Pathophysiology: Arterial Blood Gases (ABG's)

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88 Terms

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arterial blood gases

___ is the measurment of partial pressure of O2, CO2, pH, and HCO3 in arterial blood

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O2, CO2, pH, and HCO3

ABG is the measurement of partial pressure of what 4 thing in arterial blood?

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Acidosis

___ is a pathologic state characterized by an increased in H+ ions in the arterial blood

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increase

Acidosis is a pathologic state characterized by an ___ in H+ ions in the arterial blood

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unbound

only ___ H+ ions are harmful in acidosis

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< 7.35

when is a persons blood considered to be acidosis?

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H+, CO2, and H2CO3

what are 3 acids

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lungs; kidneys

some acids exit the body via ___; other acids are buffered and excreted via ___

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metabolic

acids are produced during a ___ process

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alkalosis

___ is a pathologic state characterized by a decrease in H+ ions in the arterial blood

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decrease

Alkalosis is a pathologic state characterized by a ___ in H+ ions in the arterial blood

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> 7.45

when is a persons pH in the blood considered alkalosis?

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Anion Gap

___ is the difference between the extracellular anions (potassium is not always factored in) and cations; assists in identifying the cause of metabolic acidosis

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Base excess

___ is the amount of excess or insufficient level of bicarbonate in the system (a negative base excess indicates deficient amount of base in the blood)

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HCO3

what is an example of a base?

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buffer

___ is a chemical substance that reduce changes in systemic pH by releasing or binding H+ ions

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H+

buffer is a chemical substance that reduce changes in systemic pH by releasing or binding ___ ions

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normal

buffers try to keep the pH in ___ range

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compensatory mechanisms

___ is mechanisms that try to prevent large changes in pH and/or attempt to correct alterations in acid-base balance

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always

compensatory mechanisms ___ alter the pH toward a normal level

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lungs and kidneys

what are the two most important organs for compensatory mechanisms

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pressure exerted by a single gas

what is partial pressure?

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number of H+ ions

what is pH?

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pH decreases

if H+ increases, what happens to the pH?

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pH increases

if the H+ decreases, what happens to the pH

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CO2

___ is a normal byproduct of cellular metabolism; this is transported in the lungs via circulatory system and is exhaled

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carbonic acid (CO2 + H2O = H2CO3)

excess CO2 will be combine with H2O and form ___

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-acidotic

-alkalotic

excess CO2 will be combine with H2O and form carbonic acid (CO2 + H2O = H2CO3). the blood pH will then change to a more ___ state due to an increase in acid (carbonic acid) or to an ___ state due to a decrease in acid

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increase (acidosis) or decrease (alkalosis)

excess CO2 will be combine with H2O and form carbonic acid (CO2 + H2O = H2CO3). the blood pH will then change to a more acidotic state due to an increase in acid (carbonic acid) or to an alkalotic state due to a decrease in acid. the lungs will then be stimulated to either ___ or ___ the rate and depth of respiration to compensate for this change and to get the pH back to the normal level

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keep the pH within normal limits. (acid-base ratio 1:20)

what is the goal of buffers, lungs, and kidneys

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no

are buffers able to excrete?

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bind or release

buffers ___ or ___ H+ ions to minimize changes in pH - unable to excrete

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moment-by-moment

buffers are a ___ regulation

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proteins, carbonic acid-bicarbonate, phosphate

what are 3 examples of buffers that bind to or release H+?

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expiration

the lungs eliminate CO2 by ___

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1-3 minutes

12-24 hrs

the activation of the lungs occurs within ___ and last up to ___

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cannot eliminate H+

what can the lungs NOT eliminate?

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excrete:

-HCO3 (alkalosis)

-H+

Increase production and retain:

-HCO3 (acidosis)

what do the kidneys excrete when regulating the pH and also increase production and retain?

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24hrs

pH is within normal limits

the kidneys begin to work within approximately ___ and last until ___

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H2O + CO2 <--> H2CO3 <--> H + HCO3

what is the formula the body uses to keep the pH WNL?

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CO2

___ is NOT an acid singly, but can lead to carbonic acid with water

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7.35 - 7.45

what is the normal range of pH?

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80-100 mmHg

what is the normal range of PO2?

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35-45 mmHg

what is the normal range of PCO2?

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22-26 mEq/L

What is the normal range for HCO3?

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95-100%

What is the normal range of SaO2?

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-2 -+ 2 mEq/L

what is the normal range of base excess

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Step 1: Check the pH

-is it WNL? (7.35-7.45)

-Acidotic? (< 7.35)

-Alkalotic? (>7.45)

Step 2: check the CO2

-is it WLN? (35-45)

-low? (<35)

-high? (>45)

Step 3: Check HCO3

-is it WNL? (22-26)

-low? (<22)

-high (>26)

what are the first 3 steps when interpreting ABG's

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the pH and CO2 arrows will be going in OPPOSITE directions

how do we determine an ABG is a respiratory problem?

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pH and HCO3 arrows will be going in the SAME direction

how do we determine an ABG is a metabolic problem?

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-pH: decrease

-PCO2: increase

-HCO3: normal

what will the pH, PCO2, and HCO3 of respiratory acidosis look like?

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-pH: increase

-PCO2: decrease

-HCO3: normal

what will the pH, PCO2, and HCO3 of respiratory alkalosis look like?

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-pH: decrease

-PCO2: normal

-HCO3: decrease

what will the pH, PCO2, and HCO3 of metabolic acidosis look like?

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-pH: increase

-PCO2: normal

-HCO3: increase

what will the pH, PCO2, and HCO3 of metabolic alkalosis look like?

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-pH and CO2 are out of range ONLY

or

-pH and HCO3 are out of range ONLY

for step 5 of interpretation of the ABG's, how do we asses for if something is uncompensated?

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pH, CO2, and HCO3 are ALL out of range

for step 5 of interpretation of the ABG's, how do we asses for if something is partially compensated?

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-pH is WNL

-CO2 and HCO3 are out of range

is the pH closer to acidosis or alkalosis?

-if pH is < 7.40 = acidosis

-if pH is > 7.40 = alkalosis

for step 5 of interpretation of the ABG's, how do we asses for if something is fully compenated?

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-hypoxemia

-hyperventilation

with step 6 of ABG Interpretation, a low PO2 indicates ___ and can cause ___

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PO2

with step 6 of ABG Interpretation, a low ___ indicates hypoxemia and can cause hyperventilation

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respiratory acidosis

___ is the most common respiratory arterial blood gas

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inadequate ventilation (Hypoventilation)

what is respiratory acidosis caused by?

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-H2O

-H2CO3

the lungs do not ride the body for CO2 during respiratory acidosis; excess CO2 binds with ___ forming ___

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-decreased pH (< 7.35)

-increased CO2 (>45)

what are 2 characteristics of respiratory acidosis

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-hypoventilation

-CNS depression

-narcotics, sedatives, anesthesia

-impaired respiratory function d/t trauma

-pneumonia, atelectasis, pulmonary edema

-pulmonary embolism

what are 6 causes of Respiratory acidosis?

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-causes dilation of cerebral vessels- cerebral and behavioral changes

-weakness

-tremors

-paralysis

-stupor: coma

-warm/flushed skin

what are the 6 manifestations of Respiratory Acidosis

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renal compensation: kidneys produce more HCO3

what is the compensation for Respiratory acidosis

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-increased pH (> 7.45)

-decreased CO2 (<35)

what are 2 characteristics of Respiratory Alkalosis

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HYPERVENTILATION (rapid respiratory rate) secondary to pain, anxiety, fear, fever, sepsis, CNS lesion

what is the cause of Respiratory Alkalosis

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-constriction of cerebral vessels

-dizziness/ panic

-light headedness

-tetany

-numbness/ tingling of fingers/toes

-seizures

-cardiac dysrythmias

what are the 7 manifestations of Respiratory Alkalosis

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renal compensation: kidney decrease production of HCO3

what is the compensation for Respiratory Alkalosis

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metabolic acidosis

___ is the most common metabolic arterial blood gas

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-decreased pH (< 7.35)

-decreased HCO3 (<22)

what are 2 characteristics of metabolic acidosis

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DKA and CKD

Metabolic Acidosis is usually secondary to significant health problems such as ___ and ___

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-decreased production of HCO3 (renal failure)

-increased loss of HCO3 (diarrhea)

-decreased acid secretion of kidneys (renal failure)

-increased production of acids (lactic acidosis)

-ASA toxicity

-starvation

-anaerobic metabolism

-hypoxia

what are the 8 causes of Metabolic Acidosis?

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-hyperkalemia (acidosis)

-anorexia (N/V)

-abdominal pain

-weakness

-confusion

-stupor/coma

-peripheral vasodilation

-dysrhythmias

-warm/flushed skin

-bone disease

what are 10 manifestations of metabolic acidosis?

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respiratory compensation: increased respiratory rate and depth (Kussmauls respiration)

what is the compensation for Metabolic Acidosis

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-increased pH (> 7.45)

-increased HCO3 (>26)

what are 2 characteristics of Metabolic Alkalosis?

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-increased renal production of HCO3

-excess ingestion of alkali (antacids or baking soda)

-GI suctioning, vomiting, bulimia, diuretic therapy

-excess adrenocorticosteroid hormones

what are 4 causes of Metabolic Alkalosis?

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-hypokalemia

-hyperactive reflexes

-tetany

-confusion/ seizures

-hypotension

-dysrhythmias

what are 6 manifestations of Metabolic Alkalosis

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respiratory compensation: decreased respiratory rate

what is the compensation for Metabolic Alkalosis

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partially compensated respiratory acidosis

what is ABG Interpretation:

-pH = 7.33

-PCO2 = 60

-HCO3 = 34

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uncompensated metabolic alkalosis

what is ABG Interpretation:

-pH = 7.48

-PCO2 = 42

-HCO3 = 30

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normal ABG

what is ABG Interpretation:

-pH = 7.38

-PCO2 = 38

-HCO3 = 24

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uncompenstated respiratory acidosis

what is ABG Interpretation:

-pH = 7.21

-PCO2 = 60

-HCO3 = 24

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Fully compensated respiratory alkalosis

what is ABG Interpretation:

-pH = 7.45

-PCO2 = 26

-HCO3 = 16

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uncompensated metabolic alkalosis

what is ABG Interpretation:

-pH = 7.50

-PCO2 = 42

-HCO3 = 33

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fully compensated respiratory acidosis

what is ABG Interpretation:

-pH = 7.35

-PCO2 = 48

-HCO3 = 28

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-R: respiratory

-O: opposite

-M: metabolic

-E: equal

what is a way to remember the ABG interpretation?