Dose-Response Characteristics of Spinal Bupivacaine in Volunteers: Clinical Implications for Ambulatory Anesthesia

Background: Small doses of bupivacaine may be a reasonable choice for spinal anesthesia for patients having ambulatory surgery. However, few dose-response data are available to guide the selection of reasonable doses of bupivacaine for different ambulatory procedures.

Methods: Eight volunteers per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind manner. Sensory block was assessed with pinprick, transcutaneous electrical stimulation equivalent to surgical incision at the ankle, knee, pubis, and umbilicus, and with duration of tolerance to pneumatic thigh tourniquet. Motor block at the quadriceps and gastrocnemius muscles was assessed with isometric force dynamometry. Times until recovery from spinal anesthesia were recorded. Dose-response relationships were determined by linear regressions. Mean (95% confidence intervals) for durations of sensory and motor block per milligram of bupivacaine administered were calculated from linear regressions.

Results: Significant dose-response relationships (P < 0.006) were determined for sensory block, motor block, and time until recovery (R from 0.6 to 0.9). Within the range of doses studied, each additional milligram of bupivacaine was associated with an increase in duration of tolerance to transcutaneous electrical stimulation of 10 (7 to 13) min, an increase in tolerance to tourniquet of 7 (2 to 11) min, an increase in duration of motor block of 8 (5 to 12) min, and an increase in time until recovery of 21 (17 to 25) min.     

Titration of duration discrimination in behavioral pharmacology and toxicology

This study investigated a discrete-trial, titration duration discrimination procedure in behavioral pharmacology. Pentobarbital and d-amphetamine, measured with this procedure, selectively affected discrimination more than response tendencies. Pentobarbital also tended to affect selectively discrimination of longer durations, whereas d-amphetamine did not. Further experiments showed that (1) other algorithms for modulating stimulus duration are useful in behavioral pharmacology and toxicology, (2) threshold estimates are similar with the method of constant stimuli and the method of titration, and (3) this titration procedure permits the separate examination of drug effects upon discrimination and upon response tendencies; the fixed-interval procedure does not. Baseline variability was an important correlate of drug effects in that the endpoints with more variable baselines were also more sensitive to drugs.     

Immunology

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in immunology.     

Finishing techniques for amalgam restorations: Clinical assessment at three years

Use of the optimum finishing technique for an amalgam restoration may enhance the marginal integrity of the restoration and discourage its unnecessary early replacement. Two hundred and twenty-eight high copper amalgam restorations in 56 patients were evaluated, using clinical assessment criteria, up to three years after placement. Each patient had received at least one carved-only amalgam, at least one immediately finished restoration, and at least one amalgam that was polished at a subsequent appointment. Regardless of the finishing technique, the restorations exhibited similar marginal integrity up to three years after placement. Polished restorations were found to have substantially superior surface texture and less likelihood of surface discoloration. No evidence was found to support the use of immediate finishing techniques. The clinical significance of these findings, with respect to the need to polish amalgam restorations, is discussed.     

PULMONARY RESECTION FOR METASTATIC BREAST CANCER

Background : A patient with a solitary pulmonary metastasis who had breast cancer in the past may benefit from pulmonary resection. Methods : Between 1984 and 1996, 17 patients underwent metastatectomy for metastatic breast cancer. There were 15 females and two males whose average age was 59 (range: 40–74 years). The median tumour-free interval after the primary breast-cancer operation was 5.1 years (range: 8 months-18.2 years). Sixteen patients had complete resections, which included six lobectomies and 10 lesser resections. Results : The postoperative mortality was nil and the morbidity rate was 6%. Follow-up was complete in all patients. Recurrent disease developed in four patients and two patients died of their disease. The 5-year survival was 62%. Conclusion : An aggressive surgical approach is warranted in patients with isolated resectable pulmonary metastases from breast cancer.     

Self-representations and physical impairment: a social constructionist approach.

In this paper a social constructionist approach is used to frame an analysis of the effects of physical impairment on self-perception. The results are reported of a recent study in which questionnaires were mailed to 314 people who were paraplegic and 284 who were post-polio, as well as to a control group of 327 who had no visible physical impairments. While the people who were paraplegic and those who made up the control group gave similar answers to most of the survey questions, those who were post-polio displayed a consistent, but different, way of reporting on their self-representations. Moreover, this discourse, which included such self-described characteristics as self-control, a sense of duty, and a concern for meticulousness, was consistent in the post-polio group across sex and age. It is concluded that the date of onset of physical impairment is significant in influencing the self-representation of persons with physical impairments. The socio-historical evolution of social practices and cultural expectations and norms with respect to persons with disabilities in Western cultures were taken into account in interpreting the results of this survey.