Regulation of Acid-Base Balance Flashcards
1
Q
pH is __________ related to the H+ concentration
A
inversely
2
Q
A low pH corresponds to a ________ H+ concentration and a high pH corresponds to a ________ H+ concentration
A
high / low
3
Q
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.
A
7.4 / 7.35 / carbon dioxide
4
Q
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 ____.
A
acidosis / alkalosis / 6.8 / 8.0
5
Q
An acid is a proton (H+) _______ while a base is a proton ______
A
donor / acceptor
6
Q
A strong acid almost completely dissociates into ____ and a conjugate _______ while a strong base avidly binds _____
A
H+ / anion / H+
7
Q
A weak acid or base ______ donates or accepts a proton
A
reversibly
8
Q
The Henderson–Hasselbalch equation describes the relationship between what?
A
pH, PaC02, and serum bicarbonate
9
Q
An increase in bicarbonate concentration causes the pH to ______, and shifts the acid-base balance toward _______
A
rise / alkalosis
10
Q
An increase in PC02 causes the pH to ________ and shifts the acid-base balance towards _______
A
decrease / acidosis
11
Q
The HC03 concentration is regulated by the ________, whereas the PC02 in extracellular fluid is controled by the rate of _______
A
kidneys / respiration
12
Q
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
A
dissociated / undissociated
13
Q
Solutions of weak acids or bases act as buffers as they minimize pH changes by donating or accepting _________
A
electrons
14
Q
Buffers are most efficient when ?
A
pH=pKa
15
Q
When disturbances of acid-base balance result from a primary change in extracellular fluid HC03 concentration, they are referred to as _______ acid-base disorders
A
metabolic
16
Q
Body Buffers
A
Bicarbonate (H2C03 / HC03), Hgb, intracellular proteins, Phosphate, Ammonia
17
Q
________ are by far the most powerful of the acid-base regulatory systems
A
kidneys
18
Q
Three prieary systems that regulate H+ concentration in the body fluids to prevent acidosis or alkalosis
A
the chemical acid-base buffer systems of the body fluids, the respiratory center, and the kidneys
19
Q
The chemical acid-base buffer systems of the body fluids, which immediately combine with an acid or base to prevent excessive changes in _____ concentration
A
H+
20
Q
The respiratory center regulates the removal of C02 and therefore ________ from the extracellular fluid
A
H2C03
21
Q
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.
A
acid / alkaline / slow
22
Q
The bicarbonate buffer is effective against ______ but not ________ acid-base disturbances
A
metabolic / respiratory
23
Q
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 _____.
A
6.1 / buffer / ECF / lungs and kidneys
24
Q
What is the most powerful extracellular buffer in the body?
A
bicarbonate buffer system
25
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
26
Keep in mind that for each HCO3 reabsorbed a H+ must be ______
secreted
27
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
28
Review slide 10
Review slide 10
29
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
30
____ to ____% of filtered bicarbonate is reabsorbed in the _______ ______
80-90% / proximal tubule
31
review slide 13
intercalated cells of collecting duct
32
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
33
H+ secreted in tubule lumen can combine with HP04 to form H2PO4 that not ________ and becomes trapped in urine
reabsorbable
34
H2P04 is _______ _______
dihydrogen phosphate
35
Phosphate is effective buffer in ______ fluid
tubular
36
Phosphate has a pKa of _____ which in acidic urine allow to be more effective ________
6.8 / buffer
37
Review slides 16 and 17
phsophate buffer
38
Ammonium (NH4) is an important tubular fluid buffer in what areas?
PT, thick loop, DT
39
Ammonium is synthesized from _________ which comese mianly from the metabolism of amino acids in the liver. BICARBONATE is generated in the process
glutamine
40
In collecting tubules production of NH4 by different mechanism. H+ combines with NH3 to form NH4 which is _______
excreted
41
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
42
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
43
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
44
During renal compensation for alkalosis large amounts of ________ can be excreted if necessary
bicarbonate
45
Metabolic alkalosis is mainly possible in 2 situations. What are they?
Na+ depeltion, Increased Aldosterone (mineralcorticoid)
46
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
47
Contraction alkalosis can occur with what?
long term diuretic use
48
Metabolic alkalosis due to increased ALDOSTERONE activity increases ____ reabsorbtion and _____ secretion in the DISTAL tubule
Na+ / H+
49
_________ __________ is calculated as the urine flow rate multiplied by urinary HCO3 concentration
bicarbonate excretion
50
In alkalosis, the loss of _______ helps return the plasma pH towards normal
bicarbonate
51
In alkalosis, there is a ________ net acid secretion
negative
52
_____ _______ 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
53
With base excess, a positive value indicates ______ ______ and a negative value is _____ _______
metabolic alkalosis / metabolic acidosis
54
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
55
Review slide 22
Acid-base balance
56
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
57
Situations that generate metabolic alkalosis from EXCESSIVE HCO3 loads
Oral or parenteral HCO3, metabolic conversion of the salts of organic acids to HCO3
58
T/F Metabolic alkalosis occur from Posthypercapnic states?
TRUE
59
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
60
Factors that maintain metabolic alkalosis
decreased GFR, volume contraction, hypokalemia, passive backflus of HCO3, aldosterone
61
Review proposed mechanisms on slide 24
slide 24
62
_________ ____________ 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
63
Alkalmeia may reduce tissue oxygen availability by shifting the oxyhemoglobin curve to the _____ and by decreasing cardiac output
left
64
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
65
In metabolic alkalosis, The PaC02 increases ___ to ___mmHg per 1 mEq/L increase in HCO3
0.5 to 0.6
66
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
67
In metabolic acidosis, PaC02 decreases ___ mmHg per 1 mEq/L in HCO3 to a minimum of 10-15 mmHg
1.2
68
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
69
Differential diagonsis of metabolic acidosis with an elevated anion gap are what 3 diseases?
uremia, ketoacidosis, lactic acidosis
70
Differential diagonsis of metabolic acidosis with an elevated anion gap can be from what toxins? (4)
Methanol, Ethylene glycol, salicylates, paraldehyde
71
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
72
________ ________ occurs as a consequence of buffering by bicarbonate of endogenous acid loads or as a consequence of abnormal external loss of bicarbonate
metabolic acidosis
73
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
74
In metabolic acidosis associated with high anion gap, bicarbonate ions are consumed in buffering hydrogen ions, while the associated anion replaces ________ in serum.
bicarbonate
75
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
76
In acidosis, there is a net addition of ______ back to the blood as more ____ and urinary titratable acid are excreted.
bicarbonate / ammonium
77
Failure of a patient to appropriately hyperventilate in response to metabolic acidosis is physiologically equivalent to ________ ________ and suggests clinical deterioration
respiratory acidosis
78
Preoperative assessment should emphasize _______ status and ________ function
volume / renal
79
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
80
______ should rarely be used to treat acidemia induced by metabolic acidosis
Sodium Bicarb (NaHCO3)
81
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
82
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
83
IV HCL is used in rare cases to treat ________
alkalosis
84
If alkalosis is due to increased mineralcorticoid activity what medication may be given?
spironolactone
85
________ are the main contributing cause of CHLORIDE sensitive metabolic alkalosis
diuretics
86
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+
87
Hypokalemia will also augment H+ __________
secretion
88
Loss of gastric fluid from NG suction or vomiting will cause ________ through loss of HCL
alkalosis
89
Is Respiratory Alkalosis ALWAYS characterized by hypocarbia (PaCO2 less than or equal to 35mmHg)
yes
90
Respiratory alkalosis is usually characterized by an alkalemic pH of _______
> 7.45
91
Can respiratory alkalosis result from an INCREASE in minute alveolar ventilation?
Yes
92
Respiratory alkalosis may be a sign of what? (5)
pain, anxiety, hypoxemia, central venous systemic disease, systemic sepsis
93
Respiratory alkalosis may produce what? (6)
hypokalemia, hypocalcemia, cardiac dysrhythmias, bronchoconstriction, hypotension, and may potentiate the toxicity of digoxin
94
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
95
In metabolic acidosis, an excess of H+ over HCO3 occurs in the tubular fluid primarily because of dereased filtration of _________
HCO3
96
In respiratory acidosis, the excess H+ in the tubular fluid is due mainly to the rise in extracellular luid PC02 which stimulates _____ secretion
H+
97
Review Slides 32 and 33
diagnosing acid base disorders. Www.glowm.com/lab_text/item/3
98
Hypobicarbonatemia associated with an increased anion gap is never ________
compensatory
99
Metabolic acidosis associated with increased anion gaps require specifc _______
treatments
100
Anion gap =
[Na+] - ([Cl-] + [HCO3])
101
Normal Anion Gap
7-14 mEq/L
102
The anion gap is really a measure of _______ ______
unmeasured ions
103
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
104
Three quarters of the normal anion gap consists of ________.
albumin
105
Normal anion gap metabolic acidosis is usually sseen with _________
hyperchloremia (Cl- takes the place of the bicarbonate ion)
106
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)
107
Expected level of compensation in CHRONIC RESPIRATORY ACIDOSIS
expect a 4 mEq/L increase in HCO3 for every 10 mmHg increase in C02
108
Expected level of compensation in METABOLIC ACIDOSIS
CO2 decrease 1.2 times the decrease in HCO3 (usually from 24 mEq/L)
109
Expected level of compensation in ACUTE RESPIRATORY ALKALOSIS
expect 2 mEq/L decrease in HCO3 for every 10 mmHg decrease in CO2
110
Expected level of compensation in CHRONIC RESPIRATORY ALKALOSIS
expect 4 mEq/L decrease in HCO3 for every 10 mmHg decrease in CO2
111
Expected level of compensation in CHRONIC METABOLIC ALKALOSIS
CO2 increase by 0.7 times the increase in HCO3
