acid-base imbalance Flashcards
1
Q
molecule that releases H+
A
Acid
2
Q
molecule that accepts H+
A
base
3
Q
degree to which an acid or base dissociates into ions
A
dissociation constant (pK)
4
Q
the scale we use to measure the amount of H+ in a solution
A
pH
5
Q
pH of ECF in the body
A
7.35-7.45
6
Q
4 chemical buffer systems
A
bicarbonate buffer system
proteins
H+/k+ transcellular exchange
bone buffer system
7
Q
3 systems for pH regulation
A
chemical buffer systems
respiratory acid/base control
renal acid/base control
8
Q
describe the bicarbonate buffer system
A
HCO3- can accept H+ to reduce pH
H2CO3 can contribute H+ ions if needed
body can eliminate the components that are not needed
9
Q
what is the largest buffering system in the body
A
proteins
10
Q
____ have binding sites for acid and base molecules
A
amphoteric
11
Q
why do proteins have a delayed onset
A
due to transmembrane movement of acid/base
12
Q
describe h+/k+ transcellular exchange
A
both ions move freely across the membrane
cells can exchange H+ for K+ as needed to attain equilibrium
13
Q
which is not a not considered a “buffering system”
A
bone
14
Q
how does bone help with buffering
A
- excess H+ can be exchanged for Na+ and K+ on the bone surface
- can be broken down to release NaHCO3 and CaCO3
15
Q
when is the bone buffering system mainly active
A
during acute acid loads and chronic acidemia
16
Q
what system is managed through control of extracellular CO2
A
respiratory acid/base control
17
Q
where are chemoreceptors in the body to sense changes in pH and pCO2 and alter respiratory rate
A
brainstem, carotids, aorta
18
Q
this system causes rapid changes in pH
starts within minutes, maximum effect in 12-24hrs
A
respiratory
19
Q
respiratory acid/base control is not as effective at managing pH as ___
A
kidneys
20
Q
lungs respond by increasing ventilation rate during ___
A
acidemia
low pCO2 = low formation of carbonic acid
21
Q
lungs respond by lowering ventilation rate during ____
A
alkalemia
high pCO2 = high formation of carbonic acid
22
Q
what system is managed through control of H+ and HCO3- excretion
A
renal acid/base control
23
Q
describe the renal acid/base control
A
- kidneys excrete h+ ions freely and through creation of H-containng molecules
- kidneys reabsorb HCO3- as needed for pH balance
- takes several HOURS - DAYS to reach full effect!! - can be sustained for longer periods
24
Q
Kidneys excrete H+ and reabsorb HCO3- during ___
A
acidemia
25
kidneys reabsorb H+ and excrete HCO3- during ___
alkalemia
26
describe the relationship between H+ and K+ in renal acid/base control
H+ and K+ excretion are dependent on each other
- kidneys struggle to excrete or reabsorb high amounts of both H+ and K+ simultaneously
27
increased k+ secretion, impaired H+ secretion
hyperkalemia
28
increased K+ reabsorption, impaired H+ reabsorption
hypokalemia
29
inappropriate excess of HCO3- and loss of Cl-
hypochloremic alkalosis
30
inappropriate excess of Cl- and loss of HCO3-
hyperchloremic acidosis
31
4 tools to assess acid-base status
1. hx
2. PE
3. BMP
4. ABG
32
which tool to assess acid-base status must be adjusted prior to interpretation
ABG
33
why are BMP useful in detecting acid-base disorders
easy, at-a-glance check on bicarbonate status
can calculate anion gap
34
what is an anion gap
- difference between measured cations and anions in ECF
- helps determine etiology of METABOLIC ACIDOSIS
- [Na+] - ([Cl-] + [HCO3-])
35
if the anion of the acid added to the plasma is Cl- then the anion gap will be __
normal
36
if the anion of the acid is not Cl-, then the anion gap will ___
increase
37
what gives more accurate measurements of oxygen, carbon dioxide, bicarbonate, and pH
ABG
38
when can ABGs be useful
1. establishing Dx/assessing severity
- suspected hypercapnia
- suspected severe hypoxemia
- other suspected ventilatory difficulty
2. guiding Tx/monitoring response
- ventilated patients
- dyspneic patients
- O2 therapy
39
change in normal value of extracellular pH that may result when: (2)
1. renal or respiratory function is abnormal
2. acid or base load overwhelms excretory capacity
40
4 types of acid-base disorders
1. metabolic acidosis
2. respiratory acidosis
3. metbaolic alkalosis
4. respiratory alkalosis
41
___ = decreased ventilation
respiratory acidosis
42
causes of respiratory acidosis
1. depression of CNS respiratory center
- head trauma
- drug overdose
2. lung disease
- COPD
- asthma
- pulmonary edema
-pneumonia
3. airway obstruction or msk disease
- obesity
- kyphoscoliosis
- paralysis of rsp muscles
- chest wall injury/flail chest
tumor or foreign body in airway
4. breathing air with high CO2 content
43
symptoms of respiratory acidosis
1. neuro
- HA
- confusion
- weakness
-drowsiness/stupor
- muscle twitching
- tremors
- paralysis
- coma
2. CV
- vasodilation
3. signs of underlying disease
44
patients with chronic hypercapnia often have ?
desensitized chemoreceptors for CO2 detection
45
in patients who rely on hypoxic drive, ___
- overzealous correction of hypoxemia with supplemental O2 may depress ventilation
46
____ = increased ventilation
respiratory alkalosis
47
causes of respiratory alkalosis
1. excessive ventilation
- pain
- anxiety
- mechanical ventilation
- psychogenic
2. increased stimulation of CNS respiratory center
- encephalitis
- fever
- salicylate toxicity
- elevated blood ammonia levels
- hypoxemia
48
symptoms of respiratory alkalosis
1. neuro - increased neuronal excitability
- dizziness
- panic
- light-headedness
- tetany
- numbness/tingling
- seizures
- chvostek and trosseau signs
2. CV
- arrhythmias
3. signs of underlying disease
49
4 ways metabolic acidosis can happen:
1. increased production or ingestion of acids
2. inability to renally excrete acid
3. increased plasma Cl-
4. excessive loss of HCO3-
50
excessive loss of HCO3- through kidneys or GI tract = ___ anion gap
normal
kidneys preserve Cl- to keep balanced charge = hyperchloremic metabolic acidosis
51
ingestion of exogenous acid or elevation of unmeasured endogenous acid = ____ anion gap
elevated
lactate, salicylate, B-hydroxybutyrate
larger gap = worse acidosis
52
when can decreased anion gap be seen
decreased anions - hypoalbuminemia
increased IgG/cations - multiple myeloma, elevations in Ca, K, or Mg
53
allows us to determine if a secondary, "hidden" acid-base disturbance is also prsent besides the anion gap metabolic acidosis
delta gap
= anion gap - normal AG (12)
54
if metabolic acidosis value is <24, =
another metabolic acidosis process present
55
if metabolic acidosis value >24, =
metabolic alkalosis process also present
56
delta gap that is done without bicarbonate value
modified delta gap
- delta gap = (Na+) - (Cl-) - 36
- -6 or less = Mixed high and normal anion gap metabolic acidosis
- -6 to 6 = Only high anion gap metabolic acidosis
- 6 or greater = Mixed high anion gap metabolic acidosis and metabolic alkalosis
57
causes of metabolic acidosis
1. increased anion gap (MUDPILES)
- excess production of metabolic acids
-- lactic acidosis
-- ketoacidosis
-- poisoning
- renal failure
-- accumulation of renal wastes
2. normal anion gap (HARDUP)
- HCO3- losses
-- renal tubular acidosis
-- diarrhea
-- carbonic anhydrase inhibitors
-- urinary diversion/intestinal fistula
- inability to excrete H+
-- adrenal insufficiency
-- renal failure
- excess administration of Cl
-- IV infusions
-- ammonium chloride
58
symptoms of metabolic acidosis
1. neuro
- confusion
- weakness
- drowsiness/stupor
- coma
2. CV
- vasodilation
-cardiac arrhythmias
3. gastrointestinal
- ABD pain
- N/V and anorexia
4. respiratory
- increased depth and rate of respiration
5. bone
- decreased density/osteoporosis
6. signs of underlying disease
59
impaired HCO3- excretion frequently related to depletion of ___, ___, and ____, often due to _____ or ____
chloride, potassium, and sodium ions
vomiting or diuretics
60
causes of metabolic alkalosis
1. excess amounts of bicarbonate/alkali
- NaHCO3 administration
- administration of alkaline solutions
2. excessive loss of hydrogen ions
- vomiting
- gastric suction (NG tube)
- hypokalemia
- milk-alkali syndrome
3. increased bicarbonate retention
- loss of chloride
4. volume depletion
- including diuretic therapy
61
symptoms of metabolic alkalosis
1. neuro - increased excitability
- dizziness
- panic
- light-headedness
- tetany
- numbness/tingling
- seizures
- chvostek and trosseau signs
2. CV
- arrhythmias
3. signs of underlying disease
62
primary respiratory disturbance and primary metabolic disturbance occur simultaneously
mixed acid-base disorder
63
process by which either kidneys or the lungs make automatic adjustments when the other system is overwhelmed
compensation
64
what two organs work together to help maintain a normal pH level in the body
kidneys and lungs
65
respiratory acidosis compensatory mechanism
kidney reabsorb more HCO3- in proximal tubule
kidneys excrete more H+ in disstal tubule
66
respiratory alkalosis compensatory mechanism
kidneys excrete more HCO3- in proximal tubule
kidneys reabsorb more H+ in distal tubule
67
metabolic acidosis compensatory mechanism
lungs increase ventilation
68
metabolic alkalosis compensatory mechanism
lung decrease ventilation
69
acute compensation for respiratory acidosis
↑ HCO3- = 0.1 x Δ pCO2
70
chronic compensation for respiratory acidosis
↑ HCO3- = 0.35 x Δ pCO2
71
acute compensation for respiratory alkalosis
↓ HCO3- = 0.2 x Δ pCO2
72
chronic compensation for respiratory alkalosis
↓ HCO3- = 0.6 x Δ pCO2
73
compensation formula for metabolic acidosis and alkalosis
↓ pCO2 = 1.2 x Δ HCO3-
