2450 acid base abg Flashcards
1
Q
define pH
A
potential of hydrogen, pH of a solution is inversely proportional to the concentration of hydrogen ion in a solution
2
Q
define acid
A
a substance which can donate hydrogen ions in aqueos solution
3
Q
define base
A
a substance which can accept hydrogen ions
4
Q
define buffer
A
a substance which minimizes any change in pH when either an acid or a base is added to a solution containing the buffer
5
Q
define compensation, give example
A
- is what one system (system not affected) does to make up for another system that is not functioning, the primary disorder is not corrected in compensation
- in respiratory acidosis, kidneys compensate by retaining HCO3 to maintain norm acid-base balance
6
Q
define correction, give examples
A
- the system primarily affected is repaired, returning pH toward normal. is what we do to move the sick system toward regaining normal funx
- bronchial hygeine measures, bronchodilators, mechanical ventilation
7
Q
compensation is a __ __ of the body, correction almost always involves the initiation of interventions to ___ __ ___ of the acid base distrubance
A
physiological response
treat the cause
8
Q
the body never ___-___, however it is possible that health care providers ___-___ when treating acid base disorder
A
over-compensates
over-correct
9
Q
define volatile acid & give example
A
can move from liquid to gas state and then be exhaled via lungs (carbonic acid)
10
Q
define non-volatile Acids
A
cannot exchange into a gas state and therefore cannot be exhaled and are excreted via kidneys
11
Q
what non-volatile acids are excreted through kidneys and what are they a product of (3)
A
lactic acid- from muscle from glucose breakdown
ketoacids from fat metabolism
sulfuric & phosphoric acid from protein metab
12
Q
what determines pH balance
A
depends on ratio of HCO3- & H2CO3
13
Q
why is acid-base balance important
A
- nearly all chemical & enzyme reaxns funx optimally in narrow pH range
- H+ and HCO3- & other ions involved in acid-base balance affect the excitability/responsivity of neural, muscle, & other cells
14
Q
2 types of normal endogenous acid production
A
- carbonic (volatile)
2. Non-carbonic (non-volatile)
15
Q
describe pH & H+ ion concentration relationship
A
inversely related more H+ pH decreases (acidic)
less H+ pH increases (alkalotic)
16
Q
what is normal range of pH for blood
A
7.35-7.45
17
Q
pH relationship to acid-base relationship
- acids are formed as __ ___ of __, __, ___ metabolism
- to maintain normal pH, the __ must be __ or __.
- major organs involved with regulation of acid & base balance
A
- end products, of protein, CHO, & fat metab
- H+, neutralized or excreted
- lungs & kidneys
18
Q
3 mechanisms involved in acid-base regulation & balance
A
- buffers
- excretion
- cellular ion exchage
19
Q
What happens in with buffers, excretion, & cellular ion exchange to regulate acid-base balance
A
- buffers soak up or give up hydrogen ion, prevent large pH changes
- excretion: lungs excrete co2 kidneys excrete bicarb & H+, GI tract plays a role in developing imbalances
- cellular ion exchange: exchange of H+ or bicarb for another like charge ion across the cell membrane
20
Q
what comprises the buffer system
A
weak acid: that does not dissociate easily in h2o or plasma, thereby has relatively small effect on pH or H+ concentration
conjugate base: anion of the weak acid
21
Q
4 buffer systems
A
- bicarb
- hemoglobin
- protein
- phosphate
22
Q
bicarbonate weak acid
conjugate base
location
A
H2CO3 (carbonic acid)
HCO3- (bicarb)
plasma (primarily) & interstitial fluid (also in kidney tubules)
23
Q
hemoglobin weak acid
conjugate base
location
A
HHB
HB-
RBC
24
Q
Protein weak acid
conjugate base
location
A
Proteins have a (-) charge
Hprot
Prot-
plasma & in cells
25
Phosphates weak acid
conjugate base
location
H2PO4-
HPO4=
in renal cells & on some proteins Kidney tubules
26
how does the buffer system funx
1. if ACID is added or BASE is lost so there is excess H+ ions ->excess H+ ions bind with conjugate base, use up conjugate base to form weak acids-> thus little H+ remains free & pH change is minimized
2. if base is added or lose acid -> excess reacts with weak acid to form h2o & salt (ie conjugate base) -> decreases effect of stronger base on pH
27
2 components (effect) of excretion of excess acid or base
respiratory (ventilatory effect)
| metabolic (renal effect)
28
4 ventilatory effects on pH
1. hypervent: faster deeper breaths greater CO2 loss lower blood carbonic acid levels (alkalosis)
2. hypovent: slower shallower breaths will cause less CO2 loss & higher H2CO3 levels (acidosis)
3. lungs exhale CO2: decreasing blood levels of carbonic acid
4. increase or decrease in CO2 can lead to acid-base imbalance or compensate for one
29
overall & 2 renal effects on pH
maintain pH balance by regulating bicarb & excreting H+ion
1. selective reabsorption of filtered bicarb from renal tubules
2. excretion of titratable acids
30
what is titratable acid, give examples of 2
combo of secreted H+ ion & buffers in the renal nephron tubular fluid that are excreted in urine
1. hydrogen phosphate
2. ammonia
31
K+ role in pH balance & what happens acidosis
1. maintains equilibrium & it has significant & inverse relationship to pH, decrease in pH increases K+
2. K+ moves from RBC into ECF
32
Ca+ role in alkalosis & acidosis
1. alkalosis: high pH causes increase binding of Ca+ to albumin in exchange for H+ (hypocalcemic)
2. acidosis: low pH causes decrease binding of Ca+ to albumin (release into circulation) as H+ binds to albumin
33
define Cl- (chloride shift)
shift of CL- from plasma into RBC upon release of bicarb into plasma, & the reverse movement into lungs. it is a mechanism for electroneutrality when maintaining constant pH of blood
34
what does venous blood draw reflect
CO2 reflects HCO3 in venous sample
35
what lab values are seen in ABG
arterial pH, pCO2, HCO3
36
what does the venous blood draw reflect
chem 7 or BMP (basic metabolic panel
37
what values are important to acid base in chem 7 and what does venous blood draw reflect that is important
- first look @ CO2, if abnormal look @ Cl- for chloride shift
- CO2 in venous blood draw reflects bicarb level
38
normal PCO2 & HCO3
pco2=35-45
| hco3=22-26
39
ABG values for resp. alkalosis
low (arterial) pco3 (7.45)
40
cause & compensation (& time frame for peak of compenstion) of resp. alkalosis
cause: condition which induce hyperventilation (blowing of co2)
compensation: renal excretion of bicarb & retention of H+ which decreases pH (2-4 days for peak)
41
clinical manifestation of resp alkalosis (4)
1. hi pH of CSF which causes irritability of Central & periph nerve cells (also due to hyperCa+)
2. hyperventilation
3. dizziness, muscle contrax (CNS)
4. changes in LOC
42
ABG laab values for resp acidosis
hi pco3 (>45) & low pH (<7.35)
43
what causes resp acidosis & give examples
conditions which induce hypoventilation
examples
1. obstructive lung dz
2. restrictive lung dz
3. disruption of neural controls of breathing
4. hypoventilation w/mech ventilator (rate or volume too low)
44
resp acidosis compensation mechanism & time frame for peak compensation
bircab renal reabsorption into blood & secretion of
H+ into renal tubule to be excreted in urine
-2-4 days
45
resp acidosis manifestations
neurological depression & increased cerebral blood flow due to decreased pH of CSF.
1. hypoventil (may also be cause)
2. vasodilation induced headache
3. behavior changes (restlessness)
4. LOC changes (lethargy & coma)
46
why are symptoms more prevalent in resp acidosis as opposed to metab acidosis
more prevalent in resp. acidosis than in metab acidosis b/c co2 readily crosses blood-brain-barrier
47
metabolic alkalosis ABG lab values
Hi Bicarb (>26) & hi pH (>7.45)
48
3 causes of metab. alkalosis & examples
1. loss of acid (HCL) vomitting or diuresis (Rx diuretic)
2. increased bicarb levels (taking antacids)
3. electrolyte levels (both cause & effect)
- hypoK+ cellular shifts w/H+
- hypoCl- (this is will shift b/c it regularly maintains steady balance with HCO3 as 2 major anions in ECF)
49
metab. alkalosis compensation
lungs compensate by hypoventilating to increase PaCO2 thus increasing carbonic acid (occurs almost immediately)
50
Metab alkalosis clinical manifestation
1. hypoventilation
2. sx related to hypovolemia if cause is due to GI loss or diuretics (low bp & dizziness)
3. low pH can cause neurological irritability but this does not happen with metab alkalosis b/c HCO3 cannot cross blood brain barrier
51
metab acidosis ABG lab values & cause
1. lo bicarb (<7.35)
| 2. non-volatile acid is gained &/or bicarb or other base is lost
52
2 types of causes for metab acidosis & examples
1. with increased anion gap (increase in unmeasured anions)
- starvation acidosis
- diabetic ketoacidosis
- lactic acid acidosis (b/c of breaking down of cells)
- alcoholic ketoacidosis
- uremic acidosis
- ingestion of toxins
2. normal anion gap (hyperchloremic acidosis)
- if Chloride high bicarb will go down, if bicarb goes down chloride goes up (inversely related)
53
define anion gap
is the difference btw major cations & anions that are usually measured in a clinical lab serum chemistry profile
54
1. Na+ % of circulating cations
2. Cl- & Bicarb % of anions
3. What does AG represent
1. 90%
2. 85%
3. AG represents anion not routinely measured: PO4- proteins sulfates
55
1. describe relationship btw cations & anions
2. what is the AG used to distinguish
3. why does AG occur
4. describe relationship btw abnorm & measured anioins
1. cations & anions must be = in blood to maintain proper electrical charge balance
2. used to distinguish different types of metabolic acidosis
3. AG occurs as b/c an increased level of an unmeasured anion
4. as abnorm anions increase measured anions decrease to maintain electroneutrality
56
5 types of metab acidosis that cause high anion gap
1. lactic acid
2. alcohol
3. uremia
4. toxins/poisons
5. ketones
57
- what does metabolic acidosis with normal anion gap mean in terms of something being lost and gained
- normal range anion gap
1. gained chloride
2. lost bicarb
- 10-14
58
what does the gap refer to & when does it occur
gap refers to what we usually measure by routine lab electrolyte panels and the increased gap occurs when there is an increase in the # of anions not routinely measured
59
what is the application of anion gap and why is it important
once metabolic acidosis has been determined via ABG calculating anion gap will help differentiate btw 2 major categories of metabolic acidosis and appropriate treatment can be determined
60
how do you calculate anion gap
(Na+K)- (Cl-HCO3)
61
2 compensations for metab. acidosis
1. lungs compensate by hypervent. causing decrease of PaCO3 and increase in pH. (happens within minutes to a few hours)
2. protei and cellular buffering systems can augment compensation process
62
manifestations of metabolic acidosis
1. hypervent
2. neuromuscular depression (poor muscle funx & change of LOC lethary or coma)
3. N/V due to decreased GI motility
4. cardiac dysarrhythmias, hypotension, decreased cardiac contractility
5. decreased resonsiveness to inotropic agents (Drugs that increase contractility)
3.
63
what are main differences btw pCO2 & serum CO2
pCO2 partial pressure of carbon dioxide in blood, reported as part of ABG, normal level 35-45, uses the ratio of 20 parts HCO3 to 1 part H2CO3 (20:1)
venous/serum CO2 total CO2 in blood
64
4 other characteristics of pCO2
1. important indicator
2. control
3. indirect measurement
4. critical value
1. important indicator of ventilation
2. contolled by lungs
3. carbonic acid level is indirectly measured by pCO3
4. critical values: 67
65
7 characteristics of serum/venous CO2
1. reported
2. normal
3. reflects
4. %
5. controlled
6. indirect measurement
7. critical levels
1. reported as part of Chem 7 (electrolyte panel)
2. 22-26
3. reflects majority of CO2 in the body,
4. 90-95% of CO2 circulates as Bicarb
5. controlled mainly by kidneys
6. bicarb level is indirectly measured by total CO2 content
7. 40
66
rule for ABG interpretation
the two values in agreement= problem
the odd one out = compensation
CO2 resp
Bicarb metab
67
normal ranges for ABG
```
pH= 7.35-7.45
PCO2= 35-45
HCO3= 22-26
```
68
rules for determining compensation
odd = N no compensation
if pH is abnorm = partial compensation
if pH is normal = complete compensation
69
interpretation for three matches but abnormal
combination disorder or mixed disorder no compensation
