Our data suggest that screening for impulsivity and ICDs should be performed prior to DBS, and that patients should be monitored for these problems during follow-up. Prospective trials are needed to confirm the findings of this exploratory study and to elucidate the reasons of a possible induction of impulsivity by STN DBS.

We studied if ethnicity influences patient-controlled analgesia (PCA) for the treatment of post-operative pain. Using a retrospective record review, we examined data from all patients treated with PCA for post-operative pain from January to June 1993. We excluded patients who did not have surgery prior to the prescription of PCA or were not prescribed PCA in the immediate post-operative period. The sample consisted of 454 subjects. While there were no differences in the amount of narcotic self-administered, there were significant differences in the amount of narcotic prescribed among Asians, Blacks, Hispanics, and Whites (F--7,352, P < 0.01). The ethnic differences in prescribed analgesic persisted after controlling for age, gender, pre-operative use of narcotics, pain site, and insurance status. Patient's ethnicity has a greater impact on the amount of narcotic prescribed by the physician than on the amount of narcotic self-administered by the patient.

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There is little information as to the optimal use of mannitol. To determine the dose-response relationship, the osmotic gradient required, and the time course of intracranial pressure (ICP) reduction produced by mannitol, eight patients with acute head injury were studied in whom ICP was monitored with a ventriculostomy and found to be elevated. Ventilation was controlled to a pCO2 of 25 +/- 3 mm Hg and all were paralyzed with Pavulon. None had received barbiturates. Before mannitol administration the intracranial volume-pressure response was determined. Mannitol was administered as a bolus of 0.25 gm/kg, 0.5 gm/kg, and in six patients, 1 gm/kg, separated by at least 8 hours. In all patients the ICP reduction with 0.25 gm/kg (41.3 +/- 10.2 mm Hg leads to 16.4 +/- 5.6, p less than 0.01) was equivalent to that achieved with the larger doses. Serum osmolality rises of 10 mOsm or more were associated with a reduction in ICP. Much smaller doses than those previously recommended were effective in reducing the ICP acutely, although at 5 hours there was a trend toward persistent reduction when the larger dose is used. This trend was small and indicates that smaller and more frequent doses are as effective in reducing the ICP while avoiding the risk of osmotic disequilibrium and severe dehydration.