PREMEDICATION WITH FENTANYL AND MIDAZOLAM DECREASES THE RELIABILITY OF INTRAVENOUS LIDOCAINE TEST DOSE

This study was performed to determine whether premedication with midaz olam and fentanyl prevents reliable detection of an TV lidocaine test dose. Thirty ASA physical status I or II patients received either 3 mt of saline or 1.5 mg of midazolam (1.5 mt) plus 75 mu g of fentanyl (1 .5 mt) IV in a randomized, double-blind fashion. Five minutes later, l idocaine 1 mg/kg was injected N. At 1.5 min before and every minute af ter lidocaine administration, each subject was questioned regarding th e presence of four symptoms of systemic lidocaine toxicity. Any new ti nnitus, perioral numbness, metallic taste, or light-headedness within 5 min after lidocaine administration was considered a positive respons e. All 15 patients in the saline group (100% sensitivity) had a positi ve response to IV lidocaine, but only 9 of 15 patients in the sedation group had a positive response (60% sensitivity; P = 0.017). We conclu de that midazolam and fentanyl premedication decreases the reliability of subjective detection of TV lidocaine. Implications: Anesthesiologi sts often rely on subjective symptoms to prevent local anesthetic toxi city while performing regional anesthesia. Sedatives are often adminis tered during the administration of regional anesthesia. This study dem onstrates that typical sedation decreases the reliability of detection of local anesthetic toxicity by subjective symptoms.