THE EFFECT OF AGE ON RETRIEVAL OF LOCAL-ANESTHETIC SOLUTION FROM THE EPIDURAL SPACE

1 We conducted this prospective study to determine whether advancing a ge is correlated with retrieval of local anesthetic solution from the epidural space. Three hundred forty-six patients (ASA physical status I or II, 20-93 yr of age, 177 female and 169 male patients) undergoing epidural anesthesia were enrolled. The epidural space was identified by a loss of resistance technique using air, and a catheter was introd uced 3 cm. Three milliliters of 2% lidocaine with epinephrine was inje cted as a study dose by hand at a rate of 1 mL/s with the patient in t he supine position. The syringe was immediately aspirated to retrieve the local anesthetic solution. A retrieved volume of 0.5 mt or more wi th a glucose concentration less than 6 mg/dL was defined as retrieval positive, and a volume of less than 0.5 mt was defined as retrieval ne gative. There was a significant correlation between age and retrieval volume among all the patients (Y = 0.008X-0.222, P < 0.0001) with a si gnificant increase in the positive retrieval incidence and volume from the patients in their 50s (11%, 0.6 +/- 0.3 mL) to the patients in th eir 60s (26%, 1.0 +/- 0.6 mt) (P < 0.05 for both). The incidence of po sitive retrieval and the retrieval volume were greater in the patients in their 60s and older (30%, 1.1 +/- 0.63 mt) than in the younger tha n 60 (10%, 0.6 +/- 0.3 mt) (P < 0.0001 and P < 0.001). The glucose con centration was 2.3 +/- 1.2 mg/dL in the positive cases. We conclude th at there is a weak positive correlation between age and the local anes thetic solution retrieved from the epidural space. Implications: We co nducted a study in 346 patients to determine whether advancing age cou ld be correlated with retrieval of local anesthetic solution from the epidural space. We found a weak positive correlation between advanced age and the amount of solution retrievable from the epidural space. Fu rther studies are required to determine whether this phenomenon may ca ll for dose adjustments in patients aged more than 60 yr.