Ketamine has been used for many years for sedating possums captured in the wild in New Zealand, but its recent reclassification as a Class III drug under the Misuse of Drugs Act (1975) has made its continued use impractical. Consequently, four other injectable anaesthetic compounds (Zoletil, xylazine-butorphanol, medetomidine-butorphanol and Fentazin) were evaluated as replacements for ketamine. Zoletil (a combination of zolazepam and tiletamine) was the only effective alternative. Brushtail possums (Trichosurus vulpecula) were sedated adequately for general procedures, such as fitting radio-collars, at an intramuscular dose of 5 mg kg−1. At this dose, possums were sedated on average in 3.6 min, and recovery took 65 min on average. Zoletil did not cause sudden arousal as seen with some other anaesthetics, but most possums showed involuntary chewing during recovery, and in some cases excessive salivation. In contrast, Fentazin and combinations of xylazine-butorphanol and medetomidine-butorphanol failed to produce sedation at doses known to be effective in other mammalian species. Zoletil proved similar to ketamine in both performance and cost, and is therefore recommended as a cost-effective anaesthetic and humane method for sedating possums captured in the wild.

Background: Successful local anaesthesia is of critical importance for the success of septoplasty, and many surgeons prefer to use cocaine for this purpose. The aim of this study was to evaluate the efficacy of cocaine 4 per cent solution, compared with tetracaine 2 per cent plus adrenaline, as a local anaesthetic for patients undergoing septoplasty.

Methods: From December 2002 to February 2005, a prospective, randomized, controlled trial was conducted. One hundred and eight patients underwent septoplasty under local anaesthesia. Patients were randomly classified into group A and group B, in which was used respectively cocaine 4 per cent solution and tetracaine 2 per cent solution plus adrenaline. A visual analogue scale was used to evaluate the severity of patients' pain during their procedure.

Results: Group B (tetracaine; mean rank=43.77) reported significantly less pain (p<0.001) compared with group A (cocaine; mean rank=65.23).

Conclusions: On the basis of these findings, we recommend tetracaine as the first choice anaesthetic for nasal septoplasty; the use of cocaine should be limited.

Two studies were performed to determine whether topical phenol is a safe and well tolerated local anaesthetic for grommet insertion. Study 1 was a retrospective examination of audiological outcomes and complications. Data were obtained regarding 71 procedures in 57 patients. One late infection and nine early extrusions were noted. No statistically significant changes between pre- and post-operative bone conduction thresholds were found. Study 2 was a prospective analysis of patients' perceptions of the procedure. Data from 17 patient questionnaires were analysed as follows: pain rating – not painful, three patients; slightly painful, 14 patients. Overall experience rating – pleasant, four patients; slightly unpleasant, 10; unpleasant, three. All patients stated that they would undergo the procedure again. In conclusion, we found no evidence of phenol-induced hearing loss. The complication rate was within normal limits and patients were satisfied with the procedure. Grommet insertion using phenol as a local anaesthetic is safe and acceptable to patients.

This aim of this study was to determine the effect of anaesthetic agents on stapedius reflex (SR) thresholds and transient evoked otoacoustic emissions (TEOAE). Fifty patients who were scheduled for operation and who had normal hearing were included in the study. All were given midazolam for premedication and propofol for induction. Anaesthesia was maintained in five different ways in each group of 10 patients. Groups I–IV received inhalational anaesthesia: group I received 70 per cent N2O plus 30 per cent O2, group II sevoflurane, group III desflurane and group IV halothane. Group V received total intravenous anaesthesia with propofol plus sufentanil. The SR and TEOAE of the patients were measured four times: on the day before surgery (first measurement), after premedication (second measurement), after induction of anaesthesia (third measurement) and during maintenance of anaesthesia (fourth measurement). Midazolam significantly increased ipsilateral and contralateral SR thresholds and decreased TEOAE wave reproducibility. Propofol significantly increased only the SR thresholds. The other anaesthetic agents significantly increased only the contralateral reflex thresholds. Of these, the highest increase was seen after sevoflurane and the lowest after halothane. The changes in TEOAE wave reproducibility due to anaesthetic agents used for maintenance were not significant. We concluded that midazolam premedication may affect audiological evaluation with SR and TEOAE tests, and sevoflurane should not be used when it is necessary to measure SR under general anaesthesia.

Summary

Background and objective: To compare the perioperative effects of melatonin and midazolam given in premedication, on sedation, orientation, anxiety scores and psychomotor performance.

Methods: Exogenous administration of melatonin not only facilitates the onset of sleep but also improves its quality. A prospective, randomized, double-blind, placebo-controlled study was performed in 66 patients undergoing laparoscopic cholecystectomy. Patients were given melatonin 5 mg, midazolam 15 mg or placebo, 90 min before anaesthesia, sublingually. Sedation, orientation and anxiety were quantified before; 10, 30, 60 and 90 min after premedication; and 15, 30, 60 and 90 min after admission to the recovery room. Neurocognitive performance was evaluated at these times, using the Trail Making A and B and Word Fluency tests. The differences between the groups were analysed by ANOVA. Two-way comparisons were performed by Scheffé analysis. Sedation and amnesia were analysed by the χ2 test.

Results: Patients who received premedication with either melatonin or midazolam had a significant increase in sedation and decrease in anxiety before operation compared with controls. After operation, there was no difference in sedation scores of all groups. Whereas, 30, 60 and 90 min after premedication the melatonin and midazolam groups exhibited a significantly poorer performance in Trail Making A and B tests compared with placebo, there were no significant differences among the groups in terms of neuropsychological performance after the operation. Amnesia was notable only in the midazolam group for one preoperative event.

Conclusion: Melatonin premedication was associated with preoperative anxiolysis and sedation without postoperative impairment of psychomotor performance.

Summary

Background and objective: Pain is often experienced when propofol is injected, and intravenous lidocaine is often effective in preventing such pain. We decided to determine whether metoprolol, given before the injection of propofol, is as effective as lidocaine in reducing the incidence and severity of the pain.

Methods: Ninety patients scheduled for elective surgery under general anaesthesia were randomly allocated to one of three groups to receive either metoprolol 2 mg, lidocaine 20 mg or saline 2 mL before any propofol was injected. Each patient was given one of these agents intravenously via a 20-G cannula on the dorsum of the hand whilst the venous drainage was occluded manually, at the middle of the forearm, for 45 s. After the occlusion was released, propofol 2.0–2.5 mg kg−1, at room temperature, was injected at 2 mL (20 mg) every 4 s. Pain was assessed verbally and scored as none (0), mild (1) or severe (2).

Results: The incidence of severe pain in the control group (56.7%) was significantly higher than in the metoprolol and lidocaine groups (16.6 and 10%, respectively). The number of patients who were free of pain was significantly higher in those who had been given either metoprolol or lidocaine.

Conclusions: Pretreatment with intravenous metoprolol was equally as effective as lidocaine in reducing the pain associated with propofol injection.

Summary

Ion channels regulate a diversity of physiological functions such as neuronal signalling, cardiac excitability and immune cell response. All of these systems may be affected during the conduct of general as well as local anaesthesia. Thus, the investigation of anaesthetic action on ion channels has become the focus of an increasing number of laboratory studies. Consequently, the concepts of ion channel physiology are becoming important for understanding the scientific and pharmacological basis of clinical anaesthesia. This brief guide is intended to help in understanding the increasing number of studies concerned with the effects of anaesthetic agents on ionic currents. The generation of ionic currents requires a complex molecular interplay of ions, ion channel proteins and lipid membranes. Anaesthetic agents frequently exhibit more than a single effect on ion channel function. Their effects can be described by quantifying the pharmacological alteration of ion channel activation, conductance and inactivation. Many physiological functions are directly influenced by ion channels. Pharmacological action on ion channels is thus fundamental to effects as well as side-effects of anaesthetic agents. The alteration of ion channel function by anaesthetic agents consequently determines their clinical effects.

Background and objective: A critical factor that delays patient discharge following day-surgery is severe postoperative pain and the requirement for strong analgesics. Laparoscopic sterilization is a day case procedure and is associated with additional postoperative pain compared with diagnostic laparoscopy. This pain, associated with application of Filshie clips, may be ischaemic or spasmodic in aetiology. Papaverine relaxes smooth muscle, and the aim of the study was to investigate if papaverine would be effective in improving postoperative pain if administered directly to the Fallopian tubes. Bupivacaine is used commonly in day-surgery and so we compared the effect of this local anaesthetic with saline placebo.

Methods: Sixty-six ASA I-II females undergoing laparoscopic sterilization were entered into the prospective, randomized, double-blind, placebo-controlled clinical trial. They received intrauterine papaverine (30 mg) or bupivacaine (0.375% 30 mL) or normal saline (30 mL) via the transcervical route before application of Filshie clips.

Results: There were no significant differences in the postoperative period between the three groups in the number of patients needing analgesia in the first 60 min postoperatively, the time to first analgesia, the rescue analgesic or antiemetic consumption, the incidence of postoperative nausea and vomiting, and the sedation and visual analogue pain scores.

Conclusions: From the data presented, we would not recommend routine transcervical administration of papaverine or bupivacaine for pain following laparoscopic sterilization.

Background and objective: Epidural analgesia with bupivacaine plus either sufentanil or fentanyl is widely used during labour, but it is not clear which opioid is to be preferred. The study compared these opioids at equianalgesic doses in terms of analgesia, onset time and side-effects.

Methods: Ninety females in active labour were entered into the randomized, double-blind trial. A test dose of bupivacaine was given into the epidural space. Parturients in Group S received sufentanil 8 mL as a bolus dose, followed by an infusion at a rate of 5 mL h−1 of a mixture containing sufentanil 1 µg mL−1 and bupivacaine 1 mg mL−1. Patients in Group F received fentanyl 8 mL as a bolus, followed by an infusion at 5 mL h−1 of a solution containing fentanyl 3.5 µg mL−1 and bupivacaine 1 mg mL−1. Additional boluses of 5 mL were of the relevant solution were given if necessary.

Results: In a ratio of 1.0 : 3.5 (sufentanil 1 µg versus fentanyl 3.5 µg), both groups reported the same analgesia with the same onset time. The onset time to obtain 50% of the initial visual analogue score was 10 and 11 min for Groups S and F, respectively. Mean visual analogue scores in Groups S and F respectively declined from 77 and 82 before epidural blockade, to 29 and 27 during the first stage of labour, and to 69 and 59 respectively during the second stage. Overall satisfaction among parturients was high (98 and 96%), particularly during the first stage (98 and 98%), and also to a large degree during the second stage of labour (74 and 79%). Furthermore, only a few extra bolus doses were required (mean 0.9 and 1.2, Groups S and F, respectively). All the females could stand on their own, and almost all (81% Group S; 79% Group F) could walk 20 m without help. There were no serious adverse effects. Moderate side-effects occurred equally often with the possible exception of less nausea and vomiting in the fentanyl group.

Conclusions: Epidural analgesia for ambulatory parturients with bupivacaine plus either sufentanil or fentanyl (ratio 1.0 : 3.5) provides good analgesia with a low frequency of modest side-effects. No clinical differences were found between the opioids.

Background and objective: The effects of altering the concentration of a local anaesthetic on the development of epidural anaesthesia in pregnant females are unclear. We compared the anaesthetic effects of a constant dose of two different concentrations of epidural lidocaine for Caesarean section.

Methods: After Institutional Review Board approval and informed consent, patients undergoing elective Caesarean section were randomized to receive either lidocaine 1% 30 mL (+epinephrine 5 μg mL−1) or lidocaine 2% 15 mL (+epinephrine 5 μg mL−1) (n = 20 each) for epidural anaesthesia at the L1-L2 interspace. The spread of the sensory block to pinprick and the degree of motor block (modified Bromage scale) were measured at 5, 10, 15, 20 and 30 min after injection.

Results: No significant differences in the progression of analgesia and motor block were observed at any time between 1 and 2% lidocaine. The maximum cephalad spread was observed 30 min after injection; the median was at T4 (range T3–T5) and at T4 (range T3–T6) for lidocaine 1 and 2%, respectively.

Conclusions: The same doses but different volumes of lidocaine 1 and 2% produced comparable anaesthetic effects in pregnant females. The effects of epidural anaesthesia depend primarily on the total dose of the local anaesthetic.

Background and objective: The study was designed to compare the costs of propofol versus sevoflurane for the maintenance of the hypnotic component of anaesthesia during general anaesthesia, guided by the bispectral index, for gynaecological laparoscopic surgery.

Methods: Forty ASA Grade I—II female patients scheduled for gynaecological laparoscopy were randomly allocated to two groups. All patients received a continuous infusion of remifentanil (0.25 µg kg−1 min−1) for 2 min. Then anaesthesia was induced with propofol 1% at 300 mL h−1 until loss of consciousness. To guide the bispectral index between 40 and 60, Group 1 patients received propofol 10 mg kg−1 h−1 initially, which was increased or decreased by 2 mg kg−1 h−1 steps; Group 2 patients received sevoflurane, initially set at 2 vol.% and adjusted with steps of 0.2–0.4%. The time and quality of anaesthesia and recovery were assessed in two postoperative standardized interviews.

Results: Patient characteristics, the propofol induction dose, the bispectral index and the haemodynamic profiles during induction of anaesthesia, and its duration, were similar between the groups. In Group 1, 7.55 ± 1.75 mg kg−1 h−1 propofol and in Group 2, 0.20 ± 0.09 mL kg−1 h−1 liquid sevoflurane were used for maintenance. The cost for maintenance, including wasted drugs, was higher when using propofol (€25.14 ± 10.69) than sevoflurane (€12.80 ± 2.67). Postoperatively, recovery profiles tended to be better with propofol; however, the day after discharge no differences were found.

Conclusions: When applying the bispectral index to guide the administration of hypnotic anaesthetic drugs, propofol-based maintenance of anaesthesia was associated with the highest cost. A trend towards a better recovery profile was obtained with propofol. However, on the day after discharge, no differences in quality were observed.

Background and objective: Thiopental prolongs the QT interval more than propofol, and the two induction agents were compared in patients with subarachnoid haemorrhage predisposed to electrocardiographic abnormalities and cardiac dysrhythmias.

Methods: Twenty-nine patients were studied randomly. Anaesthesia was induced with either thiopental or propofol and fentanyl; vecuronium was used as a neuromuscular blocking agent. The electrocardiogram and arterial blood pressure were monitored from before the induction of anaesthesia to 2 min after endotracheal intubation.

Results: The median QT interval was at baseline 423 ms in the thiopental group and at 432 ms in the propofol group, and it increased in the thiopental group to 446 ms and decreased in the propofol group to 425 ms (P < 0.01 between groups). After induction and endotracheal intubation, the number of patients with increased QT dispersion was greater in the propofol group (P < 0.05). The incidence of cardiac dysrhythmias was similar in the study groups.

Conclusions: Thiopental and propofol are equally suitable for the induction of anaesthesia in patients with subarachnoid haemorrhage.

Background and objective: We assessed the analgesic efficacy of postoperative epidural infusions of ropivacaine 0.1 and 0.2% combined with sufentanil 1 μg mL−1 in a prospective, randomized, double-blinded study.

Methods: Twenty-two ASA I—III patients undergoing elective total-knee replacement were included. Lumbar epidural blockade using ropivacaine 0.75% was combined with either propofol sedation or general anaesthesia for surgery. After surgery, the epidural infusion was commenced. Eleven patients in each group received either an epidural infusion of ropivacaine 0.1% with 1 μg mL−1 sufentanil (Group 1) or ropivacaine 0.2% with 1 μg mL−1 sufentanil (Group 2) at a rate of 5–9 mL h−1. All patients had access to intravenous pirinatrimide (piritramide) via a patient-controlled analgesia (PCA) device.

Results: Motor block was negligible for the study duration in both groups. There was no significant difference with the 100 mm visual analogue scale (VAS) scores, with the consumption of rescue analgesia or with patient satisfaction. Patients in Group 1 experienced significantly less nausea (P < 0.05) than those in Group 2. Both treatment regimens provided effective postoperative analgesia with only a minimal use of supplemental opioid PCA.

Conclusions: We recommend the use of ropivacaine 0.1% with 1 μg mL−1 sufentanil for postoperative analgesia after total knee replacement as it provides efficient pain relief with no motor block of the lower limbs. In addition, compared with 0.2% ropivacaine with sufentanil, the mixture reduces local anaesthetic consumption without compromise in patient satisfaction or VAS scores. Patients even experience less nausea.

Background and objective: Isoflurane is a chiral, volatile anaesthetic with low metabolic rate (0.17%) that is routinely administered in its racemic form. Knowledge about the distribution of the enantiomers in human beings may give some important information about the understanding of the mechanisms of volatile anaesthetics.

Methods: Blood samples were drawn immediately after tracheal extubation and daily up to 8 days postoperatively from patients undergoing general anaesthesia with isoflurane racemate. The enantiomer enrichment of isoflurane was determined by headspace gas chromatography-mass spectrometry.

Results: At all time points, there was a statistically significant accumulation of the S(+) enantiomer in blood, especially at days 2 (52.01%) and 7 (52.1%). Separate analysis of obese patients or in a small group of patients with co-existing lung disease did not show any difference to the total population. In addition, duration of anaesthesia did not influence the enantiomer concentrations.

Conclusions: We suggest that a slower association and dissociation rate is responsible for the S(+) enrichment.

Background and objective: A new posterior approach to the sciatic nerve in the subgluteal region was developed. We describe our clinical experiences on 135 consecutive patients.

Methods: All blocks were performed with a nerve stimulator (stimulation frequency 2 Hz; intensity from 1 reduced to ≤0.5 mA before application). A line was drawn from the greater trochanter to the ischial tuberosity of the femur; then, from the mid-point of this line, a second line was drawn perpendicularly and extended caudally for 4 cm: the end of this line represented the entry point of the needle. Sciatic stimulation was elicited at ≤0.5 mA; then ropivacaine 0.75% 20 mL was injected. An independent observer recorded the time from needle insertion to successful sciatic nerve stimulation (performance time), the depth of appropriate sciatic stimulation and the number of needle redirections, as well as the quality of nerve block, the discomfort during the procedure and patient acceptance.

Results: The performance time was 41 ± 25 s (mean ± SD) and the mean (SD) depth at which the sciatic nerve stimulation was found was 45 ± 10 mm. The median (range) number of needle redirections required to find the proper sciatic stimulation was 2 (1–5). The tibial response was observed in 77 patients (57%), while the common peroneal response was observed in 58 patients (43%). The degree of discomfort reported was very low and only 16 patients (12%) reported severe pain during placement of the block. The onset time (mean ± SD) of sensory and motor block was 7 ± 4 and 17 ± 13 min respectively, and the surgical procedure was completed with only the peripheral nerve block in 127 patients (94%). The same anaesthesia procedure was acceptable by 127 patients (94%) and only eight patients (6%) would prefer a different anaesthesia technique in the future.

Conclusions: The study demonstrated that the sciatic nerve can be easily blocked using this new posterior subgluteal approach, suggesting that it represents a safe and effective alternative to block the sciatic nerve at a proximal level, with the potential for reducing the discomfort experienced by the patient during block placement.

Background and objective: The effect of anaesthesia and surgery on gastric emptying is not constant, and this has not been previously studied in patients undergoing thoracotomy for lung resection with a bupivacaine-fentanyl epidural infusion for analgesia. There are important implications in this group of patients with regards to the recommencement of important oral medication as well as the risks of aspiration of gastric contents. The study examined gastric emptying in these patients until the second postoperative day.

Methods: In a prospective repeated measures study, the effect of fentanyl-bupivacaine epidural analgesia at the mid-thoracic level on gastric emptying was assessed in 11 patients undergoing thoracotomy for lung resection. Gastric emptying was measured using a paracetamol absorption technique. Patients acted as their preoperative controls and were assessed 4 h postoperatively and on the second postoperative day.

Results: The mean (SEM) maximum plasma paracetamol concentration was 204.6 (20.4) μmol L−1 before operation, 61 (9.5) μmol L−1 4 h postoperatively and 114.3 (22.6) μmol L−l on the second postoperative day. Mean (SEM) paracetamol absorption at 120 min was 15 638 (1441) μmol min L−l preoperatively, 5731 (821) μmol min L−l4 h postoperatively and 9325 (1759) μmol min L−l on the second postoperative day. Postoperative values were significantly (P < 0.005) less than the preoperative values.

Conclusions: After thoracotomy, gastric emptying was delayed until at least the second postoperative day in patients receiving mid-thoracic fentanyl-bupivacaine epidural analgesia.

Background and objective: Similar doses of ketamine are employed in regional and general anaesthesia. In contrast to commonly used local anaesthetic agents, accidental systemic application of local anaesthetic doses of ketamine will not result in seizure, dysrhythmia or cardiovascular depression. However, there is some doubt about the quality of regional analgesia induced by ketamine. As human sodium channels constitute an important molecular target of local anaesthetics, the study was designed to establish concentration-dependent effects of ketamine on conductance, steady-state activation and steady-state inactivation of human neuronal sodium channels. This information — that has, so far, not been published — will help to characterize further local anaesthetic properties of ketamine.

Methods: Whole-cell patch-clamp recordings were made of sodium channels natively expressed in human neuroblastoma SH-SY5Y cells.

Results: The sodium channels activated at a threshold of −60 mV and exhibited a maximal peak current at −10 mV. The voltage of half-maximal activation was −20 mV. The Na+ currents depended on the prepulse potential. The voltage of half-maximal inactivation was —80 mV. Ketamine inhibited the sodium conductance in a concentration-dependent manner (IC50 = 1140 µmol). A concentration-dependent hyperpolarizing shift of both steady-state activation and steady-state inactivation accounted for at most 5 mV.

Conclusions: The effects of ketamine on these human ion channels occur at clinical concentrations. They are consistent with the local anaesthetic action of ketamine. Whether ketamine helps to decrease the incidence of severe side-effects during regional anaesthesia needs to be addressed in further clinical studies.