Mel's Arterial Blood Gases Lecture Nov 2006

Front 1

4 important facts on how to obtain sample of arterial blood gases

Back 1

1) sample of blood from radial artery (or arterial line) hurts!--90 degree angle--(as a note:serum tests come from a vein)
2) avoid getting air into the specimen
3) submerge in cracked ice and transport immediately
4) pressure on site for 5 min (check pulse)

Front 2

Describe the narrow margin of blood pH

Back 2

Death below 6.8
Acidosis below 7.35
Normal 7.35 - 7.45
Alkalosis above 7.45
Death above 7.8

Front 3

What are the 3 main control systems that regulate acid-base balance to counter acidosis or alkalosis?

Back 3

1) The Chemical Buffer System: the bicarbonate-carbonic system is the body's primary defense to fluctuations in pH
2) Respirations (increase or decrease in response to levels of CO2)
3) Renal system (kidneys can increase or decrease levels of bicarbonate concentration by holding back bicarbonate or excreting it)--this takes longer to "kick in"

Front 4

Name the 4 most common types of acid-base imbalances

Back 4

RESPIRATORY INDICATED BY IMBALANCE IN CARBONIC ACID H2CO3
1) respiratory acidosis: excess carbonic acid, ph decreases
2) respiratory alkalosis: deficit of carbonic acid, pH decreases
METABOLIC IMBALANCES INDICATED BY IMBALANCE IN BICARBONATE LEVEL
3) metabolic acidosis: deficit bicarbonate, pH decreases
4) metabolic alkalosis: excess bicarbonate, pH increases

Front 5

Normal Values of pH

Back 5

7.35 - 7.45

Front 6

ARTERIAL BLOOD GASES:
* Normal values of PcO2 (partial pressure of co2)
* What is this a measure of?

Back 6

* 35 - 45 mm Hg
* partial pressure of co2 measures the adequacy of alveolar ventilation

Front 7

ARTERIAL BLOOD GASES:
* Normal values of Po2
(partial pressure of oxygen)
* What is this a measure of?

Back 7

* 80 - 100
* o2 dissolved in plasma

Front 8

ARTERIAL BLOOD GASES:
* Normal values of Hco3 (bicarbonate level)

Back 8

* 22 - 26

Front 9

RESPIRATORY ACIDOSIS (retention of carbon dioxide): Common Causes

Back 9

HYPOVENTILATION FROM:
1) COPD (Chronic Obstructive Pulmonary Disease), pneumonia, pulmonary edema, pneumothorax, restrictive lung disease
2) Drug Overdose
3) Trauma (chest trauma, spinal cord injury)
4) Cardiac Arrest
5) Neuromuscular (CNS) Diseases (MS, MD)

Front 10

RESPIRATORY ACIDOSIS: DESCRIBE HOW THE BODY RESPONDS
1) Acute response to hypoventilation
2) Partial compenstation
3) Full compensation

Back 10

1) Acute Response to hypoventilation: Ph low, paO2 low, paco2 high, bicarbonate normal
2) Then the kidneys respond by increasing bicarbonate levels so:
ph low still, po2 low, pco2 high, hco3 high
3) The full response is a correction in the pH level:
pH normal, pa02 low, paco2 high, hc03 high

Front 11

How do you treat Respiratory Acidosis?

Back 11

TREAT THE CAUSE (when you can):
1) remove secretions blocking oxygen
2) give oxygen/ventilate
3) semi-fowlers position for optimum lung expansion
4) ventilator when necessary

Front 12

RESPIRATORY ALKALOSIS (Hyperventilation): Causes

Back 12

* Anxiety /Fear most common
* Giving too much oxygen (ex: ventilator settings)
* CNS disorders
* Pain
* Fever

Front 13

RESPIRATORY ALKALOSIS (hyperventilation): Common Causes

Back 13

HYPERVENTILATION FROM:
1) Anxiety /Fear
2) Giving too much oxygen (ventilation)
3) CNS disorders
4) COPD
5) Congestive heart failure

Front 14

RESPIRATORY ALKALOSIS: DESCRIBE HOW THE BODY RESPONDS
1) Acute response to hyperventilation
2) Partial compensation
3) Full compensation

Back 14

1) Acute Response to hyperventilation: pH high, pa02 high, paco2 low, bicarbonate normal
2) Then the kidneys respond by decreasing bicarbonate levels so: pH still high, po2 still high, pco2 low, bicarbonate low
3) The full response is a correction in the pH level: pH normal, pao2 high, paco2 low, bicarbonate low

Front 15

How do you treat Respiratory Alkalosis?

Back 15

TREAT THE CAUSE: anti-anxiety/ sedative meds, instruct in slow, even breathing, breathe in co2, paper bag / re-breather bag

Front 16

METABOLIC ACIDOSIS (gain of metabolic acids or loss of base): Common Causes

Back 16

INCREASE IN ACIDS:
1) diabetic ketoacidosis: inability to use glucose results in fat metabolism; ketones/acetone acid are present
2) starvation-lactic acid formation/anaerobic metabolism
3) renal failure: inability to eliminate waste products.
LOSS OF BASE
1) diarrhea

Front 17

METABOLIC ACIDOSIS: DESCRIBE HOW THE BODY RESPONDS
1) Acute response to inability to decrease acidic levels (bicarbonate deficit)
2) Partial compensation
3) Full compensation

Back 17

1) Acute response to bicarbonate deficit: pH low, pao2 normal, paco2 normal, bicarbonate low
2) The respiratory system is stimulated cause an increase in the rate and depth of respirations (Kussmaul breathing) to lower the acid concentration in the extracellular fluid by increasing the exhalation of co2. pH low, po2 high, pco2 low, hco3 still low
3) full compensation is not usually achieved, but if successful would result in pH normal, po2 high, pco2 low, hco3 low
** note the renal compensatory tries to increase the pH by exchanging sodium ions with hydrogen ions.

Front 18

METABOLIC ACIDOSIS: NURSING ALERT ABOUT ELECTROLYTE SHIFT

Back 18

Metabolic acidosis causes an electrolyte shift: hydrogen and sodium ions move into the cell, and potassium moves into the extracellular fluid. Hyperkalemia may cause ventricular fibrillation and death.

Front 19

How do you treat Metabolic Acidosis?

Back 19

1) TREAT THE CAUSE...treat blood sugar of a diabetic.
2) Can give sodium bicarbonate (antacids)

Front 20

METABOLIC ALKALOSIS (gain of base or loss of metabolic acids): Common Causes

Back 20

Not enough acid caused by:
1) Vomiting
2) Nasal Gastric Tube suctioned and acidic fluids not replaced
3) Taking too many antacids
4) abuse of diuretics or steroids(using uric acid through the kidneys)

Front 21

METABOLIC ALKALOSIS: DESCRIBE HOW THE BODY RESPONDS
1) Acute response to deficient acids
2) Partial compensation
3) Full compensation

Back 21

1) Acute Response to deficient acids: pH high, pao2 normal, paco2 normal, bicarbonate high
2) partial compensation: RESPIRATIONS DECREASE pH still high, pa02 low, paco2 high, hco3 high
3) full compensation pH normal, pao2 low, paco2 high, hco3 high

Front 22

How do you treat Metabolic Alkalosis?

Back 22

TREAT THE CAUSE.
MAINTAIN FLUID BALANCE
Give NaCL--absorption of NaCL allows for excretion of bicarbonate