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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

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2
Q

define acid

A

a substance which can donate hydrogen ions in aqueos solution

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3
Q

define base

A

a substance which can accept hydrogen ions

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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

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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
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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
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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

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8
Q

the body never ___-___, however it is possible that health care providers ___-___ when treating acid base disorder

A

over-compensates

over-correct

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9
Q

define volatile acid & give example

A

can move from liquid to gas state and then be exhaled via lungs (carbonic acid)

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10
Q

define non-volatile Acids

A

cannot exchange into a gas state and therefore cannot be exhaled and are excreted via kidneys

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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

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12
Q

what determines pH balance

A

depends on ratio of HCO3- & H2CO3

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13
Q

why is acid-base balance important

A
  1. nearly all chemical & enzyme reaxns funx optimally in narrow pH range
  2. H+ and HCO3- & other ions involved in acid-base balance affect the excitability/responsivity of neural, muscle, & other cells
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14
Q

2 types of normal endogenous acid production

A
  1. carbonic (volatile)

2. Non-carbonic (non-volatile)

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15
Q

describe pH & H+ ion concentration relationship

A

inversely related more H+ pH decreases (acidic)

less H+ pH increases (alkalotic)

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16
Q

what is normal range of pH for blood

A

7.35-7.45

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17
Q

pH relationship to acid-base relationship

  1. acids are formed as __ ___ of __, __, ___ metabolism
  2. to maintain normal pH, the __ must be __ or __.
  3. major organs involved with regulation of acid & base balance
A
  1. end products, of protein, CHO, & fat metab
  2. H+, neutralized or excreted
  3. lungs & kidneys
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18
Q

3 mechanisms involved in acid-base regulation & balance

A
  1. buffers
  2. excretion
  3. cellular ion exchage
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19
Q

What happens in with buffers, excretion, & cellular ion exchange to regulate acid-base balance

A
  1. buffers soak up or give up hydrogen ion, prevent large pH changes
  2. excretion: lungs excrete co2 kidneys excrete bicarb & H+, GI tract plays a role in developing imbalances
  3. cellular ion exchange: exchange of H+ or bicarb for another like charge ion across the cell membrane
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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

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21
Q

4 buffer systems

A
  1. bicarb
  2. hemoglobin
  3. protein
  4. phosphate
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22
Q

bicarbonate weak acid
conjugate base
location

A

H2CO3 (carbonic acid)
HCO3- (bicarb)
plasma (primarily) & interstitial fluid (also in kidney tubules)

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23
Q

hemoglobin weak acid
conjugate base
location

A

HHB
HB-
RBC

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24
Q

Protein weak acid
conjugate base
location

A

Proteins have a (-) charge
Hprot
Prot-
plasma & in cells

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25
Q

Phosphates weak acid
conjugate base
location

A

H2PO4-
HPO4=
in renal cells & on some proteins Kidney tubules

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26
Q

how does the buffer system funx

A
  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
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27
Q

2 components (effect) of excretion of excess acid or base

A

respiratory (ventilatory effect)

metabolic (renal effect)

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28
Q

4 ventilatory effects on pH

A
  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
Q

overall & 2 renal effects on pH

A

maintain pH balance by regulating bicarb & excreting H+ion

  1. selective reabsorption of filtered bicarb from renal tubules
  2. excretion of titratable acids
30
Q

what is titratable acid, give examples of 2

A

combo of secreted H+ ion & buffers in the renal nephron tubular fluid that are excreted in urine

  1. hydrogen phosphate
  2. ammonia
31
Q

K+ role in pH balance & what happens acidosis

A
  1. maintains equilibrium & it has significant & inverse relationship to pH, decrease in pH increases K+
  2. K+ moves from RBC into ECF
32
Q

Ca+ role in alkalosis & acidosis

A
  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
Q

define Cl- (chloride shift)

A

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
Q

what does venous blood draw reflect

A

CO2 reflects HCO3 in venous sample

35
Q

what lab values are seen in ABG

A

arterial pH, pCO2, HCO3

36
Q

what does the venous blood draw reflect

A

chem 7 or BMP (basic metabolic panel

37
Q

what values are important to acid base in chem 7 and what does venous blood draw reflect that is important

A
  • first look @ CO2, if abnormal look @ Cl- for chloride shift
  • CO2 in venous blood draw reflects bicarb level
38
Q

normal PCO2 & HCO3

A

pco2=35-45

hco3=22-26

39
Q

ABG values for resp. alkalosis

A

low (arterial) pco3 (7.45)

40
Q

cause & compensation (& time frame for peak of compenstion) of resp. alkalosis

A

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
Q

clinical manifestation of resp alkalosis (4)

A
  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
Q

ABG laab values for resp acidosis

A

hi pco3 (>45) & low pH (<7.35)

43
Q

what causes resp acidosis & give examples

A

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
Q

resp acidosis compensation mechanism & time frame for peak compensation

A

bircab renal reabsorption into blood & secretion of
H+ into renal tubule to be excreted in urine
-2-4 days

45
Q

resp acidosis manifestations

A

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
Q

why are symptoms more prevalent in resp acidosis as opposed to metab acidosis

A

more prevalent in resp. acidosis than in metab acidosis b/c co2 readily crosses blood-brain-barrier

47
Q

metabolic alkalosis ABG lab values

A

Hi Bicarb (>26) & hi pH (>7.45)

48
Q

3 causes of metab. alkalosis & examples

A
  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
Q

metab. alkalosis compensation

A

lungs compensate by hypoventilating to increase PaCO2 thus increasing carbonic acid (occurs almost immediately)

50
Q

Metab alkalosis clinical manifestation

A
  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
Q

metab acidosis ABG lab values & cause

A
  1. lo bicarb (<7.35)

2. non-volatile acid is gained &/or bicarb or other base is lost

52
Q

2 types of causes for metab acidosis & examples

A
  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
Q

define anion gap

A

is the difference btw major cations & anions that are usually measured in a clinical lab serum chemistry profile

54
Q
  1. Na+ % of circulating cations
  2. Cl- & Bicarb % of anions
  3. What does AG represent
A
  1. 90%
  2. 85%
  3. AG represents anion not routinely measured: PO4- proteins sulfates
55
Q
  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
A
  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
Q

5 types of metab acidosis that cause high anion gap

A
  1. lactic acid
  2. alcohol
  3. uremia
  4. toxins/poisons
  5. ketones
57
Q
  • what does metabolic acidosis with normal anion gap mean in terms of something being lost and gained
  • normal range anion gap
A
  1. gained chloride
  2. lost bicarb
    - 10-14
58
Q

what does the gap refer to & when does it occur

A

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
Q

what is the application of anion gap and why is it important

A

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
Q

how do you calculate anion gap

A

(Na+K)- (Cl-HCO3)

61
Q

2 compensations for metab. acidosis

A
  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
Q

manifestations of metabolic acidosis

A
  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
Q

what are main differences btw pCO2 & serum CO2

A

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
Q

4 other characteristics of pCO2

  1. important indicator
  2. control
  3. indirect measurement
  4. critical value
A
  1. important indicator of ventilation
  2. contolled by lungs
  3. carbonic acid level is indirectly measured by pCO3
  4. critical values: 67
65
Q

7 characteristics of serum/venous CO2

  1. reported
  2. normal
  3. reflects
  4. %
  5. controlled
  6. indirect measurement
  7. critical levels
A
  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
Q

rule for ABG interpretation

A

the two values in agreement= problem
the odd one out = compensation
CO2 resp
Bicarb metab

67
Q

normal ranges for ABG

A 
pH= 7.35-7.45 
PCO2= 35-45
HCO3= 22-26
68
Q

rules for determining compensation

A

odd = N no compensation
if pH is abnorm = partial compensation
if pH is normal = complete compensation

69
Q

interpretation for three matches but abnormal

A

combination disorder or mixed disorder no compensation

nursing (15 decks)

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