Summary

Background and objective: Postoperative nausea and vomiting (PONV) is a frequent and unpleasant experience that may increase postoperative complications and costs. For surgical procedures with a high risk of PONV, prevention is preferable to treatment. In this study, the authors explore the dose–response relationship between granisetron administered just prior to the end of surgery and post-operative nausea and vomiting in patients undergoing abdominal hysterectomy. Methods: This was a randomized, double-blind, placebo-controlled, pilot study of post-operative nausea and vomiting prevention. Patients undergoing elective open abdominal hysterectomy requiring general anaesthesia received a single dose of granisetron 0.1, 0.2 or 0.3 mg or placebo administered approximately 15 min prior to the end of surgery. The primary efficacy end-point was the proportion of patients with no vomiting in the 0–6 h interval following medication administration. No inferential statistics were planned. Results: The proportion of patients with no vomiting episode in the 0–6 h interval after administration of study medication was higher in each granisetron treatment group (>90%) than in the placebo group (77%). Proportions of patients with no vomiting episodes in the 0–24 h interval were similar across treatment groups. Results of analyses of proportions of patients with no moderate or severe nausea episodes, proportions of those requiring rescue medication and times to first use of rescue medication suggested a treatment effect of granisetron relative to placebo in both the 0–6 and 0–24 h intervals. Similar proportions of patients in each treatment group reported at least one adverse event. Conclusions: Granisetron at doses of 0.1, 0.2 and 0.3 mg administered just prior to the end of surgery suggested a trend of improved efficacy compared to placebo in preventing postoperative nausea and vomiting in the first 6 h after abdominal hysterectomy. This pilot study did not identify a dose–response relationship.

Summary

Background and objectives: This study compares three modes of patient-controlled epidural analgesia in parturients during labour.

Methods: Eighty-four women were randomized to one of three groups. The epidural solution used in all the three groups was 0.1% bupivacaine with fentanyl 2 μg mL−1. Patients were able to self administer a demand dose of 3 mL with a lockout interval of 6 min in Group A, 6 mL with a lockout interval of 12 min in Group B and 9 mL with lockout interval of 18 min in Group C. All patients received a background infusion at a rate of 6 mL h−1. Visual analogue pain scores, pinprick analgesia and motor block were assessed hourly by a blinded observer. The physician-administered supplementation and the cumulative dose of bupivacaine were also compared between the three groups.

Results: Pain scores, sensory level and motor block were not different among the study groups. Patients' satisfaction was rated good to excellent with no difference among groups. The cumulative dose of bupivacaine was not significantly different. However, there was a trend towards a decreased need for rescue analgesia in Group C. Within each group, the physician-administered supplementations were significantly higher during the second stage of labour than during the first stage (P < 0.05).

Conclusion: The three modes of patient-controlled epidural analgesia supplemented by a background infusion of 6 mL h−1 were equally effective for labour analgesia with a trend for decreased rescue analgesia in the group with a larger bolus dose and a longer lockout interval.

Summary

Background and objective: Surgical treatment of patients presenting with subarachnoid haemorrhage secondary to a leaking cerebrovascular aneurysm involves coiling or clipping. Traditionally all patients undergoing this procedure are cross-matched routinely. With ever-increasing strains on the health budget and transfusion services in particular, as well as the real, albeit low risk of transfusion transmitted disease, we propose that a simple ‘group and save’, coupled with a reliable ‘fast-issue’ blood transfusion service should replace this outdated concept. Method: To assess this assumption, we carried out a retrospective analysis of 103 patients who underwent clipping or coiling during January to December 2001 in our Neurosurgical Unit. Results: All patients but one had been cross-matched (99%). However, only 33 patients (32%) eventually required a blood transfusion. In real terms, this meant a total of 294 units of blood that had been cross-matched routinely, in our series of 103 patients, were not used. Had these patients only been ‘group and saved’ and a system of ‘fast-issue’ been adopted, assuming that none of the patients had abnormal antibodies, the blood transfusion department would have made a saving of £4815.72 for this group of patients. Conclusion: We conclude that advances in surgical technique have made routine cross-matching of blood in cerebral aneurysm surgery unnecessary.

Summary

Background and objective: MDA-MB-468 breast carcinoma cells respond to non-volatile anaesthetics such as propofol with an increased migration. Here we investigated the relationship between GABA-A receptor modulators, the mode of calcium oscillation and actin reorganization with regard to breast carcinoma cell migration. Methods: Expression of the GABA-A receptor was determined by Western blot analysis. Calcium-imaging experiments of individual MDA-MB-468 cells as well as visualization of the F-actin distribution were performed by confocal laser scanning microscopy. Cell migration was investigated in a three-dimensional collagen matrix by time-lapse video microscopy. The GABA agonist propofol was used in a final concentration of 6 μg mL−1. GABA-A receptor antagonist bicuculline (50 μmol) and selective L-type calcium channel blocker verapamil (5 μmol) were used to modulate the propofol effects. Results: A functional GABA-A receptor is expressed by MDA-MB-468 cells. Activation with propofol resulted in sustained increased intracellular calcium concentrations concomitant with actin reorganization and induction of migration in MDA-MB-468 cells. These propofol effects were completely blocked by verapamil. Spontaneous migration of MDA-MB-468 cells (64.4 ± 7.0%) was significantly increased by propofol to 85.0 ± 5.0%. MDA-MB-468 cells co-treated with propofol and verapamil showed a migratory activity of 63.0 ± 2.0% indicating that verapamil blocked the propofol effect. Similar results were achieved with the GABA-A receptor inhibitor bicuculline (control: 56.3 ± 8.5%; propofol: 80.5 ± 7.1%; propofol + bicuculline: 52.5 ± 8.6%). Conclusion: Activation of GABA-A receptor by propofol correlated with an increased migration of MDA-MB-468 breast carcinoma cells, mediated by calcium influx via L-type calcium channels and reorganization of the actin cytoskeleton.

Summary

Background and objective: ProSeal™ Laryngeal Mask Airway (PLMA) and Laryngeal Tube Suction™ (LTS), supraglottic airway devices allowing gastric drainage, were compared in this prospective, randomized study for airway management under conditions with elevated intra-abdominal pressure induced by capnoperitoneum.

Methods: Fifty patients undergoing elective gynaecological laparoscopic surgery were randomized to two groups of 25 each. After induction of general anaesthesia, devices were inserted, correct placement was verified, airway leak pressure was measured, and a gastric tube was inserted. Ease of insertion, quality of airway seal, risk of gastric insufflation and patient comfort were investigated.

Results: There were no differences in patient characteristics data for both groups. First-time insertion success rates were comparable for both groups: 92% – first attempt, 8% – second attempt for PLMA and LTS. Time until delivery of the first tidal volume for PLMA and LTS was 23.2 ± 6.1 and 23.5 ± 6.6 s, airway leak pressure was 45.4 ± 4.9 cmH2O and 45.6 ± 6.7 cmH2O with cuff pressures adjusted to 60 cmH2O. No gastric insufflation, gas loss or signs of regurgitation were detected. Placement of a gastric tube was successful in all patients. Patients were questioned for sore throat and dysphagia after removal of devices. Sore throat was stated in 1%/0% (PLMA) and 8%/4% (LTS) after 6/24 h, dysphagia in 4%/4% (PLMA) and 12%/4% (LTS).

Conclusions: Both devices provide a secure airway even under conditions of elevated intra-abdominal pressure. In this pilot study, no differences concerning handling or quality of airway seal were detected between PLMA and LTS.

Summary

Background and objectives: To compare the analgesic effects of intrathecal fentanyl and low-dose intravenous ketamine as adjuvants to intrathecal bupivacaine for Caesarean section. Methods: Ninety elective Caesarean section patients were randomized into three groups. Spinal anaesthesia was performed with 15 mg hyperbaric bupivacaine in all groups. Ketamine (0.15 mg kg−1) or an equal volume of normal saline was given intravenously immediately after initiating spinal anaesthesia in the ketamine and control group, respectively. In the fentanyl group, 10 μg fentanyl was added to the intrathecal bupivacaine. Arterial pressures, heart rate values, adverse effects, the time of first request for postoperative analgesia, visual analogue pain scores, total analgesic consumptions at 24 and 48 h were recorded in all patients. Results: The time to first request for analgesia was significantly longer in the ketamine (197 min) and fentanyl (165 min) groups compared to the control group (144 min). Postoperative pain scores were significantly lower in the ketamine group than in both other groups. Although the analgesic requirements during first 24 h were significantly lower in the ketamine group, there was no significant difference between the groups during the following 24 h. Conclusion: Intravenous low-dose ketamine combined with intrathecal bupivacaine for Caesarean section provides longer postoperative analgesia and lower postoperative analgesic consumption than bupivacaine alone suggesting a pre-emptive effect.

Summary

Background and objective: Xenon may have favourable applications in the setting of cardiac surgery. Its advantages include a desirable haemodynamic profile as well as potential cardiac and neuroprotective properties. However, its low solubility may lead to enhanced diffusion into enclosed gas spaces. The purpose of this study was to compare the effects of xenon (Xe), nitrous oxide (N2O) and nitrogen (N2) on gas bubble size during cardiopulmonary bypass (CPB).

Methods: Rats were randomized to receive 70% Xe, 26% oxygen (O2), 4% carbon dioxide (CO2) (xenon group); 70% N2O, 26% O2, 4% CO2 (nitrous oxide group) or 70% N2, 26% O2, 4% CO2 (nitrogen group) during 90 min of normothermic CPB. Small gas bubbles (300–500 μL; n = 12 per group) were injected into a bubble chamber on the venous side of the bypass circuit. After 10 min of equilibration, they were removed for volumetric analysis.

Results: The increase in bubble size was 2 ± 2% with nitrogen, 17 ± 6% with xenon (P = 0.0192 vs. nitrogen) and 63 ± 23% with nitrous oxide (P = 0.0001 vs. nitrogen). The nitrous oxide group had significantly increased bubble size compared to the xenon group (P = 0.0001).

Conclusions: During CPB, xenon anaesthesia produced a small increase in gas bubble size compared to nitrogen. Nitrous oxide resulted in significantly larger bubbles compared to both nitrogen and xenon.

Summary

Background and objective: Anaesthesia may affect the regulatory balance of postoperative immune response. The aim of this study was to investigate the effects of different volatile and non-volatile anaesthetic agents and particularly of clinically used agent combinations on the proliferation capacity and cytokine production of immune cells. Methods: Peripheral blood mononuclear cells from healthy donors were PHA-activated in the presence or absence of various concentrations of thiopental, propofol, fentanyl, sufentanil, sevoflurane, nitrous oxide and combinations of these anaesthetics. Cell proliferation was assessed by tritiated thymidine uptake. Interleukin-2 production and release of the soluble IL-2 receptor were determined by enzyme immunoassays and used as measures of lymphocyte activation. Results: Thiopental inhibited cell proliferation in a dose dependent manner (P < 0.001) and reduced sIL-2R release (2090–970 pg mL−1; P < 0.05). Propofol reduced sIL-2R release at the high concentration of 10 μg mL−1 (2220 pg mL−1–1780 μg mL−1; P < 0.05). Fentanyl and sufentanil did not compensate for or enhance the inhibitory effects of thiopental. Nitrous oxide, but not sevoflurane, reduced the proliferation of human peripheral blood mononuclear cells (P < 0.05). In combinations with thiopental or nitrous oxide, sevoflurane compensated the inhibitory effects of these two agents. Fentanyl, sufentanil, sevoflurane and nitrous oxide did not affect PHA-induced IL-2 and sIL-2 receptor release by human peripheral blood mononuclear cells. Conclusion: Thiopental and nitrous oxide have immunosuppressive activity. In contrast, sevoflurane may have a beneficial effect by alleviating the immunosuppressive effects of both substances.

Summary

Background and objective: The aim of this study was to assess target-controlled propofol infusion as a technique of sedation for shoulder surgery under interscalene brachial plexus block in the sitting position and to evaluate the effect of sedation on hypotensive/bradycardic events during this procedure. Methods: One hundred and forty patients undergoing elective shoulder surgery in the sitting position under interscalene brachial plexus block (with 30 mL of ropivacaine 0.75%) were prospectively enrolled. All patients were premedicated with hydroxyzine 1 mg kg−1, none received beta-blockers. No patients were given atropine except for the patients who experienced a vasovagal event either during the block procedure or intravenous catheter placement. The target-controlled propofol infusion was started immediately after positioning the patient on the operating table. The initial target concentration was 1 μg mL−1. The infusion rate was adjusted every 15 min by increasing or decreasing the target concentration by 0.2 μg mL−1 steps to maintain the patient rousable to verbal commands (score of 3 on Wilson sedation scale). The following parameters were assessed: minimal, maximal, optimal target concentration, respiratory and haemodynamic parameters, total propofol dose, additional alfentanil needs, occurrence of hypotensive/bradycardic events, complications. Results are mean ± SD. Statistical analysis used t-test and χ2-tests. Results: The optimal propofol target concentration was 0.8 μg mL−1. No respiratory complications or conversion to general anaesthesia was reported. Two patients experienced transient and inconsequential intraoperative agitation. The incidence of hypotensive/bradycardic events during the procedure was 5.7% (eight patients). Conclusion: Target-controlled propofol infusion (0.8–0.9 μg mL−1) following hydroxyzine premedication is a safe and effective technique for sedation when combined with interscalene brachial plexus block during shoulder surgery in the sitting position.

Summary

Background: This study was designed to investigate the impact of patient age on propofol consumption and recovery time using a propofol–remifentanil anaesthetic standardized with Narcotrend™ EEG monitoring. The Narcotrend is a monitor for measuring the depth of anaesthesia based upon a six-letter classification from A (awake) to F (increasing burst suppression) including 14 substages.

Methods: In 200 patients scheduled for minor orthopaedic surgery Narcotrend EEG electrodes were positioned on the patient's forehead as recommended by the manufacturer. Anaesthesia was induced with remifentanil 0.4 μg kg−1 min−1 and 2 mg kg−1 propofol. Immediately after intubation remifentanil was reduced to a constant rate of 0.2 μg kg−1 min−1 whereas a propofol infusion was now started at 3 mg kg−1 h−1 and then adjusted accordingly to achieve a target Narcotrend stages of D0–2 indicating general anaesthesia. At the end of surgery the propofol and remifentanil infusions were stopped without tapering, the time to unstimulated opening of eyes was determined, and the propofol consumption (given as mg kg−1 h−1) was calculated from the total amount of infused propofol but without the induction bolus, from the actual body weight and the duration of propofol infusion. Furthermore, a linear regression analysis was applied for propofol consumption vs. age.

Results: The ages of the patients studied ranged from 16 to 83 yr old and patients were classified as ASA I–III. Propofol consumption significantly decreased with the patients' age: 30 yr of age or below the propofol consumption was calculated as 5.9 ± 1.7 mg kg−1 h−1, for 31–50 yr as 5.4 ± 1.8 mg kg−1 h−1, for 51–70 yr as 4.5 ± 1.7 mg kg−1 h−1 and above 70 yr as 3.5 ± 1.4 mg kg−1 h−1. Linear regression analysis revealed propofol (mg kg−1 h−1) = 9.136 − (0.0597 × age (yr)); R = 0.53. Concomitantly, the recovery time to opening of eyes increased with the patients' age: ≤30 yr, 7.4 ± 3.7 min; 31–50 yr, 9.5 ± 4.0 min; 51–70 yr, 9.8 ± 4.1 min; and ≥71 yr, 14.9 ± 12.1 min.

Conclusions: We conclude that with Narcotrend guidance, mean propofol consumption and recovery times are age dependent. However, as a result of large inter-individual variability, age per se does not allow a prediction of individual propofol need or recovery time.

Summary

Background and objective: The aim of this study was to determine the duration of onset and regression time of sensory and motor blocks, the quality of anaesthesia and postoperative analgesia by the addition of dexmedetomidine to local anaesthetic solution in intravenous regional anaesthesia (IVRA).

Methods: Forty patients scheduled for elective hand surgery participated in this prospective randomized double-blind study. The IVRA was achieved using 3 mg kg−1 lidocaine diluted with saline to a total volume of 40 mL in the control group or 1 μg kg−1 of dexmedetomidine +3 mg kg−1 lidocaine diluted with saline to a total volume of 40 mL in the dexmedetomidine group. The onset and regression times for sensory and motor blocks were recorded. Qualities of anaesthesia, intraoperative and postoperative analgesic requirements were noted.

Results: There was no difference between the groups with respect to sensory and motor blocks onset and regression time. The quality of anaesthesia was better in the dexmedetomidine group than the control group and the difference was statistically significant. Intraoperative and postoperative analgesic requirements were greater in the control group than in the dexmedetomidine group.

Conclusions: Addition of dexmedetomidine to local anaesthetic solution in IVRA improved the quality of anaesthesia and decreased analgesic requirements, but had no effect on the sensory and motor blocks onset and regression times.

Summary

Background and objective: Although lidocaine has been used extensively for spinal anaesthesia since 1949, it has been associated with transient neurological symptoms only in the past 10 yr. It has been suggested that early ambulation after spinal anaesthesia, as opposed to traditional 24 h recumbency, might be the causative factor for the development of transient neurological symptoms. The purpose of this study was to examine the effect of early ambulation on the incidence of transient neurological symptoms after single injection spinal anaesthesia with lidocaine 2%.

Methods: Sixty patients undergoing minor surgery under spinal anaesthesia were included. All patients received lidocaine 60 mg. After the establishment of successful subarachnoid block, patients were randomly allocated to two groups of 30 patients. Patients in Group 1 were ambulated as soon as possible, whereas patients in Group 2 were kept recumbent until 6 h after subarachnoid injection. Two days after surgery patients were contacted by a blinded observer and interviewed of transient neurological symptoms using a standardized questionnaire. Patients were asked to express the intensity of pain/discomfort on a verbal rating scale from 0 (no pain) to 10 (worst pain imaginable).

Results: There was no significant difference in the incidence of transient neurological symptoms (23% vs. 27%). In all patients, symptoms resolved completely within 6–24 h. The median pain score was 5 (range 2–8) in Group 1 and 7 (range 1–8) in Group 2.

Conclusions: Under the conditions of this study, there is no correlation between the time of ambulation after spinal anaesthesia with lidocaine and the incidence of transient neurological symptoms.

Summary

Background and aim: The neuromuscular effects of a bolus dose of rocuronium 0.6 mg kg−1 under propofol anaesthesia in renal failure patients are prolonged compared to healthy patients. The present study aims to describe the neuromuscular effects of 0.3 mg kg−1 rocuronium under propofol anaesthesia in patients with renal failure and to compare these effects with healthy control patients. Methods: With institutional approval and informed consent, 18 healthy patients and 18 patients with renal failure took part in this prospective open label study. The renal failure patients were undergoing either renal transplantation or insertion of a shunt. Rocuronium 0.3 mg kg−1 was given intravenously after induction of anaesthesia with propofol 1–2 mg kg−1 and fentanyl 2 μg kg−1. Propofol 6–12 mg kg−1 h−1 was used for maintenance of anaesthesia. Four acceleromyographic responses of the thumb after supramaximal stimulation of the ulnar nerve using surface electrodes at 2 Hz every 15 s were measured and recorded. The onset time, the time to recovery of the first twitch to 25% recovery and the time to a train-of-four ratio of 0.7 were all recorded. Wilcoxon rank sum testing was used to compare the pharmacodynamics and to see if medication, gender or electrolytes influenced the duration of the block. P < 0.05 was significant. Results: No statistical differences were seen in the neuromuscular blocking effects of rocuronium between the two groups but there was a significant difference (P < 0.00001) in the variability of the total duration of the block. Conclusions: Rocuronium 0.3 mg kg−1 is suitable for use in patients with renal failure when endotracheal intubation and neuromuscular block for a short period of time are needed. Tracheal intubation is facilitated within 4 min and the block can be antagonized within 20 min.

Summary

Background and objective: Even moderate hyperglycaemia increases mortality/morbidity after coronary artery bypass grafting, stroke and myocardial infarction. The goal of this prospective study was to determine if using thoracic epidural analgesia from start of surgery until the end of the third postoperative day would blunt postoperative hyperglycaemia. Methods: Forty-four patients had diabetes mellitus, 60 did not; half of each group had an epidural with continuous local anaesthetics. All patients received continuous insulin infusions during the initial 24 h period beginning with surgery. Blood glucose was measured four times daily (fasting or 2–3 h post-prandial) until end of the third postoperative day. Results: For patients without diabetes, the epidural group had lower mean blood glucose and insulin requirements (P < 0.02) than controls during the initial 24 h period beginning with surgery. For patients with diabetes mellitus, thoracic epidural analgesia reduced mean blood glucose (P = 0.017) with unchanged insulin requirements. Epidural did not diminish the increase (vs. preoperative) in fasting blood glucose on the third postoperative day (32% vs. 22%, P < 0.001) for non-diabetics. Epidural analgesia was not able to attenuate hyperglycaemia during the first 3 postoperative days. Conclusions: Epidural analgesia improved glucose homeostasis minimally during the initial 24 postoperative hours but did not attenuate hyperglycaemia during the subsequent 3 postoperative days.

Summary

Background and objective: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed.

Methods: After Institutional Review Board approval and written informed consent, 14 consecutive women with epidural anaesthesia for Caesarean section received either hydroxyethyl starch 500 mL or gelatine 500 mL. Haemodynamic variables monitored were maternal arterial pressure, maximal blood flow velocity and pulsatility indices of the uterine artery derived from Doppler measurements.

Conclusions: Maternal arterial pressure and pulsatility indices in both groups did not change from baseline after intravenous colloid infusion. However, uterine blood flow increased significantly in both groups. The effectiveness of volume preloading may therefore be better described by changes in maximum uterine blood flow velocity than by pulsatility indices or maternal arterial pressure.

Summary

Background and objective: Inhalational anaesthetics have been associated with hepatotoxicity. Even desflurane, with its low solubility in blood and tissues, and its minimal hepatic biotransformation, is known to affect hepatic integrity. The effects of propofol on hepatic function are, however, a matter of controversy. Alpha-glutathione S-transferase (α-GST), a sensitive and specific biomarker for hepatic integrity, was measured to assess the influence of total intravenous anaesthesia (TIVA) with propofol vs. anaesthesia with desflurane.

Methods: Forty-two patients scheduled for elective prostatectomy were randomly allocated to receive either desflurane, fentanyl and thiopental (desflurane group) or propofol and remifentanil (TIVA group). Depth of anaesthesia was guided by bispectral index. Plasma concentrations of α-GST and aminotransferases were measured before induction of anaesthesia (T0), at the end of surgery (T1), as well as 2 h (T2) and 24 h (T3) postoperatively. Haemodynamic parameters and bispectral index values were documented.

Results: α-GST increased significantly in the desflurane group from T0 (3.0 ± 2.2 μg L−1) to T1 and T2 (5.5 ± 4.3 and 5.6 ± 3.7 μg L−1, respectively), whereas no changes were seen in the TIVA group. α-GST values above the normal upper limit (>7.5 μg L−1) were seen in 24% of the patients receiving desflurane. Aminotransferases remained unchanged in both groups throughout the study period.

Conclusions: The use of propofol as part of a TIVA regimen seems to have no influence on hepatocellular function during and after surgery. In contrast, patients receiving desflurane showed a transient slight, but significant, increase of α-GST to above the normal upper limit after anaesthesia, although this was without further clinical relevance.

Summary

Background and objective: The objective of this study was to determine the influence of preoperative anxiety on the activity of plasma cholinesterase and heart rate (HR) variability.

Methods: A total of 50 subjects were studied, 25 male patients one day preoperatively and 25 male volunteers without surgical intervention as a control group. Blood samples were taken to determine plasma cholinesterase activity. HR variability was recorded for a period of 256 beat-to-beat intervals and analysed by frequency domain analysis into very low frequency (VLF: 0.02–0.04 Hz), low frequency (LF: 0.04–0.15 Hz) and high frequency (HF: 0.15–0.4 Hz). LF/HF ratio and total power over the 0.02–0.4 Hz range were calculated. Anxiety levels were assessed using the hospital anxiety and depression scale, the self-rating anxiety scale and a visual analogue scale.

Results: The patient group had significantly higher anxiety scores. Plasma cholinesterase activity was significantly higher in patients vs. controls (6646 vs. 5324 units L−1). Total power, LF and HF were significantly lower in the patients (1489 vs. 2581 ms2; 656 vs. 1186 ms2; 491 vs. 964 ms2, respectively).

Conclusions: Preoperative anxiety increases plasma cholinesterase activity and decreases HR variability.

Summary

Background and objective: Volatile anaesthetics depress excitatory signal transmission by potentiating the inhibitory action of GABAA receptors and there is strong evidence that this is related with anaesthesia. Using primary hippocampal cultures we analyzed the possibility that the volatile anaesthetics enflurane and sevoflurane depress excitatory signal transmission by activation of adenosine A1 receptors. Methods: Primary rat hippocampal cultures on 4 cm poly-l-lysine coated glass coverslips were loaded with the Ca2+-indicator fluo-3 and incorporated in a gastight, temperature-controlled perfusion chamber. The intracellular Ca2+-concentration was monitored with a confocal laser-scanning microscope (BioRad) using the 488 nm laser line of a krypton–argon laser for excitation and the Lasersharp Acquisition software for analysis. Results: Continuous perfusion in Mg2+-free medium generated spontaneous synchronized calcium oscillations, which were dose dependently depressed by the volatile anaesthetics enflurane and sevoflurane (0.25–1 minimum alveolar concentration). Addition of 100 nmol of 2-chloro-N6-cyclopentyladenosine, a specific adenosine A1 receptor antagonist, partly reversed the anaesthetic-induced inhibition of the oscillation amplitude of the oscillating cells. The effect of the anaesthetics was mimicked by the addition of S-(p-nitrobenzyl)-6-thioguanosine, an adenosine transport inhibitor and by the addition of 5-amino-5-deoxyadenosine, an inhibitor of adenosine kinase. Conclusions: The volatile anaesthetics sevoflurane and enflurane activate adenosine A1 receptors in primary rat hippocampal cultures. This effect is mediated by liberation of adenosine most likely by an interaction of the volatile anaesthetics with adenosine transport or key enzymes in adenosine metabolism.

Summary

Background and objective: We have investigated the concentrations of epinephrine, norepinephrine, vasopressin and angiotensin converting enzyme activity to explore the role of these mediators in the neuroendocrine response to laryngoscopy and tracheal intubation. Methods: One hundred (50 male, 50 female) ASA I patients aged 20–50 yr (mean ± SEM; 35.59 ± 0.99) were included in the study. They were undergoing elective surgery under standard anaesthesia induction and maintenance using tracheal intubation. Plasma concentrations of epinephrine, norepinephrine and vasopressin as well as plasma angiotensin converting enzyme activity were determined at four time points, before (T1) and after (T2) induction, and 2 (T3) and 5 min (T4) after intubation. Blood pressure and heart rate were recorded at corresponding times to reveal if any correlation existed between haemodynamic parameters and neuroendocrine response. Results: Heart rate increased after induction and intubation (P < 0.05) and decreased significantly at T4 (P < 0.05). Systolic blood pressure decreased significantly (P < 0.05) after induction and increased slightly after intubation decreasing to below baseline value (P < 0.05) at T4. Diastolic blood pressure increased slightly after intubation and decreased significantly (P < 0.05) at T4. Plasma epinephrine and norepinephrine concentrations decreased after induction and increased at T3 and T4 without reaching significance. Vasopressin concentrations increased slightly at T2 and T3 and decreased significantly at T4 (P < 0.05). Angiotensin converting enzyme activity was unaffected when compared with baseline values. Conclusions: Blood pressure, heart rate, plasma epinephrine, norepinephrine and vasopressin concentrations increased slightly in response to laryngoscopy and intubation, all returning to or below baseline 5 min later with no change in angiotensin converting enzyme activity in normotensive patients.

Summary

Background and objective: The target effect-site concentration of propofol to insert a laryngeal mask airway was recently reported as almost 5 μg mL−1. The present study aimed to determine the target effect-site concentration with target-controlled infusion of propofol to place classical larnygeal mask airway or current laryngeal tube in adult patients. Methods: We included 40 patients scheduled for short gynaecological and radiological procedures under general anaesthesia in a randomized, double-blind manner using the Dixon's up-and-down statistical method. Monitoring included standard cardiorespiratory monitors, and bispectral index monitoring was used for all patients. Anaesthesia was conducted with a target-controlled infusion system: Diprifusor™. The initial target plasma concentration of propofol was 5 μg mL−1, and was changed stepwise by 0.5 μg mL−1 increments according to Dixon's up-and-down method. Criteria for acceptable insertion were: Muzi's score ≤2, and mean arterial blood pressure, heart rate or bispectral index variation <20% the baseline values.Results: Target effect-site concentration of propofol required to insert laryngeal tube was 6.3 ± 0.3 μg mL−1 with Dixon method and ED50 was 6.1 μg mL−1 (5.9–6.4) with logistic regression method. In the case of larnygeal mask airway they were 7.3 ± 0.2 μg mL−1 (Dixon method) and 7.3 μg mL−1 (7.1–7.5; with logistic regression) respectively (P < 0.05). ED95 (logistic regression) was 6.8 μg mL−1 (5.9–7.6) for laryngeal tube and 7.7 μg mL−1 (7.3–8.0) for larnygeal mask airway (P < 0.05). Haemodynamic incidents were 55% in the larnygeal mask airway group vs. 30% in the laryngeal tube group (P < 0.05). Conclusions: The target effect-site concentration of propofol for insertion of laryngeal tube was lower than for larnygeal mask airway (P < 0.05), with a consequent reduction of the propofol induced haemodynamic side-effects.