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Biomedical subjects

J M Vernon

Publications and source records attributed to J M Vernon.

9 recordsLinked to original sources
PubMed1995

Prediction of movement using bispectral electroencephalographic analysis during propofol/alfentanil or isoflurane/alfentanil anesthesia.

Conventional electroencephalographic (EEG) analysis techniques do not use the phase information from the Fourier analysis. This study used a new technique of EEG analysis, bispectral analysis, which measures interfrequency phase relationships in the EEG. Using a reference database, and a process of multivariate discriminant analysis, we developed a univariate bispectral variable, the bispectral index (BIS). This study was designed to test the efficacy of BIS in predicting movement to incision during either an isoflurane/alfentanil anesthetic or a propofol/alfentanil anesthetic technique. Fifty consenting patients were randomized to two groups; one received isoflurane/alfentanil and the other, propofol/alfentanil for anesthesia. EEG was recorded using a microcomputer system and the data were analyzed off-line. Hemodynamic variables were also recorded. After skin incision, each patient was observed carefully for 2 min to detect purposeful movement. A significant difference was found between the BIS values for movers versus nonmovers within each of the two treatment groups (P < or = 0.002). However, isoflurane/alfentanil nonmovers could not be distinguished from propofol/alfentanil movers (P < or = 0.180), suggesting a treatment group effect independent of response classification. Preincision hemodynamic variables did not predict patient movement in response to skin incision. These findings suggest the possibility that different anesthetics have different effects on BIS, and thus BIS may not be independent of the anesthetic. Interfrequency phase coupling, a nonlinear feature of the EEG which is measured with bispectral analysis, may contain clinically useful information for the assessment of anesthetic adequacy. In this study, BIS was a better predictor of patient response than other currently available variables including hemodynamic status.

Adult↗
PubMed1994

Returns to R&D on new drug introductions in the 1980s.

This study finds that the mean IRR for 1980-84 U.S. new drug introductions is 11.1%, and the mean NPV is 22 million (1990 dollars). The distribution of returns is highly skewed. The results are robust to plausible changes in the baseline assumptions. Our work is also compared with a 1993 study by the OTA. Despite some important differences in assumptions, both studies imply that returns for the average NCE are within one percentage point of the industry's cost of capital. This is much less than what is typically observed in analyses based on accounting data.

Commerce↗
PubMed1992

Factors influencing epidural catheter migration.

The incidence and amount of migration of epidural catheters was investigated in a prospective randomised study of 153 women who required analgesia in labour. Inward or outward migration occurred in 36% of patients. Inward migration by 1-3 cm occurred in 21 (13.7%) patients and outward migration by 1 cm or more occurred in 34 (22.2%); three (2%) catheters migrated out through the skin. There were significant positive correlations between outward migration and weight, body mass index, and depth of the epidural space. There was no relationship between migration and height, age, intervertebral space used or duration of catheterisation. Problems with epidural block were no more likely in patients in whom migration of 1 cm or more occurred compared with those in whom migration was limited to a maximum of +/- 0.5 cm. However, the pattern of problems was different. All cases of failed epidural block occurred in patients whose epidural catheter migrated outward by 2.5 cm or more. Unilateral blockade was not more likely if migration of 1 cm or more occurred.

Adhesives↗