Arterial Blood Gas Flashcards
1
Q
What Can an ABG tell us about the Pt
A
Oxygenation (PaO2 and SaO2)
Ventilation (PaCO2)
Acid-Base Balance (pH)
Oxygen Carrying Capacity of the Blood (HbO2, Total Hb, and Dyshemoglobins)
Electrolytes
Sugars
2
Q
Main reasons to get an ABG
A
Assessment of pt.
Discharge and to see if they qualiify for home oxygen
3
Q
What Should We check the patient’s Chart for before we do the ABG
A
Current Diagnosis
What FiO2 is the pt on
INR
aPTT
Fribrinogin
Platlets
Thrombolytics
Anticoagulants
Blood disorders
If any of the lab values are critical you have to call the physician to veryify that you should do the ABG
4
Q
International Normalized Ratio (INR)
A
Normals-0.9-1.1 (1.0-1.2)
Critical Value >6
Assess time for the extrinsic and common coagulation pathways (secondary hemostasis)
5
Q
Activated Partial Thromboplastin Time (aPTT)
A
Normals-23-24 sec (22-26) sec
Critical value >120 seconds
Assess time for the intrinsic and common coagulation pathways (secondary hemostasis)
6
Q
Fribrinogin
A
Normals-1.6-4.1 g/L
Critical value <0.6 g/L
Factor 1 in the coagulation cascade
7
Q
Platelets
A
Measure of primary hemostasis
Normals-150 000-300 000/ uL (150 000-450 000/uL)
Critical Value < 10 000/ul
Decreased platelet count - Thrombocytopenia
8
Q
Thrombolytics
A
Streptase (Stretokinase)
Retavase (Reteplase)
Activase rt-PA (alteplase)
9
Q
Anticoagulants
A
- Heparin Standard
- Heparin Sodium
- Heparin Low Molecular Weight
- Fragmin (Dalteparin Sodium)
- Innohep (tinzaparin)
- Lovenox (Enoxaparin Sodium)
- Heparinoids
- Orgaran (danaparoid sodium)
- Vitamin K Antagonist
- Couamdin (Warfarin Sodium)
- Sintrom (nicoumalone)
- Various Anticoagulants
- Refludan (Lepirudin)
10
Q
Blood Disorders
A
Hemophilia
11
Q
Why do we use ABG as oppose to other blood samples for accurate blood gas analysis
A
Venous samples will vary in their results due to local tissue metabolism
Capillary samples are prone to venous admixture and air contamination
12
Q
ABG Indication
A
- A patient that is believed to have an alteration in acid-base balance, ventilation, and/or oxygenation
- Ex. Emphysema, drug OD, Cardiac arrest, and diabetic coma
- A patient who has developed unexpected tachypnea, dyspnea, restlessness, anxiety, irritability, drowsiness, or confusion
- To help establish baseline values in a patient with a chronic lung disease and monitor improvement/deterioration
- A patient with a chronic lung disease prior to surgery
- A patient with a deteriorating clinical condition
- A patient who is on a ventilator
- To evaluate the changes in the delivery of specific respiratory care
- Ex. Ventilation, oxygenation, medication
13
Q
Relative Contraindications of an ABG
A
The need for an accurate measurement of blood gases and acid-base balance in a patient may outweigh the contraindications
- Bilateral negative modified Allen’s test
- Patient on anticoagulant or thrombolytic medication
- Patient with a coagulation disorder
- Patient with severe hypotension
- Patient with deformities at the puncture site
- Ex. Arthritis of hand or wrist, congenital arm or hip deformities
- A patient with Raynaud’s Disease
- Patient with fibrosed arteries
- Patient with large hematoma of the puncture site area
- A patient who refuses to cooperate
- The puncture should not be performed distal to a surgical shunt
- Ex. An arterial puncture should not be performed on a patient who is undergoing dialysis.
- A blood gas can be asked for during CPR even though we know that the pt will be acidotic as we still want a baseline in which to measure progress
* If you are worried about any possible contraindications to arterial puncture, discuss this matter with the physician
14
Q
What is the only Absolute Contraindications for an ABG
A
A skin graft at the puncture area
15
Q
Raynaud’s Disease
A
A peripheral vascular disease that is characterized by an intermittent attack of pallor (unhealthy pale appearance) or cyanosis of the digits or toes
It causes the blood vessels to narrow when you are cold or feeling stressed. When this happens, blood can’t get to the surface of the skin and the affected areas turn white and blue. When the blood flow returns, the skin turns red and throbs or tingles.
16
Q
ABG Hazards for a Pt.
A
- Hematoma
- Hemorrhage- In order to minimize this risk you have to hold pressure on the puncture site for five min
- Infection
- Thrombosis
- Arterial Spasm
- Laceration of blood vessel or nerves
- Air or blood clotted emboli
- Anaphylaxis from local anesthesia
- Arterial occlusion
- Vasovagal response
- * The pt. will need to know all of these hazards in order to get informed consent from the patient
17
Q
ABG Hazards for a Medical Staff
A
Blood borne infections
18
Q
Troubleshooting Can’t Locate Artery
A
Withdraw the needle slightly so that the bevel is just below the skin, then redirect towards the palpated artery
Only two redirects allowed
If an adequate pulse cannot be found then another site should be selected or a non-invasive approach should be considered such as a pulse oximetry
Ultrasounds guidance may be useful in this situation
19
Q
When do we chose the Femoral artery
A
Used in low perfusion states, deformities, and a failed modified Allen’s test
20
Q
ABG Syringe
A
- Usually plastic but sometimes glass
- Plastic should be vented
- Set plunger to 1.5cc
- Allows self filling from blood pressure
21
Q
Plastic Vented Syringe
A
- 20-25 gauge
- Pre-filled heparin
- Can usually be seen in hub as white fluffy stuff
- Lithium heparin
- Glass or regular syringes
- Heparinize with sodium heparin (1000U/ml)
- Balanced for electrolytes should be used
- Higher [heparin] (10,000IU/ml) may cause altered pH
22
Q
Transporting the Sample
A
Always be prepared to transport the sample
Blood is still metabolizing
When using the plastic syringe analyze the ABG within 30 min at room temperature
Calgary Health Region recommends > 10 min to analyze place the sample in the ice slurry
Ice may be required if elevated leukocyte or platelets count is present
23
Q
Informed Consent
A
- Description of procedure
- Why it needs to be done.
- What you are going to do.
- Description of the potential complications.
- What could go wrong? (bleeding from site, bruising, infection)
- How you are going to limit the potential complications?
- Do they understand?
- Do they consent?
24
Q
Advantages of Radial Artery
A
- Collateral Circulation
- The deep and superficial palmar arches are supplied with blood from both the radial and ulnar arteries, therefore, if the radial artery becomes obstructed collateral blood flow to the hand should be available via ulnar artery
- The radial artery at the wrist is superficial, therefore relatively easy to palpate, stabilize and puncture
- The wrist is generally easily accessible
- The radial artery typically does not have any major nerves in close proximity (at the wrist) therefore as long as puncture of the bony periosteum is avoided, the patient should only feel discomfort similar to that of a venous puncture
25
Disadvantages of Radial Artery
* The radial artery is more peripheral than the femoral artery therefore somewhat more likely to go into spasm
* However as long as ulnar flow is present this is not a problem (assessed during the modified Allen’s test)
* There is a radial vein located on each side of the radial artery therefore it is possible to inadvertently draw a venous sample
* However these veins are of smaller diameter than the artery and normally have a much lower pressure
26
Arterial Puncture Anatomy
* The optimal site for the radial arterial puncture is the natural tunnel between the styloid process of the radial bone and the flexor carpi radialis tendon
* ~1-2 cm proximal to the wrist crease
* The site is considered optimal due to the isolation of the artery from other structures and proximity to the skin surface
* Artery is just below the surface
* More difficult on obese or very edematous patients
27
Brachioradialis Tendon
The tendon lies laterally to the radial artery and inserts its associated muscle into the styloid process of the radial bone
The action of the brachioradialis muscle is to flex the forearm
28
Flexor Carpi Radialis Tendon
This tendon lies medial to the radial artery and inserts its associated muscle into the second and third metacarpal
The action of the flexor carpi radialis is to flex the 3rd and 2nd digits
29
Flexor Pollicis Longus Tendon
This tendon lies medial to the radial artery beneath the flexor carpi radialis tendon and inserts is associated muscle into the phalanges of the 1st digit (thumb)
Action of this tendon is to flex the thumb
30
Pronator Quadratus Muscle
Originates on lower ¼ of the ulna and inserts into the lower ¼ of the radius’Its action is to pronate the hand (turn hand backward)
A portion of the muscle lies directly posterior to the radial artery and may be pierced if a needle is inserted deep past the radial artery
During the radial arterial puncture if the patient complains of a sharp pain and a solid structure is encountered the needle may have made contact with the periosteum of the radius·
31
Brachioradialis Tendon
The tendon lies laterally to the radial artery and inserts its associated muscle into the styloid process of the radial bone
The action of the brachioradialis muscle is to flex the forearm
32
Flexor Carpi Radialis Tendon
This tendon lies medial to the radial artery and inserts its associated muscle into the second and third metacarpal
The action of the flexor carpi radialis is to flex the 3rd and 2nd digits
33
Flexor Pollicis Longus Tendon
This tendon lies medial to the radial artery beneath the flexor carpi radialis tendon and inserts is associated muscle into the phalanges of the 1st digit (thumb)
Action of this tendon is to flex the thumb
34
Pronator Quadratus Muscle
Originates on lower ¼ of the ulna and inserts into the lower ¼ of the radius’Its action is to pronate the hand (turn hand backwards)
A portion of the muscle lies directly posterior to the radial artery and may be pierced if a needle is inserted deep past the radial artery
During the radial arterial puncture if the patient complains of a sharp pain and a solid structure is encountered the needle may have made contact with the periosteum of the radius
35
Arterial Supply of the Arm, Wrist, and Hand
Arterial supply of the right arm is via the brachiocephalic artery from the arch of the aorta to the right subclavian artery
Arterial supply to the left arm is via the left subclavian artery, which arises directly from the arch of the aorta
The subclavian artery on each side passes between the clavicle and first rib to become the axillary artery as it enters the axilla and the brachial artery as it leaves the axilla
At the elbow, the brachial artery divides into the radial and ulnar arteries
36
The radial and ulnar artery
The radial artery will course along the lateral side of the arm (thumb side) over the radius while the ulnar artery courses along the medial side of the arm over the ulna
The radial and ulnar arteries meet in the palm of the hand at the superifical and deep palmar arteries. From the palmar arches the various digits of the hand are supplied and thus collateral blood supply to the hand is provided
There are 2 small radial veins that lie alone either side of the radial artery but the major nerves are separated from the artery by tendons at this optimal site
37
Lateral Cutaneous Nerve
A continuation of the musculocutaneous nerve
It has a general sensory function for skin over the radial (lateral) side of the forearm
At the wrist, it will pass over the brachioradialis tendon
38
Median Nerve
Supplies motor function to most flexor muscle of the forearm and lateral three digits of the hand
It also supplies sensory functions to the anterior (palmar) aspects of the lateral four digits of the hand
It is separated from the radial artery by the flexor carpi radialis tendon and the deeper flexor pollicislongustendon
Radial Nerve, Superficial Branch
The radial nerve descends in the back of the arm and forearm ultimately distributed for motorfunction to extensor muscles on the back of the arm, forearm andhand and sensory function to heskin of the same region
The superficial branch of the radial nerve is primarily involved in sensory supply to the lateral 3 digits
It is separated from the radial artery by the brachioradialtendon and travels along the later side of the radius in the area of the wrist
39
Radial Nerve, Superficial Branch
The radial nerve descends in the back of the arm and forearm ultimately distributed for the motor function to extensor muscles on the back of the arm, forearm, and hand and sensory function to the skin of the same region
The superficial branch of the radial nerve is primarily involved in sensory supply to the lateral 3 digits
It is separated from the radial artery by the brachioradial tendon and travels along the later side of the radius in the area of the wrist
40
Veins of the Arms
* There are generally 2 sets of veins that drain the hand and arm, superficial and deep
* The major superficial veins are basilic and cephalic
* The deep veins lie in close proximity to the arteries
* Two radial veins lie in close proximity on each side of the radial artery
* Two ulnar veins are also situated in such a pattern close to the ulnar artery
* These radial and ulnar veins eventually meet to drain into the brachial veins
* The brachial basilic and cephalic veins all join to the axillary vein
* The axillary vein becomes the subclavian vein when it passes between the clavicle and first rib
* The subclavian vein joins with the internal jugular vein to become the brachiocephalic veins that drain into the superior vena cava
41
Why Do We Use a Arterial Sample for Gas Analysis
Venous samples will vary in their results due to local tissue metabolism
Capillary samples are prone to venous admixture and air contamination
42
Causes of a high INR
Warfarin
Liver disease
Some cephalosporin antibiotics
43
INR vs Prothrombin Time
INR results are independent of reagents used and more uniform method of reporting than straight prothrombin time (PT) times.
44
Causes of High aPTT
Heparin
Various clotting factor deficiencies
45
Platlet Aggregation Inhibitors
Aggrenox (Dipyridamole)
Plavix (Clopidogrel Bisulfate)
Integrilin (Eptifibatide)
Aggrastat (Tibrofiban Hydrochloride)
Reopro (Abciximab)
Ticlid (Ticlopidine Hydrochloride)
ASA (Acetylsalicylic Acid)
46
ABG Problem
Deficient Sample Return
If a clinical only gets a small spurt of blood, then the needle has probably passed through the artery and the needle should be slowly withdrawal to find the blood flow
The tip of the needle is never redirected without first being withdrawn into subcutaneous tissue
If the needle is completely withdrawn, then a new sample kit must be used
Small sample volumes or the need to apply suction may indicate the venous blood has been obtained
When drawing arterial blood from hypotensive patients or when using small needle (23 guage) the clinical may need to pull gently on the synring barrel
47
ABG Problem
Altered Test Results
Alteration of test results due to the patients response
If it is suspected that pain and anxiety. Altered the test results (causing hyperventilation or breath holding) they should consider the use of local anesthetic for the next blood sampling attempts
Pre-analytic errors are problems that occur before the sample is analyzed and will alter the accuracy of the results Altered Test Results
48
ABG Pre-Analytical Errors
Air in the Sample
**Effect on Paarmeter:** Decreased PCO2, Increased pH, Increased Low PO2, Decreased high PO2
**How to Recongnize:** Visible bubbles or froth, Low PCO2, inconsistent with patient status
**How to Avoid:** Discard frothy samples, Fully explel bubbles, analyze only after air is expelled, Cap synringe quickly
49
ABG Pre-Analytical Errors
Metabolic Effects
**Effect on Parameters:** Increased PCO2, Decreased pH, Decreased PO2
**How to Recognize:** Excessive time lag since sample collection, Values inconsisyent with patient status
**How to Avoid:** Analyze within 15 mins, Place sample in ice slush
50
ABG Pre-Analytical Errors
Excess Anticoagulant (Dilution)
**Effect on Parameters:** Decreased PCO2, Increased pH, Increased low PO2, Decreased high PO2
**How to Recognize:** Visible heparin remain in the synringe before sampling
**How to Avoid:** Use premade lyophilized dry heparin blood gas kits, Fill dead space only, Collect 2 ml for adults and 0.6 ml in infants
51
ABG Pre-Analytical Errors
Venous Admixture
**Effect on Parameters:** Increased PCO2, Decreased pH, Can greatly lower PO2
**How to Recognize:** Failure of synringe to fill by pulsations
**How to Avoid:** Avoid brachial and femoral sites, Do not aspirate sample, Use short bevel needles, Avoid artery”overshoot”, Cross check SpO2
52
Hwo can clinican advoid most pre analytical errors with an ABG
\*Clinicians can avoid most pre analytical errors though ensuring that the sample is obtained aerobically (with immediate expulsion of air bubbles), properly coagulated, and analyzed quickly
53
Analysis of the Sample
Blood gas results have to be analyzed with the knowledge of the patients status when the blood gas was obtained
Whenever there is a change in condition or therapy we should wait for steady state to emerge until we take the blood gas
Patient with health lung can achieve steady state in 5 mins whereas patients with diseases may take up to 30 min
54
Oxygenation
PaO2
Partial pressure of oxygen dissolved in the plasma of arterial blood and is the result of gas exchange between the blood and lungs
PaO2\< 40 mmHg is severe hypoxemia
PaO2 40-50 mmHg is moderate hypoxemia
PaO2 \> 60 mmHg is mild hypoxemia
55
Oxygenation
SaO2
Arterial oxygenation saturation
Degree to which hemoglobin (Hb) is saturated
This is calculated b the blood gas analyzer
56
Oxygenation
CaO2
Arterial O2 concentration
Content of O2 in 100 ml of arterial blood
Function of the amount of Hb present and the degree of saturation
A normal measure is 18-20ml od O2 per 100 ml of blood
Measurements of SaO2 and hb content is need for this measure
57
The sample volume needed will depend upon
Anticoagulant used
Requirements of analyzer
Point of care analyser tend to require less blood than laboratory analyzers
Whether other teste will be performed on the same
58
What is the normal value for COHB?
Less than 3.0%.
59
What does the COHB indicate?
It indicates if the patient was exposed to carbon monoxide or a house fire.
60
What is the normal value for MetHb?
Less than 2.0%.
61
What does the MetHb indicate?
It indicates if the patient is a smoker.
62
Where are mixed venous blood samples drawn?
They are drawn from the right atrium or from the pulmonary artery.
63
What does CO2 do in the body
Will cause systemic vasodilation
In the brain though it will cause vasoconstriction
