Collection of Arterial Blood Gas Samples
Iowa Neonatology Fellows
Revised John Dagle MD, PhD
Peer Review Status: Internally Peer Reviewed
Any infant, especially those born preterm, receiving greater than ambient oxygen concentration must have his arterial oxygen tension or saturation monitored.
An ill infant without an indwelling arterial catheter should have arterial O2 tension monitored by arterial puncture or transcutaneous PO2 monitor. An acceptable alternative would be continuous pulse oximetry with the upper saturation alarm limit set at 95%, but caution should always be used to prevent exposure to high amounts of oxygen. If questions arise regarding the appropriate level of oxygen saturation, peripheral arterial puncture should be performed.
Frequency of sampling depends on the clinical situation and the reliability of the other monitoring devices. Generally, a significant change in ventilator or CPAP setting should be followed by a capillary or arterial sample within 15 minutes to an hour. If performing a peripheral arterial puncture for blood gas purposes, note should be made of the location, as many infants have shunting through the ductus arteriosus that may affect the interpretation.
The amount of blood needed for laboratory tests with peripheral arterial puncture should be determined prior to puncture. The syringes used for blood gas sampling can be obtained from the blood gas laboratory.
Arterial puncture, although not as commonly used in NICU's as other methods of monitoring, can be performed with relative ease, using the radial, temporal, posterior tibial, or dorsalis pedis artery. The brachial and femoral artery should be used only in emergency situations, because of the risk of complications at those sites. Indwelling catheters may be placed in the radial, posterior tibial or dorsalis pedis artery but should not be placed in the temporal or brachial artery.
Prep the site with 3 alcohol swabs and wear appropriately fitting gloves. Goggles or eyeglasses are also recommended. The artery should be easily palpable or visible with transillumination. If using the radial artery, an Allen test should be performed prior to puncture. An arm board may be useful to prevent extreme dorsiflexion of the wrist which makes the procedure more difficult. A 25 gauge butterfly needle, with TB or 3 ml syringe should be used. The bevel up position should be used, except in the most superficial arteries. The angle of insertion should be 25o for a superficial and 45o for a deep artery, against the flow of the artery. Blood should flow spontaneously or with gentle suction.
After the needle is removed, continuous pressure should be applied for 5 minutes, with care not to squeeze with the fingertips. If hematoma formation is prevented, the artery may be used multiple times. Observe the extremity for 15-20 minutes after the procedure for arterial spasm.