Pathophysiology: Arterial Blood Gases (ABG's)

arterial blood gases

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

O2, CO2, pH, and HCO3

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

Acidosis

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

increase

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

unbound

only ___ H+ ions are harmful in acidosis

< 7.35

when is a persons blood considered to be acidosis?

H+, CO2, and H2CO3

what are 3 acids

lungs; kidneys

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

metabolic

acids are produced during a ___ process

alkalosis

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

decrease

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

> 7.45

when is a persons pH in the blood considered alkalosis?

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

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)

HCO3

what is an example of a base?

buffer

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

H+

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

normal

buffers try to keep the pH in ___ range

compensatory mechanisms

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

always

compensatory mechanisms ___ alter the pH toward a normal level

lungs and kidneys

what are the two most important organs for compensatory mechanisms

pressure exerted by a single gas

what is partial pressure?

number of H+ ions

what is pH?

pH decreases

if H+ increases, what happens to the pH?

pH increases

if the H+ decreases, what happens to the pH

CO2

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

carbonic acid (CO2 + H2O = H2CO3)

excess CO2 will be combine with H2O and form ___

-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

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

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

what is the goal of buffers, lungs, and kidneys

no

are buffers able to excrete?

bind or release

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

moment-by-moment

buffers are a ___ regulation

proteins, carbonic acid-bicarbonate, phosphate

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

expiration

the lungs eliminate CO2 by ___

1-3 minutes

12-24 hrs

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

cannot eliminate H+

what can the lungs NOT eliminate?

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?

24hrs

pH is within normal limits

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

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

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

CO2

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

7.35 - 7.45

what is the normal range of pH?

80-100 mmHg

what is the normal range of PO2?

35-45 mmHg

what is the normal range of PCO2?

22-26 mEq/L

What is the normal range for HCO3?

95-100%

What is the normal range of SaO2?

-2 -+ 2 mEq/L

what is the normal range of base excess

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

the pH and CO2 arrows will be going in OPPOSITE directions

how do we determine an ABG is a respiratory problem?

pH and HCO3 arrows will be going in the SAME direction

how do we determine an ABG is a metabolic problem?

-pH: decrease

-PCO2: increase

-HCO3: normal

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

-pH: increase

-PCO2: decrease

-HCO3: normal

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

-pH: decrease

-PCO2: normal

-HCO3: decrease

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

-pH: increase

-PCO2: normal

-HCO3: increase

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

-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?

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?

-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?

-hypoxemia

-hyperventilation

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

PO2

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

respiratory acidosis

___ is the most common respiratory arterial blood gas

inadequate ventilation (Hypoventilation)

what is respiratory acidosis caused by?

-H2O

-H2CO3

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

-decreased pH (< 7.35)

-increased CO2 (>45)

what are 2 characteristics of respiratory acidosis

-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?

-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

renal compensation: kidneys produce more HCO3

what is the compensation for Respiratory acidosis

-increased pH (> 7.45)

-decreased CO2 (<35)

what are 2 characteristics of Respiratory Alkalosis

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

what is the cause of Respiratory Alkalosis

-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

renal compensation: kidney decrease production of HCO3

what is the compensation for Respiratory Alkalosis

metabolic acidosis

___ is the most common metabolic arterial blood gas

-decreased pH (< 7.35)

-decreased HCO3 (<22)

what are 2 characteristics of metabolic acidosis

DKA and CKD

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

-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?

-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?

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

what is the compensation for Metabolic Acidosis

-increased pH (> 7.45)

-increased HCO3 (>26)

what are 2 characteristics of Metabolic Alkalosis?

-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?

-hypokalemia

-hyperactive reflexes

-tetany

-confusion/ seizures

-hypotension

-dysrhythmias

what are 6 manifestations of Metabolic Alkalosis

respiratory compensation: decreased respiratory rate

what is the compensation for Metabolic Alkalosis

partially compensated respiratory acidosis

what is ABG Interpretation:

-pH = 7.33

-PCO2 = 60

-HCO3 = 34

uncompensated metabolic alkalosis

what is ABG Interpretation:

-pH = 7.48

-PCO2 = 42

-HCO3 = 30

normal ABG

what is ABG Interpretation:

-pH = 7.38

-PCO2 = 38

-HCO3 = 24

uncompenstated respiratory acidosis

what is ABG Interpretation:

-pH = 7.21

-PCO2 = 60

-HCO3 = 24

Fully compensated respiratory alkalosis

what is ABG Interpretation:

-pH = 7.45

-PCO2 = 26

-HCO3 = 16

uncompensated metabolic alkalosis

what is ABG Interpretation:

-pH = 7.50

-PCO2 = 42

-HCO3 = 33

fully compensated respiratory acidosis

what is ABG Interpretation:

-pH = 7.35

-PCO2 = 48

-HCO3 = 28

-R: respiratory

-O: opposite

-M: metabolic

-E: equal

what is a way to remember the ABG interpretation?