When frequent arterial blood samples are required and an umbilical arterial catheter cannot be placed or has been removed because of complications.
When intra-arterial blood pressure monitoring is required.
Equipment. A 22- or 24-gauge needle with a 1-in catheter encasement. A 24-gauge is recommended for infants <1500 g. An arm board (or two tongue blades taped together), adhesive tape, sterile drapes, povidone-iodine and alcohol swabs, gloves, antiseptic ointment, a needle holder, suture scissors, 4–0 or 5–0 silk sutures, 0.5 normal saline or 0.25 normal saline solution (the latter preferred in premature infants to decrease hypernatremia risk) in a 1- or 3-mL syringe with heparinized saline solution (1 unit of heparin/mL saline) in a pressure bag, and connecting tubing. Pressure transducer for continuous blood pressure monitoring.
Procedure. Two methods are described here; both use the radial artery, the most common site, and can be adapted to other arteries. Another common site is the posterior tibial artery. Ulnar and dorsalis pedis arteries are alternative sites but not routinely recommended. The temporal artery and femoral arteries are not recommended. Axillary artery cannulation is very difficult and also not recommended. Lateral or posterior wrist transillumination may be helpful in locating the artery in premature infants. Arterial catheterization requires a great deal of patience.
Verify adequate collateral circulation in the hand using the Allen test. (See Chapter 21.)
Place the infant's wrist on an armboard; some prefer to use an intravenous bag. Hyperextend the wrist by placing gauze underneath it. Tape the arm and hand securely to the board (Figure 22–1). Put on gloves, and place sterile drapes around the puncture site. Cleanse the site, first with povidone-iodine swabs and then with alcohol swabs.
Use of topical local anesthetic agents may diminish pain. Oral sucrose (0.1–1.5 mL, amount depending on gestational age, of a 24% solution) and/or pacifier are preferred. (See Chapter 69.)
Puncture both the anterior and posterior walls of the artery at a 30- to 45-degree angle. Remove the stylet. There should be little or no backflow of blood.
Pull the catheter back slowly until blood is seen; this signifies that the arterial lumen has been entered.
Advance the catheter after attaching the syringe and flush the catheter. Never use hypertonic solutions to flush an arterial catheter.
Secure the catheter with 4–0 or 5–0 silk sutures in two or three places. Occasionally, it is not possible to suture the catheter, and it should be securely taped instead.
Connect the tubing from the heparinized saline pressure bag to the catheter.
Place povidone-iodine ointment on the area where the catheter enters the skin and cover the area with gauze taped securely in place.
Method 2 (alternative method, preferred for premature infants)
Perform steps 1, 2, and 3 as described earlier.
Puncture the anterior wall of the artery until blood return is seen. At this point, the catheter should be in the lumen of the artery. Vasospasm is common, and the procedure should be performed slowly.
Advance the catheter into the artery while simultaneously withdrawing the needle. The blood ...
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