LEC 11 ARTERIAL PUNCTURE

• Arterial puncture - is technically difficult and potentially more painful and hazardous than venipuncture.
• The primary reason for arterial puncture is to obtain blood for arterial

  blood gas (ABG) tests, which evaluate respiratory function.
• Capillary blood - which is similar to arterial blood in composition provided that the puncture site is warmed prior to specimen collection, is sometimes used to test blood gases in infants
• In addition to direct puncture of an artery, ABG specimens can be collected from an indwelling arterial line using a needle-less blood sampling device such as the VAMP by personnel trained to do so.
• ABG evaluation - is used in the diagnosis and management of respiratory disorders such as lung disease to provide information about a patient’s oxygenation, ventilation (air entering and leaving the lungs), and acid–base balance and in the management of electrolyte and acid–base balance in patients with diabetes and other metabolic disorders.
• ABG specimens are very sensitive to the effects of preanalytical errors; therefore accurate patient assessment and proper specimen collection and handling are necessary to ensure accurate results.
• For accurate results, an ABG specimen must not be exposed to air. Consequently, the specimen must be collected in an anaerobic manner, which must be maintained throughout the collection, handling, and testing process.
• Most ABG testing instruments directly measure o hydrogen ion activity (pH), o partial pressure of carbon dioxide (PaCO2), o and partial pressure of oxygen (PaO2).
• pH - 7.35–7.45
• PH - A measure of the acidity or alkalinity of the blood; used to identify a condition such as acidosis or alkalosis.
• PaO2 - 80–100 mm Hg
• PaCO2 - 35–45 mm Hg
• HCO3 - 22–26 mEq/L
• O2 saturation - 97%–100%
• Base excess (or deficit) - (-2)–(+2) mEq/L
• Base excess (or deficit) - A calculation of the nonrespiratory part of acid–base balance based on the PaCO2, HCO3, and hemoglobin.
• Paramedical personnel - (healthcare workers other than physicians) who may be required to perform arterial puncture include nurses, medical technologists and technicians, respiratory therapists, emergency medical technicians, and level II phlebotomists.
• Phlebotomists - who collect arterial specimens must have extensive training involving theory, demonstration of technique, observation of the actual procedure, and performance of arterial puncture with supervision before performing arterial punctures on their own.
• Personnel who perform ABG testing are designated level I or level II depending on their formal education, training, and experience.
• Level II personnel - supervise level 1 personnel and perform testing as well.
• For quality assurance purposes, individuals performing arterial puncture must undergo periodic evaluation.
• Collateral circulation is the - primary site selection criterion.
• Collateral circulation is the primary site selection criterion. It can be evaluated using a portable ultrasound instrument or by performing a simple test called the modified Allen test.
• SonositeM-Turbo®point- of-care ultrasound system displaying a brachial artery imaged with a high- frequency linear transducer.
• Arterial puncture sites include the radial artery (most common), brachial artery, femoral artery, dorsalis pedis artery, posterior tibial artery, axillary artery, and ulnar artery.
• radial artery - first choice and most commonly used site, located on the thumb side of the wrist
• radial pulse - can be felt on the thumb side of the wrist approximately 1 inch above the wrist crease.
• The biggest advantage of using the radial artery is the presence of good collateral circulation.
• both the radial artery and the ulnar artery supply the hand with blood.
• ulnar artery - is normally off limits for arterial specimen collection. It is generally easy to palpate because it lies fairly close to the surface of the skin. There is less chance of hematoma formation . There is a reduced risk of accidentally puncturing a vein or damaging a nerve because no major veins or nerves are immediately adjacent to the radial artery.
• Adequate circulation via the ulnar artery must be verified before puncturing the radial artery. If ulnar blood flow is weak or absent, the radial artery should not be punctured.