Regulation of Acid-Base Balance Flashcards
pH is __________ related to the H+ concentration
inversely
A low pH corresponds to a ________ H+ concentration and a high pH corresponds to a ________ H+ concentration
high / low
The normal pH of arterial blood is ______, whereas the pH of venous blood and interstitial fluids is about ______ because of the extra amounts of _____ _______ released from the tissues to form H2C03 in these fluids.
7.4 / 7.35 / carbon dioxide
Because the normal pH of arterial blood is 7.4, a person is considered to have ________ when the pH falls below this value and _________ when the pH rises above 7.4. The lower limit of pH at which a person can live more than a few hours is about ____ and the upper limit is about ____.
acidosis / alkalosis / 6.8 / 8.0
An acid is a proton (H+) _______ while a base is a proton ______
donor / acceptor
A strong acid almost completely dissociates into ____ and a conjugate _______ while a strong base avidly binds _____
H+ / anion / H+
A weak acid or base ______ donates or accepts a proton
reversibly
The Henderson–Hasselbalch equation describes the relationship between what?
pH, PaC02, and serum bicarbonate
An increase in bicarbonate concentration causes the pH to ______, and shifts the acid-base balance toward _______
rise / alkalosis
An increase in PC02 causes the pH to ________ and shifts the acid-base balance towards _______
decrease / acidosis
The HC03 concentration is regulated by the ________, whereas the PC02 in extracellular fluid is controled by the rate of _______
kidneys / respiration
Based on the H/H equation we know that the pH of a solution is related to the ratio of the ________ anion to the __________ acid
dissociated / undissociated
Solutions of weak acids or bases act as buffers as they minimize pH changes by donating or accepting _________
electrons
Buffers are most efficient when ?
pH=pKa
When disturbances of acid-base balance result from a primary change in extracellular fluid HC03 concentration, they are referred to as _______ acid-base disorders
metabolic
Body Buffers
Bicarbonate (H2C03 / HC03), Hgb, intracellular proteins, Phosphate, Ammonia
________ are by far the most powerful of the acid-base regulatory systems
kidneys
Three prieary systems that regulate H+ concentration in the body fluids to prevent acidosis or alkalosis
the chemical acid-base buffer systems of the body fluids, the respiratory center, and the kidneys
The chemical acid-base buffer systems of the body fluids, which immediately combine with an acid or base to prevent excessive changes in _____ concentration
H+
The respiratory center regulates the removal of C02 and therefore ________ from the extracellular fluid
H2C03
The kidneys can excrete either ___ or _____ urine, thereby readjusting the extracellular fluid H+ concentration toward normal during acidosis or alkalosis. The kidneys are relatively _____ to respond.
acid / alkaline / slow
The bicarbonate buffer is effective against ______ but not ________ acid-base disturbances
metabolic / respiratory
The pKa of bicarbonate is _____. Nonetheless it is a good _____ because it is present in high concentration in the _____ and because PaC02 and HCO3 are closely regulated by the ____ and _____.
6.1 / buffer / ECF / lungs and kidneys
What is the most powerful extracellular buffer in the body?
bicarbonate buffer system
The pH of the extracellular fluid can be precisely controlled by gthe relative rate of removal and addition of ______ by the kidneys and the rate of removal of ______ by the lungs
HCO3 / CO2
Keep in mind that for each HCO3 reabsorbed a H+ must be ______
secreted
Explain Renal compensation during acidosis
Increased HC03 reabsorption: C02 combines with water to form H2C03 which rapidly dissociates into H+ and HC03, H+ is secreted into the PROXIMAL TUBULE and BICARBONATE is reabsorbed to blood, H+ in the tubule combines with filtered HCO3 to form carbonic acid, carbonic anhydrase HYDROLYZES this water and CO2 which goes into the cell replacing original CO2
Review slide 10
Review slide 10
The epithelial cells of the proximal tubule, the THICK segment of the ascending LOH, and the early Distal Tubule all secrete ________ into the tubular fluid by ______-_______ counter-transport
H+ / sodium-hydrogen
____ to ____% of filtered bicarbonate is reabsorbed in the _______ ______
80-90% / proximal tubule
review slide 13
intercalated cells of collecting duct
Reabsorption and secretion of bicarbonate involves 4 steps. Step 1: Sodium ions are reabsorbed filtrate in exchange for _____ by a antiport mechanism in the apical membranes of cells lining the renal tubule. Step 2: The cells produce ________ ions that can be shunted to PERITUBULAR CAPILLARIES. Step3: When CO2 is available, the reaction is driven to the formation of ______ ______, which dissociates to form a bicarbonate ion and a hydrogen ion. Step 4: The bicarbonate ion passes into the peritubular capillaries and returns to the blood. The hydrogen ion is _________ into the filtrate, where it can become part of new water molecules and be reabsorbed as such or removed in the _______.
H+ / bicarbonate / carbonic acid / secreted / urine
H+ secreted in tubule lumen can combine with HP04 to form H2PO4 that not ________ and becomes trapped in urine
reabsorbable
H2P04 is _______ _______
dihydrogen phosphate
Phosphate is effective buffer in ______ fluid
tubular
Phosphate has a pKa of _____ which in acidic urine allow to be more effective ________
6.8 / buffer
Review slides 16 and 17
phsophate buffer
Ammonium (NH4) is an important tubular fluid buffer in what areas?
PT, thick loop, DT
Ammonium is synthesized from _________ which comese mianly from the metabolism of amino acids in the liver. BICARBONATE is generated in the process
glutamine
In collecting tubules production of NH4 by different mechanism. H+ combines with NH3 to form NH4 which is _______
excreted
With CHRONIC Acidosis, the dominant mechanism by which acid is eliminated is excretion of _____. This process also provides the most importnt mechanism for generating new _________ during chornic acidosis.
NH4 / bicarbonate
With ammonium production and secretioin, NH4 is secreted into the tubular lumen by ____ _______ mechanism in exchange for SODIUM, which is _________. The HCO3 is transported across the ______ __________, along with the reabsorbed Na+, into the INTERSTITIAL fluid and is taken up by the __________ capillaries.
counter transport / reabsorbed / basolateral membrane / peritubular
One of the most important features of the renal ammonium-ammonia buffer system is that it is subject to PHYSIOLOGIC CONTROL. An increase in extraceullular fluid H+ concentration stimulates _____ _________ metabolism and, thererfore, increases the formation of _____ and new ______ to be used in H+ buffering; a DECREASE in H+ concentration has the opposite effect.
renal gluatamine / NH4 / HCO3
During renal compensation for alkalosis large amounts of ________ can be excreted if necessary
bicarbonate
Metabolic alkalosis is mainly possible in 2 situations. What are they?
Na+ depeltion, Increased Aldosterone (mineralcorticoid)
Metabolic alkalosis due to Na+ depletion happens when more sodium is reabsored in the _______ tubule, and as this occurs _____ moves with it to preserve neutrality, thus as Cl- in the tubule decreases, _________ must be reabsorbed. This is also know as what?
proximal / Cl- / bicarb
Contraction alkalosis can occur with what?
long term diuretic use
Metabolic alkalosis due to increased ALDOSTERONE activity increases ____ reabsorbtion and _____ secretion in the DISTAL tubule
Na+ / H+
_________ __________ is calculated as the urine flow rate multiplied by urinary HCO3 concentration
bicarbonate excretion
In alkalosis, the loss of _______ helps return the plasma pH towards normal
bicarbonate
In alkalosis, there is a ________ net acid secretion
negative
_____ _______ is defined as the amount of acid or base that must be added to return blood pH to 7.4 with PaC02 = 40 mmHg and temp 37 degrees Celsius
base excess
With base excess, a positive value indicates ______ ______ and a negative value is _____ _______
metabolic alkalosis / metabolic acidosis
The most important stimuli for increasing H+ SECRETION by the tubules in acidosis are what?
An increase in PC02 of the extracellular fluid in respiratory acidosis AND an increase in H+ concentration of the extracellular fluid (decreased pH) respiratory or metabolic acidosis
Review slide 22
Acid-base balance
Situations that generate metabolic alkalosis from LOSS OF ACID FROM THE EXTRACELLULAR SPACE
loss of gastric fluid (HCL), acid loss in the urine from increased distal Na+ delivery in presence of hyperaldosteronism, acid shifts into cells, loss of acid into stool
Situations that generate metabolic alkalosis from EXCESSIVE HCO3 loads
Oral or parenteral HCO3, metabolic conversion of the salts of organic acids to HCO3
T/F Metabolic alkalosis occur from Posthypercapnic states?
TRUE
Factors that generate metabolic alkalosis include vomiting and diuretic administration. MAINTENANCE of metabolic alkalosis depends on continued stimulus, such as renal _________, hypokalemia, hypochloremia, or hypovolemia, for ________ tubular reabsorption of HCO3
hypoperfusion / distal
Factors that maintain metabolic alkalosis
decreased GFR, volume contraction, hypokalemia, passive backflus of HCO3, aldosterone
Review proposed mechanisms on slide 24
slide 24
_________ ____________ is associated with hypokalemia, ionized hypocalcemia, secondary ventricular arrhythmias, increased digoxin toxicity, and compensatory hypoventilation (hypercarbia), although compensation rarely results in PaC02 above _____ mmHg.
metabolic alkalosis / 55
Alkalmeia may reduce tissue oxygen availability by shifting the oxyhemoglobin curve to the _____ and by decreasing cardiac output
left
During anesthetic management, inadvertent addition of iatrogenic respiratory alkalosis to pre-existing metabolic alkalosis may produce severe __________ and precipitate cardiovascular depression, dysrhythmias and hypokalemia
alkalemia
In metabolic alkalosis, The PaC02 increases ___ to ___mmHg per 1 mEq/L increase in HCO3
0.5 to 0.6
The last two digits of the pH should appoximate the HCO3 + ____
15 / example. pH 7.40, so subtract 15 from 40 which is 25 which should approximate what the bicarb is
In metabolic acidosis, PaC02 decreases ___ mmHg per 1 mEq/L in HCO3 to a minimum of 10-15 mmHg
1.2
For metabolic alkalosis, treatment could be expansion of intravascular volume or administration of potassium. Infusion of 0.9% saline will dose-dependentlhy increase serum _____ and decrease serum _____
Cl- / HCO3
Differential diagonsis of metabolic acidosis with an elevated anion gap are what 3 diseases?
uremia, ketoacidosis, lactic acidosis
Differential diagonsis of metabolic acidosis with an elevated anion gap can be from what toxins? (4)
Methanol, Ethylene glycol, salicylates, paraldehyde
Differential diagnosis of metabolic acidosis with a normal anion gap includes what (8)?
Renal tubular necrosis, diarrhea, carbonic anyhydrase inhibition, ureteral diversions, early renal failure, hydronephrosis, HCL administration, Saline administration
________ ________ occurs as a consequence of buffering by bicarbonate of endogenous acid loads or as a consequence of abnormal external loss of bicarbonate
metabolic acidosis
Metabolic acidosis associated with a high Anion Gap which is greater than _____ mEq/L, occurs because excess production of decreased excretion of organic acids or ingestion of one of several toxic compounds.
13
In metabolic acidosis associated with high anion gap, bicarbonate ions are consumed in buffering hydrogen ions, while the associated anion replaces ________ in serum.
bicarbonate
Physiologic effects of acidosis
(1) potassium increases 0.6 mEq/L for each 0.1 unit decrease in pH (2) a rightward shift is seen in the oxy-hemoglobin dissociation curve (3) Cardiac contractility is decreased (4) There is decreased responsiveness to catecholamines
In acidosis, there is a net addition of ______ back to the blood as more ____ and urinary titratable acid are excreted.
bicarbonate / ammonium
Failure of a patient to appropriately hyperventilate in response to metabolic acidosis is physiologically equivalent to ________ ________ and suggests clinical deterioration
respiratory acidosis
Preoperative assessment should emphasize _______ status and ________ function
volume / renal
in planning intravenous fluid therapy, consider that balanced salt solutions like LR tend to _________ pH and HCO3 and 0.9% saline tends to ________ pH and HCO3
increase / decrease
______ should rarely be used to treat acidemia induced by metabolic acidosis
Sodium Bicarb (NaHCO3)
Treating metabolic acidosis.
Treat the underlying cause (hypovolemia, anemia, cardiogenic shock), NaHCO3 (do not give to patient with respiratory failure as C02 will go up, refractory acidosis may require dialysis
T/F Although many clinicians choose to administer NaHCO3 to patients with persistent lactic acidosis and ongoing deterioration, there are no clinical trials that demonstrate improved outcome
TRUE
IV HCL is used in rare cases to treat ________
alkalosis
If alkalosis is due to increased mineralcorticoid activity what medication may be given?
spironolactone
________ are the main contributing cause of CHLORIDE sensitive metabolic alkalosis
diuretics
When diuretics are the cause of metabolic alkalosis _____ is actively reabsorbed secondary to ECF fluid ____________, Cl- goes with it to maintain elctroneutrality and not enough is available so HCO3 is reabsorbed and _____ is secreted
Na+ / depletion / H+
Hypokalemia will also augment H+ __________
secretion
Loss of gastric fluid from NG suction or vomiting will cause ________ through loss of HCL
alkalosis
Is Respiratory Alkalosis ALWAYS characterized by hypocarbia (PaCO2 less than or equal to 35mmHg)
yes
Respiratory alkalosis is usually characterized by an alkalemic pH of _______
> 7.45
Can respiratory alkalosis result from an INCREASE in minute alveolar ventilation?
Yes
Respiratory alkalosis may be a sign of what? (5)
pain, anxiety, hypoxemia, central venous systemic disease, systemic sepsis
Respiratory alkalosis may produce what? (6)
hypokalemia, hypocalcemia, cardiac dysrhythmias, bronchoconstriction, hypotension, and may potentiate the toxicity of digoxin
Both brain pH and cerebral blood flow are tightly regulated and respond rapidly to changes in PaC02. Doubling minute ventilation reduces PaC02 to 20 mmHg and _______ cerebral blood flow; conversely, halving minute ventilation _______ PaC02 and _________ cerebral blood flow.
halves / doubles / doubles
In metabolic acidosis, an excess of H+ over HCO3 occurs in the tubular fluid primarily because of dereased filtration of _________
HCO3
In respiratory acidosis, the excess H+ in the tubular fluid is due mainly to the rise in extracellular luid PC02 which stimulates _____ secretion
H+
Review Slides 32 and 33
diagnosing acid base disorders. Www.glowm.com/lab_text/item/3
Hypobicarbonatemia associated with an increased anion gap is never ________
compensatory
Metabolic acidosis associated with increased anion gaps require specifc _______
treatments
Anion gap =
[Na+] - ([Cl-] + [HCO3])
Normal Anion Gap
7-14 mEq/L
The anion gap is really a measure of _______ ______
unmeasured ions
An acidosis with a high anion gap is caused by relatively strong non-volatile acids. In this case H+ consumes HCO3 and an unmeasured anion accumulates and takes the place of ________. Examples?
bicarbonate / uremia, DKA, lactic acidosis
Three quarters of the normal anion gap consists of ________.
albumin
Normal anion gap metabolic acidosis is usually sseen with _________
hyperchloremia (Cl- takes the place of the bicarbonate ion)
Expected level of compensation in ACUTE RESPIRATORY ACIDOSIS
expect a 1 mEq/L increase in HCO3 for every 10 mmHg increase in CO2 (usually from 40 mmHg)
Expected level of compensation in CHRONIC RESPIRATORY ACIDOSIS
expect a 4 mEq/L increase in HCO3 for every 10 mmHg increase in C02
Expected level of compensation in METABOLIC ACIDOSIS
CO2 decrease 1.2 times the decrease in HCO3 (usually from 24 mEq/L)
Expected level of compensation in ACUTE RESPIRATORY ALKALOSIS
expect 2 mEq/L decrease in HCO3 for every 10 mmHg decrease in CO2
Expected level of compensation in CHRONIC RESPIRATORY ALKALOSIS
expect 4 mEq/L decrease in HCO3 for every 10 mmHg decrease in CO2
Expected level of compensation in CHRONIC METABOLIC ALKALOSIS
CO2 increase by 0.7 times the increase in HCO3
