Dextrose 5% in water: fluid medium for maintaining electrical stimulation of peripheral nerves during stimulating catheter placement

It is well documented that a higher electrical current is required to elicit a motor response following a normal saline (NS) injection during the placement of stimulating catheters for peripheral nerve block. We present three cases of continuous brachial plexus catheter placement in which Dextrose 5% in water (D5W) was used to dilate the perineural space instead of NS. Three brachial plexus blocks (two interscalene and one axillary) were performed in three different patients for pain relief. In each case, an insulated needle was advanced towards the brachial plexus. A corresponding motor response was elicited with a current less than 0.5 mA after needle repositioning. A stimulating catheter was advanced with ease after 3–5 ml of D5W was injected to dilate the perineural space. A corresponding motor response was maintained when the current applied to the stimulating catheter was less than 0.5 mA. Local anesthetic was then injected and the motor response immediately ceased. All blocks were successful and provided excellent pain relief with the continuous infusion of local anesthetics.     

Medical graduates of the National University of Ireland in 1978: who and where are they?

To inform debate on medical manpower planning and aspects of medical education, we gathered data on graduates of three Irish medical schools in 1978. Twenty six years later, four of the 236 graduates had died and seven were untraceable. All but one of the remainder were in clinical practice and in a wide range of disciplines. A third were overseas. The implications of these findings are briefly discussed.     

The effects of low-intensity ultrasound on medial collateral ligament healing in the rabbit model

BACKGROUND: Ruptured medial collateral ligaments are capable of healing over time, but biomechanical and biochemical properties remain inferior to normal tissue. Low-intensity ultrasound may improve healing. HYPOTHESIS: Medial collateral ligaments treated with ultrasound will demonstrate superior healing. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one late-adolescent male rabbits underwent bilateral ligament transection. One ligament from each rabbit received ultrasound treatment every other day for 6 total treatments. Contralateral ligaments received sham treatments. After 3 or 6 weeks, ligaments were evaluated biomechanically and assayed for collagen concentration and the relative proportions of types I and III collagen. RESULTS: Areas of sonicated specimens were significantly larger (10.6% +/- 4.90%) at 6 weeks. Ultimate load (39.5% +/- 17.0%), ultimate displacement (24.5% +/- 8.0%), and energy absorption (69.1% +/- 22.0%) were significantly higher for sonicated specimens at 6 weeks. No significant biomechanical differences were observed at 3 weeks. The relative proportion of type I collagen was significantly higher in sonicated ligaments at 3 weeks (8.61% +/- 4.0%) and 6 weeks (6.91% +/- 3.0%). No significant differences in collagen concentration were observed at either 3 or 6 weeks. CONCLUSION: Subtle improvement with ultrasound treatment may be apparent by 3 weeks after injury, suggested by increased proportion of type I collagen. Ultrasound appears to improve some structural properties and to modestly increase scar cross-sectional area and type I collagen present at 6 weeks after injury in this model. CLINICAL RELEVANCE: Ultrasound treatments after ligament injury may facilitate earlier return to activities and decrease risk of reinjury.     

The threshold current in the intrathecal space to elicit motor response is lower and does not overlap that in the epidural space: a porcine model

Purpose

Using electrical epidural stimulation, a current of 1 to 10 mA is required to confirm the presence of the tip of an epidural catheter in the epidural space. The purpose of this study was to examine the hypothesis that the threshold current required to elicit a motor response in the intrathecal space is significantly lower than that in the epidural space in a porcine model.

Methods

Four 20-kg pigs were used in this experiment. Eighteen gauge, insulated, Tuohy needles were advanced into the epidural space using the loss of resistance technique at five different spinal levels in each pig. When the epidural space was entered, an electrical current was applied to the needle and increased progressively until a motor response was elicited. The needle was then further advanced until cerebrospinal fluid (CSF) was observed or until the needle had been advanced a maximum of 1 cm. At this point, the current was reapplied and increased until motor activity was evident.

Results

A total of 20 needles were inserted in four pigs. The current required to produce a motor response in the epidural space was 3.45 ± 0.73 mA (mean ± SD). The current required to produce a motor response in the intrathecal space (entry confirmed by the presence of CSF) was 0.38 ± 0.19 mA (mean ± SD). Two needles were advanced 1 cm without obtaining CSF but the current thresholds were similar to those obtained when CSF was evident (0.4 mA and 0.3 mA, respectively).

Conclusion

The threshold current of an insulated needle required to elicit a motor response in the intrathecal space, was significantly (P < 0.01) lower than that in the epidural space in a porcine model.