Summary

Background and objective: Adenosine, by intravenous and intrathecal routes, is known to alleviate various types of pain. However, the role of intrathecal adenosine in providing postoperative analgesia has not been confirmed. The aim of the present study was to evaluate the efficacy of intrathecal adenosine for postoperative pain relief, and to determine its role for pre-emptive analgesia. Methods: Ninety ASA I and II females, undergoing elective abdominal hysterectomy, were randomly divided into three groups of 30 patients each. Patients in the ‘early adenosine’ group received intrathecal adenosine 1000 μg, 30 min before induction of anaesthesia. Patients in the ‘late adenosine’ group received the same dose before reversal of neuromuscular blockade. Control patients did not receive any test drug. A balanced general anaesthesia technique was used in all patients. Pain intensity scores using a visual analogue scale, sedation scores, time to first rescue analgesic and total morphine requirement were recorded. Results: There was no significant difference in pain intensity scores, sedation scores, total morphine requirements and time to first rescue analgesic among the three groups. Conclusion: Intrathecal adenosine 1000 μg is not effective as an analgesic for postoperative pain relief, and there is no pre-emptive effect.

Summary

Background and objective: Thiopental has been reported to reduce sympathetic tone, however, it is not clear whether change in heart rate variability is associated with depth of anaesthesia. The purpose of the present study was to evaluate changes in heart rate variability at different depths of hypnosis during induction of anaesthesia with thiopental. Methods: We studied 17 ASA I patients scheduled for minor surgery. The depth of hypnosis was monitored by the BIS. Spectral analysis of heart rate variability using a maximum entropy method resulted in a characteristic power spectrum with two main regions, a high frequency and a low frequency. Haemodynamics, entropy, low frequency, high frequency and low frequency/high frequency were monitored in an awake state and after the induction of anaesthesia. Results: Heart rate increased in a BIS-dependent manner, whereas blood pressure showed no significant changes during the study period. High frequency, entropy and low frequency decreased with a reduction in the BIS value. Low frequency/high frequency showed no significant change during the study period. Conclusions: Induction of anaesthesia with thiopental increased heart rate and decreased high frequency, entropy and low frequency in a BIS-dependent manner, indicating that thiopental reduces cardiac parasympathetic tone depending on the depth of hypnosis.

Summary

Background and objective: Combined (local and general) anaesthesia or Balanced (intravenous analgesics and inhalational hypnotics) anaesthesia are commonly used in paediatrics. The authors have investigated the influence of both types of anaesthesia on the requirements of sevoflurane to maintain an adequate level of hypnosis as measured by Bispectral index (at around 50) monitoring in paediatric orthopaedic patients. Methods: Twenty-six orthopaedic surgery patients aged 2–15 yr were randomized to receive, during general sevoflurane anaesthesia, 5 μg kg−1 of intravenous fentanyl (Balanced anaesthesia group) or 1 mL kg−1 of caudal-epidural bupivacaine 0.25% (Combined anaesthesia group). The end-tidal sevoflurane concentration was adjusted every 5 min in order to maintain Bispectral index values at around 50. Results: Patients showed very similar Bispectral index values (P > 0.05) in both the Combined and the Balanced groups before anaesthesia (96.7 ± 2.7 vs. 96.9 ± 1.8), after induction (48.5 ± 2.9 vs. 49.8 ± 3.6) and after administration of analgesia (50.9 ± 3.8 vs. 50.3 ± 4.3). The sevoflurane end-tidal concentration requirements were similar in both the Combined and Balanced groups before administration of analgesia (2.1 ± 0.2 vs. 2.1 ± 0.4, P = 0.9415), but lower end-tidal concentrations were required by the Combined group than by the Balanced group (0.81 ± 0.4 vs. 1.5 ± 0.5, P < 0.0001) in the first 20 min after administration of analgesia. Conclusion: Combined anaesthesia with epidural bupivacaine maintains the same Bispectral index values as Balanced anaesthesia during orthopaedic surgery in children without fentanyl and with a lower sevoflurane requirement.

Summary

Background: This study was designed to evaluate the feasibility of propofol infusion by a closed-loop system for the titration of anaesthetic induction guided by Bispectral Index. Methods: Forty patients were prospectively and randomly allocated into two groups: the target control infusion (TCI) group, where propofol titration was performed manually guided by the Bispectral Index using a commercial pharmacokinetic model (Diprifusor device) and the closed-loop group where titration was performed using a proportional differential algorithm. For both groups, the objective was to achieve a Bispectral Index of 50. Remifentanil TCI was infused at a target of 2 ng mL−1 and was maintained constant throughout the study. Feasibility of automatic induction was evaluated with performance error and haemodynamic data. Results: Bispectral Index overshoot (−9 ± 13% vs. −16 ± 20%, P = 0.035) and mean duration of induction (381 ± 106 s vs. 490 ± 131 s, P = 0.004) were lower in the closed-loop group than in the TCI group. Haemodynamic data were similar between groups with a similar use of ephedrine bolus. Conclusion: The system was able to allow induction clinically for all patients. Automated titration guided by Bispectral Index for propofol infusion was feasible without increase in haemodynamic adverse effects.

Summary

Background and objective: This study was designed to determine if subhypnotic propofol reduces postoperative behavioural disturbances in children undergoing sevoflurane induction compared with intravenous propofol induction for elective adenoidectomy and tonsillectomy. Methods: Following Ethics Committee approval and parental informed consent, ASA I–II, 120 children (2–10 yr) were recruited. Parents were not allowed to accompany their child. Unpremedicated children were randomly allocated to groups receiving inhalation induction with sevoflurane, 2–2.5 mg kg−1 intravenous propofol induction or inhalation induction with sevoflurane followed by subhypnotic dose of propofol (1 mg kg−1). Anaesthesia was maintained with 2–4% sevoflurane, O2 and N2O. Anxiety on arrival to operating theatre, at anaesthesia induction and 30 min after emergence was assessed. Parents completed a state–trait anxiety inventory test preoperatively and a post hospitalization behaviour questionnaire a week later to assess children's postoperative behavioural disturbances. Kruskal–Wallis test, Wilcoxon signed rank sum test, Bonferroni's test, Paired t-test, t-test, Pearson and Spearman's rank correlation test, χ2-test were used for statistical analysis. Results: The anxiety level at induction was high in all groups (P < 0.05). There was no difference between groups in respect to anxiety at other measurement times. A relation between preoperative anxiety level and postoperative behavioural disturbances was determined (P < 0.05). Some behavioural disturbances as nightmare/night fear and desire of sleeping with parents were rarely seen in intravenous propofol induction group (P < 0.05). Conclusion: Addition of subhypnotic dose of propofol to sevoflurane induction did not reduce the incidence of postoperative behavioural disturbances.

Summary

Background and objective: In small children, the placement of arterial catheters can be technically challenging for even the most experienced anaesthetist. We investigated whether ultrasound imaging would improve the success rate and reduce time demand and complications of radial artery cannulation. Method: In this prospective randomized study, we performed radial artery cannulation in 30 small children (age 40 ± 33 months) using two different techniques for localization of the vessel. In Group 1 (n = 15), the traditional palpation method was used, while in Group 2 (n = 15) cannulation was directed by vascular ultrasound imaging. In addition, we used ultrasound to determine the cross-sectional area of the radial artery with and without dorsiflexion. For statistical analysis, the non-parametric U-test for non-paired data and the Wilcoxon signed rank sum test for paired data were used. Differences were considered significant, when P < 0.05. Results: Ultrasound-guided puncture was successful in all children of Group 2 compared to only 12 of 15 (80%) children in Group 1. Fewer attempts with the imaging technique were required than with the traditional technique (20 vs. 34, P < 0.05). Dorsiflexion significantly reduced the mean cross-sectional area of the artery by 19%. Conclusion: The current pilot study suggests that ultrasound guidance is appropriate for radial artery catheter insertion, sharing many of the benefits of ultrasound-guided central vein catheter insertion.

Summary

Background and objective: To compare the anaesthetic characteristics in terms of onset and offset times of the sensory and motor blocks of prilocaine 1% and ropivacaine 0.75% alone and in different combinations when used for brachial plexus anaesthesia in axillary perivascular blocks. Methods: After informed consent 96 ASA I–III patients undergoing forearm or hand surgery participated in this prospective, randomized, double-blind study. Patients received either prilocaine 1% 40 mL (G1), prilocaine 1% 30 mL and ropivacaine 0.75% 10 mL (G2), prilocaine 1% 20 mL and ropivacaine 0.75% 20 mL (G3) or ropivacaine 0.75% 40 mL (G4) for axillary perivascular brachial plexus anaesthesia. Onset and duration of sensory and motor blocks in the distribution of the musculocutaneous, radial, median and ulnar nerves were assessed. Results: The onset time of the sensory and motor blocks of the whole brachial plexus differed only between patients in G4 with ropivacaine 0.75% 40 mL demonstrating a later motor onset in comparison to all other groups and a later sensory onset in comparison to G1 and G2 (P < 0.01). The addition of ropivacaine resulted in longer offset times of the sensory and motor blocks. The median offset time of the motor block was 179.5 min in G1, 262 min in G2, 389.5 min in G3 and 745 min in G4 (P < 0.01). The median offset time of the sensory block was 163.5 min in G1, 277 min in G2, 383.5 min in G3 and 784 min in G4 (P < 0.01). There was no difference in onset and offset times between sensory and motor blocks within the groups. Conclusions: For axillary perivascular brachial plexus block prilocaine 1% alone and in combination with ropivacaine 0.75% was similar in terms of onset of sensory and motor blocks but different in duration of sensory and motor blocks without a differential sensory and motor offset.

Summary

Background and objective: The low cardiovascular and neurological toxicity of levobupivacaine has led to its application as a local anaesthetic in a wide variety of specialist applications including peribulbar block for cataract surgery. The aim of this study was to evaluate the efficacy of levobupivacaine 0.5% and to compare block quality vs. ropivacaine 0.75% in peribulbar anaesthesia. Methods: We examined 208 patients subjected to cataract surgery by phacoemulsification who were randomized into two groups according to the anaesthetic used for peribulbar block, namely levobupivacaine 0.5% or ropivacaine 0.75%, both with the addition of hyaluronidase. Nerve block was carried out by injection of 6 mL of the anaesthetic mixture equally distributed between the inferotemporal and superonasal areas. The success of the block was evaluated by determining the time of motor and sensory onset, akinesia score, times of motor and sensory offset and satisfaction of the patient and surgeon after 24 h. Pre-block, post-block and postoperative intraocular pressure as well as the duration of surgical intervention was also determined. Results: With respect to ropivacaine, levobupivacaine showed a significant reduction (P < 0.001) in the average motor and sensory onset. Both the akinesia score (P < 0.01) and mean motor and sensory offset times were also higher (P < 0.001). Neither the average intervention times nor the satisfaction of the patient/surgeon showed any significant differences between the two groups. Conclusions: Levobupivacaine (0.5%) has better anaesthetic properties with respect to 0.75% ropivacaine and is well-suited for peribulbar block in cataract surgery.

Summary

Background and objective: Unilateral spinal anaesthesia is a useful anaesthesia technique in lower abdominal surgery, especially in an outpatient setting. Patient posture is pivotal in the achievement of unilateral anaesthesia. Nevertheless, no studies have elucidated the influence of patient posture during the anaesthetic injection on unilaterality. Thus, the aim was to compare the effect of patient posture, during the induction phase of spinal anaesthesia, on block characteristics. Methods: Eighty patients, ASA I–II, scheduled for unilateral hernioplasty were randomized into two groups. Anaesthesia was performed in lateral position in Group 1 (G1) with operative side down and in sitting position in Group 2 (G2) whose patients were then immediately turned on their lateral side. All patients were maintained for 20 min in lateral position with their operative side down. Hyperbaric bupivacaine 1% 10 mg were used. Results: Unilateral anaesthesia was seen in 80% (32/40) and 12.5% (5/40) of G1 and G2, respectively. The readiness for surgery was faster in G1 (P < 0.0001). The motor block in the non-operative side was stronger in G2 (P < 0.0001). The offset of sensory block was faster in G1 (P = 0.0001). The offset of motor block was slower in G1 (P = 0.0008). The time for voiding was shorter in G1, although not significant. Conclusions: Lateral posture during the induction of spinal anaesthesia is pivotal for a higher success of unilateral block, a fast readiness to surgery, and a fast recovery. Therefore, this technique can be considered feasible and time-saving for lower abdominal surgery.

Summary

Background and objective: Arterial grafts are prone to vasospasm. Opioid analgesics are commonly used in the perioperative course of cardiac surgical procedures. Therefore, we investigated the direct effects of morphine, meperidine, fentanyl and remifentanil on the human radial artery. Methods: Radial artery segments, obtained from 20 patients, were precontracted with phenylephrine. Using the organ bath technique, the endothelium-independent vasodilatation was tested in vitro by addition of cumulative concentrations of morphine, meperidine, fentanyl and remifentanil in separate organ baths, in the presence or absence of naloxone. Indomethacin and NG-nitro-l-arginine methyl ester was added to all organ bath in order to determine the effects of prostaglandins and nitric oxide, respectively. Results: Morphine (10−8–10−4mol L−1), meperidine (10−10–10−6mol L−1), fentanyl (10−10–10−6mol L−1) and remifentanil (10−8–10−4mol L−1) caused a concentration-dependent vasorelaxation in the human being artery rings. The relaxations in the presence of naloxane did not change. The maximal relaxant effects of meperidine and fentanyl were significantly greater than those of morphine and remifentanil (P < 0.05). Conclusions: These findings indicate that morphine, meperidine, fentanyl and remifentanil produce concentration-dependent and endothelium-independent relaxations in human being radial artery rings. Meperidine and fentanyl are more potent relaxant agents than morphine and remifentanil in the human being radial artery in vitro.

Summary

Background and objective: The present study was designed to compare cerebral oxygenation measured with near infrared spectroscopy and local brain tissue oxygen partial pressure, respectively, in pigs during cardiopulmonary resuscitation. Since tissue overlying the brain may have an impact on near infrared spectroscopy readings, we tested whether optode placement on intact skin or on the skull yielded comparable results. Methods: Twelve healthy pigs were anaesthetized and subjected to continuous haemodynamic, near infrared spectroscopy and brain tissue oxygen partial pressure monitoring. After 4 min of untreated ventricular fibrillation, cardiopulmonary resuscitation was started and arginine vasopressin was administered repeatedly three times. Near infrared spectroscopy values recorded were both the tissue oxygenation index and the tissue haemoglobin index as well as relative changes of chromophores (haemoglobin and cytochrome oxidase). Four animals served as control and were measured with both near infrared spectroscopy optodes mounted on the intact skin of the forehead, while in the remaining eight animals, one near infrared spectroscopy optode was implanted directly on the skull. Results: Near infrared spectroscopy readings at the skin or at the skull differed consistently throughout the study period. After arginine vasopressin administration, near infrared spectroscopy values at the different locations showed a transient dissociation. In contrast to near infrared spectroscopy measured on intact skin, near infrared spectroscopy readings obtained from skull showed a significant correlation to brain tissue oxygen partial pressure values (r = 0.67, P < 0.001). Conclusion: Near infrared spectroscopy readings obtained from skin and skull differed largely after vasopressor administration. Near infrared spectroscopy optode placement therefore may have an important influence on the tissue region investigated.

Summary

Background and objectives: The aim of this prospective, randomized, double-blind study was to determine the effects of adding two different target-controlled concentrations of remifentanil (1 and 3 ng mL−1) on the desflurane requirement for blunting sympathetic responses after surgical incision (minimum anaesthetic concentration (MACBAR)). Methods: 67 patients, aged 20–50 yr, ASA I, undergoing general anaesthesia for elective abdominal surgery were enrolled and randomly allocated to receive no remifentanil infusion (n = 21) or a target-controlled effect-site concentration of 1 ng mL−1 (n = 24) or 3 ng mL−1 remifentanil (n = 22). All patients were anaesthetized with propofol, cisatracurium and desflurane with a mixture of 60% nitrous oxide in oxygen. Sympathetic responses to surgical incision were determined after a 20-min period of stable end-tidal desflurane and target-controlled remifentanil concentrations. Predetermined end-tidal desflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential-allocation technique. Results: The MACBAR of desflurane was higher in the group receiving no remifentanil (6.25% [95% confidence interval: 5.9–6.5%]) as compared with patients of the groups receiving 1 ng mL−1 (2.7% [2.6–2.8%]; P < 0.001) and 3 ng mL−1 remifentanil (2% [1.9–2.2%]; P < 0.01). When considering a MAC value in this age population and the contribution of 60% nitrous oxide (0.55 MAC), the combined MACBAR values, expressed as multiples of the MAC, were 1.9, 0.8 and 0.6 MAC, in the three groups, respectively. Conclusion: A target-controlled concentration of 1 ng mL−1 remifentanil results in a 57% decrease in the MACBAR of desflurane combined with 60% nitrous oxide. Increasing the target concentration of remifentanil to 3 ng mL−1 produces a further 26% decrease in the MACBAR values of desflurane.

Summary

Background and objectives: The GlideScope® is a new video laryngoscope. The aim of our study was to assess its use compared to a Macintosh blade in airway scenarios on the Airman™ airway simulator. The scenarios were: ‘normal’ or resting state of the manikin, pharyngeal obstruction, cervical rigidity and tongue oedema. Methods: Thirty anaesthetists from the Christchurch Anaesthetic Department attempted to pass a bougie or stylet through the vocal cords of the manikin with a size 3 Macintosh blade, then the GlideScope. View at laryngoscopy, ease of ‘intubation’ and whether they thought the GlideScope would be useful in clinical practice were recorded. Results: Forty three percent (P = 0.02) found an improved view with the GlideScope in the pharyngeal obstruction scenario. In the other scenarios there was no significant difference in view. Reportage of ease of intubation showed no statistical difference in any scenarios. However, 93% of anaesthetists considered having the GlideScope would be useful if faced clinically with one or more of the studied scenarios. Conclusions: The GlideScope improved the view in one of three difficult airway situations when used by anaesthetists with no formal training in its use. No single airway device offers a solution to all scenarios, however, we consider that the GlideScope is a useful addition to the range of difficult airway devices available.

Summary

Background and objective: The GlideScope® videolaryngoscope is a newly developed laryngoscope for tracheal intubation recently introduced into clinical anaesthesia. In this randomised clinical study, we compared the haemodynamic responses to orotracheal intubation using a GlideScope® videolaryngoscope and a fibreoptic bronchoscope. Methods: Fifty-six adult patients, ASA I–II scheduled for elective plastic surgery under general anaesthesia requiring orotracheal intubation were randomly allocated to either the GlideScope® videolaryngoscope group or the fibreoptic bronchoscope group. After a standard intravenous anaesthetic induction, orotracheal intubation was performed. Noninvasive blood pressure and heart rate were recorded before and after induction, at intubation and for 5 min after intubation at 1 min intervals. Results: As compared with the post-induction values the orotracheal intubations using a fibreoptic bronchoscope and a GlideScope® videolaryngoscope resulted in the significant increases in blood pressures which did not exceed their baseline values. In the two groups, heart rates at intubation and within 2 min after intubation were significantly higher than their baseline values. However, there were no significant differences in blood pressures and heart rates at all time points, their maximal values and maximal percent changes during the observation and the times required to reach their maximal values between the two groups. Conclusions: The orotracheal intubations using a fibreoptic bronchoscope and a GlideScope® videolaryngoscope produce similar haemodynamic responses.