Arterial Blood Gases (ABGs) analysis

WHAT SHOULD WE RECORD?? Number one we should have an order from the physician •Date/Time/Site •Results of the Modified Allen Test •Patient’s body temp, position, activity level, RR •Fi02 and/or all ventilator settings •This will help us interpret the results!!! HOW DO WE DETERMINE OXYGENATION STATUS? •PaO2-represents the partial pressure of O2 dissolved in the plasma of the arterial blood and is the result of gas exchange between the lung and the blood. (Mild, Moderate, Severe) •SaO2-represents the degree to which the hemoglobin is saturated with O2. •CaO2-represents the content of O2 in arterial blood and is the function of the amount of Hb present and the degree to which it it saturated HOW DO WE DETERMINE ACID-BASE STATUS? •pH •PaC02 •HC03 CLINICAL INDICATIONS •Sudden, unexplained Dyspnea •Cyanosis •Abnormal breath sounds •Severe, unexplained tachypnea •Heavy use of accessory muscles •Changes in ventilator settings •Cardiopulmonary resuscitation (CPR) •Acute hypotension •Acute deterioration in neurologic function ARTERIAL LINE: ANALYZING •The primary parameters of pH, PCO2, and PO2 are measured with a blood gas analyzer. •These values compute other, secondary values such as HC03, BE/BD, Hb Saturation. •If ACTUAL measurement of total Hb saturation, Methemoglobin, or Carboxyhemoglobin is required, what needs to be utilized? Electrochemical O2 Analyzers •Polargraphic electrode( Clark electrode) Has battery!!!-check for troubleshooting! •Galvanic fuel cell

Advantages of the Galvanic: No batteries, and makes its own current

Advantages of the Polargraphic: Relies on an O2 mediated chemical reaction to produce a current " Clark Electrode" Faster response due to the battery

Both analyzers are affected ( Disadvantages) are the same, Temp, pressure increase and humidity and altitude decrease and they must be recalibrated Electrochemical O2 Analyzers •Polargraphic electrode( Clark electrode) Has battery!!!-check for troubleshooting! •Galvanic fuel cell

Advantages of the Galvanic: No batteries, and makes its own current

Advantages of the Polargraphic: Relies on an O2 mediated chemical reaction to produce a current " Clark Electrode" Faster response due to the battery

Both analyzers are affected ( Disadvantages) are the same, Temp, pressure increase and humidity and altitude decrease and they must be recalibrated ANALYZING •To measure P02 blood gas analyzers use the Clark polarographic electrode •pH uses the Sanz electrode •C02 measured by Servinghaus electrode •04:10 QUALITY CONTROL •More in depth than automatic QC •The results of control media analyses are plotted on a graph and compared with statistically derived limits, usually + - 2 standard deviation (SD) ranges. •Fig. 19-9 •If results fall outside of this, indicates analytic error •Random error •Systemic error POINT OF CARE TESTING

Takes blood gas analysis from the specialized lab to the patient’s bedside. •Leads to quicker diagnosis and treatment •Chemistry, hematology, LA, PT,PTT, troponin •Must be ran within 1-2 mins •Disposable cartridge

TRANSCUTANEOUS BLOOD GAS MONITORING •Provides continuous noninvasive estimates of arterial PO2 and PCO2 through a surface skin sensor. •Heats the skin (similar to capillary gas) •Used primarily with babies

PULSE OXIMETRY •Measurement of blood Hb saturations using spectrophotometry. •POX combines spectrophotometry and photoplethysmography •One red light (660 nm), one infrared(940nm) •Unreliable at SpO2 <80% •Problems with POX •Set alarms appropriately

CAPNOGRAPHY •Capnometry vs Capnography vs. Volumetric capnography •Rapid responding CO2 analyzer •Indications?? Pg. 394 •Mainstream vs. Side stream •Rapid responding CO2 analyzer •Infrared absorption, raman scattering, mass spectroscopy, or photoacoustic technology •Infrared Most common!

What is the difference between capnography and capnometry? Why do rising CO2 levels cause increases in intracranial pressure? How would you modify your technique if you had to perform ABGs on a patient receiving anticoagulation?

Anatomical Locations for Arterial Puncture •Radial Artery –Located in the wrist on the radial side –Advantage •Safety due to presence of collateral circulation –Disadvantage •Small size of the artery

Anatomical Locations for Arterial Puncture (continued) •Brachial Artery –Advantage •Large size of the artery –Disadvantages •Close to a large vein and a nerve •No collateral circulation

Anatomical Locations for Arterial Puncture (continued) •Femoral Artery –Advantages •Large size •Easily palpated •Presents a large target

Anatomical Locations for Arterial Puncture (continued) –Disadvantages •Proximity of a major vein •Lack of collateral circulation •May be deep and difficult to locate •Atherosclerotic plaques commonly form in femoral artery

Complications of Arterial Puncture •Potential Complications Include: –Vessel spasm –Formation of thrombi or emboli –Infection –Loss of blood flow –Loss of circulation

Complications of Arterial Puncture (continued) •Techniques used to minimize potential complications –Modified Allen’s Test •Done before arterial puncture to determine the adequacy of circulation from the ulnar artery –Pulse Oximetry •Used to assess collateral circulation of the hand –Sampling Syringes •Specialized plastic syringes used for arterial

Blood Gas Sampling Errors •Bubbles –Air bubbles must be expelled immediately upon collection. –Carbon dioxide in the blood diffuses into the air bubbles and can potentially lower the carbon dioxide tension measured

Delay in Sample Analysis –Samples held longer than ten minutes may show lower PaO2, higher PaCO2 or a pH less than the patient’s actual Ph.

Blood Gas Sampling Errors (continued) •Use of the Proper Anticoagulant –Anticoagulants can cause acidosis in the blood sample. –Sodium heparin is the best anticoagulant to use in arterial blood sampling.

Blood Gas Sampling Errors (continued) •Venous Sampling –If a sample is drawn from a hypoxemic patient, it is difficult to distinguish arterial blood from venous blood. •Patient Anxiety –May lead to hyperventilation and altering of the PaCO2

‹#› © 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Capillary Blood Gas Sampling •Technique –Obtained most commonly from an infant’s heel (referred to as a heel stick) or from the finger –Arterialization is done before sampling. –A lancet is used to puncture the skin surface.

Capillary Sampling Errors •Potential Capillary Sampling Errors: –Poor blood flow –Introduction of air into the sample –Inadequate mixing of heparin

Puncture Techniques •Standard Precautions –Wear personal protective equipment. –Exercise caution when using sharps. –Properly dispose of sharps into an approved biohazard sharps container.

Puncture Techniques (continued) •Patient-Related Considerations –Check for required physician’s order –It may be necessary to put pressure on the site for up to 15 minutes. –ABG analysis to judge adequacy of oxygen therapy –Re-assess patient 20-30 minutes following arterial puncture

Puncture Techniques (continued) •Use of an Anesthetic •Puncture Preparation –Perform the modified Allen’s test. –Palpate the puncture site. –Cleanse the site with an iodine-based prep pad. –Repeat with an alcohol prep pad.

Puncture Techniques (continued) •Obtaining the specimen –Radial Site •Hold the syringe like a pencil, palpate pulse and visualize artery location •With needle bevel up, puncture skin at a 45° angle •Visualize the artery location and slowly advance the needle toward the artery. •When the artery is punctured, blood will quickly appear in the needle hub. Do not move. Allow the syringe to fill.

Puncture Techniques (continued) –Brachial Site •With the needle bevel up, puncture skin at a 45° to 90° angle •Visualize the artery location and slowly advance the needle toward the artery. •Watch for the flash and allow the syringe to fill. Puncture Techniques (continued) –Femoral Site •May require longer needle •With the bevel of the needle facing patient’s head and perpendicular to the skin’s surface, puncture the skin. •Watch for the flash and allow the syringe to fill.

Postpuncture Care •After the sample is collected: –Withdraw the needle and apply firm pressure with a gauze pad. –Expel air and insert the needle into rubber stopper. –While applying pressure, mix the sample in the syringe. –Ice the sample. –Check the puncture site. –Label and transport the sample.

Indwelling Arterial Catheter Sampling •Supplies moment-by-moment pressure monitoring •Allows repeated arterial sampling with minimal trauma to the patient •To reduce clotting, a continuous drip of sodium heparin is used. •The line must be flushed before drawing a sample.