Abg

1. pH: 7.39, CO2: 49, HCO3: 37 2. pH: 7.35, CO2: 27, HCO3: 21 3. pH: 7.2, CO2: 25, HCO3: 19 4. pH: 7.32, CO2: 31, HCO3: 14 5. pH: 7.55, CO2: 32, HCO3: 20 6. pH: 7.59, CO2: 45, HCO3: 38 7. pH: 7.2, CO2: 26, HCO3: 18 8. pH: 7.85, CO2: 27, HCO3: 23 9. pH: 7.67, CO2: 33, HCO3: 17 10. pH: 7.82, CO2: 20, HCO3: 12

1. pH: 7.39, CO2: 49, HCO3: 37 - Fully Compensated Respiratory Acidosis 2. pH: 7.35, CO2: 27, HCO3: 21 - Fully Compensated Metabolic Acidosis 3. pH: 7.2, CO2: 25, HCO3: 19 - Partially Compensated Metabolic Acidosis 4. pH: 7.32, CO2: 31, HCO3: 14 - Partially Compensated Metabolic Acidosis 5. pH: 7.55, CO2: 32, HCO3: 20 - Partially Compensated Respiratory Alkalosis 6. pH: 7.59, CO2: 45, HCO3: 38 - Uncompensated Metabolic Alkalosis 7. pH: 7.2, CO2: 26, HCO3: 18 - Partially Compensated Metabolic Acidosis 8. pH: 7.85, CO2: 27, HCO3: 23 - Uncompensated Respiratory Alkalosis 9. pH: 7.67, CO2: 33, HCO3: 17 - Partially Compensated Respiratory Alkalosis 10. pH: 7.82, CO2: 20, HCO3: 12 - Partially Compensated Respiratory Alkalosis

Normal Values and Acceptable Ranges of the ABG Elements

ABG Element

Normal Value Range

pH 7.4 7.35 to 7.45 Pa02 90mmHg 80 to 100

mmHg Sa02

93 to 100% PaC02 40mmHg 35 to 45

mmHg HC03 24mEq/L 22 to 26mEq/L

Remember: Definitions

Acidosis (acidemia) occurs when pH drops below 7.35

Alkalosis (alkalemia) occurs when the pH rises above 7.45

A primary respiratory problem is determined if the PaC02 is less than 35mmHg(alkalosis) or greater than 45 mmHg(acidosis).

A primary metabolic problem is when the HC03 is less than 22mEq/L (acidosis) or greater than 26mEq/L(alkalosis).

Etiology and Clinical Manifestations ::

Metabolic Acidosis

Etiology: Loss of base: such as in cases of severe diarrhea

or

Gain of metabolic acids: Anaerobic metabolism; Drug overdose (e.g.salicylates); Renal failure; Diabetic ketoacidosis

Manifestations: headache and lethargy are early symptoms; warm flushed skin; seizures; mental confusion; muscle

twitching; agitation; coma (severe acidosis); anorexia, nausea, vomiting and diarrhea; deep and rapid respirations

(Kussmaul respirations); hyperkalemia (shift of acid to the ICF and K+ to the ECF); cardiac dysrhythmias.

Decreased blood pH; decreased HCO3; normal PaCO2 or decreased if compensation is occurring.

(The "nursing interventions" button on the homepage will lead the user to these nursing interventions listed under each

problem. It would be nice to have a pull-down menu under "nursing interventions" for metabolic acidosis, metabolic

alkalosis, respiratory acidosis, and respiratory alkalosis) on the homepage).

Nursing Interventions: Assess the clinical symptoms, health history, and lab results. Identify the underlying cause to

intervene appropriately. When there is sever acidosis (pH < 7.1), sodium bicarbonate is necessary to bring the pH to a safe

level. Correct the sodium and water deficits, as well.

Metabolic Alkalosis

Etiology: Loss of metabolic acids: such as in cases of prolonged vomiting or gastrointestinal suctioning. Hyperaldosteronism

can cause sodium retention and loss of hydrogen ions and potassium.

or

Gain of Base: an increased intake of bicarbonate. Diuretics (e.g. furosemide) can cause sodium, potassium, and chloride

excretion more than bicarbonate excretion.

Manifestations: general weakness, muscle cramps, hyperactive reflexes, tetany (due to a decrease in calcium); shallow and

slow respirations; confusion and seizures may occur in severe situations. Increased blood pH; increased HCO3; normal

PaCO2 or elevated if compensation is occurring.


intervene appropriately. If potassium levels are decreased administer potassium as ordered per physician. If acid-base

disturbance is due to hypochloremic alkalosis with volume depletion, administer a sodium chloride IV solution. If the

condition is caused by hyperaldosteronism, administer potassium.

Respiratory Acidosis

Etiology: Carbon dioxide is retained when ventilation is depressed; therefore, leading to acidosis and hypercapnia (excess

PaCO2).

Clinical Manifestations: restlessness, apprehension and then lethargy are initial signs; muscle twitching, tremors, seizures,

and coma can ensue; rapid respirations initially and then decreased due to adaptation; vasodilation due to acidosis (CO2 is

a vasodilator), therefore the skin might be pink, unless there is hypoxemia; tachycardia.

Decreased blood pH; Increased PaCO2; Normal HCO3 or elevated if compensation is occurring.


intervene appropriately. Restore alveolar ventilation (this will remove excess CO2), and if spontaneous ventilation is

compromised (e.g. due to drug overdose or neuromuscular disorders) provide mechanical ventilation. Monitor the pH,

PaCO2, PaO2, and HCO3 very closely. A rapid decline of the PaCO2 can lead to respiratory alkalosis with seizures and death.

Check for hypoxemia and hypercapnia when administering oxygen. Oxygen can work as a respiratory depressant when the

person's respiratory center is no longer stimulated by a low pH and elevated PaCO2. Renal buffering generally corrects an

uncomplicated chronic respiratory acidosis.

Respiratory Alkalosis

Etiology: occurs when there is alveolar hyperventilation and a decrease in PaCO2 (hypocapnia). Hypoxemia (caused by pulmonary

disease, high altitudes, or congestive heart failure), hypermetabolic conditions (fever or anemia), gram-negative sepsis, hysteria, or

cirrhosis of the liver can stimulate hyperventilation.

Clinical Manifestations: confusion, dizziness, paresthesias (tingling of extremities), seizures and coma; tachypnea (deep and rapid

respirations) causes respiratory alkalosis. Nausea and vomiting might be present. Increased blood pH; Decreased PaCO2; Normal

HCO3 or decreased if compensation is occurring.

Nursing Interventions: Assess the clinical symptoms, health history, and lab results. Identify the underlying cause to intervene

appropriately. Correct the hypoxemia and reverse the hypermetabolic states if present. Correct symptoms from hysterical

hyperventilation by rebreathing from a paper bag (increases PaCO2).

Assessment :: Assessment Step 1 :: pH

Step One: Determine the acid/base status of the arterial blood. Keep in mind what is Normal

If the blood's pH is less than 7.35 this is an acidosis, and if it is greater than 7.45 this is an alkalosis.

You may hear nurses or doctors say: "The patient is 'acidotic' or 'alkalotic'

Assessment :: Assessment Step 2 :: Respiratory vs. Metabolic

Step Two: Once you have determined the pH, you can move on to determine the 'primary' problem, or which system, respiratory or

metabolic is the prime messenger. Let's look at the two systems and understand the rationale behind determination of the 'primary'

problem.

Respiratory System

If you keep in mind that carbon dioxide acts as the acid of the human body, you will be able to determine if the primary acid-base

imbalance is respiratory. Chemically speaking, there is an equilibrium between carbonic acid and bicarbonate. Therefore, just

remember that an increased PaCO2 (greater than 45mmHg) along with an acidosis (pH less than 7.35) represents a RESPIRATORY

ACIDOSIS. If you have a situation where there is a decreased PaCO2 (less than 35mmHg) and an alkalosis (pH greater than 7.45) you

will have a RESPIRATORY ALKALOSIS! Easy. Right?

Metabolic System

Keep in mind that HCO3 represents a base situation, and if there is an increased HCO3 (greater than 26 mEq/L) in an alkalotic

environment (pH greater than 7.45) there is a METABOLIC ALKALOSIS. On the opposite side of the coin, if there is a decreased HCO3

(less than 22 mEq/L) in an acidic environment (pH less than 7.35) this will be representative of METABOLIC ACIDOSIS.

If you need to review the above steps, that is OK. If you understand the above material, let's move on to COMPENSATION!

Assessment :: Assessment Step 3 :: Compensation

Step Three: Our bodies have compensatory mechanisms that assist us to return to a state of homeostasis (equilibrium). The body

attempts to compensate for whatever the primary problem is in an effort to return the acid-base balance to normal. An illustration

of COMPENSATION is given below:

A newly diagnosed Type 1 diabetic client has a primary problem of metabolic acidosis (pH 7.29; HCO3 16 mEq/L) due to an

increase in ketone bodies (ketoacidosis). The nurse notes that the ABGs show a below normal PaCO2 value (27mmHg) and the client

is breathing faster in an attempt to blow off the carbon dioxide (CO2:acid) to create a respiratory alkalosis, the opposite of

metabolic acidosis!

Hint! In order to recognize compensation look for a change in the buffering system that was not involved in the primary

problem.

Example: If a client is demonstrating signs and symptoms of respiratory acidosis and the ABG results are something like: pH 7.27

and a PaCO2 of 58 mmHg and the body is compensating for this primary abnormality, the other buffer system (primarily HCO3) will

be changed (e.g. elevated HCO3: 30mEq/L).

The convenience is that the other buffer system change will be in the same direction as the primary problem. In this example

the PaCO2 is elevated and the compensatory system (HCO3) is above the normal range. Consequently, they are both elevated! This

tells you that the human body is compensating for the primary problem!

Therefore, you were able to determine that there was an elevated PaCO2 (increase in acid or a respiratory acidosis) and an

increased HCO3 (increased base or metabolic alkalosis). But you were able to determine respiratory acidosis as the primary

problem due to the pH being less than 7.35! This example illustrates a respiratory acidosis with a compensatory metabolic alkalosis.

The opposite system will come to the rescue!

Review ::

Ok...now it is time to review the three essential steps of ABG analysis!

Number One!

Determine if the client is demonstrating an acidotic (remember: pH less than 7.35) or alkalotic (pH greater than 7.45).

Number Two!

What is the 'primary problem'

If the client is acidotic with a PaC02 greater than 45 mmHg it is RESPIRATORY

If the client is acidotic with a HC03 less than 22 mEq/L it is METABOLIC!

If the client is alkalotic with a PaC02 less than 35 mmHg it is RESPIRATORY!

If the client is alkalotic with a HC03 greater than 26 mEq/L it is METABOLIC!

Number Three!

Is the client compensating?

Are both components (HCO3 and PaCO2) shifting in the same direction? Up or down the continuum? Above or below the

normal ranges? If this is noted, you know that the clients buffering systems are functioning and are trying to bring the acid-

base balance back to normal.

Would you like to try some examples? Come on...let's give it a try!

Case Studies :: Case Study 1

A client recovering from surgery in the post-anesthesia care unit (PACU) is difficult to arouse two hours following surgery. The nurse in the PACU has been administering Morphine Sulfate intravenously to the client for complaints of post-surgical pain. The clients respiratory rate is 7 per minute and demonstrates shallow breathing. The patient does not respond to any stimuli! The nurse assesses the ABCs (remember Airway, Breathing, Circulation!) and obtains ABGs STAT!

The STAT results come back from the laboratory and show:

pH = 7.15 Pa C02 = 68 mmHg HC03 = 22 mEq/L

Once you have interpreted the ABG results, click on one of the following links

o Compensated Respiratory Acidosis o Uncompensated Metabolic Acidosis o Compensated Metabolic Alkalosis o Uncompensated Respiratory Acidosis

Clinical Manifestations Of Respiratory Acidosis

PaCo2; HCO3 is normal or > with renal compensation

vasodilatation; cardiac dysrhythmias, tachycardia, somnolence, decreased ventilation

Clinical Manifestations Of Metabolic Acidosis

hyperkalemia: shift of acid to ICF and K+ to the ECF

anorexia, nausea, and vomiting

warm, flushed skin

cardiac dysrhythmias & CNS dysfunction

headache, diarrhea, tremors

Clinical Manifestations Of Metabolic Alkalosis

cardia dysrhythmias; seizures; confusion; muscle twitching, agitation

>pH;>HC03; normal PaCo2 or elevated if compensation occurs

Uncompensated Respiratory Acidosis -answer

An infant, three weeks old, is admitted to the Emergency Room. The mother reports that the infant has been irritable, difficult to

breastfeed and has had diarrhea for the past 4 days. The infants respiratory rate is elevated and the fontanels are sunken. The

Emergency Room physician orders ABGs after assessing the ABCs.

The results from the ABGs come back from the laboratory and show:

pH = 7.37

Pa C02 = 29 mmHg

HC03 = 17 mEq/L


Compensated Respiratory Alkalosis

Uncompensated Metabolic Acidosis

Compensated Metabolic Acidosis -answer

Uncompensated Respiratory Acidosis

Clinical Manifestations Of Respiratory Alkalosis

pH PaC02; HCO3 normal or low due to compensation

nausea, vomiting, tingling of fingers

A client, 5 days post-abdominal surgery, has a nasogastric tube. The nurse notes that the nasogastric tube (NGT) is draining a large

amount (900 cc in 2hours) of coffee ground secretions. The client is not oriented to person, place, or time. The nurse contacts the

attending physician and STAT ABGs are ordered.


pH = 7.52

Pa C02 = 35 mmHg

HC03 = 29 mEq/L



Compensated Metabolic Acidosis

Uncompensated Metabolic Alkalosis answer

A client is admitted to the hospital and is being prepared for a craniotomy (brain surgery). The client is very anxious and scared of

the impending surgery. He begins to hyperventilate and becomes very dizzy. The client looses consciousness and the STAT ABGs

reveal:


pH = 7.57

Pa C02 = 26 mmHg

HC03 = 24 mEq/L


Compensated Metabolic Acidosis


Uncompensated Respiratory Alkalosis -answer

Uncompensated Respiratory Acidosis

A two-year-old is admitted to the hospital with a diagnosis of asthma and respiratory distress syndrome. The father of the infant

reports to the nurse that he has observed slight tremors and behavioral changes in his child over the past three days. The attending

physician orders routine ABGs following an assessment of the ABCs. The ABG results are:


pH = 7.36

Pa C02 = 69 mmHg

HC03 = 36 mEq/L




Compensated Respiratory Acidosis -answer

Uncompensated Respiratory Alkalosis

A young woman, drinking beer at a party, falls and hits her head on the ground. A friend dials "911" because the young woman is

unconscious, depressed ventilation (shallow and slow respirations), rapid heart rate, and is profusely bleeding from both ears.

Which primary acid-base imbalance is this young woman at risk for if medical attention is not provided?

metabolic acidosis

metabolic alkalosis

respiratory acidosis -answer

respiratory alkalosis

An elderly gentleman is seen in the emergency department at a community hospital. He admits to taking many tablets of aspirin

(salicylates) over the last 24-hour period because of a severe headache. He complains of an inability to urinate. His vital signs are:

Temp = 98.5; apical pulse = 92; respiration = 30 and deep.

Which primary acid-base imbalance is the gentleman at risk for if medical attention is not provided?

metabolic acidosis -answer

metabolic alkalosis

respiratory acidosis

respiratory alkalosis

A young man is found at the scene of an automobile accident in a state of emotional distress. He tells the paramedics that he feels

dizzy, tingling in his fingertips, and does not remember what happened to his car. Respiratory rate is rapid at 34/minute.

Which primary acid-base disturbance is the young man at risk for if medical attention is not provided?

metabolic acidosis

metabolic alkalosis

respiratory acidosis

respiratory alkalosis - answer

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