes of dilute urine |
| Thirst mechanism is the driving force odor water intake | true |
| An increase in plasma osmolality of only 2-3% excites the hypothalamic thirst center | true |
| Dry mouth occurs also because | the rise in plasma colloid osmotic pressure causes less fluid to leave the bloodstream. Because the salivary glands obtain the water they require from the blood, they produce less saliva, reinforcing the drive to drink. |
| A decrease in the blood volume (or pressure) also triggers the thirst mechanism. However, because a substantial decrease (10-15%) is required, this is the less potent stimulus | true |
| Hypothalamic thirst center neurons are stimulated when their osmoreceptors lose water by osmosis to the hypertonic ECF, or are active at by angiotensin II, by baroreceptor inputs, or other stimuli | true |
| collectively, these events cause a subjective sensation of thirst, which motivates us to get a drink | t |
| thirst is quenched almost as soon as we begin drinking water, even though the water has yet to be absorbed into the blood. Mucosa of the mouth and throat is moistened and continues as stretch receptors in the stomach & intestines are activated | t |
| Obligatory water losses | output of certain amounts of water is unavoidable. |
| Obligatory water loss includes | insensible water losses described above pg1000, water that accompanies undigested food residues in feces, and a minimum daily sensible water loss of 500ml in urine |
| Sensible water loss | 500ml urine |
| Obligatory water loss in urine reflects the fact that kidneys must normally flush 600mmol per day of urine solutes (end products of metabolism and so forth) out of the body in water | t |
| Maximum concentration of urine is about 1200 mOsm, so a minimum of 500ml of water must be excreted | t |
| Beyond obligatory water loss, the solute concentration and volume of urine excreted deepen on fluid intake, diet, and water loss via other avenues | t |
| Diuresis reaches a peak in 1 hour after drinking and then declines to its lowest level after 3 hrs | t |
| The body's water volume is closely tied to a powerful water " magnet", ionic sodium. | t |
| our ability to maintain water a lance through urinary output is really a problem of sodium and water balance because the two are always regulated in tandem by mechanisms that serve cardiovascular function and blood pressure. | t |
| Amount of water reabsorbed in the renal collection ducts is proportional to ADH release. | t |
| ADH levels low | most of the water reaching the collecting ducts is not reabsorbed but simply allowed to pass through because the lack of aquaporins in the luminal membranes of the principal cells prevent the movement of water. |
| ADH levels low results in dilute urine and a reduced volume of body fluids. | t |
| ADH levels high | aquaporins are inserted in the principal cell luminal membranes, nearly all of the filtered water is reabsorbed, and a small volume of concentrated urine is excreted |
| Osmoreceptors of the hypothalamus sense the ECF solute concentration and trigger or inhibit ADH release from the posterior pituitary accordingly | t |
| Decrease in ECF osmolaity inhibits ADH release and allows more water to be excreted in urine, restoring normal blood osmolality | t |
| Increase in ECF osmolality stimulates ADH release by stimulating the hypothalamic osmoreceptors | T |
| ADH secretion is also influenced by large changes in blood volume or blood pressure. | t |
| Decrease in BP triggers an increase in ADH secretion form the posterior pituitary both directly via baroreceptors in the atria and various blood vessels, and indirectly via the renin-angiotensin mechanism | t |
| Changes in ECF osmolality are much more important as stimulatory or inhibitory factors. | t |
| Factors that trigger ADH release by reducing blood volume include | prolonged fever, excessive sweating, vomiting, or diarrhea, severe blod loss, and traumatic burns |
| ADH also acts to constrict arterioles, directly increasing BP- hence its other name Vasopressin | T |
| ADH is also called Vasopressin | t |
| pg1001 De/hydra/tion | water OUTPUT exceeds INTAKE over a period of time and the body is in negative fluid balance |
| Hypo/tonic hydration, | increase of fluid in all compartments; overhydration of cells |
| Hypo/natr/emia | low ECF Na+ concentration |
| EDEMA | "a swelling"of tissue, but not cell. Increase of volume ONLY in IF |
| Increase CAPILLARY PERMEABILITY | usually due to ongoing inflammatory response |
| pg 1002 Hypo/protein/emia | a condition of unusually low levels of plasma proteins, results in tissue edema; result form protein malnutrition, liver disease, or glomerul/o/nephr/itis |
| Electr/o/lyte balance pg1002 | refers to the salt balance in the body |
| Addison's disease pg 1002 | a disorder entailing deficient mineralocorticoid hormone production by the adrenal cortex |
| pica | APPETITE for ABNORMAL substances |
| NaHCO3 and NaCl account for 90-95% of all solutes in ECF; | True |
| Na+ in ECF concentration normally remains stable because of immediate movement of water into or out of the ICF and longer term adjustments due to the ADH and thirst mechanisms | true |
| water FOLLOWS salt | true |
| A CHANGE in plasma Na+ levels affects not only plasma volume and blood pressure, but also the ICF and IF volumes. | true |
| CAUSES and CONSEQUENCES of electrolyte imbalances pg 1003 | t |
| Aldosterone pg 1004 | Increases ECF volume; "has most to say about renal regulation of sodium ion concentrations in ECF" |
| 65% os Na+ in renal filtrate is reabsorbed in proximal tubules of the kidneys and 25% is reclaimed in the LOOPS OF HENLE | True |
| Most important TRIGGER for ALDOSTERONE release is RENIN-ANGIOTENSIN mechanism | true |
| Juxtaglomerular Apparatus (JG) repsonds to | sympathetic stimulation, decreased filtrate NaCl concentration, or decreased stretch(due to decreased blood pressure) it's granular cells release renin |
| Angiotensin II | important in linking renin to aldosterone release; PRODS the adrenal cortex to release aldosterone and also directly increases Na+ reabsorption by kidney tubules; its aim is to raise blood volume and blood pressure |
| Atrial natriuretic peptide (ANP) | reduces blood pressure and blood volume by inhibiting nearly all events that promote vasoconstriction and Na+ and water retention; |
| Atrial natriuretic peptide (ANP) cont'd | a HORMONE;has diuretic and natriuretic effects. Promote excretion of Na+ and water by the kidneys by inhibiting the ability of collecting ducts to reabsorb Na+ and suppressing release of ADH, renin, and aldosterone |
| Estrogens | chemically similar to adlosterone; enhance NaCl reabsorption by renal tubules |
| Progesterone | decrease Na+ reabsorption by blocking the effect aldosterone has on the renal tubules; Has a diuretic-like effect and promotes Na+ and water loss |
| Glucocorticoids | cortisol and hydrocortisol; enhance tubular reabsorption of Na+; also promote an increased glomerular filtration rate that may mask their effects on the tubules; PLASMA LEVELS HIGH, exhibit potent aldosterone-like effects and promote edema |
| Potassium Pg 1006 | chief intracellular cation; required for normal neuromuscular functioning |
| K+ balance maintained by renal mechanisms | True |
| proximal tubules REABSORB 60-80% of filtered K+ and Thick ascending limb of HENLE"S LOOP absorbs another 10-20% | true |
| most important factor INFLUENCING K+ secretion is K+ concentration in blood plasma Pg 1006 | true |
| second factor INFLUENCING K+ secretion is aldosterone | true |
| Regulation of CALCIUM and PHOSPHATE balance Pg 1008 | 99% of calcium is in bones |
| IONIC Calcium | in ECF is important for normal blood CLOTTING, cell membrane PERMEABILITY, and SECRETORY behavior. BUT MOST important in NEUROMUSCULAR EXCITABILITY |
| Hypo/calc/emia | increases EXCITABILITY and causes muscle TETANY |
| Hyper/calc/emia | inhibits neurons and muscle cells and may cause life-threatening cardiac arrhythmias |
| Para/thyroid hormone (PTH) | regulates ECF calcium ion levels; rarely deviate from normal limits |
| DECLINING levels of Ca2+ directly stimulate the parathyroid glands to release PTH, which promotes an increase in calcium levels by targeting the | BONES-PTH activates bone-digesting osteoclasts, which break down the bone matrix pg 1008 SMALL INTESTINES- PTH enhances intestinal absorption of Ca2+ KIDNEYS- PTH increases Ca2+ reabsorption by renal tubules |
| Most Ca+ is reabsorbed passively in the PCT via diffusion through the paracellular route (a process driven by electrochemical gradient) | true |
| DISTAL NEPHRON | does "fine tuning" of Ca+ reabsorption |
| 98% of the filtered Ca+ | is reabsorbed owing to the action of PTH |
| PTH INHIBITS | active transport of PHOSPHATE by DECREASING its Tm |
| ECF CALCIUM levels | normal limit (9-11mg/100ml of blood); IF it is HIGHER, PTH secretion is inhibited; Consequently, release of Ca+ from bone is inhibited |
| PHOSPHATE REABSORPTION; insulin increases it while glucagon decreaes it | Hormones OTHER THAN PTH alter |
| CHLORIDE is the major ANION accompanying Na+ in ECF pg1008 | and, like NA+, Cl helps MAINTAIN the OSMOTIC pressure of the blood |
| Due to abundant hydrogen bonds, ALL FUNCTIONAL PROTEINS (enzymes, hemoglobin, cytochromes, and others) | influenced by H+ concentration |
| Nearly ALL BIOCHEMICAL REACTIONS | are influenced by the pH of their fluid environment; and acid-base balance of body fluids is closely regulated |
| Normal pH | arterial blood is 7.4 venous blood and IF is 7.35 ICF averages 7.0 |
| LOWER pH in cells and venous blood | reflects their greater amounts of acidic metabolites and carbon dioxide, which combines with water to form CARBONIC ACID |
| ALKALOSIS or ALKALEMIA | pH of arterial blood rises above 7.45 a person is |
| ACIDOSIS | DROP in arterial pH to below 7.35 results in |
| PHYSIOLOGICAL ACIDOSIS | any ARTERIAL pH between 7.35-7.0 is called |
| Most H+ ions ORIGINATE Pg 1009 | as metabolic by products or end products |
| H+ CONCENTRATION in blood is regulated by | chemical buffers; brain stem respiratory centers; and renal mechanisms |
| Chemical buffers ; FIRST LINE OF DEFENSE | act within a fraction of a second to resist pH changes |
| ACIDS are proton DONORS; | BASES are proton ACCEPTORS |
| ACIDITY of a solution | REFLECTS only the FREE hydrogen ions, not those bound to anions |
| STRONG ACIDS | dissociate completely and liberate all their H+ in water; can dramatically change pH |
| WEAK ACIDS | dissociate only partially; have a much smaller effect on pH |
| STRONG BASES | dissociate easily in water and quickly tie up H+ |
| WEAK BASES are slower to accept protons | true |
| CHEMICAL BUFFER; system of one or more compounds that acts to resist changes in pH when a strong acid or base is added | They do this by binding to H+ whenever the pH drops and releasing them when pH rises |
| 3 major CHEMICAL BUFFER systems in the body | bicarbonate, phosphate, and protein buffer system |
| Anything that causes a SHIFT in H+ concentration | in one fluid compartment simultaneously causes a change in the others |
| BICARBONATE BUFFER SYSTEM | a mixture of carbonic acid (H2CO3, a weak acid) and its salt, sodium bicarbonate (NaHCO3, a weak base) in the same solution; Although it buffers the ICF, it is the ONLY important ECF buffer |
| Carbonic acid | weak acid, does not dissociate to any great extent in neutral or acidic solutions. |
| NCO3- is the important ion, NOT the cation it is paired with | true |
| alkaline reserve (available HCO3-) | when these are tied up, the buffer system becomes ineffective and blood pH changes. |
| Bicarbonate ion concentration in ECF | is normally around 25 mEq/L and is closely regulated by the kidneys |
| Concentration of H2CO3 is just over 1 mEq/L | but the supply of H2CO3 (which comes from the CO2 released during cellular respiration) is almost limitless |
| Phosphate buffer system | nearly identical to bicarbonate buffer. Components of Phosphate system are the sodium salts of dihydrogen phosphate (H2PO4-) and Monodydrogen phosphate (HPO4-) |
| NaH2PO4 acts as WEAK ACID. | Na2HPO4, with one less hydrogen atom, acts as a WEAK BASE |
| PHOSPHATE buffer system is present in LOW concentrations | in the ECF (approximately one-sixth that of the bicarbonate buffer system), it is relatively unimportant for buffering blood plasma, it is VERY effective buffer in urine and in ICF where phosphate concentrations are usually higher |
| Protein Buffer system Pg 1010 | Proteins in plasma and in cells are the body's most plentiful and powerful source of buffers |
| BUFFERING POWER of FLUIDS | 3/4 resides in cells, and most of this reflects the buffering activity of intracellular proteins |
| Organic acid (carboxyl) groups(-COOH) | dissociate to release H+ when pH begins to rise |
| AMPHOTERIC molecules: reversibly as either an acid or a base | single protein molecule can function reversibly as either acid or base depending on the pH of its environment; |
| RESPIRATORY REGULATION Pg1010 PHYSIOLOGICAL buffering systems | control pH by controlling the amount of acid or base in the body; Act more slowly than chemical buffer systems, but, they have many times the buffering power of all the body's chemical buffers combined |
| Anything that impairs respiratory system functioning | causes ACID-BASE IMBALANCEs |
| NET CARBON DIOXIDE retention (hypoventilation) | leads to ACID/OSIS |
| NET ELIMINATION of CO2 (hyperventilation) | causes ALKAL/OSIS |
| RENAL MECHANISMS of ACID-BASE balance Pg 1011 Ultimate acid-base regulatory organs are | the kidneys (act slowly, but surely) |
| CHEMICAL BUFFERS can | tie up excess acids or bases temporarily, but they CANNOT ELIMINATE them from the body |
| LUNGS can DISPOSE of VOLATILE ACIDs | by eliminating CO2 |
| Only the kidneys can eliminate acids generated by | cellular metabolism: phosphoric, uric, and lactic acids, and ketone bodies (referred to as METABOLIC FIXED ACIDS, but that is wrong!) |
| ONLY THE KIDNEYS can | can regulate blood levels of alkaline substances and renew chemical buffers that are used up in regulating H+ levels in ECF |
| Most important RENAL MECHANISMS for regulating | CONSERVING (REABSORBING) new HCO3- EXCRETING HCO3- |
| To REABSORB BICARONATE the kidney has to | secrete H+, and when it excretes excess HCO3-, H+ is retained |
| REGULATING ACID-BASE balance depends on | H+ being secreted into the filtrate |
| CECRETION of H+ | occurs mainly in the PCT and in type A intercalated cells of collecting ducts |
| CARBONIC ANHYDRASE | enzyme that facilitates the combination of carbon dioxide with water to form carbonic acid |
| The RATE of H+ SECRETION | rises and falls with CO2 levels in the ECF |
| The MORE CO2 in the peritubular capillary blood, | the FASTER the rate of H+ SECRETION |
| BICARBONATE IONS (HCO3-) | the most important INORGANIC blood buffer |
| ALKALINE RESERVE | reservoir of base |
| TUBULE CELLS cannot reclaim HCO3- directly from filtrate | they can and do SHUNT HCO3- generated within them (as a result of splitting H2CO3) |
| Reaerbsorption of HCO3- depends on | the active secretion of H+, mostly by a Na+ -H+ ANTIPORT, but also by a H+ ATPase |
| for each FILTERED HCO3- that disappears | a HCO3- generated within the tubule cells enters the blood - a one-for-one exchange |
| When large amounts of H+ are secreted | correspondingly large amounts of HCO3- enter the peritubular blood. The NET EFFECT is that HCO3- is almost completely removed from the filtrate. |
| GENERATING NEW BICARBONATE IONS VIA EXCRETION of Buffered H+ pg 1012 | as long as filtered bicarbonate is reclaimed, the secreted H+ IS NOT excreted or lost from the body in urine |
| Once filtered HCO is "used up" | any additional H+ secreted is EXCRETED in urine |
| When additional H+ (like from food) is introduced to body then | to balance, new HCO3- has to be generated to counteract acidosis |
| Excreted H+ also must | Bind w/ Buffers in the filtrate, otherwise urine pH INCOMPATABLE w/ LIFE would result. |
| H+ secretion ceases when | when urine pH falls to 4.5 |
| MOST IMPORTANT URINE buffer | phosphate buffer system, specifically its weak base MONOHYDROGEN PHOSPHATE (HPO42-) |
| 75% of filtered PHOSPHATE is reabsorbed | HOWEVER, reabsorption is inhibited during ACIDOSIS |
| When H+ is being EXCRETED | brand new bicarbonate ions are addded to the blood OVER AND ABOVE those reclaimed from the filtrate |
| In response to ACIDOSIS the KIDNEYS | generate new HCO and add it to the blood (ALKALINIZING the blood); while adding an equal amount of H+ to the filtrate (ACIDIFYING the uriine) |
| GENERATING NEW BICARBONATE IONS VIA NH4+ EXCRETION Pg 1012 | second and MORE IMPORTANT MECHANISM for excreting acid uses the AMMONIUM ION (NH4+) produced by GLUTAMINE metabolism in the PCT cells |
| AMMONIUM IONS are | weak acids that donate few H+ at physiological pH |
| BICARBONATE ION SECRETION Pg 1014 | when body is in alkalosis, another population of INTERCALATED cells (type B)exhibit net HCO3- SECRETION (rather than net HCO3- REABSORPTION) while reclaiming H+ to acidify the blood |
| Type B cells are "flipped" type A cells | HCO secretion process opposite of HCO reabsorption process |
| Predominant process in the NEPHRONS and COLLECTING DUCTS is HCO3- REABSORPTION | and even during alkalosis, the amount of HCO excreted is much less that amount conserved. |
| RESPIRATORY ACIDOSIS Pg 1014 | Respiratory pH imbalances result from some failure of the respiratory system to perform its normal pH-balancing role |
| Single MOST IMPORTANT INDICATOR of adequacy of respiratory function | The PARTIAL PRESSURE of carbon dioxide (Pco2) |
| When Respiratory function is normal, | the Pco2 fluctuates between 35 and 45 mm Hg; HIGHER values indicate RESPIRATORY ACIDOSIS; LOWER values indicate RESPIRATORY ALKALOSIS |
| Respiratory ACIDOSIS Characterized by falling blood pH and rising Pco2 | most common cause of acid-base imbalance. |
| Respiratory ALKALOSIS | results when carbon dioxide is eliminated from the body faster than it is produced (hyperventilation; results in blood becoming more alkaline |
| Respiratory alkalosis is often due to stress or pain | true |
| METABOLIC Acidosis and Alkalosis pg 1014 | pH imbalances include all abnormalities of acid-base imbalance EXCEPT thos caused by too much or too little carbon dioxide in the blood |
| Bicarbonate ion levels below or above the normal range of 22-26 mEq/L | indicate a metabolic acid-base imbalance |
| Metabolic acidosis; second most common cause | low blood pH and HCO3- levels |
| typical causes of metabolic acidosis | too much alcohol(which is metabolized to ACETIC acid)and excessive loss of HCO3- (as might result form persistent diarrhea) |
| other causes: | accumulation of lactic acid during exercise or shock, the ketosis that occurs in diabetic crisis or starvation, and infrequently, kidney failure |
| METABOLIC ALKALOSIS | indicated by rising blood pH and HCO3- levels |
| ALKALOSIS is much less common than ACIDOSIS | true |
| typical causes: | vomiting of the acidic contents of the stomach (or loss of those secretions through gastrointestinal suctioning) and intake of excess base (antacids, for example) |
| Affects of Acidosis and Alkalosis Pg1014 | absolute pH LIMITS FOR LIFE are a low of 7.0 and a high of 7.8 |
| when pH falls below 7.0 | central nervous system is so depressed that the person goes into coma and death soon follows |
| when pH rises above 7.8 | nervous system is overexcited, leading to such characteristic signs as muscle tetany, extreme nervousness, and convulsions. Death often results from respiratory arrest |
| RESPIRATORY and RENAL compensations | one of the physiological buffer systems then the other system tries to compensate |
| RESPIRATORY COMPENSATION: Respiratory system attempts to compensate for | metabolic acid-base imbalances |
| Kidneys (though much slower) work to correct | imbalances caused by respiratory disease. |
| RENAL and RESPIRATORY compensations can be recognized by | changes in plasma Pco2 and bicarbonate ion concentrations |
| Respiratory Compensations | changes in respiratory rate and depth are evident when the respiratory system is attempting to compensate for metabolic acid-base imbalances |
| In METABOLIC ACIDOSIS | respiratory rate and depth are usually elevated- an indication that the respiratory centers are stimulated by the high H+ levels; blood pH is low(below 7.35) and HCO3- level is below 22mEq/L |
| As respiratory "blows off" CO2 to rid blood of excess acid; | Pco2 falls below 35mm Hg |
| In RESPIRATORY ACIDOSIS | respiratory rate is often depressed and IS the IMMEDIATE cause of teh ACIDOSIS |
| Metabolic ALKALOSIS | respiratory compensation involves slow, shallow breathing, which allows CO2 to accumulate in the blood |
| Metabolic alkalosis being compensated by respiratory mechanisms is revealed by | a pH over 7.45, elevated bicarbonate levels (over 26 mEq/L), and a Pco2 above 45 mm Hg |
| RENAL COMPENSATIONS | hypoventilating individual will exhibit acidosis; When renal compensation is occurring, BOTH Pco2 and HCO3- levels are HIGH. |
| High Pco2 is the cause for the acidosis, | Rising HCO3- level indicates that the kidneys are retaining bicarbonate to offset the acidosis |
| RENAL compensations for ALKALOSIS | high blood pH and low Pco2. Bicarbonate ion levels begin to fall as the kidneys eliminate more HCO3- from the body by failing to reclaim it or by actively secreting it |
| Kidneys CANNOT compensate for alkalosis or acidosis if the condition reflects renal problems | true |
| Developmental aspects of fluid, electrolyte and acid-base balance Pg 1015 | problems with acid-base imbalances is most common in infancy |
| conditions | very low residual volume of infant lungs (1/2); high rate of fluid intake and output in infants (7 X); relatively high infant metabolic rate (2 X); high rate of insensible water loss in infants (3 X);inefficiency of infant kidney (1/2) |
| ANALYSIS a person's ACID-BASE balance Pg 1017 | Step 1. Note the pH; this tells you whether the person is in acidosis (pH below 7.35) or alkalosis (pH above 7.45); but it cannot tell cause |
| Step 2. Check the Pco2 | to see if this is the cause of the imbalance. Because the respiratory ssytem is a fast acting system, an excessively high or low Pco2 may indicate either that the condition is respiratory caused or respiratory is compensating |
| Pco2 is over 45mm Hg, | then the respiratory system is the cause of the problem and the condition is respiratory acidosis |
| Pco2 is below normal limits (below 35mm Hg | then the respiratory system is not the cause but is compensating |
| Pco2 is within normal limits | then the condition is neither caused nor compensated by the respiratory system |
| Step 3. Check bicarbonate level | If step 2 proves that the respiratory system is not responsible for imbalance, teh the condition is METABOLIC and should be reflected in increased or decreased bicarbonate levels |
| Metabolic acidosis is indicated by | HCO3- values below 22 mEq/L |
| Metabolic alkalosis is indicated by | values over 26 mEq/l |
| Pco2 levels vary INVERSELY w/ blood pH (Pco2 rises as blood pH falls) | HCO3- levels vary directly w/ blood pH (increased HCO3- results in increased pH) |
| If an imbalance is fully compensated, the pH may be normal even while the patient is in trouble! | Hence, when the pH is normal, carefully scrutinize the Pco2 or Hco3- values for clues to what imbalance my be occurring |
Created by:
tammiemcconnell