med 18

 

toma formation, or rarely, compartment syndrome. Finally,

a known history of insufficient blood flow through the

4

patient's acid-base status and carboxyhemoglobin,

methemoglobin, and electrolyte levels.

• Arterial puncture is a useful way to obta in blood for

ana lysis when traditional phlebotomy is limited or difficult on the basis of patient characteristics.

palmar arch or previous surgery to the radial or ulnar

arteries should also be considered a contraindication. The

Allen test, described later, has been used as a way to determine adequacy of collateral circulation, however, its necessity has been questioned.

EQUIPMENT

Many commercially prepared kits for arterial puncture are

available, and if a commercial kit is not available, then

equipment is easily found in most EDs. The following

equipment is typically used to perform the procedure

(Figure 2-1).

� Required Equipment

Alcohol, chlorhexidine, or iodine prep pads

2- to 3-rnL heparinized syringe with a 23- to 25-gauge

needle

Syringe cap

Appropriate personal protective equipment

Gauze or other dressing

� Suggested Equipment

Anesthetic (eg, lidocaine)

Ultrasound or Doppler (if the artery is difficult to palpate)

ARTERIAL BLOOD GAS

Figure 2-1. Eq ui pment used for an arterial puncture.

Rolled towel or kidney basin (to stabilize and extend

the wrist)

Ice (for specimen process times > 10 minutes)

Local anesthesia is not strictly required for the procedure;

however, studies have shown that pain, as well as the

number of attempts required to obtain a sample, are

reduced when appropriate anesthesia is provided.

Traditionally, 1% lidocaine is used, avoiding epinephrine

because of concern for vasospasm. Recent studies have

suggested that jet-injected 2% lidocaine also provides

reasonable anesthesia.

PROCEDURE

Before selecting an appropriate wrist, the Allen test may

be used to assess collateral circulation. Manually occlude