Ultrasound controlled nerve stimulation in the elbow region: high currents and short distances needed to obtain motor responses.

BACKGROUND: Electrical nerve stimulation is commonly used to perform peripheral nerve blocks. The purpose of this study was to investigate the relation between stimulating currents and the distance between the needle-tip and stimulated nerves. METHODS: In 18 volunteers the radial and ulnar nerves were stimulated in the elbow region from opposite directions. Needle-to-nerve distances were measured by high-frequency ultrasound when motor responses to electrical stimulation were elicited with currents of 5, 2, 1 and 0.5 mA and impulse widths of 0.1 ms. Additionally, current thresholds for nerve stimulation were identified when the needle-tip was in contact with the nerve. RESULTS: The ulnar nerves responded to electrical stimulation from a significantly greater distance than the radial nerves. Threshold levels at needle-to-nerve contact ranged from 0.4 to 4.5 mA for the radial nerve and from 0.32 to 2.0 mA for the ulnar nerve. They were significantly lower for the ulnar nerve than for the radial nerve. Currents required to obtain neuromuscular responses often exceeded the recommended current levels for nerve stimulation. CONCLUSIONS: Our results show significant differences in the ease of stimulation between the radial and ulnar nerves. High current thresholds and short nerve-to-needle distances were often needed to obtain neuromuscular responses in two nerves in the elbow region.

Composite to tilted vortex lattice transition in Bi2Sr2CaCu2O8+delta in oblique fields.

Precision measurements of the vortex phase diagram in single crystals of the layered superconductor Bi2Sr2CaCu2O8+delta in oblique magnetic fields confirm the existence of a second phase transition, in addition to the usual first-order vortex-lattice melting line Hm(T). The transition has a strong first-order character, is accompanied by strong hysteresis, and intersects the melting line in a tricritical point (Hm perpendicular, Hcr parallel). Its field dependence and the changing character of the melting line at the tricritical point strongly suggest that the ground state for magnetic fields closely aligned with the superconducting layers is a lattice of uniformly tilted vortex lines.

Double-blind comparison of the variability in spontaneous recovery of cisatracurium- and vecuronium-induced neuromuscular block in adult and elderly patients.

BACKGROUND: This study was designed to compare variability in the offset of two neuromuscular blocking agents with different elimination pathways. METHODS: The spontaneous recovery profiles of cisatracurium and vecuronium were compared in adult (18-64 years) and elderly (> or =65 years) patients receiving N2O/O2/fentanyl/propofol anaesthesia. Patients were randomised to receive an initial bolus dose and maintenance doses of 3xED95, respectively, 0.6xED95 for cisatracurium (0.15 and 0.03 mg.kg-1) or 2xED95, respectively, and 0.4xED95 for vecuronium (0.1 and 0.02 mg.kg(-1)), as recommended in their prescribing information. Administration of the study drugs was double-blinded, and neuromuscular transmission was monitored using mechanomyography of the evoked response of the adductor pollicis, following ulnar nerve stimulation. RESULTS: The clinically effective duration (minutes) of the initial bolus dose, defined as the mean time to 25% T1 recovery (+/-SD), for the adult and elderly patients was 53.5+/-9.8 and 57.3+/-11.5 for cisatracurium, respectively, and 34.1+/-9.0 and 47.5+/-14.4 for vecuronium, respectively. The duration of spontaneous sufficient recovery (SSR), defined as the mean (+/-SD) time interval in minutes from 25% T1 recovery to a T4:T1 ratio > or =0.8 after the last bolus dose, for the adult, respectively, elderly patients was 28.3+/-8.0 and 31.7+/-10.0 for cisatracurium and 38.5+/-13.2 and 60.3+/-26.1 for vecuronium. CONCLUSION: Whereas both the clinically effective duration and the duration of SSR are comparable between the adult and the elderly patients receiving cisatracurium, they differ substantially between these two age groups for vecuronium. Furthermore, the variability in offset is significantly lower in patients receiving cisatracurium, especially in the elderly, which may be of particular clinical interest.

Vortex collisions: crossing or recombination?

We investigate the collision of two vortex lines moving with viscous dynamics and driven towards each other by an applied current. Using London theory in the approach phase we observe a nontrivial vortex conformation producing antiparallel segments; their attractive interaction triggers a violent collision. The collision region is analyzed using the time-dependent Ginzburg-Landau equation. While we find that vortices will always recombine through the exchange of segments, a crossing channel appears naturally through a double collision process.

Additive analgesic effect of codeine and paracetamol can be detected in strong, but not moderate, pain after Caesarean section. Baseline pain-intensity is a determinant of assay-sensitivity in a postoperative analgesic trial.

BACKGROUND: A randomized, double-blind, placebo-controlled single oral dose study was done in order to examine whether codeine has an additive analgesic effect to that of paracetamol for moderate and strong postoperative pain after abdominal surgery. The maximum recommended single dose of paracetamol 1000 mg (Paracet) was compared with a combination of a submaximal dose of paracetamol 800 mg plus codeine 60 mg (Paralgin forte) and placebo for pain relief after Caesarean section in 125 patients. METHODS: Visual analogue pain intensity score (VAS 0-100 mm) and categorical pain relief score were recorded for 6 hours after the study drug intake. The main efficacy variables analyzed were: pain intensity difference and summed pain intensity differences during the first 3 and 6 h after study drug intake, total pain relief during the first 3 and 6 h, global evaluation score at the end of the observation period, and time to rescue analgesic. RESULTS: Because of protocol violations, 17 patients were excluded from the analysis of effects. Among the 108 patients included in the analysis of analgesic effect, 49 patients had moderate baseline pain (VAS between 40 and 60 mm on a 100 mm scale), and 59 patients had strong baseline pain (VAS more than 60 mm). In patients with strong baseline pain, statistically highly significant differences were documented in efficacy variables between the active drugs and placebo and between the two active drugs. However, in patients with moderate baseline pain, no differences were found between the study drugs in any of the analgesic efficacy variables. CONCLUSION: This study thus confirms that codeine has additive analgesic effect to paracetamol in pain after surgery. Our results show the importance of initial pain intensity in postoperative assessment of analgesic drugs. Assay-sensitivity and test power are increased by selecting patients with sufficiently high initial pain intensity and by comparing groups of patients with identical surgery and similar demographic variables.

Antagonism of flunitrazepam-induced sedative effects by flumazenil in patients after surgery under general anaesthesia. A double-blind placebo-controlled investigation of efficacy and safety.

This study aimed to assess the efficacy and safety of flumazenil and a placebo in reversing the residual effects of flunitrazepam used to induce anaesthesia for elective laparoscopy in 49 female patients aged 16 to 52 years. In contrast to the placebo, flumazenil gave reductions in amnesia, sedation score, mood rating for mental sedation and physical sedation, and time taken to complete a psychomotor performance test which lasted throughout the study. There were no significant changes in pulse rate, respiration rate or blood pressure, and no unwanted effects were attributed to flumazenil.

Antagonism of diazepam-induced sedative effects by Ro15-1788 in patients after surgery under lumbar epidural block. A double-blind placebo-controlled investigation of efficacy and safety.

The aim of this study was to assess the efficacy of Ro15-1788 and a placebo in reversing diazepam-induced effects after surgery under epidural block, and to evaluate the local tolerance and general safety of Ro15-1788. Fifty-seven patients were sedated with diazepam for surgery under epidural anaesthesia. Antagonism of diazepam-induced effects by Ro15-1788 was investigated postoperatively in a double-blind placebo-controlled trial. The patient's subjective assessment of mood rating, an objective test of performance, a test for amnesia, and vital signs were recorded for up to 300 min after administration of the trial drug. No significant differences between the two groups were observed for mood rating, amnesia, or vital signs. The Ro15-1788 group showed a significant improvement in the performance test up to 120 min after administration of the drug. There was no evidence of reaction at the injection site.

Effect of chronic bupivacaine infusion on seizure threshold to bupivacaine.

Thirty rats were pretreated with a continuous infusion of bupivacaine or placebo. On the fourth day the acute seizure threshold to bupivacaine was determined for both groups. The seizure dose, blood and brain concentration of bupivacaine showed no difference between the groups. The tachyphylaxis seen clinically when bupivacaine is used for a regional nerve blockade does not seem to evolve for the CNS-effects.

Halothane-associated liver damage and renal failure in a young child.

A case of halothane-associated liver damage and renal failure is described in an 18-month-old girl after her third halothane anaesthetic. There had been two uneventful enflurane anaesthetics. The diagnosis was confirmed by detecting antibodies specific for halothane-associated liver failure using a recently developed enzyme-linked immunosorbent assay.

Atracurium compared with suxamethonium for outpatient laparoscopy.

I.v. atracurium 0.3 mg kg-1 and suxamethonium 1.6 mg kg-1 plus infusion were compared for use in outpatient laparoscopy. Thirty patients were randomly assigned to receive one of the two blocking drugs. Both drugs proved suitable for use in outpatient laparoscopy, but atracurium may have advantages if the operation proceeds directly to laparotomy.

Isoflurane v fentanyl for outpatient laparoscopy.

Isoflurane and fentanyl have been compared as anaesthetic agents for outpatient laparoscopy. In 50 female patients anaesthesia was induced with thiopentone and maintained with nitrous oxide 66% in oxygen combined with either isoflurane 1-2% or fentanyl 0.3 mg according to a randomized list. Suxamethonium was used to facilitate intubation and for further muscle relaxation. Immediate recovery from anaesthesia was assessed by eye opening and time before giving the date of birth. Additional observations made hourly for 4 h were: nausea or vomiting; clinical assessment of wakefulness; psychic or motor agitation; antiemetic or analgesic drugs given; reaction time; respiratory depression. Immediate recovery was more rapid in the fentanyl group (P less than 0.05). Reaction times in the isoflurane patients returned to control by 3 h, whereas the fentanyl patients were 10% slower than control at 4 h (P less than 0.05 at 2 h, 3 h, 4 h). Nausea and vomiting were more frequent in the fentanyl group, and four of the fentanyl patients required naloxone. Both anaesthetic techniques provided satisfactory operating conditions, but isoflurane appeared to provide a better recovery with less side effects than fentanyl.