Peripheral Arterial Cannulation
Suhasini Kaushal
Jayashree Ramasethu
Arterial access is required for continuous hemodynamic monitoring and blood sampling when caring for a sick neonate. When it is not possible to catheterize the umbilical artery for either technical or clinical reasons, peripheral arterial cannulation may be required. As a rule, the most peripheral/distal artery should be used, to reduce potential sequelae from any associated vascular compromise or thromboembolic event.
Common sites for peripheral arterial cannulation include the radial, ulnar, and posterior tibial arteries (1, 2, 3, 4). The dorsalis pedis artery is occasionally used (5). Although cannulation of the axillary (6) and brachial (7) arteries have been described, these sites are not recommended because of the limited collateral blood flow and high potential for ischemic complications. The temporal artery is also usually avoided because of the potential for neurologic sequelae (8, 9).
A. Indications
1. Monitoring of arterial blood pressure
2. Frequent monitoring of blood gases or laboratory tests (e.g., critically ill ventilated neonates or extremely low-birth-weight premature infants)
3. When preductal monitoring is required (e.g., with persistent pulmonary hypertension) (right upper extremity cannulation)
B. Contraindications
1. Bleeding disorder that cannot be corrected
2. Pre-existing evidence of circulatory insufficiency in limb being used for cannulation
3. Evidence of inadequate collateral flow (i.e., occlusion of the vessel to be catheterized may compromise perfusion of extremity)
4. Local skin infection
5. Malformation of the extremity being used for cannulation
6. Previous surgery in the area (especially cut down)
7. Potential for adverse neurologic sequelae following cannulation
C. Equipment
Sterile
1. Gloves
2. Antiseptic solution (e.g., iodophor/povidone, chlorhexidine)
3. 4- × 4-in gauze squares
4. 0.5 to 0.95 normal saline (NS) with 1 to 2 U/mL heparin). Quarter NS (0.25 N saline) is often used in extremely preterm infants <24 weeks’ gestational age, who are at risk for hypernatremia. Using heparinized saline has been shown to maintain line patency longer than hypotonic solutions such as heparinized 5% dextrose water or unheparinized NS (10, 11)
5. 3- or 5-mL syringe
6. 20-gauge venipuncture needle (if using larger-sized 22-gauge cannula)
7. Appropriate-sized cannula: 22-gauge × 1-in (2.5 cm), 24-gauge × 0.75 in, or 24-gauge × 0.56 in tapered or nontapered cannula with stylet for larger to smaller neonates, respectively
8. Arterial pressure transducer and extension tubing (see Chapter 10)
9. T connector primed with heparinized flush solution
10. Transparent, semipermeable dressing
Non Sterile
2. 0.5 in, water-resistant adhesive tape
3. Materials for restraint of limb following arterial cannulation (see Chapter 5)
4. A constant-infusion pump capable of delivering flush solution at rate of 0.5 to 1 mL/hr against back pressure
Additional Equipment Required for Cut-Down Procedure
All equipment except mask must be sterile.
1. Gown and mask
2. 0.5% lidocaine hydrochloride in labeled 3-mL syringe
3. No. 11 scalpel and holder
4. Two curved mosquito hemostats
5. Nerve hook
6. 5-0 nylon suture
Anesthesia/Analgesia
Eutectic mixture of lidocaine-prilocaine (EMLA) cream 2.5% may be applied for local anesthesia prior to placing arterial line in addition to sedation in critical infants.
D. Precautions
1. When performing radial artery cannulation, check ulnar collateral circulation using the Allen test prior to undertaking the procedure. This test is recognized to have limitations regarding accuracy and interrater reliability (14), so careful observation for signs of impaired distal perfusion is still required during and after the procedure. Doppler ultrasound may also be useful in assessing collateral circulation.
2. When performing dorsalis pedis or posterior tibial cannulation, a modified Allen test can be performed by raising the foot, occluding the dorsalis pedis and posterior tibial arteries, releasing pressure over one, and monitoring for tissue perfusion within 10 seconds, although this technique is less reliable than testing in the hand (15).
3. When performing radial or ulnar cannulation, avoid excessive hyperextension of wrist, because this may result in occlusion of artery and a false-positive Allen test (16) and has been associated with median nerve conduction block (17).
4. Never ligate artery.
5. Leave all fingertips/toes exposed so that circulatory status may be monitored. Examine limb frequently for changes in perfusion.
6. Inspect cannula insertion site at least daily.
a. If signs of cellulitis are present, remove the cannula and send the cannula tip for culture. Also, send a wound culture if there is inflammation at the cutdown site.
b. Obtain a blood culture from a peripheral site if signs of sepsis are present.
c. Inspect the area distal and proximal to the insertion site for blanching, redness, cyanosis, or changes in temperature or capillary refill time.
7. Make sure that a continuous pressure waveform tracing is displayed on a monitor screen at all times after cannulation.
8. Take care not to introduce air bubbles into cannula while assembling infusion system or taking blood samples.
9. Use cannula for sampling only; no fluids other than heparinized saline flush solution should be administered via cannula.
10. Do not administer a rapid bolus injection of fluid via line. Flush infusion after sampling should be:
a. Minimal volume (0.3 to 0.5 mL)
b. Injected slowly
11. To reverse arteriospasm, see Chapter 36.
12. Remove cannula at first indication of clot formation or circulatory compromise (e.g., dampening of waveform on monitor). Do not flush to remove clots.
13. Remove cannula as soon as indications no longer exist.
E. Technique
Standard Technique for Percutaneous Arterial Cannulation
1. Choose a site for cannulation and secure the appropriate limb.
a. Radial artery: This is the most common site for cannulation (1, 2, 3, 18). The infant’s forearm and hand can be transilluminated with the wrist in extension 45 to 60 degrees (Fig. 33.1), making sure that fingers are visible to monitor distal perfusion. The artery can be palpated proximal to the transverse crease on the palmar surface of the wrist, medial to the styloid process of the radius, and lateral to the flexor carpi radialis (19) (Fig. 33.2).
b. Ulnar artery: In a small number of infants, the ulnar artery may be easier to locate than the radial artery (20). If an Allen test indicates that the collateral
blood supply is adequate, the ulnar artery may be cannulated using the same method as for a radial artery. The ulnar artery runs along the palmar margin of the flexor carpi ulnaris. Caution is necessary when cannulating the ulnar artery because it runs next to the ulnar nerve and is smaller in caliber than the radial artery (Fig. 33.2).
blood supply is adequate, the ulnar artery may be cannulated using the same method as for a radial artery. The ulnar artery runs along the palmar margin of the flexor carpi ulnaris. Caution is necessary when cannulating the ulnar artery because it runs next to the ulnar nerve and is smaller in caliber than the radial artery (Fig. 33.2).
 FIGURE 33.1 Transillumination of the radial artery. |
 FIGURE 33.2 Anatomic relations of the major arteries of the wrist and hand. |
c. Dorsalis pedis artery: The dorsalis pedis artery can be found in the dorsal midfoot between the first and second toes with the foot held in plantar flexion (Fig. 33.3). It should be noted that the vascular anatomy of the foot is variable and the dorsalis pedis artery may be absent in some patients, whereas it may provide the main blood supply to the toes in others (21, 22).
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