Test II - Acid/Base & ABG's

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Flashcards for ABG's section.

Acidosis

condition characterized by a proportionate excess of hydrogen ions in the extracellular fluid, in which the pH falls below 7.35

Alkalosis

abnormally high alkalinity (low hydrogen-ion concentration) of the blood and other body tissues. It can be due to respiratory metabolic malfunctions.

Compound that accepts hydrogen ions (H+) in solution. A substance that increases the hydrogen ion concentration of a solution

What is an Acid?

A substance that reduces the hydrogen ion concentration of a solution. Any compound that increases the number of hydroxide ions when dissolved in water

What is a Base?

pH: 7.35-7.45

What is a normal pH level in the body?

A function of the ratio of (20:1) carbonic acid (CO2) and bicarbonate (HCO3-)

What is pH?

An arterial blood draw

What blood do we look at to determine blood pH?

Inverse relationship. One goes up while the other goes down.

What is the relationship between Acid/Base, H+?

CO2 dissolved in the blood instead of exhaled. CO2 is expelled by the lungs. A high level of this in the blood leads to acidosis.

What is Carbonic acid?

The expulsion of bicarbonate is controlled by the kidneys.

What controls bicarbonate levels in the blood?

ABG

Used to determine pH balance. Drawn from artery rather than vein. Arterial blood gases test measures the level of oxygen and carbon dioxide in arterial blood. Assess pH, PaO2, PaCO2, SaO2 and HCO3 (bicarbonate).

Metabolic Acidosis

acidosis and bicarbonate concentration in the body fluids resulting either from the accumulation of acids or the abnormal loss of bases from the body (as in diarrhea or renal disease).
Hyperventilation (Kussmaul's Breathing), Nausea, Vomiting, Cardiac Dysrhythmias, Lethargy, Coma, Decreased DTR

Metabolic Alkalosis

alkalinity caused by an increase in plasma bicarbonate resulting from acid loss by the body. Causes include diuresis, vomiting, or ingestion of too much sodium bicarbonate.

Respiratory Acidosis

develops when the respiratory system cannot eliminate all CO2 generated by peripheral tissues;
primary sign is low plasma pH due to hypercapnia;
primary cause is Hypoventilation.
Causes: Anxiety, Restlessness, Dyspnea, Disorientation, Confusion, Coma, Decreased DTR.

Respiratory Alkalosis

Alkalosis resulting from increased gas exchange in the lungs (as in hyperventilation associated with extreme anxiety or aspirin intoxication or metabolic acidosis).
Can Cause: pulmonary embolus, anxiety, early bronchial asthma, restrictive lung disease.

ABG Guide: Normal Ranges

*pH: 7.35 to 7.45
*PaCO2: 35 to 45 mmHg
if elevated=more carbonic acid-acidotic
if low=less CO2 in blood-alkalotic
*PaO2: 80 to 100 mmHg
*HCO3: 22 to 26 mEq/L
more bicarb=alkalotic
less bicarb=acidotic
*O2 sat: 95 to 100%

1. Buffer system

2. Respiratory Regulation: (Easier than Kidneys). Body changes respiratory patterns to increase CO2-carbonic acid.

3. Kidneys: (Most powerful, but takes days to initiate-bicarb production).

How does the body respond to changes in its Acid/Base balance?

Their pH will rise, becoming alkalotic because they are exhaling lots of carbonic acid (CO2)

What happens to a patients pH if they are hyperventilating?

They can produce Bicarbonate (takes 1 to 3 days) in addition to regular excretion.

What can Kidneys make to regulate H+ balance?

The lungs begin the quickest, but they will never return the body to the initial level by themselves. They can't get rid of H+, only CO2.

What responds to Acid/Base imbalances within the body first?

Uncompensated Acidosis

decreased pH, increased PaCO2, normal HCO3-

Uncompensated Alkalosis

increased pH, decreased PaCO2, normal HCO3-

Excess acid in the blood=acidosis

What does an ABG reading of elevated PaCO2 indicate?

Less acid in the blood=alkalosis

What does an ABG reading of lowered PaCO2 indicate?

The problem is not a respiratory issue.

What does an ABG reading of normal PaCO2 indicate?

Decreased base in body=acidosis

What does an ABG reading of lowered HCO3- indicate?

Excess base in body=alkalosis

What does an ABG reading of elevated HCO3- indicate?

Not a Kidney problem.

What does an ABG reading of normal HCO3- indicate?

What is this person experiencing?
pH: 7.26
pCO2: 37
HCO3: 18

Metabolic acidosis with no respiratory compensation.

What is this person experiencing?
pH: 7.49
CO2: 52
HCO3: 29

Metabolic alkalosis w/ partial respiratory compensation. This person will need to retain CO2 (shallow breathing to fix internal environment).

What is this person experiencing?
pH: 7.32
pCO2: 27
HCO3: 18

Metabolic acidosis with partial respiratory compensation.

What is this person experiencing?
pH: 7.52 (alkalosis)
pCO2: 22 (low- basic alkalosis)
HCO3: 24 (normal)

Respiratory alkalosis with no compensation.
This can happen since metabolic hasn't kicked in (takes kidney 3 days).

What is this person experiencing?
pH: 7.27
pCO2: 49
HCO3: 25

Respiratory acidosis with no compensation

RAMS

Respirations alternate w/pH (pH down/pCO2 up).
Metabolic the same as pH (pH down/HCO3- down).

Renal response: the burden of removing excess H+ falls directly on the kidneys.
Hydrogen ions are excreted in combination with urinary buffers
the kidneys add new HCO3- to the ECF to replace HCO3- used to buffer strong acids
The kidneys also excrete the anions (phosphate, chloride, sulfate) that are liberated from strong acids.
The kidneys affect blood pH more slowly than other buffering mechanisms in the body; full renal compensation may take 1 to 3 days

If there is excess acid in the body, the kidneys remove H+
if there is excess base, the kidneys remove HCO3-

Describe the Renal response to pH imbalances?

Metabolic Acidosis results from a Gain of Noncarbonic Acid or a loss of Bicarbonate

What causes metabolic acidosis?

Metabolic Alkalosis Results From a Gain of Strong Base or Bicarbonate or a Loss of Noncarbonic Acid

What causes metabolic alkalosis?

What is the pH?
Normal 7.35-7.35
-Is it Acidosis or Alkalosis?

What is the first step in evaluating a patient's ABG's?

What is the pCO2 level?
Normal 35-45
If Normal= it's not a respiratory problem.
If Elevated: more CO2 retained; more carbonic acid in blood= Acidosis
If Decreased: less acid in blood= alkalosis

After determining a patient's pH from an ABG draw, what would a nurse check next?

What is the HCO3- level?
Normal value 22-26
If Normal= it's not a kidney problem.
If Elevated=excess base in body= alkalosis.
If Decreased=not enough base=acidosis

After determining a patient's pCO2 from an ABG draw, what would a nurse check next?

If pH & HCO3 both point the same direction, then the problem is metabolic (kidney)

If pH & pCO2 point in opposite directions, then the problem is respiratory (lung)

How do you determine whether metabolic or respiratory acidosis/alkalosis is occuring?

Compensation: present if arrows for pCO2 and HCO3 are opposite

Partial Compensation: present if CO2 and HCO3 are in the same direction.

None if one of these values is normal.

How do you determine whether or not compensation is occurring when deciphering ABG draws?

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