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NUR 120 (Unit 4) Test 4 ABG's
Mrs Ardis Nur 120 CCTC Spring 2012
Terms in this set (43)
Elements Measured to determine ABG's
- pH = 7.35 - 7.45 (hydrogen ion concentration)
- PaCO2 = 35 - 45 mmHg (partial pressure of CO2 in arterial
- PaO2 = 80 -100 mmHg (partial pressure of O2 in arterial blood)
- HCO3- = 22 to 26 mEq/L (bicarbonate concentration in plasma)
- BE = +5 / -5 mEq/L or mmol/L (base excess)
ABG's are drawn how?
they are drawn from arterial blood usually from the radial artery
What information does blood gas data provide?
- info on our body's acid/base relationship
Why is our body's acid/base relationship important?
- This relationship is critical for homeostasis
- Significant deviations from normal pH ranges are poorly tolerated and may be life threatening
- Balance is achieved by Respiratory and Renal systems
pH and our blood
- The acceptable pH range of our blood is 7.35 - 7.45, which is lightly alkaline.
- Relationship of H+ and pH is inverse.
the more H+ --> the lower the pH (acidic)
the fewer H+ --> Higher pH (alkaline or base)
What is the preferred ratio for Base to Acid?
20 (base) to 1 (acid)
How does the body regulate the Acid/Base balance?
By increasing or decreasing the acid base levels in the body by producing or limiting production of acids and base substances
What type of acids does the body produce?
Body produces basically 2 categories of acids.
- Volatile acids (CO2)
- Nonvolatile acids (Lactic Acid)
What are the buffers that the body produces?
- The main extracellular buffer system is the Bicarbonate-Carbonic Acid Buffer System
- These buffers are linked to the respiratory and renal compensatory system (LUNGS and KIDNEYS)
- Lungs can adjust ventilation in response to CO2 based on carbonic acid in ECF. (quick)
- Kidneys can excrete/retain H+ and conserve/ excrete bicarbonate (slow)
Acid-base Disorders Fall into 2 Major Categories
Respiratory Acidosis: Increased CO2
Metabolic Acidosis: Decreased HCO3-
Respiratory Alkalosis: Decreased CO2
Metabolic Alkalosis: Increased HCO3-
How do you know if the acid-base imbalance is Respiratory ?
- Respiratory Disorders --> the primary change is in the concentration of carbonic acid.
-- Respiratory Acidosis: PaCO2 is retained. pH < 7.35 & PaCO2 > 45 mmHg
-- Respiratory Alkalosis: PaCO2 is "blown off". pH > 7,45 & PaCO2 < 35 mmHg
How do you know if the acid-base imbalance is Metabolic?
Metabolic disorders --> the primary change is concentration of bicarbonate.
- Metabolic acidosis - decrease in bicarbonate or excess of nonvolatile acids. pH < 7.35 & bicarbonate < 22 mEq/L
- Metabolic alkalosis - excess of bicarbonate in relation to amt. of hydrogen ions. pH > 7.45 & bicarbonate > 26 mEq/L
Four Basic Types of Imbalance
- Respiratory Acidosis
- Respiratory Alkalosis
- Metabolic Acidosis
- Metabolic Alkalosis
Repsiratory Acidosis is
- a condition that occurs when the lungs cannot remove all of the carbon dioxide the body produces. This causes body fluids, especially the blood, to become too acidic.
Respiratory Acidosis Causes:
- Diseases of the airways (such as asthma and chronic obstructive lung disease)
- Diseases of the chest (such as sarcoidosis)
- Diseases affecting the nerves and muscles that "signal" the lungs to inflate or deflate
- Drugs that suppress breathing (including powerful pain medicines, such as narcotics, and "downers," such as benzodiazepines), especially when combined with alcohol
- Severe obesity, which restricts how much the lungs can expand
Respiratory Acidosis S/Sx
- Easy fatigue
- Shortness of breath
think CNS depression
Respiratory Acidosis Tx
- Bronchodilator drugs to reverse some types of airway obstruction
- Noninvasive positive-pressure ventilation (sometimes called CPAP or BiPAP) or a breathing machine, if needed
- Oxygen if the blood oxygen level is low
- Treatment to stop smoking
think increase airflow
Respiratory Alkalosis is
Respiratory alkalosis is a condition marked by low levels of carbon dioxide in the blood due to breathing excessively.
think panic --> hyperventilation
Respiratory Alkalosis causes
Respiratory Alkalosis S/Sx
- Numbness of the hands and feet
Respiratory Alkalosis Tx
- Treatment is aimed at the condition that causes respiratory alkalosis.
- Breathing into a paper bag -- or using a mask that causes you to re-breathe carbon dioxide -- sometimes helps reduce symptoms.
control excessive loss of CO2
Metabolic Acidosis is
Metabolic acidosis is a condition in which there is too much acid in the body fluids.
Metabolic Acidosis Causes
- Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body.
There are several types of metabolic acidosis:
- Diabetic acidosis (also called diabetic ketoacidosis and DKA) develops when substances known as ketone bodies, which are acidic, build up during uncontrolled type 1 diabetes
- Hyperchloremic acidosis results from excessive loss of sodium bicarbonate from the body, as can happen with severe diarrhea
- Lactic acidosis is a buildup of lactic acid. It can be caused by: Alcohol, Cancer, Exercising for a very long time, Liver failure, Low blood sugar (hypoglycemia), Medications such as salicylates, Prolonged lack of oxygen from shock, heart failure, or severe anemia, Seizures
- Other causes of metabolic acidosis include: Kidney disease (distal tubular acidosis and proximal renal tubular acidosis), Poisoning by aspirin, ethylene glycol (found in antifreeze), or methanol, Severe dehydration
Metabolic Acidosis S/Sx
Most symptoms are caused by the underlying disease or condition that is causing the metabolic acidosis. Metabolic acidosis itself usually causes rapid breathing. Confusion or lethargy may also occur. Severe metabolic acidosis can lead to shock or death. In some situations, metabolic acidosis can be a mild, chronic (ongoing) condition.
Metabolic Acidosis Tx
Treatment is aimed at the underlying condition. In certain circumstances, sodium bicarbonate (baking soda) may be given to improve the acidity of the blood.
Metabolic Alkalosis is
a primary increase in serum bicarbonate (HCO3-) concentration. This occurs as a consequence of a loss of H+ from the body or a gain in HCO3-.
Metabolic Alkalosis causes
- Vomiting or diarrhea - GI losses of HCl
- Renal failure - Alkali-loading alkalosis develops only when impairment of renal function occurs
- Drug use (eg, loop or thiazide diuretics; licorice; tobacco chewing; carbenoxolone; fludrocortisone; glucocorticoids; antacids [eg, magnesium hydroxide]; calcium carbonate)
- Previous GI surgery
Metabolic Alkalosis S/Sx
- Symptoms not specific.
- Because hypokalemia is usually present, the patient may experience weakness, myalgia, polyuria, and cardiac arrhythmias.
- Hypoventilation develops because of inhibition of the respiratory center in the medulla. Symptoms of hypocalcemia (eg, jitteriness, perioral tingling, muscle spasms) may be present.
Metabolic Alkalosis Tx
- The management of metabolic alkalosis depends primarily on the underlying etiology and on the patient's volume status.
- In the case of vomiting, administer antiemetics, if possible. If continuous gastric suction is necessary, gastric acid secretion can be reduced with H2-blockers or more efficiently with proton-pump inhibitors.
- In patients who are on thiazide or loop diuretics, the dose can be reduced or the drug can be stopped if appropriate.
- Alternatively, potassium-sparing diuretics or acetazolamide can be added.
stop them from vomiting, decrease gastric secretions, stop or reduce diuretics or use spironolactone to prevent or inhibit hypokalemia
How to interpret ABG's
- Must Memorize ABGs.
- Determine if the pH indicate acidosis or alkalosis?
- Is the cause of pH imbalance respiratory (lung) or metabolic (renal)?
- Is there compensation for the acid-base imbalance?
ABG's results can be
- Partly Compensated
- Fully Compensated
ABG's Acid/Base Parameters (diagram)
ABG's Acid/Base Parameters
pH Normal: 7.35 - 7.45
PaCO2 Normal: 35 - 45 mmHg
HCO3- Normal: 22-26 mEq/L
easy way to remember: pH is 7.35 - 7.45 --> remove the 7 and you get the PaCO2: 35 - 45 --> HCO3- = 22-26 mEq/L
Setup Your Tic Tac Toe
Questions to ask yourself when setting up your Tic Tac Toe box
- What is the pH?
< 7.35 = acidic
> 7.45 = alkalotic
- What is the PaCO2?
< 35 mmHg = alkalotic
> 45 mmHg = acidotic
- What is the HCO3?
< 22 mEq/L = acidotic
> 26 mEq/L = alkalotic
How to Determine if an Acid/Base Disorder is Respiratory or Metabolic
- 1ST: Match the PaCO2 or the HCO3- with pH to determine the acid-base disorder.
- 2ND: If the pH and PaCO2 match then the disorder is caused by RESPIRATORY SYSTEM.
- 3RD: If the pH and HCO3- match then the disorder is caused by METABOLIC (RENAL) SYSTEM.
ABG Example Problem #1
pH 7.26; PaCO2 52 mmHg; HCO3- 24 mEq/L
Partially Compensated Disorders
- Does either the PaCO2 or HCO3- go in the opposite direction of the pH? --> This shows compensation by the system opposite the pH.
- so if the HCO3- is high and and the pH and PaCO2 are acidodic = respiratory acidosis partially compensated
ABG Example Problem #2
pH 7.48; PaCO2 51; HCO3- 29
Metabolic Alkalosis Partially Compensated
- Look at pH, PaCO2 & HCO3-.
- If the pH is within the normal range and the other parameters (PaCO2 & HCO3-) are not, you are looking at a case of COMPLETE COMPENSATION.
Compensation is an effect of
The body's attempt to return the acid/base status to normal (i.e. pH closer to 7.4)
Complete Compensation Correction
- Recalculate the pH using 7.4 as the midpoint.
< 7.4 = acidotic
> 7.4 = alkalotic
ABG Example Problem #3
pH 7.36; PaCO2 50; HCO3- 34
Respiratory Acidosis with Complete Compensation
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