A clearly visible endoscopic instrument shaft on the monitor facilitates hand-eye coordination.

BACKGROUND: Passing an instrument through a small incision alters the kinematics of the instrument, thus hampering hand-eye coordination. Nevertheless, the incision provides a stable, nearly invariant, point of rotation for instrument movements. Therefore, we set out to evaluate the effects of the altered kinematics on hand-eye coordination. In addition, we assessed the hypothesis that the hand-eye coordination of laparoscopic surgeons incorporates the incision as a point of reference. METHODS: Eight surgeons with experience in laparoscopy repeatedly performed a positioning task on a two-dimensional endoscopic manipulation simulator. Task time was measured. In the first experiment, normal endoscopic manipulation was compared to a condition in which the kinematic effects of the incision were compensated for. In the second experiment, the instrument shaft on the monitor was not visible during half of the trials, so that all visual information about the location of the incision was obscured. RESULTS: Task performance improved significantly when the kinematic effects of the incision were compensated for (p = 0.001). Task performance improved when the instrument shaft was clearly visible on the monitor (p <0.05). CONCLUSIONS: Compensating for the kinematic effects introduced by the incision improves hand-eye coordination. The results of this study indicate that the incision provides a point of reference for hand-eye coordination during endoscopic manipulation.

Biotransformation of 1,2-dibromopropane in rats into four mercapturic acid derivatives.

1,2-Dibromopropane was administered orally in doses of 50-350 mg/kg to male Wistar rats. Four mercapturic acids were identified in urine by GC/MS, viz. N-acetyl-S-(2-oxopropyl)-L-cysteine (I), N-acetyl-S-(2-hydroxypropyl)-L-cysteine (II), N-acetyl-S-(1-carboxyethyl)-L-cysteine (III), and N-acetyl-S-(2-bromo-2-propenyl)-L-cysteine (IV). Mercapturic acid IV was a minor metabolite which could only be measured at doses of 200 mg/kg or higher. In 24 hr, urinary excretion of mercapturic acids amounted to about 36% of the dose (11% I, 21% II, 4% III, 0.2% IV). No dose dependency was found up to the highest dose. A unified scheme is proposed for the metabolism of 1,2-dibromopropane in the rat, which accounts for the identified mercapturic acids. The role of direct glutathione conjugation in the route leading to the major metabolite II, presumably involving thiiranium ion formation, is discussed. This route probably is biologically not very important because of the absence of detectable activity of 1,2-dibromopropane toward glutathione S-transferases in vitro, the very low mutagenicity of 1,2-dibromopropane, and the high mutagenic activity of N-acetyl-S-(2-bromopropyl)-L-cysteine methyl ester which was studied as a model compound for direct conjugation.