acid- base chapter 21 (more from the book) Flashcards
1
Q
Acid
A
proton (H+) donor
2
Q
Base
A
proton (H+) acceptor
3
Q
What is acidity of a solution a reflection of?
A
Hydrogen ion concentration.
4
Q
What are most biological compounds?
A
Most biological compounds are either weak acids or weak bases
5
Q
What does the pH scale represent?
A
Scale represents the hydrogen ion concentration.
6
Q
If pH decreases what does that tell you?
A
As the value or pH decreases, the hydrogen ion concentration increases and therefore the acidity increases.
7
Q
If the pH increases what does that tell you?
A
As the value or pH increases, the hydrogen ion concentration decreases and therefore the acidity decreases.
8
Q
Common pH measurements of common household liquids or products?
A
Lemon juice is 2.0 wine is 4.0 rain is 5.5 your blood is 7.5 baking soda 8.5 detergent 10.0 bleach is 12.5
9
Q
hydrogen ion (H+) concentration compared to hydroxide (OH-) ion concentration?
A
A solution with a high number of hydrogen ions is acidic and has a low pH value. A solution with a high number of hydroxide ions is basic and has a high pH value. The pH scale ranges from 0 to 14, with a pH of 7 being neutral.
10
Q
What does the henderson-hasselbach equation describe?
A
Describes the relationship between the plasma pH and the ratio of plasma PCO2 and HCO3.
11
Q
What is the primary determinant of plasma pH?
A
The ratio of plasma PCO2 and HCO3.
Not individual values alone!
12
Q
what ratio is hydrogen and bicarb produced in?
A
one to one ratio
13
Q
large changes in H+ concentration equal what kind of changes in bicarb? WHY?
A
large changes in H+ = small changes in HCO3.
Bc H+ is represented in nEq/L (nanommole) one billionth, where as HCO3 is represented in mEq/L (one thousandth)
14
Q
water plus CO2 yields what?
A
carbonic acid a weak acid.
15
Q
why are the concentrations of hydrogen and bicarb precisely regulated?
A
to optimize enzyme activity, oxygen transport, and rates of chemical reactions within the cell.
16
Q
What three regulation processes does the body use to keep acid base concentrations in balance?
A
Buffers
pulmonary excretion of CO2
renal elimination of acid
(buffer, ventilation, renal excretion)
17
Q
blood PH less than 7.35 is called?
A
acidemia
18
Q
blood pH greater than 7.45 is called?
A
alkalemia
19
Q
the underlying process that lowers the pH is called?
A
acidosis
20
Q
the underlying process that raises the pH is called?
A
alkalosis
21
Q
can you have mixed acidosis and alkalosis?
A
Yes!
22
Q
can you be both acidemia and alkalemia?
A
No! the osis can occur together as a mixed disorder but not the emia, you will be have either acidemia or alkalemia with acidosis or alkalosis or both.
23
Q
What does the blood gas machine use to determine BE?
A
An algorithm utilizing plasma pH, blood PCO2, and hemoglobin concentration.
24
Q
In clinical practice the BE is often used as a surrogate measure for what?
A
lactic acidosis, which is one measurement to help determine adequacy of intravascular volume resuscitation.
25
A BE greater than zero suggest what? and a BE less than zero suggests what?
greater than zero = metabolic alkalosis
| less than zero (base deficit) = metabolic acidosis.
26
What is normal hydrogen ion concentration (CO2) in arterial blood and extracellular fluid?
PCO2 = 35-45 nmol/L which is equivalent to an arterial pH of 7.45-7.35.
27
Normal bicarb?
22-26mEq/L
28
intraCELLular hydrogen ion concentration?
160 nmol/L which is about a 6.8 pH
29
Response times of each compensatory mechanism?
buffer- immediate
Ventilatory= minutes whenever possible
Renal= slowly provides nearly complete restoration of pH, but it can take days.
30
What is a buffer and what is it composed of?
a substance within a solution that can prevent extreme changes in pH.
A buffer system is composed of a base molecule and its weak conjugate acid.
31
What does pKa stand for and what is it telling you?
pKa means dissociation ionization constant.
| it indicates the strength of an acid.
32
hydrochloric acids pKa and carbonic acids pKa?
hydrochloric acid is a strong acid = -7 pKa
| carbonic acid is a weak acid = 6 pKa
33
what enzyme speeds up the reaction that makes carbonic acid?
carbonic anhydrase
34
CO2 + H20 yields H2CO3 yields H+ + HCO3- tells you what?
and which system uses this?
Hydration of carbon dioxide results in carbonic acid, which dissociates into bicarbonate and hydrogen ions.
carbonic acid-bicarbonate buffer system.
35
buffer systems in order of importance?
1. bicarbonate buffer system
2. hemoglobin buffer system
3. other protein buffer systems
4. phosphate buffer system
5. ammonia buffer system
36
```
In the henderson-hasselbach equation what do the following symbols tell you?
A-
HA
HB+
B
```
A- = conjugate base
HA = undissociated weak acid
HB+ = conjugate acid
B = weak base
37
what is acidosis
what is alkalosis
metaboic?
respiratory?
Acidosis – disorder that lowers pH
Alkalosis – disorder that raises pH
Metabolic – primarily affects HCO3-
Respiratory – primarily affects PaCO2
38
where is carbonic anhydrase present?
endothelium, erythrocytes, and kidneys.
39
Most important buffer system in the human body? (extracellular fluid mostly, but most important in the human body also)
carbonic acid-bicarbonate buffer system (when combined with renal control of bicarbonate and pulmonary control of carbon dioxide)
40
what ratio does the bicarbonate buffer system maintain?
ratio of 20 parts bicarbonate to 1 part carbonic acid
41
Does the bicarbonate buffer system prevent a pH change?
NO!
42
Most important NONcarbonic buffer in extracellular fluid?
Hemoglobin protein
43
Important BLOOD buffer?
Hemoglobin buffer system
44
The other three buffer systems manage buffering how?
Intracellular proteins – intracellular fluid compartment
Phosphates – urinary buffer
Ammonia – urinary buffer
45
Urinary buffer would be which two buffer systems?
Phosphates and Ammonia buffer system.
46
Explain the hemoglobin buffer system?
Carbon dioxide freely diffuses into RBC where it combines with water to form carbonic aicid, (with the help of carbonic anhydrase which resides inside of RBC) which rapidly deprotonates. the protons generated are bound up by hemoglobin. The bicarbonate anions are exchanged back into plasma with chloride.
47
Hyperventilation causes what acid base disorder and can cause Hydrogen and Potassium to move how?
Hyperventilation can lead to respiratory alkalosis thereby driving H+ out of the cell and K+ into the cell leading to hypokalemia.
48
In acidosis does blood potassium increase or decrease?
Acidosis-serum K+ increases there is a H+/K+ shift across the cell membrane H+ into the cell and K+ out. (Hydrogen is trying to go to a lower concentration of acid and away from the blood plasma that is acidic)
49
As plasma potassium increases (bc of acidosis and hydrogen going into the cell) what is the amount of potassium increase to unit of pH decrease?
Plasma K+ increases approx. 0.6 mEq/L for each 0.1 unit decrease in pH.
(The reverse would be true for potassium decrease in alkolosis and an increase in pH)
50
Other ways to buffer extracellular compartments.
Exchange of extracellular H+ for Na+ and Ca 2+ from bone
Exchange of extracellular H+ for intracellular K+
Acid loads can demineralize bone and release alkaline compounds
Alkaline loads increase deposition of carbonate in bones
51
how much does plasma potassium increase of decrease for every 10 mmHg reduction in PACO2
Plasma K+ is decreases/increase approx. 0.5 mEq/l for every 10 mmHg reduction in PaCO2.
52
Deoxyhemoglobin takes up more?
```
hydrogen ions
(it does not have oxygen taking up space so it takes hydrogen)
```
53
Oxyhemoglobin favors?
The release of hydrogen ions
| wants oxygen so it releases hydrogen
54
deoxyhemoglobin has a greater affinity for?
carbon dioxide, so venous blood carries more carbon dioxide than arterial blood
(makes sense)
55
Alveolar ventilation increases or decreases as pH decreases?
If pH is decreasing that means you are holding onto CO2 (an acid) thus your ventilation needs to increase to blow it off. Rate and Depth increases.
56
carbonic acid produced in the lungs is converted to what and excreted by the lungs?
H2CO3 is converted to CO2 and excreted by the lungs.
57
How fast is the respiratory system response to acid base imbalances?
acts within minutes, maximal in 12 -24 hours.
58
When the respiratory system comes into play is the pH ever completely restored to normal? WHY?
No.
as the pH approaches 7.4 the stimulus from central and peripheral chemoreceptors to either increase or decrease ventilation diminishes, such that complete correction or over correction is not possible.
59
What develops at very high PaCO2?
Carbon dioxide necrosis.
60
What is reached at very low PaCO2?
Apneic threshold
61
apneic threshold difference in an awake patient and a patient under general anesthesia?
during general anesthesia, spontaneous ventilation will cease when the Paco2 decreases to less than the apneic threshold, in the awake patient cortical influences prevent apnea, so the apnea threshold is not ordinarily observed.
62
Which patients have almost no hypoxic ventilatory drive due to a specific surgery?
Patients who have had bilateral carotid endarterectomies bc it abolishes the peripheral chemoreceptor response.
63
How does the respiratory system regulate CO2?
by increasing or decreasing rate and depth of respiration.
64
why is the pulmonary response to metabolic alkalosis usually less than the response to metabolic acidosis?
in metabolic acidosis the body increases rate and depth of breathing to blow of CO2, but with metabolic alkalosis you want to increase CO2 so the mechanism for that is to breath less. But the body can only decrease breathing and depth by so much before hypoxia (when breathing room air) occurs and then the body at a point will not let resp. drop or become any more shallow in an attempt to regulate oxygen concentration.
65
PaCO2 does not typically rise above what amount in response to Met. Alk for a patient using NO supplementary oxygen?
55 ( normal 35-45) (because the body will only let you become so hypercapnic/hypoxic without supplementary oxygen.)
66
Renal response, occurs via three mechanisms, what are they?
1. reabsorption of filtered HC03-
2. Excretion of titratable acids
3. ammonia
67
How do the kidneys regulate blood PH?
by excreting H+ and reabsorbing HCO3-
68
Primarily regulates amounts of what? (decides if it is absorbed or excreted)
bicarbonate
69
what OTHER things does the renal system regulate which can effect acid-base?
Ammonia and electrolytes
70
what do the proximal tubules reabsorb?
filtered HCO3- and they reabsorb 80-90% of the filtered bicarbonate.
71
What do the distal tubules take care of?
the remaining 10-20% of bicarbonate that the proximal tubules did not reabsorb.
72
when carbonic acid dissociates what does it produce?
hydrogen and bicarbonate
73
2) excretion of titratable acids, explain that process?
hydrogen ions can combine with HP04^2- to form H2P04-, which is eliminated in the urine.
74
explain the process of reabsorption of the filtered HCO3-?
1) CO2 combines with water in the renal tubules cell to make carbonic acid which readily disassociates into hydrogen and HCO3-. The produced bicarb enters the blood stream while the hydrogen ion is exchanged with sodium and is released into the renal tubules (bc it was just in the cell and not the tubule structure).
2) In the renal tubule hydrogen combines with filtered HCO3- and dissociates into C02 and water, and the CO2 diffuses back into the renal tubule cell.
75
explain Ammonia's role in excretion of hydrogen?
Ammonia is formed from deamination of glutamine, an amino acid (so it should be availble) The ammonia passively crosses the cell membrane to enter the renal tubular fluid. In the tubular fluid it combines with hydrogen ion to form NH4+, which is trapped within the tubule and excreted in the urine.
76
Because of the massive ability of the kidneys to make, move, absorb, or excrete bicarb they are great with compensation in which metabolic disorder?
Alkalosis
77
The kidneys are highly effective in protecting the body against alkalosis except in association with which two disorders?
sodium deficiency or mineralocorticoid excess.
| sodium is needed in the kidneys to transport hydrogen out of the cell or fluid and into the renal tubule
78
another word for too much bicarbonate in the blood?
hypercarbonatemia (27 or greater mEq/L)
79
Causes of metabolic alkalosis?
| you have gastric reasons, renal, chlorid-resistance
```
vomiting
gastric drainage
chloride diarrhea
villous adenoma
diuretics
low chloride intake
sweat
cystic fibrosis
sever hypokalemia
increased mineralocorticoid activity which would be cushing's syndrome
licorice ingestion
bartter's syndrome
primary hyperaldosteronism
```
80
what disorder is described here- decreased acid or increased base, high pH, tachycardia, nausea vomiting diarrhea, confusion, restlessness followed by lethargy. HCO3- increased.
metabolic alkalosis
81
multiple bags of blood given in a short amount of time can cause?
metabolic alkalosis from the citrate binding to calcium, they will need some calcium given.
82
vomiting or cont. NG suctioning can result in marked metabolic alkalosis but what else will it cause?
extracellular volume depletion and hypokalemia.
83
physiologic effects of metabolic alkalosis
compensatory hypoverventilation,
decreased CO,
decreased ionized calcium,
leftward shift of oxyhemoglobin dissociation curve,
decrease in serum potassium
84
treatment of metabolic alkalosis that is etiologic (trying to fix the underlying problem rather than just patch it)
increased IV volume to increase renal perfusion (to pee out bicarb)
potassium to revers hypokalemia
NS preferable to LR (bc of the sodium and chloride present)
decrease in min. ventilation
85
nonetiologic treatment of metabolic alkalosis?
giving H+
diamox (acetazolamide) enhances excretion of bicarb and inhibts carbonic anhydrase
86
hyperaldosteronism explain what it does?
and if you have it what acid base imbalance will you have?
excessive secretion of aldosterone, which causes increases in sodium reabsorption and loss of potassium and hydrogen ions. (which will cause metabolic alkalosis)
87
What is Cushing's syndrome?
Excess levels of the hormone cortisol are responsible for Cushing syndrome. Cortisol, which is produced in the adrenal glands, plays a variety of roles in your body. For example, cortisol helps regulate your blood pressure and keeps your cardiovascular system functioning normally.
88
What does cortisol do?
cortisol helps regulate your blood pressure and keeps your cardiovascular system functioning normally.
Cortisol also helps your body respond to stress and regulates the way you convert (metabolize) proteins, carbohydrates and fats in your diet into usable energy. However, when the level of cortisol is too high in your body, you may develop Cushing syndrome.
89
What disorders can cause Cushing's syndrome?
A pituitary gland tumor (pituitary adenoma) (More common)
A primary adrenal gland disease. (more common)
Cancerous tumors of the adrenal cortex (adrenocortical carcinomas) are rare
Familial Cushing syndrome.
An ectopic ACTH-secreting tumor (RARE)
90
key characteristics of Cushing's syndrome?
```
buffalo hump
upper body obesity with thin arms and legs
red, round face (moonface)
high blood sugar
high blood pressure
acne
osteoporosis
gynecomastia in men
Na and fluid retention
lack of a period or period irregular
bruises and petechiae
personality changes
female balding
thin skin
poor wound healing
severe depression
sleep disorders
fatigue
```
91
what is bartter sydrome and what acid base disorder does it cause?
represents a set of closely related, autosomal recessive renal tubular disorders characterized by hypokalemia, hypochloremia, metabolic alkalosis, and hyperreninemia with normal blood pressure. The underlying renal abnormality results in excessive urinary losses of sodium, chloride, and potassium.
92
licorice poisoning (rare) what does it cause to be out of whack?
regular licorice ingestion can result in hypokalemia, hypernatremia, and water retention. Emergency treatment of licorice poisoning is largely supportive and consists primarily of monitoring for electrolyte abnormalities (especially of potassium) and other complications, with correction if necessary.
93
are red licorice's dangerous?
Candies marketed as licorice (eg, red licorice) have artificial licorice flavoring and do not contain glycyrrhizin.
94
what is milk-alkali syndrome?
Milk-alkali syndrome is caused by the ingestion of large amounts of calcium and absorbable alkali, with resulting hypercalcemia. If unrecognized and untreated, milk-alkali syndrome can lead to metastatic calcification and renal failure. This syndrome was originally recognized in the 1920s during administration of the Sippy regimen, consisting of milk and bicarbonate, for treatment of peptic ulcer disease.
95
because of nonabsorbable alkali and histamine 2 blockers as treatment for peptic ulcer dz, milk alkali syndrome became a rare cause of hypercalcemia; however what has caused a resurgence?
however, with the increased use and promotion of calcium carbonate for dyspepsia and for calcium supplementation, a resurgence of milk-alkali syndrome has occurred.
96
lack of what ions impairs the kidneys ability to excrete excessive bicarb?
sodium, potassium, (cations)
| chloride (anion)
97
How to calculate anion gap?
cloride plus bicarb and then subtract sodium = anion gap
anion gap= [Na+] - ([Cl-] + [HCO3-])
98
what is anion gap?
the difference between the cations and anions equals the concentration of unmeasured anions in the serum.
99
what is a normal anion gap?
8-12 mEq/L
100
Most common unmeasured anions are? (what would increase the anion gap)
lactic acid and keto acid
101
when does metabolic acidosis occur with a normal anion gap?
| what can cause it?
when chloride replaces the lost bicarbonate.
bicarbonate- wasting process in the kidneys (renal tubular acidosis) or GI (diarrhea).
Aggressive fluid resuscitation with normal saline (>30ml/kg/hr).
excessive chloride administration which impairs the kidneys ability to reabsorb bicarb (bicarb is an anion and so is chloride so it just reabsorbs an anion)
