Lab 14 (sem 2) - Acid-base balance

name 6 conditions that cause metabolic acidosis (decrease HCO3-):

- renal tubular acidosis - diarrhea - vomiting of intestinal contents - diabetes mellitus - ingestion of acids - chronic renal failure

metabolic acidosis results from: 1 metabolic alkalosis results from: 2

1: decreased extracellular fluid HCO3− concentration 2: increased extracellular fluid HCO3− concentration

ammonium ion is synthesized from 1, which comes mainly from the metabolism of amino acids in the liver

1: glutamine

hydrochloric acid (HCl) ionizes in water to form 1 carbonic acid (H2CO3) ionizes in water to form 2

1: hydrogen ions (H+) and chloride ions (Cl−) 2: hydrogen ions (H+) and bicarbonate ions (HCO3−)

the HCO3− concentration is regulated mainly by the 1, whereas the PCO2 in extracellular fluid is controlled by the 2

1: kidneys 2: rate of respiration

acidosis caused by a primary decrease in HCO3− concentration is called 1 alkalosis caused by a primary increase in HCO3− concentration is called 2

1: metabolic acidosis 2: metabolic alkalosis

combination of excess H+ with 1 in the tubule generates new HCO3−

1: phosphate buffers and ammonia buffers

acidosis caused by an increase in PCO2 is called 1 alkalosis caused by a decrease in PCO2 is called 2

1: respiratory acidosis 2: respiratory alkalosis

for the treatment of acidosis, 1 can be administered by mouth for the treatment of alkalosis, 2 can be administered by mouth

1: sodium bicarbonate 2: ammonium chloride

primary active secretion of H+ occurs in special types of cells called the 1 of the late distal tubule and in the collecting tubules

1: type A intercalated cells

name the 3 primary systems that regulate the H+ concentration in the body fluids to prevent acidosis or alkalosis:

1st line of defense: chemical acid-base buffer systems of the body fluids 2nd line of defense: respiratory center 3rd line of defense: kidneys

what is the lower limit of pH that can be achieved in normal kidneys?

4.5

name the 3 main buffer systems:

bicarbonate-carbonic acid buffer phosphate buffer protein buffer

Henderson-Hasselbalch equation:

for the bicarbonate buffer system, the pK is 6.1

the net acid excretion by the kidneys can be assessed as:

net acid excretion = NH4+ excretion + urinary titratable acid - HCO3- excretion

"in simple respiratory acidosis, one would expect to find reduced plasma pH, increased P(CO2), and increased plasma HCO3− concentration after partial renal compensation" - (true/false)

true

"in simple respiratory alkalosis, one would expect to find increased pH, decreased P(CO2), and decreased HCO3− concentration in the plasma" - (true/false)

true

"increasing alveolar ventilation decreases extracellular fluid H+ concentration and raises pH" - (true/false)

true

"precise H+ regulation is essential because the activities of almost all enzyme systems in the body are influenced by H+ concentration. Therefore, changes in H+ concentration alter virtually all cell and body functions" - (true/false)

true

"primary active secretion of H+ in the intercalated cells of late distal and collecting tubules" - (true/false)

true

"proteins are important intracellular buffers" - (true/false)

true

"respiratory and metabolic acidosis both cause a decrease in the ratio of HCO3− to H+ in the renal tubular fluid" - (true/false)

true

"respiratory and metabolic alkalosis both cause an increase in the ratio of HCO3− to H+ in the renal tubular fluid" - (true/false)

true

"respiratory regulation of acid-base balance is a physiological type of buffer system because it acts rapidly and keeps the H+ concentration from changing too much until the slowly responding kidneys can eliminate the imbalance" - (true/false)

true

"the amount of new HCO3− contributed to the blood at any given time is equal to the amount of H+ secreted that ends up in the tubular lumen with non-bicarbonate urinary buffers" - (true/false)

true

"the bicarbonate buffer system is the most powerful extracellular buffer in the body" - (true/false)

true

"the most important stimuli for increasing H+ secretion by the tubules in acidosis are (1) an increase in P(CO2) of the extracellular fluid in respiratory acidosis and (2) an increase in H+ concentration of the extracellular fluid (decreased pH) respiratory or metabolic acidosis" - (true/false)

true

"the phosphate buffer is especially important in the tubular fluids of the kidneys" - (true/false)

true

"the phosphate buffer system is also important in buffering intracellular fluid" - (true/false)

true

the kidneys regulate extracellular fluid H+ concentration through 3 fundamental mechanisms. Name them:

(1) secretion of H+ (2) reabsorption of filtered HCO3− (3) production of new HCO3−

name 4 conditions that cause metabolic alkalosis (increase HCO3-):

- administration of diuretics (except the carbonic anhydrase inhibitors) - excess aldosterone - vomiting of gastric contents - ingestion of alkaline drugs

Interpreting AGBs:

1) pH? (7.35-7-45) 2) PaCO2? (35-45mmHg) 3) HCO3-? (22-26mEq/L) and base excess (BE)? (-2 - +2mEq/L) 4) determine level of compensation uncompensated: - pH abnormal - one component abnormal (high or low CO2 or HCO3-) partly compensated: - pH abnormal (but moving toward normal) - both CO2 or HCO3- are outside normal range compensated: - pH normal - other values abnormal in opposite directions (one is acidotic the other alkaline) 5) determine amount of hypoxemia present normal PaO2: - <70 years: 80-100mmHg - 70-79 years: 70-100mmHg - (drops 10mmHg for each decade) abnormal PaO2: - mild: 60-80mmHg - moderate: 40-60mmHg - mild: <40mmHg 6) oxygen saturation (pulse oximetry) - normal: 95-100% - <91% confusion - <70% life threatening

what can lead to respiratory acidosis?: 1 what can lead to respiratory alkalosis?: 2

1: - damage to the respiratory center in the medulla oblongata - obstruction of the passageways of the respiratory tract - pneumonia - emphysema - decreased pulmonary membrane surface area - any factor that interferes with the exchange of gases between the blood and the alveolar air 2: - psychoneurosis - when a person ascends to high altitude

the main elements of the phosphate buffer system are: 1

1: H2PO4− HPO4=

respiratory acidosis results from: 1 respiratory alkalosis results from: 2

1: decreased ventilation, and increased P(CO2) 2: increased ventilation, and decreased P(CO2)

secondary active secretion of H+ in: 1 primary active secretion of H+ in: 2

1: proximal tubule loop of Henle (thick ascending limb) early distal tubule 2: late distal tubule collecting tubules

name 4 important unmeasured cations: 1 name 6 important unmeasured anions: 2

1: sodium calcium magnesium potassium 2: chlorid bicarbonate albumin phosphate sulfate other organic anions

the minimal urine pH is about 4.5, corresponding to an H+ concentration of 10^−4.5mEq/L, or 1mEq/L

1: 0.03mEq/L

the solubility coefficient for CO2 is 1 mmol/mmHg at body temperature

1: 0.03mmol/mmHg

increasing alveolar ventilation to about twice (double) normal raises the pH of the extracellular fluid by about 1 decreasing alveolar ventilation to about one fourth (1/4) normal decreases the pH of the extracellular fluid by about 2

1: 0.23 (7.4 + 0.23 = 7.63) 2: 0.45 (7.4 - 0.45 = 6.95)

concentration of sodium (Na+) in extracellular fluid: 1 concentration of hydrogen (H+) in extracellular fluid: 2

1: 142 mEq/L 2: 0.00004 mEq/L (40 nEq/L)

the normal value for P(CO2) is about 1, and the normal value for HCO3− is 2

1: 40 mm Hg 2: 24 mEq/L

about 1.2 mol/L of dissolved CO2 normally are in the extracellular fluid, corresponding to a P(CO2) of 1

1: 40mmHg

each day the kidneys filter about 1 of HCO3− under normal conditions

1: 4320mEq (180 L/day × 24 mEq/L)

a total of 1 of H+ is secreted into the tubular fluid each day

1: 4400mEq (4320mEq + 80mEq)

under normal conditions; the rate of tubular H+ secretion is about 1mEq/day, and the rate of filtration by HCO3− is about 2mEq/day

1: 4400mEq/day 2: 4320mEq/day

the respiratory mechanism for controlling H+ concentration is approximately 1% effective, corresponding to a feedback gain of 1 to 3

1: 50-75%

the phosphate buffer system has a pK of 1

1: 6.8

the lower limit of pH at which a person can live more than a few hours is about 1, and the upper limit is about 2

1: 6.8 2: 8.0

approximately 1% of the total chemical buffering of the body fluids is inside the cells, and most of this buffering results from the intracellular proteins

1: 60-70%

the normal pH of arterial blood is 1 the normal pH of venous blood and interstitial fluids is 2

1: 7.4 2: 7.35

the plasma anion gap ranges between 1mEq/L. The plasma anion gap will increase if unmeasured 2 rise or if unmeasured 3 fall

1: 8-16mEq 2: anions 3: cations

HCO3− reabsorption (and H+ secretion): in proximal tubule: 1% in thick ascending loop of Henle: 2% in distal tubules and collecting ducts: 3%

1: 80-90% 2: 10% 3: >4.9%

each day the body produces about 1 of nonvolatile acids, mainly from the metabolism of proteins

1: 80mEq

an increase in ventilation reduces 1 from extracellular fluid, which reduces the 2 a decrease in ventilation increases 1 from extracellular fluid, which increase 2

1: CO2 2: H+ concentration

buffer systems: bicarbonate buffer is active in: 1 phosphate buffer is active in: 2 protein buffer is active in: 3

1: ECF and ICF 2: ICF 3: albumins and globulins (ECF) hemoglobin (ICF)

the opposite reactions take place when a strong base, such as sodium hydroxide (NaOH), is added to the bicarbonate buffer solution in this case, the OH− from the NaOH combines with H2CO3 to form additional HCO3−. Thus, the weak base NaHCO3 replaces the strong base NaOH. At the same time, the concentration of 1 decreases (because it reacts with NaOH), causing more CO2 to combine with H2O to replace the H2CO3 the net result, therefore, is a tendency for the 2 levels in the blood to decrease

1: H2CO3 2: CO2

when a strong acid such as HCl is added to the bicarbonate buffer solution, the increased H+ released from the acid (HCl → H+ + Cl−) is buffered by HCO3−. As a result more 1 is formed, causing increased 2 production

1: H2CO3 2: CO2 and H2O

in metabolic alkalosis, there is an excess of 1 over 2 in the urine in metabolic acidosis, there is an excess of 2 over 1 in the urine

1: HCO3− 2: H+

give 1 example of: a strong acid: 1 a weak acid: 2 a strong base: 3 a weak base: 4

1: HCl 2: H2CO3 3: OH− 4: HCO3−

for each molecule of glutamine metabolized in the proximal tubules, 2 1 are secreted into the urine and 2 2 are reabsorbed into the blood

1: NH4+ 2: HCO3−

renal control of acid-base balance: if more H+ is secreted than HCO3− is filtered, there will be a net loss of 1 from the extracellular fluid if more HCO3− is filtered than H+ is secreted, there will be a net loss of 2 from the extracellular fluid

1: acid 2: base

a molecule that can release hydrogen ions (H+) in solutions are referred to as: 1 a molecule that can accept hydrogen ions (H+) in solutions are referred to as: 2

1: acids 2: bases

1 increases NH4+ excretion

1: chronic acidosis

plasma or extracellular fluid factors that increase or decrease H+ secretion and HCO3− reabsorption by the renal tubules:

hypokalemia: low level of potassium (K+) hyperkalemia: high level of potassium (K+)

acid-base nomogram:

if a value is within the shaded area, this suggests that there is a simple acid-base disturbance if the values for pH, bicarbonate, or PCO2 lie outside the shaded area, this suggests that the patient may have a mixed acid-base disorder

name 2 factors that affects P(CO2) in extracellular fluid:

rate of alveolar ventilation metabolic formation of CO2

titration curve for bicarbonate buffer system:

the buffer system is still reasonably effective for 1.0 pH unit on either side of the pK, which for the bicarbonate buffer system extends from a pH of about 5.1 to 7.1 units. Beyond these limits, the buffering power rapidly diminishes

"alveolar ventilation rate increases 4 to 5 times normal as the pH decreases from the normal value of 7.4 to the strongly acidic value of 7.0. Conversely, a rise in plasma pH above 7.4 causes a decrease in the ventilation rate" - (true/false)

true

"an alkali is a molecule formed by the combination of one or more of the alkaline metals—sodium, potassium, lithium, and so forth—with a highly basic ion such as a hydroxyl ion (OH−)" - (true/false)

true

"an impairment of lung function, such as severe emphysema, decreases the ability of the lungs to eliminate CO2, which causes a buildup of CO2 in the extracellular fluid and a tendency toward respiratory acidosis" - (true/false)

true

"because increased H+ concentration stimulates respiration and because increased alveolar ventilation decreases the H+ concentration, the respiratory system acts as a typical negative feedback controller of H+ concentration" - (true/false)

true

"because the normal pH of arterial blood is 7.4, a person is considered to have acidosis when the pH falls below this value and alkalosis when the pH rises above 7.4" - (true/false)

true

"bicarbonate excretion is calculated as the urine flow rate multiplied by urinary HCO3− concentration" - (true/false)

true

"by increasing the rate of respiration, the lungs remove CO2 from the plasma, and by decreasing respiration, the lungs elevate PCO2" - (true/false)

true

"carbonic anhydrase catalyses the reaction between carbon dioxide (CO2) and water (H2O) to form carbonic acid (H2CO3)" - (true/false)

true

"diffusion of the elements of the bicarbonate buffer system causes the pH in intracellular fluid to change when there are changes in extracellular pH" - (true/false)

true

"each time a H+ is formed in the tubular epithelial cells, a HCO3− is also formed and released back into the blood" - (true/false)

true

"for each HCO3− reabsorbed, a H+ must be secreted" - (true/false)

true

"for each NH4+ excreted, a new HCO3− is generated and added to the blood" - (true/false)

true

"from the Henderson-Hasselbalch equation, it is apparent that an increase in HCO3−concentration causes the pH to rise, shifting the acid-base balance toward alkalosis. An increase in PCO2 causes the pH to decrease, shifting the acid-base balance toward acidosis" - (true/false)

true

"in acidosis, there is a net addition of HCO3− back to the blood as more NH4+ and urinary titratable acid are excreted, while in alkalosis, there is a negative net acid secretion" - (true/false)

true

"in metabolic acidosis, the primary compensations include increased ventilation rate, which reduces PCO2, and renal compensation, which, by adding new HCO3− to the extracellular fluid, helps minimize the initial fall in extracellular HCO3− concentration" - (true/false)

true

"in metabolic alkalosis, the primary compensations are decreased ventilation, which raises PCO2, and increased renal HCO3− excretion, which helps compensate for the initial rise in extracellular fluid HCO3−concentration" - (true/false)

true

"in respiratory acidosis, the compensatory response is an increase in plasma HCO3−, caused by the addition of new HCO3− to the extracellular fluid by the kidneys" - (true/false)

true

"in respiratory alkalosis, the compensatory response to a primary reduction in PCO2 is a reduction in plasma HCO3− concentration, caused by increased renal excretion of HCO3−" - (true/false)

true

"in simple metabolic acidosis, one would expect to find a low pH, a low plasma HCO3− concentration, and a reduction in P(CO2) after partial respiratory compensation" - (true/false)

true

"in simple metabolic alkalosis, one would expect to find increased pH, increased plasma HCO3−, and increased P(CO2)" - (true/false)

true

"the proteins in the body also function as bases because some of the amino acids that make up proteins have net negative charges that readily accept H+. The protein hemoglobin in the red blood cells and proteins in the other cells of the body are among the most important of the body's bases" - (true/false)

true

"under normal conditions, the amount of H+ eliminated by the ammonia buffer system accounts for about 50% of the acid excreted and 50% of the new HCO3− generated by the kidneys" - (true/false)

true

"whenever an H+ secreted into the tubular lumen combines with a buffer other than HCO3−, the net effect is addition of a new HCO3− to the blood" - (true/false)

true

buffer: "when the H+ concentration increases, the reaction is forced to the right and more H+ binds to the buffer, as long as buffer is available. Conversely, when the H+ concentration decreases, the reaction shifts toward the left and H+ is released from the buffer" - (true/false)

true

"filtered HCO3− is reabsorbed by interaction with H+ in the tubules" - (true/false)

true (HCO3− + H+ --> H2CO3 --> CO2 + H2O)

"if the rate of metabolic formation of CO2 increases, the PCO2 of the extracellular fluid is likewise increased" - (true/false)

true (and vice versa)

"H+ is secreted by secondary active transport in the early tubular segments" - (true/false)

true (include: proximal tubule, thick segment of ascending loop of Henle, and early distal tubule)

carbonic anhydrase is present in the:

walls of the lung alveoli (abundant here) epithelial cells of the renal tubules

isohydric principle:

whenever there is a change in H+ concentration in the extracellular fluid, the balance of all the buffer systems changes at the same time