[Safety of continuous epidural anesthesia during heart surgery--change of coagulation-fibrinolysis under heparinization]

To confirm the safety of continuous epidural anesthesia during extracorporeal circulation under heparinization, we investigated epidural hematoma formation following the cardiopulmonary bypass in both humans and dogs. In fifteen dogs, divided into three groups, heparin was administered at the dose of 300, 600, or 900 U.kg-1, respectively. In fourteen patients, a dose of 300 U.kg-1 haparin was administered for cardiopulmonary bypass. Although blood coagulation-fibrinolysis dropped into abnormal ranges following heparinization, no epidural hematoma was observed in dog and no patient revealed spinal complication associated with epidural hematoma. These data indicate that continuous epidural anesthesia would be a safe tool for intraoperative anesthesia even during extracorporeal circulation under heparinization.

Concentration of lidocaine affects intensity of sensory block during lumbar epidural anesthesia

We investigated the effects of a twofold difference in concentration and volume of lidocaine on lumbar epidural block using a cutaneous current perception threshold (CPT) quantitative sensory testing device. Twenty ASA I patients scheduled for elective gynecological surgery were randomly divided into two equal groups to receive either 20 mL of 1% lidocaine or 10 mL of 2% lidocaine through an epidural catheter inserted at the L1-2 interspace. CPTs at 2000-, 250-, and 5-Hz stimulation and sensation to light touch, temperature, and pinprick at ipsilateral dermatomes V, T9, and L2 were measured before and every 5 min until 60 min after the epidural lidocaine. Epidural anesthesia with both solutions produced a significant increase in all CPTs at dermatomes T9 and L2. Alterations in CPTs were similar for both groups at T9 but were significantly greater in patients given 2% lidocaine than in those given 1% lidocaine at L2. There were no differences in the upper level of sensory block to cold, pinprick, and touch between the two groups. We conclude that lumbar epidural anesthesia with 10 mL of 2% lidocaine produces more intense blockade of both large- and small-diameter sensory nerve fibers than that with 20 mL of 1% lidocaine.

IMPLICATIONS

The effects of local anesthetic concentration and volume on the quality of epidural anesthesia have not been adequately investigated. The results of the present study suggest that the concentration affects the intensity of sensory block during epidural anesthesia with lidocaine.