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Acid & Bases 2 Flashcards

1
Q

Arterial Blood Gases Test (ABGs)

A

-sample from an artery (usually the radial artery)
-not a routine test (acute)
-more painful than a venous sample
-and RN requires special training

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2
Q

What do AGBs Measure?

A

Ph, paO2 (partial pressure), paCO2, HCO3

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3
Q

When are AGBs used?

A

-Reserved for people who have acute illnesses and are unstable (sepsis/acute respiratory distress syndrome)
-diabetic ketoacidosis, acute exacerbation of chronic pulmonary disease
-sometimes used to qualify a patient for certain treatments like home oxygen

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4
Q

PaO2

A

-Normal values: 80-100mmHg
-Not the same as O2 saturation
-O2 levels do not factor into your assessment for acid-base imbalances but is an accurate measurement of how much oxygen is in the arterial blood
-A low paO2 is reflective of hypoxemia
-You can see amounts over 100 when a pt is getting supplemental oxygen

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5
Q

PaCO2

A

-Normal values: 35-45mmHg
-Measures the amount of CO2 gas in the blood
-Helps you ability to analyze ABG results if you label this as “respiratory acid”

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6
Q

HCO3 (bicarbonate)

A

-Normal Values: 22-26mmol/L
-Is the metabolic base

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7
Q

Venous Blood Gases (VBG)

A

-Can also be preformed
-Normal values different the ABG
-The average VBG pH is 0.03-0.04 less than the ABG pH values
-CO2 values are difficult to measure on VBGs (not accurate)
-VBGs are useful in ongoing monitoring and response to treatment for metabolic disorders but are not useful if the pt has a resp acid-base disorder

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8
Q

Arterial Lines

A

-Only used in critical care setting (step down, ED, ICU)
-Used to continuously monitor BP
-Used to easily collect blood
-CANNOT be used for medication infusions
-RNs require additional training
-Carry many risks for complications
-Not like CVADs

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9
Q

Acid-Base Imbalances

A

-When an imbalance occurs, it means the buffering systems have failed (disease/injury cannot be corrected with buffering alone)
-While acidosis/alkalosis disrupts cellular function and needs to be addressed, the primary focus is identifying and treating the CAUSE of the imbalance
-Can either be metabolic or respiratory in nature

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10
Q

Abnormal arterial blood gas findings are simply evidence of…

A

An underlying pathology

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11
Q

Causes of an imbalance: Metabolic

A

-Too little or too much bicarbonate

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12
Q

Causes of an imbalance: Respiratory

A

-Too little or too much carbon dioxide

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13
Q

Once an imbalance has occurred..

A

The OPPOSITE system will attempt to fix the problem (compensate)

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14
Q

If the cause of the imbalance is respiratory …

A

-Then the metabolic system (bicarbonate) will compensate

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15
Q

If the cause of the imbalance will s metabolic ..

A

The respiratory system (paCO2) will compensate

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16
Q

What the body cares about

A

-ultimately the imbalance is not resolved until the source of the problem is addressed, but in short term, all the body cares about is getting the pH between 7.35-7.45

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17
Q

Respiratory Acidosis

A

-Seen in patients who are RETAINING carbon dioxide (acid)
-This means they are having troubles breathing out CO2
-This means the CO2 (acid) is remaining in their blood =acidosis

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18
Q

Examples of causes of Respiratory Acidosis

A

-COPD (CO2 trapped in alveoli)
-Opioid OD (hypoventilating)

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19
Q

Respiratory Alkalosis

A

-Seen in patients who are losing too much carbon dioxide (acid)
-This means they are “breathing out” too much CO2
-This means CO2 is no longer in the blood = alkalosis

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20
Q

Examples of Causes of Respiratory Alkalosis

A

-Pt in pain or panicking (hyperventilating)

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21
Q

Respiratory imbalances occur when..

A

-Something (disease, injury, drugs) affect the lungs ability to function normally (and when buffering system failure)
-CO2 is an acid so retaining it will result in acidosis and blowing too much out will result in alkalosis

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22
Q

Labelling Resp vs Metabolic

A

-Labelling paCO2 as the respiratory ACID and HCO3 bicarb as the metabolic BASE is the best way rot apply acid base concepts

23
Q

Respiratory Imbalances pH (resp acidosis/alkalosis)

A

pH respiratory acidosis: decrease
pH respiratory alkalosis: increase

24
Q

Respiratory imbalances: PaCO2 (resp acidosis/alkalosis)

A

PaCO2 respiratory acidosis: Increase
PaCO2 respiratory alkalosis: decrease

25
Respiratory Imbalances: HCO3 (resp acidosis/alkalosis)
HCO3 Respiratory acidosis: Kidbeys compensation increase HCO3 respiratory Alkalosis: Kidneys compensation decrease
26
Respiratory Acidosis Process
-If occuring, means there is an inability to move CO2 out of the body through the alveoli -If pt not exhaling the CO2 = hypoventilation -The excess in CO2 will cause an increase in carbonic acid present in the blood -Since carbonic acid already has as many H+ as it can compensate, the kidneys increase the excretion of H+ and the reabsorption of bicarb to try to increase pH -means in acute short term elevations of PaCO2 you will not see any elevation of HCO3 in response -if elevation of HCO3 this tells you elevation of paCO2 (resp acid) has been present for at least 48 hours -kidneys try ti offset resp acidosis by creating metabolic alkalosis
27
Respiratory Alkalosis Process
-Mean lungs have expelled too much CO2 (hyperventilation) -Results in an accelerated loss of carbonic acid -If pt exhaling too rapidly, leads to a deficit of carbonic acid in the blood, increasing the pH of the blood -To compensate kidneys will hold onto H+ ions and increase the excretion of bicarb to compensate for lack of respiratory acid -Kidneys are trying to create a metabolic acidosis to offset resp alkalosis
28
Most causes of resp alkalosis are due to …
-Anxiety or pain responses, increasing RR -Once underlying problem is resolved and RR decreases, the pH will normalize = most self limiting and usually least harmful and will not usually see chronic conditions that cause ongoing respiratory alkalosis
29
Metabolic Acidosis
-By far the most common metabolic imbalance -Have multiple causes -Seen in patients who produce or retain too much H+ = acidosis -Seen in patients losing too much bicarb
30
Metabolic Acidosis: Retaining/producing too much H+ examples
-Eg: diabetic ketoacidosis (DKA), sepsis, acute kidney injury (AKI)
31
Metabolic Acidosis: Patient losing too much bicarb examples
Eg: Diarrhea (lower GI tract is full of bicarb)
32
Metabolic Alkalosis
-Seen in patients who are loosing too much H+ =alkalosis -Seen in patients who are hypokalemic (low potassium)
33
Metabolic Alkalosis: Loosing to much H+ examples
-Eg: Vomiting (upper GI tract full of H+)
34
Metabolic Alkalosis: pt who are hypokalemic examples
- pt taking too much diuretic
35
Metabolic Imbalance pH: metabolic acidosis
-ph increase
36
Metabolic imbalance ph: metabolic alkalosis
ph increase
37
Metabolic imbalance PaCO2 (lungs): metabolic acidosis
Lungs compensate: decrease
38
Metabolic imbalance PaCO2 (lungs): Metabolic alkalosis
Lungs compensate: increase
39
Metabolic imbalance HCO3 (kidneys): Metabolic acidosis
Kidneys HCO3 decrease
40
Metabolic imbalance HCO3 (kidneys): Metabolic Alkalosis
Kidneys HCO3 increase
41
Kussmaul Respiration
-When there is metabolic acidosis there is an excess of carbonic acid and a deficit of bicarb -Resp system will IMMEDIATELY compensate by exhaling more CO2 -The rapid deep breathing that accelerates exhalation of CO2 is triggered by central chemoreceptors sensing the higher CO2 and lower pH content in the blood -happens immediately -Resp system trying to create a respiratory alkalosis to offset metabolic acidosis
42
Metabolic Alkalosis and Resp compensation
-The elevated pH triggers a decrease in ventilation via slow, shallow respiration’s in an attempt to retain PaCO2 -Resp system trying to create a respiratory acidosis to offset the metabolic alkalosis
43
Venous Blood Test
-Venous blood sent to biochemistry can tell us a little about METABOLIC imbalance (when you don’t have an ABG) -It cannot tell you anything about RESPIRATORY imbalances
44
Other Blood Tests
-2 Plasma Tests help to inform acid base balance -1. Total CO2 -2. Anion Gap
45
Total CO2 Test Normal Values
22-30 mmol/L (TCO2)
46
What Does Total CO2 Measure?
-is a measurement of the amount of BICARB (HCO3)
47
Total CO2 Test
-Plasma test (cannot measure gases in plasma) -Because so much CO2 is hidden in the bicarb, this measurement is an excellent estimator of serum bicarbonate -Use processes in the lab to separate CO2 from the bicarb so technically they are measuring CO2
48
TCO2 Low Levels
-Low levels of TCO2 (bicarb) result from either metabolic acidosis or as a compensation for respiratory alkalosis -However if TCO2 is VERY low (below 10mmol) we can assume this is due to metabolic cause because compensation for respiratory alkalosis wouldn’t drive the bicarbonate that low
49
High TCO2
-Means there is metabolic alkalosis OR this could be compensation for chronic hypercapnia like in COPD patients
50
Anion Gap Test
-NOT relevant to respiratory disorders -Only helps us know what contributed to a known METABOLIC acidosis -Automatically reported with electrolytes -If more of these unmeasured anions are present than normal, you have an elevated anion Gap which supports metabolic acidosis due to excess production of acids
51
What causes an elevated anion Gap?
-caused by conditions where excess acids have been ADDED to the plasma Eg: DKA, AKI, lactic acidosis -= Elevated AG = Acids gained (AG)
52
Non AG Acidosis results form …
A LOSS of bicarbonate -the most common cause is prolonged diarrhea -biliary, pancreatic, and duodenal secretions are alkaline and neutralize the acidity of gastric secretions so when they are lost, the balance shifts toward acidity
53
When you don’t have an ABG you can look at..
TCO2 and AG on a venous blood test to get clues about a patients metabolic imbalances

Pharm 1 (4 decks)

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