Regulation of proprioceptive memory by subarachnoid regional anesthesia.

BACKGROUND: Patient perception of limb position during regional anesthesia is frequently incorrect. The existing model ascribes this misperception, or phantom sensation, as a reversion to a fixed, slightly flexed, body schema. A model was developed to evaluate the influence of limb position changes on the incidence of incorrect or phantom sensations during regional anesthesia. METHODS: Forty American Society of Anesthesiologists physical status I-III adult patients undergoing genitourinary procedures under subarachnoid anesthesia were assigned to a lidocaine or bupivacaine treatment group and randomly assigned to one of four time groups (1, 4, 7, and 10 min). After blockade, patients were placed supine and blinded to limb positioning manipulations. One leg was flexed and the contralateral leg extended, with leg positions subsequently reversed at the assigned time point. At 10 min, patients were asked to identify the position of each leg. Percentage of incorrect response was analyzed using a logistic regression model with two independent variables: treatment and time. A supplemental study was undertaken to evaluate the observed difference in incorrect perceptions relative to flexed first versus extended limb first sequencing. RESULTS: The inability to perceive a change in limb position under regional anesthesia is dependent on the time after the block that the position change is initiated in relation to the onset characteristics of the local anesthetic. A phantom sensation of an extended leg position clearly exists. The flexed-first limb has a significantly higher incidence of incorrect or phantom perceptions. CONCLUSION: Proprioceptive memory involves a dynamic neuroplastic imprinting process that is influenced by limb or joint position prior to onset of regional anesthesia. This contrasts with previously held beliefs of a purely fixed body schema.

Two antimicrobial alkaloids from heartwood of Liriodendron tulipifera L.

Alcoholic extracts of the heartwood of Liriodendron tulipifera have demonstrated antimicrobial activity against Staphylococcus aureus, Mycobacterium smegmatis, Candida albicans, and Aspergillus niger. The antimicrobial activity was associated only with the alkaloidal fraction. Separation of the active alkaloidal fraction by chromatography led to the isolation and identification of dehydroglaucine and liriodenine as the active components. Several other alkaloidal derivatives were prepared and tested. In addition to the active alkaloids, michelabine was also identified in the tertiary nonphenolic base fraction along with the lignan, lirioresinol-B-dimethyl ether, and two N-acetylnoraporphine alkaloids from the nonbasic fraction.