The most common test dose is 3 mL of local anesthetic solution containing 5 µg/mL of epinephrine (1:200,000).
This dose is sufficient to produce evidence of spinal anesthesia if accidental subarachnoid injection occurs.
IV injection of the epinephrine dose typically increases the heart rate an average of 30 beats per minute.
Reflex bradycardia may occur in patients being treated with α-blockers. (A increase in systolic blood pressure of 20 mm Hg or more may be a more reliable indicator of intravascular injection in these patients.)
The sensitivity of epinephrine as a test dose in parturients is questionable because maternal heart rate increases during contractions are often as large as those produced by epinephrine.
Aspirating the catheter or needle to check for blood or CSF is helpful if positive, but the incidence of false-negative aspirations is too high to rely on this technique alone.