A quantitative analysis of variability in brachial plexus anatomy.

The aim of this study was to quantify the lengths of nerve segments within the brachial plexus. Twenty cadavers were dissected bilaterally, giving a total of 40 brachial plexuses for measurement. Individual lengths of plexus segments were measured and recorded, and means and standard deviations were calculated for all data. Differences between the means were statistically evaluated using the Student's t-test. Only 3 of 16 segments were found to be longer in women on average, which included the anterior division of the superior trunk, the anterior division of the middle trunk and the posterior division of the inferior trunk. All three cords (medial, lateral, and posterior) were found to be significantly different between genders, the longer segments being in males. Significant bilateral differences were also observed when right and left brachial plexuses from each cadaver were compared. Extra lateral heads (ELHs) to the median nerve were found in 50% of brachial plexuses, the anatomy of which varied bilaterally as well as between genders. Awareness of this variability is important both to anatomists and to clinicians who operate on and around the brachial plexus.

Stability of meperidine in an implantable infusion pump using capillary gas chromatography-mass spectrometry and a deuterated internal standard.

A capillary gas chromatographic-mass spectrometric (GC MS) method is described for the analysis of meperidine using 3,3,5,5-[2H4]-meperidine as an internal standard. Chromatography was performed on a (5% phenyl) methylpolysiloxane column (30 m x 0.32 mm I.D., 0.25 microm film thickness) operated at 195 degrees C; helium carrier gas-50 cm/s(-1), tR = 2.3 min. Ionization was by electron impact (EI) and detection by selected ion monitoring of the molecular ions. The method provided high response linearity (mean r = 0.9982) and precision (< 6.5% C.V.). Application of this method to a pilot study of aqueous meperidine x HCl (10 mg/ml(-1)) stability in a surgically implantable infusion pump at 37 degrees C for 90 days revealed no demonstrable drug degradation.