The use of local anesthetic for arterial puncture is not universal. The proposed reasons for the use of local anesthetic are:

• To avoid pain
• The concern that the pain induced hyperventilation or apnea could alter the results of blood gases

This issue was specifically studied and the results indicate that an unanesthetized arterial puncture does provide an accurate measurement of resting pH and Pco2.

REF: Morgan EJ, et al. The effects of unanesthetized arterial puncture on Pco2 and pH. ARRD 1979; 120:795-798.

Glauser FL, et al. Accuracy of routine arterial puncture for the determination of oxygen and carbon dioxide tensions. ARRD 1972; 106: 776-779.

Hence, the only reason to use local anesthetic is to avoid pain to the patient. If you are proficient, the first stick can be tried without the anesthetic. I recommend the use of local anesthetic for beginners.