Dynamic Response and Residual Helmet Liner Crush Using Cadaver Heads and Standard Headforms.

Biomechanical headforms are used for helmet certification testing and reconstructing helmeted head impacts; however, their biofidelity and direct applicability to human head and helmet responses remain unclear. Dynamic responses of cadaver heads and three headforms and residual foam liner deformations were compared during motorcycle helmet impacts. Instrumented, helmeted heads/headforms were dropped onto the forehead region against an instrumented flat anvil at 75, 150, and 195 J. Helmets were CT scanned to quantify maximum liner crush depth and crush volume. General linear models were used to quantify the effect of head type and impact energy on linear acceleration, head injury criterion (HIC), force, maximum liner crush depth, and liner crush volume and regression models were used to quantify the relationship between acceleration and both maximum crush depth and crush volume. The cadaver heads generated larger peak accelerations than all three headforms, larger HICs than the International Organization for Standardization (ISO), larger forces than the Hybrid III and ISO, larger maximum crush depth than the ISO, and larger crush volumes than the DOT. These significant differences between the cadaver heads and headforms need to be accounted for when attempting to estimate an impact exposure using a helmet's residual crush depth or volume.

Spinal anaesthesia for elective surgery: a comparison of hyperbaric solutions of racemic bupivacaine, levobupivacaine, and ropivacaine.

BACKGROUND: The aim of this study was to compare the clinical effects of 'hyperbaric' bupivacaine for spinal anaesthesia with those of similar preparations of levobupivacaine and ropivacaine. METHODS: Sixty ASA grade I-II patients undergoing elective surgery under spinal anaesthesia were randomized to receive 3 ml of bupivacaine, levobupivacaine, or ropivacaine, each at 5 mg ml(-1) and made hyperbaric by the addition of glucose 30 mg ml(-1). A standard protocol was followed after which a blinded observer assessed the sensory and motor blocks. The level and duration of sensory (pinprick) block, intensity and duration of motor block, and time to mobilize and to micturate were also recorded. RESULTS: One patient (ropivacaine group) required general anaesthesia because of technical failure, but all the other blocks were adequate. There were no significant differences between the groups with regard to the mean time to onset of sensory block at T10, the extent of spread, or mean time to maximum spread. Regression of sensory block in the ropivacaine group was more rapid as demonstrated by duration at T10 (P<0.0167) and total duration of sensory block (P<0.0167). Patients in the ropivacaine group had more rapid recovery from motor block (P<0.0167) and shorter times to independent mobilization (P<0.0167). There were no significant differences between the bupivacaine and the levobupivacaine groups. CONCLUSIONS: 'Hyperbaric' ropivacaine provides reliable spinal anaesthesia of shorter duration than bupivacaine or levobupivacaine, both of which are clinically indistinguishable. The recovery profile of ropivacaine may be useful where prompt mobilization is required.

Comparison of plain and hyperbaric solutions of ropivacaine for spinal anaesthesia.

BACKGROUND: Preliminary work has shown that ropivacaine provides spinal anaesthesia of shorter duration than bupivacaine, and may be of particular use in the day-case setting. However, there are few data comparing the actions of plain and hyperbaric solutions of this drug. METHODS: Forty ASA grade I-II patients undergoing elective perineal surgery under spinal anaesthesia were randomized to receive 3 ml ropivacaine 5 mg ml(-1), either in plain solution or with glucose 50 mg ml(-1). The extent and duration of sensory and motor block, pulse rate, blood pressure, and time to mobilization were recorded. RESULTS: Two patients (one per group) were withdrawn because of total block failure. There were significant differences in median time to onset of sensory block at T10 (plain 10 min; hyperbaric 5 min; P<0.01), median maximum extent (plain T8; hyperbaric T4; P<0.05), and median duration of sensory block at T10 (plain 25 min; hyperbaric 115 min; P<0.001). However, median times to complete regression of both sensory (270 vs 240 min; P<0.05) and motor (180 vs 120 min; P<0.001) block were longer in the plain group. Patients therefore mobilized sooner in the hyperbaric group (218 [n=16] vs 286 min [n=17]; P<0.01). All the hyperbaric blocks were adequate for surgery, but three patients receiving plain ropivacaine required general anaesthesia. CONCLUSION: Addition of glucose 50 mg ml(-1) to ropivacaine 5 mg ml(-1) increases the speed of onset, block reliability, duration of useful block for perineal surgery, and speed of recovery. Plain solutions are less reliable for surgery above a dermatomal level of L1.