Arterial Blood Gas Review Flashcards
What should be the first choice for ABG draws?
Other arteries? 2
- The radial artery is superficial, has collaterals and is easily compressed
It should be the first choice - Other arteries:
- femoral,
- brachial
What test should you do to make sure the pt has collateral cicrulation before doing ABGs?
Allen test
ABGs: Performing the Procedure
12
- Put on gloves
- Prepare the site (Drape the bed and cleanse the radial area with alcohol)
- Position the wrist (hyper-extended, using a rolled up towel if necessary)
- Palpate the arterial pulse and visualize the course of the artery
- Open the ABG kit
- Line the needle up with the artery, bevel side up
- Enter the artery and allow the syringe to fill spontaneously
- Withdraw the needle and hold pressure on the site
- Protect needle
- Remove any air bubbles
- Gently mix the specimen by rolling it between your palms
- Place the specimen on ice and transport to lab immediately
What an ABG measures and the normal range? 5
- pH (7.35-7.45)
- CO2 (35-45 mmHg)
- O2 (83-102 mmHg)
- HCO3 (22-28 mmol/L)
- Anion gap (10-16 mmol/L)
Acidosis can cause what?
- Decreased force of cardiac contraction
- Decreased vascular response to catecholamines
- Decreased response to the effects and action of certain medications
Alkalosis can interfere with
what body functions? 3
- Tissue oxygenation
- Neurological and
- muscle function
Oxygen-Hgb Dissociation
- Hemoglobin transports what?
- Alterations in homeostasis will affect the rate of what?
- oxygen
2. unloading of the oxygen from the hemoglobin
- PO2 of the aterial end of the capillary?
2. PO2 of the venous end of the capillary?
- 95 mm/Hg
2. 40 mm/Hg
What controls pH?
5
- Diet
- Metabolic production of CO2
- Regulation through the GI tract
- Influence of other electrolytes
- BUFFERS
Acid/Base Balance
1. pH describes what?
- pH is inversely proportional to the what?
- Normal range?
- = how acidic or alkaline the blood is
- H+ concentration
- 7.35-7.45
3 systems maintain body pH
- Chemical buffering
- The respiratory center
- The kidneys
What substances are involved in chemical buffering? 3
- Carbonic acid
- Phosphate
- Plasma proteins
The carbonic acid buffering system is the main buffer
- Whats the equation?
- CO2 is a byproduct of what?
- CO2 is best trabsported as?
- As the CO2 increased so does the what?
- The higher the H+ (or CO2) the ______ the pH?
- H2O + CO2 ↔ H2CO3 ↔ HCO3- + H+
- CO2 is a by product of cellular metabolism
- CO2 is best transported as HCO3-
- As the CO2 increases so does the H+ concentration
- lower
The respiratory buffer
1. Concentrations of what will trigger the respiratory center?
- What will be altered to either increase or decrease ventilation? 2
- This response occurs in what amount of time?
- CO2,
- carbonic acid
- HCO3
- Respiratory rate
- tidal volume
- 1-3 minutes
THE RENAL BUFFER
1. The kidneys can excrete either acid or alkaline urine, thereby adjusting what?
- How do they do this?
- This response takes place over what timeline, but represents a more powerful regulatory system?
- the pH of the blood
- Excrete or retain HCO3- and H+
- hours or even days
Physiological Buffer Systems
- Chemical buffer systems occur how quickly?
- Respiratory and renal systems: Describe the rate and capacity of these compared to the chemical buffer system?
- almost immediately
- Act more slowly than chemical buffer systems
- Have more capacity than chemical buffer systems
Chemical Buffer Systems
Chemical buffer: system of one or more compounds that act to resist pH changes when strong acid or base is added: There are 3?
- Bicarbonate buffer system
- Phosphate buffer system
3 Protein buffer system
What are the normals for the following:
- pH?
- PCO2?
- HCO3-?
- 7.4
- 40 mmHg
- 24 mEq/L
Causes of respiratory acidosis
5
- Central nervous system depression…medications such as narcotics, sedatives, or anesthesia
- Impaired muscle function…spinal cord injury, neuromuscular diseases, or neuromuscular blocking drugs
- Pulmonary disorders…atelectasis, pneumonia, pneumothorax, pulmonary edema or bronchial obstruction
- Massive pulmonary embolus
- Hypoventilation due to pain, chest wall injury, or abdominal pain
Signs & symptoms of Respiratory Acidosis
- Respiratory? 3
- Nervous? 3
- CVS? 2
- Respiratory :
- dyspnea,
- respiratory distress and/or
- shallow respiration - Nervous:
- Headache,
- restlessness and
- confusion - CVS:
- Tachycardia
- dysrhythmias
If CO2 level extremely high what may be noted? 2
- drowsiness
2. unresponsiveness
Management of respiratory acidosis
3
- Increase the ventilation
- Causes that can be treated rapidly include pneumothorax, pain and CNS depression due to medication
- If the cause can not be readily resolved then will require mechanical ventilation
Causes of respiratory alkalosis
5
- Psychological responses, anxiety or fear
- Pain
- Increased metabolic demands such as fever, sepsis, pregnancy or thyrotoxicosis
- Medications such as respiratory stimulants
- Central nervous system lesions
Signs & symptoms of respiratory alkalosis
- CNS? 6
- CV? 2
- Other? 3
- CNS:
- Light headedness,
- numbness,
- tingling,
- confusion,
- inability to concentrate and
- blurred vision - Dysrhythmias
- palpitations
- Dry mouth,
- diaphoresis
- tetanic spasms of the arms and legs
Management of respiratory alkalosis
3
- Resolve the underlying problem
- Monitor for respiratory muscle fatigue
- When the respiratory muscles become exhausted, acute respiratory failure may ensue
Causes of metabolic acidosis
6
- Renal failure
- Diabetic ketoacidosis
- Anaerobic metabolism (tissue death, lactic acidosis)
- Starvation
- Salicylate intoxication (common board question)
- Sepsis (such bad tissue hypoxemia)
Sign & symptoms of metabolic acidosis
- CNS? 4
- CVS? 1
- Resp? 1
- Other? 2
- CNS:
- Headache,
- confusion and
- restlessness progressing to lethargy,
- then stupor or coma - CVS: Dysrhythmias
- Kussmaul’s respirations
- Warm, flushed skin as well as
- nausea and vomiting
Management of metabolic acidosis
5
- Treat the cause
- Hypoxia of any tissue bed will produce metabolic acids as a result of anaerobic metabolism even if the pao2 is normal
- Restore tissue perfusion to the hypoxic tissues
- The use of bicarbonate is indicated
- Hydration
Causes of metabolic alkalosis
- Ingestion of? 3
- Other? 5
- Ingestion of excess antacids,
- excess use of bicarbonate,
- or use of lactate in dialysis
- Protracted vomiting,
- gastric suction,
- hypochloremia,
- excess use of diuretics or
- high levels of aldosterone
Signs and symptoms of metabolic alkalosis
- CNS? 4
- M/S? 3
- Other? 2
- CNS:
- Dizziness,
- lethargy disorientation,
- seizures
- coma - M/S:
- weakness,
- muscle twitching,
- muscle cramps
- tetany - -Nausea, vomiting and
-respiratory depression
Difficult to treat
The Base Excess
- Amount of what?
- What are these values?
- A negative base excess indicates what?
- Amount of excess or insufficient level of bicarbonate
- -2 to +2mEq/L
- A negative base excess indicates a base deficit in blood
Base Excess:
1. Calculated value estimates what?
- It is an estimate of the what?
- the metabolic component of an acid based abnormality
- amount of strong acid or base needed to correct the metabolic component of an acid base disorder (restore plasma pH to 7.40 at a Paco2 40 mmHg)
Regulation of Anions
- What is the major anion in the ECF?
- What does it help do?
- Cl–
2. Helps maintain the osmotic pressure of the blood
Regulation of Anions
1. __% of Cl– is reabsorbed under normal pH conditions
- When acidosis occurs, _______ chloride ions are reabsorbed
- Other anions have transport maximums and excesses are excreted how?
- 99
- fewer
- in urine
What is the anion gap?
Calculation?
Normal range?
unmeasured anions = protein, phosphate, citrate, sulfate
AG= Na - (Cl- + Bicarbonate)
7-13 mmol/L
ABG step one?
What is the pH?
Acidemia pH less than 7.35
Alkalemia pH > 7.45
- ABG analysis Step 2
- IN primary respiratory disorders?
- In primary metabolic disorders?
- What is the PaCO2?
- In primary respiratory disorders
pH and CO2 change in opposite directions - In primary metabolic disorders
pH and CO2 change in the same direction
- ABG analysis Step 3
- If it is a respiratory problem what is happening with the bicarb?
- If it is a metabolic problem what is happening with the CO2?
- Is there compensation?
- Going up
- Going up
ABG analysis Step 4?
Assess the PaO2
Hypoxemia if
ABG analysis Step 5?
3
- Anion Gap = (Na+) – [Cl- + HCO3-]
- The number of anions (-) and cations (+) should be equal but a standard blood gas doesn’t measure them all so there is a difference of 10-16
- This may be helpful in sorting out causes of metabolic acidosis as some causes have an increased anion gap and some have a normal gap
Do problems in Slide show starting on slide 51
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