Summary

Background and objective: There are little data on nitrous oxide (N2O) concentrations in neonatal blood at delivery. We investigated the effects of the time elapsing between the induction of anaesthesia and delivery (the I–D interval) on umbilical blood N2O concentrations.

Methods: Maternal and neonatal blood N2O concentrations were measured in 27 patients undergoing Caesarean section under N2O 67% anaesthesia. The duration of N2O administration (range 2–50 min) was arbitrarily divided into three groups (each n = 9): short (2–9 min), medium (9.1–14 min) and long duration (14.1–50 min).

Results: Compared with a rapid increase in the maternal arterial N2O concentration (48.9 ± 4.7%), the umbilical venous N2O concentration (17.9 ± 8.3%) rose slowly in the short duration group, whereas the N2O concentrations became more similar (61.6 ± 4.3 and 43.2 ± 10.0%, respectively) in the long duration group. The ratio of umbilical vein to maternal artery N2O concentrations correlated with the duration of N2O anaesthesia (r = 0.739), resulting in ratios of 0.37 ± 0.18, 0.61 ± 012 and 0.70 ± 0.13 for the short, medium and long duration groups, respectively. The Apgar score at 1 min correlated inversely with the duration of anaesthesia and with the umbilical vein N2O concentration (r = −0.457 and −0.423, respectively).

Conclusions: The data suggest that placental N2O transfer during Caesarean section is time-dependent and slower compared with maternal N2O uptake. They also suggest that the Apgar score is less affected by N2O administration when the I–D interval is shorter.

Summary

Background and objective: The Datex-Ohmeda neuromuscular transmission module (M-NMT)® is a new monitor that is part of the AS/3® anaesthesia monitor. It incorporates a mechanosensor, which is a piezoelectric polymer attached to the hand. The module was compared with a force transducer in 30 patients requiring neuromuscular blockade.

Methods: Anaesthesia was induced with fentanyl and propofol, and tracheal intubation was performed without muscle relaxants. Neuromuscular blockade was assessed by the test module on one arm and the force transducer on the other arm. When the response to train-of-four stimulation had been stable in both arms for 3 min, rocuronium 0.2 mg kg−1 was injected intravenously. During recovery from blockade, the train-of-four ratio was measured in 15 patients, and the ratio of response to double-burst stimulation in the other 15 patients. Data analysis was by difference plots.

Results: Both devices had acceptable coefficients of repeatability. The M-NMT® module was biased by +1.3% (upper limit of agreement 14.2%, lower limit −12.9%) for the recovery of the train-of-four ratio, and by +1.09% (17%, −16%) for the recovery of double-burst stimulation ratio.

Conclusions: The Datex-Ohmeda M-NMT® gives measurements that are repeatable and gives good enough correspondence with a force transducer that it can be used clinically to assess recovery of neuromuscular blockade, but the limits of agreement rule out research applications.

Summary

Background and objective: Patients who require multidisciplinary intensive care after cardiac surgery have a poor prognosis. The aim was to investigate factors in the mortality of this group of patients at 6 months.

Methods: A retrospective analysis was made of the 6-month mortality rate in 301 adults who required admission to a multidisciplinary intensive care unit following cardiac surgery from 1991 to 1997. Mortality was correlated with clinical and patient characteristic variables.

Results: The intensive care mortality rate was 34% and at 6 months after patients' discharge from intensive care it was 51%. There were positive correlations with death at 6 months for ventricular failure (odds ratio of death 3.4, P = 0.002), sepsis (odds ratio 3.0, P = 0.004) and age over 80 yr (odds ratio of death 9.2, P = 0.034). Patients who had undergone isolated coronary artery graft surgery (odds ratio of death 0.28, P = 0.036) or thoracic surgery (odds ratio of death 0.22, P = 0.042) had better 6-month outcomes. Patients with respiratory or renal failure in the absence of ventricular failure or sepsis had a 6-month mortality rate of 36%; but the lower mortality rate did not achieve statistical significance.

Conclusions: The 6-month mortality rate of 51% in a group of patients requiring multidisciplinary intensive care after cardiac surgery is consistent with previous studies; mortality was particularly high in extreme old age and in patients referred with sepsis or ventricular failure. Those patients with uncomplicated respiratory or renal failure had a better outcome than the group as a whole.

Summary

Background and objective: Propofol is a phenol derivative (2,6 di-isopropylphenol) with a unique effect profile including activating effects on GABAA and blocking effects on voltage-operated sodium channels. If the substituents in the 2- and the 6-positions are replaced by tert-butyl groups, the resulting phenol derivative, 2,6 di-tert-butylphenol, despite being a close structural propofol analogue, completely lacks GABAA receptor effects. The aim of this in vitro study was to investigate the effects of 2,6 di-tert-butylphenol on voltage-operated neuronal sodium channels in order to determine whether and, if so, how these structural changes alter the sodium channel-blocking effect seen with propofol.

Methods: Whole-cell sodium inward currents through heterologously expressed rat type IIA sodium channels were recorded in the absence and presence of definite concentrations of 2,6 di-tert-butylphenol and propofol.

Results: When applied at concentrations ≥30 μmol, 2,6 di-tert-butylphenol completely and irreversibly blocked sodium inward currents. The blockade equilibrium time was about 2 min. A partial washout was possible only if the application was stopped before the equilibrium of the blockade was achieved.

Conclusions: 2,6 Di-tert-butylphenol exerts a high-affinity block of neuronal sodium channels. Apparently, the slight structural differences of 2,6 di-tert-butylphenol in comparison with propofol – which account for the lack of GABAA receptor effects – enhance its voltage-operated sodium channel-blocking effects. As 2,6 di-tert-butylphenol is much more potent than most sodium channel blockers in clinical use, it might be of interest in the development of local anaesthetics.

Summary

Background and objective: Subarachnoid block is a widely used technique for Caesarean section. Its quality can be improved by adding opioids to the local anaesthetics. We studied the quality of the block and its maternal–fetal repercussions when different doses of sufentanil were combined with hyperbaric bupivacaine using the intrathecal route in pregnant women undergoing Caesarean section.

Methods: This was a prospective, randomized, double-blind, controlled trial with 80 pregnant women, ASA I–II, who were scheduled for elective Caesarean section under subarachnoid block. Patients were distributed into four groups according to the dose of sufentanil used: no sufentanil (Group 1, control) or 2.5, or 5.0 or 7.5 μg sufentanil (Groups 2–4, respectively). In every group, the local anaesthetic used was hyperbaric bupivacaine 0.5% (12.5 mg) and the total volume of the solution 4 mL. The onset time of the block, maximum level of sensory block, motor block level, duration of analgesia, maternal side-effects and maternal–fetal cardiovascular repercussions were evaluated.

Results: Onset of the block was significantly shorter in the groups receiving opioids compared with the control group. Analgesia was significantly prolonged in Groups 3 and 4. The occurrence of pruritus and somnolence was significantly higher in the group receiving sufentanil 7.5 μg than in other groups. With the exception of pruritus, no differences were observed between groups with respect to cardiovascular or other maternal effects.

Conclusions: The addition of sufentanil 5.0 and 7.5 μg to hyperbaric bupivacaine provided adequate anaesthesia for Caesarean section and good postoperative analgesia. Pruritus was the most common side-effect and had a significantly higher incidence when a dose of sufentanil 7.5 μg was used.

Summary

Background and objective: In October 2000, we conducted a national postal survey of consultant day case anaesthetists in the UK to explore the range and variation in the practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). The survey was carried out as part of a larger study that comprised a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery). We report the findings of this national survey of adult urology and orthopaedic day case anaesthetic practice in the UK.

Methods: The survey used a structured postal questionnaire and collected data on the duration of the surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flows used for anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

Results: The overall response rate for the survey was 74% (63% for urology, 67% for orthopaedics). The survey indicated the following practice in adult urology and adult orthopaedic day case surgery: 6 and 12% used premedication; propofol was the preferred induction agent (96 and 97%) and isoflurane the preferred maintenance agent (56 and 58%); 32 and 41% used prophylactic antiemetics; 86 and 93% used a laryngeal mask.

Conclusions: This survey identifies the variation in current clinical practice in adult day surgery anaesthesia in the UK and discusses this variation in the context of current published evidence.

Summary

Background and objective: The mechanism underlying stable cuff pressure in the Brandt rediffusion endotracheal tube during anaesthesia with nitrous oxide is not fully understood. The present study assessed changes in gas concentrations in the cuff during and after nitrous oxide anaesthesia.

Methods: The pressure of an air-filled Brandt endotracheal tube cuff was measured; anaesthesia was maintained with nitrous oxide 67% and oxygen 33% for 6 h in the Continuous Group; oxygen was substituted for nitrous oxide after 3 h of nitrous oxide anaesthesia in the Discontinuous Group (n = 8 for each). In some other patients, the study was terminated at 90, 180, 270 and 360 min (n = 8 for each). Gas concentrations in the cuff were measured at the end of the study.

Results: Cuff pressures increased slightly during the first 180 min of anaesthesia (P < 0.001). Thereafter, the cuff pressure did not change significantly in the Control Group but decreased in the Discontinuous Group (P < 0.001); there was a significant difference between the two groups (P < 0.0001). Cuff pressure never exceeded 22 mmHg and there were no air leaks in either group during the 6 h anaesthesia. Nitrous oxide concentrations in the cuff were 11.3 ± 2.6% and 2.6 ± 0.8% in the Control Group and Discontinuous Groups, respectively; however, changes in carbon dioxide and oxygen concentrations in the cuff were within approximately 1%.

Conclusions: Small changes in the nitrous oxide concentration in the cuff contribute to a stable cuff pressure in the Brandt rediffusion system, but changes in carbon dioxide or oxygen concentrations have little effect.

Summary

Background and objective: This paper describes the user acceptance of an anaesthesia information management system at the University Hospital in Giessen, Germany, after 5 yr of routine use.

Methods: A questionnaire with 75 items was distributed to all anaesthesiologists and anaesthetic nurses of the Department of Anaesthesiology. The questions were answered anonymously on a five-point Likert scale.

Results: The return rate was 60% (44 physicians and 24 nurses). The results indicated that the system generally met user expectations. The respondents thought that electronic record keeping improved the quality of their work, and they did not want to switch back to paper records. Problems arose with hardware placement and software features, e.g. coding tools for diagnoses and type of surgery. The perceived quality of training strongly influenced user acceptance.

Conclusions: Despite the deficits revealed by the survey, the respondents did not want to switch back to manual record keeping. A structured user survey is a useful tool for the development, adaptation and implementation of an anaesthesia information management system. A training strategy that takes the needs of the users into account is recommended.

Summary

Background and objective: Different anaesthetic techniques are used during breast surgery but are frequently associated with unsatisfactory postoperative analgesia. Paravertebral nerve blockade has recently been proposed as a favourable alternative for this type of surgical procedure, providing excellent pain relief and a reduced incidence of postoperative nausea and vomiting. The aim of the present study was to compare the use of a nerve-stimulator guided paravertebral nerve blockade technique to regular general anaesthesia for breast surgery.

Methods: Sixty patients were prospectively randomized to receive either paravertebral nerve blockade or general anaesthesia for breast surgery. The primary end-point of the study was to assess postoperative analgesia (visual analogue scale and supplemental opioid requirements); the incidence of postoperative nausea and vomiting and length of hospital stay were considered as secondary outcome measures.

Results: Visual analogue scores both at rest and at movement, as well as the need for supplemental opioid administration during the first 3 days postoperatively, were significantly lower in patients handled with paravertebral nerve blockade compared to patients receiving general anaesthesia (P < 0.05). The number of patients free from nausea and vomiting after operation was significantly higher in the paravertebral nerve blockade group (93%) compared to the general anaesthesia group (67%) (P < 0.05). The use of paravertebral nerve blockade was also associated with a significantly shorter hospital stay (median 1 day) compared to general anaesthesia (2 days) (P < 0.01). Both the performance of the block and the intraoperative conditions was well accepted by the vast majority of patients treated by paravertebral nerve blockade (97%).

Conclusion: The use of paravertebral nerve blockade was associated with improved postoperative pain relief, a reduced incidence of nausea and vomiting after operation and a shorter duration of hospital stay compared to general anaesthesia in patients undergoing breast surgery.

Summary

Background and objective: In some situations, the use of muscle relaxants (neuromuscular blocking drugs) are undesirable or contraindicated. We compared intubating conditions without muscle relaxants in premedicated patients receiving either alfentanil 40 μg kg−1 or remifentanil 2, 3 or 4 μg kg−1 followed by propofol 2 mg kg−1.

Methods: In a randomized, double-blind study, 80 healthy patients were assigned to one of four groups (n = 20). After intravenous atropine, alfentanil 40 μg kg−1 or remifentanil 2, 3 or 4 μg kg−1 were injected over 90 s followed by propofol 2 mg kg−1. Ninety seconds after administration of the propofol, laryngoscopy and tracheal intubation were attempted. Intubating conditions were assessed as excellent, good or poor on the basis of ease of lung ventilation, jaw relaxation, laryngoscopy, position of the vocal cords, and patient response to intubation and slow inflation of the endotracheal tube cuff.

Results: Seven patients who received remifentanil 2 μg kg−1 and one patient who received remifentanil 3 μg kg−1 could not be intubated at the first attempts. Excellent intubating conditions (jaw relaxed, vocal cords open and no movement in response to tracheal intubation and cuff inflation) were observed in those who received either alfentanil 40 μg kg−1 (45% of patients) or remifentanil in doses of 2 μg kg−1 (20%), 3 μg kg−1 (75%) or 4 μg kg−1 (95%). Overall, intubating conditions were significantly better (P < 0.05), and the number of patients showing excellent conditions were significantly higher (P < 0.05) in patients who received remifentanil 4 μg kg−1 compared with those who received alfentanil 40 μg kg−1 or remifentanil 2 μg kg−1. No patient needed treatment for hypotension or bradycardia.

Conclusions: Remifentanil 4 μg kg−1 and propofol 2 mg kg−1 administered in sequence intravenously provided good or excellent conditions for tracheal intubation in all patients without the use of muscle relaxants.

Summary

Background and objective: Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes.

Methods: Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1–2%. After baseline haemodynamics were recorded, milrinone (25 or 50 μg kg−1) was administered over 10 min, followed by a continuous infusion (0.5 μg kg−1 min−1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 μg kg−1 min−1) was then administered with milrinone.

Results: Milrinone significantly increased the heart rate from 81 ± 8 to 102 ± 16 beats min−1, but it decreased the mean arterial pressure from 83 ± 10 to 66 ± 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 ± 12 beats min−1) and increased the mean arterial pressure (82 ± 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate–pressure product.

Conclusions: The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

Summary

Background and objective: We compared the effects of sub-Tenon's local anaesthetic block and placebo on perioperative opioid requirement and cardiovascular stability and on postoperative pain, nausea and vomiting in patients undergoing vitreo-retinal surgery under general anaesthesia.

Methods: We studied 43 patients undergoing vitreo-retinal surgery under general anaesthesia in a randomized double blind study. Patients received a standard general anaesthetic followed by a sub-Tenon's injection of 4–5 mL of either bupivacaine 0.75% or saline. We recorded intraoperative invasive arterial pressure, then the incidence and severity of pain and of nausea and vomiting, for 24 h postoperatively.

Results: In the sub-Tenon's bupivacaine group, there was a significant reduction in the perioperative opioid use and a reduction in the frequency of bradycardia and hypertensive episodes, defined as a rise >25% of baseline for a duration of >3 min. The sub-Tenon's bupivacaine group also had significantly lower pain scores and nausea scores at 12 h, concomitant with a lower consumption of analgesia and antiemetics.

Conclusions: This local anaesthetic technique is effective in vitreo-retinal surgery and can be safely applied to this population of patients regardless of axial length.

Summary

Background and objective: The augmentation of the effect of neuromuscular blocking drugs with volatile anaesthetics is well documented, but the mechanism remains unclear. The pharmacological interaction and relative plasma concentrations of mivacurium isomers were investigated during either propofol- or isoflurane-maintained anaesthesia.

Methods: Forty-four patients were randomly assigned to one of two groups: isoflurane or propofol. All patients received an initial dose of mivacurium 0.1 mg kg−1. After recovery of the first twitch (T1) response measured by acceleromyography to 5%, a T1 depression of 90–99% was maintained by infusion. After a steady state was reached, blood samples were taken after 10 and 30 min for analysis of mivacurium isomers. Recovery times for T1 to 25/50/75/90% (TW25–90), train-of-four ratio 25/70% and recovery index (time TW25–75) were recorded after stop of infusion.

Results: In the isoflurane group, lower infusion rates were needed (3.0 ± 1.6 versus 3.6 ± 1.6 μg kg−1 min−1) and there was a slower recovery (significant for train-of-four ratio 70%: 21.9 versus 17.9 min). The plasma concentrations of mivacurium and its trans–trans isomer (in percentage of the total) were significantly higher in the isoflurane group (10 min: 52.6 versus 25.8%; 30 min: 49.6 versus 23.2%).

Conclusions: For mivacurium, the phenomenon of ‘potentiation’ of the effect of muscle relaxants by volatile anaesthetics could be due to an increase in the plasma concentration of the potent trans–trans isomer.

Summary

Background and objective: In October 2000, we conducted a national postal survey of day case consultant anaesthetists in the UK to explore the range and variation in practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). This paper reports the findings of this national survey of paediatric day case anaesthetic practice carried out as part of a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery).

Methods: The survey used a structured postal questionnaire and collected data on the duration of surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flow rates used for general anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

Results: The overall response rate for the survey was 74 and 63% for the paediatric section of the survey. Respondents indicated that 19% used premedication, 63% used propofol for induction, 54% used isoflurane for maintenance, 24% used prophylactic antiemetics and 85% used a laryngeal mask. The findings of this national survey are discussed and compared with published evidence.

Conclusions: This survey identifies the variation in clinical practice in paediatric day surgery anaesthesia in the UK.

Summary

Background and objective: Many anaesthesiologists still interpret haemodynamic responses as signs of insufficient cortical suppression. The aim was to illustrate how haemodynamics may only poorly reflect the level of cortical suppression and that electroencephalographic monitoring could indicate different relationships between cortical effects and haemodynamics.

Methods: Anaesthesia was induced with thiopental (7 mg kg−1), and fentanyl (2 μg kg−1) with succinylcholine (1.5 mg kg−1) for neuromuscular blockade in the 11 patients of Group 1. In Group 2 (n = 15), thiopental (7 mg kg−1) and succinylcholine (1.5 mg kg−1) were given. In Group 3, the patients (n = 13) received thiopental (7 mg kg−1), fentanyl (2 μg kg−1) and cisatracurium (0.1 mg kg−1), and they were intubated 3 min later than the patients in Groups 1 and 2. We determined conventional electroencephalographic (EEG) variables and classified 14 EEG stages in real-time ranging from A (=1), indicating full wakefulness, to F1 (=14), at profound cortical suppression.

Results: All groups had profound cortical suppression 45 s after thiopental administration, which rapidly decreased (EEG stage, 11 (6–13) versus 7 (2–13) at 4 min, P < 0.0001). Decreasing EEG stages were associated with increasing SEF 95, relative α and β power and decreasing relative δ power. During tracheal intubation, profound cortical suppression remained unchanged in Groups 1 and 2. In Group 3, cortical suppression had decreased before laryngoscopy (P < 0.005). In Group 2, 11 patients had heart rate responses to tracheal intubation, whereas only two responded in Group 1 (P = 0.015) and three in Group 3 (P = 0.02). Thirteen patients in Group 2 had arterial pressure responses, and five in Group 1 (P = 0.038). Circulatory responses did not differ between Groups 1 and 3.

Conclusions: Electroencephalographic monitoring was suitable to indicate in real-time that haemodynamics only poorly reflect rapidly changing levels of cortical suppression, and how haemodynamics and cortical activity depend on the applied combination of hypnotic and analgesic drugs during anaesthesia induction with thiopental.

Summary

Background and objective: The bispectral index, a parameter derived from the electroencephalograph, has been shown to correlate with the loss of consciousness and sedation. This study was designed to assess the effects of bispectral index monitoring on sevoflurane and its recovery profiles.

Methods: Sixty ASA I and II patients undergoing open abdominal surgery were randomized into two groups: one monitored using the bispectral index (Group BIS) and the other without its use (controls). After a standardized induction, anaesthesia was maintained with sevoflurane in both groups. In Group BIS, sevoflurane was titrated to maintain the bispectral index in the range 40–60. In the control group, the administered sevoflurane concentration was adjusted according to the signs of anaesthesia. The end-tidal sevoflurane concentration, bispectral index and routine haemodynamic variables were noted every 5 min during surgery. The consumption of sevoflurane was computed. At the conclusion of surgery operations, the time to ‘open eyes on verbal command’, ‘motor response to verbal command’ and Aldrete's score were recorded by a blinded anaesthesiologist.

Results: The difference in the consumption of sevoflurane was not significant between the groups. Bispectral index monitoring was associated with a reduction of 4.73% in sevoflurane usage and 2.19 mL h−1 was saved.

Conclusions: Bispectral index monitoring during anaesthesia provides only a small advantage related to the need to monitor the depth of anaesthesia.

Summary

Background and objective: Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug.

Methods: Sufentanil citrate, 5 μg mL−1 was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1–5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter.

Results: ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 ± 0.01 μg mL−1, P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P < 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system.

Conclusions: Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Summary

Background and objective: When the endotracheal tube cuff is repeatedly aspirated to avoid excessive cuff pressure during nitrous oxide anaesthesia, a stable cuff pressure is eventually achieved. We assessed the time required to achieve a stable cuff pressure after repeated cuff deflation.

Methods: During 67% nitrous oxide and oxygen anaesthesia, air-filled cuffs of a standard tracheal tube (Mallinckrodt Hi-Contour®) were repeatedly deflated every 30 min for the first 3 or 4 h to inhibit excessive pressure (Groups Def-3 or Def-4, respectively, n = 10 for each); the cuff pressure was monitored for an additional 3 h. In some patients, the study was terminated at 1, 2, 3 and 4 h (n = 6 for each).

Results: Cuff pressure in Group Def-3, but not in Group Def-4, >22 mmHg after stopping cuff aspiration. Intracuff nitrous oxide concentrations increased during repeated cuff deflation and increased further in Group Def-3 during an additional 3 h (from 39.8 ± 4.7% to 44.3 ± 3.8%; P < 0.05), whereas intracuff nitrous oxide concentrations at 4 h were not different from those in Group Def-4 at the end of the study (43.7 ± 4.5% versus 42.3 ± 4.8%; P = 0.579).

Conclusions: When the air-filled cuff of the standard endotracheal tube is repeatedly deflated every 30 min for 4 h, but not for only 3 h, during nitrous oxide anaesthesia, a stable cuff pressure can be achieved without further deflation of the cuff. Our data also suggest that achieving an equilibrating nitrous oxide concentration in the cuff provides a subsequent stable cuff pressure.

Summary

Background and objective: To evaluate the efficacy, delay and duration of analgesia of three equianalgesic epidural doses of levobupivacaine, ropivacaine and bupivacaine during the first stage of labour.

Methods: One hundred and twenty-nine healthy primigravida in spontaneous labour who requested epidural analgesia were enrolled in a randomized observer-blinded study. Parturients were allocated to receive epidural levobupivacaine 0.0625%, ropivacaine 0.1% or bupivacaine 0.0625%. Sufentanil 10 μg was added to all solutions; the total volume of epidural solution was 20 mL. Pain was measured using a 100 mm visual analogue pain scale immediately before the epidural block, and at 5, 10, 15, 20 and 30 min thereafter. Motor block was evaluated using a modified Bromage scoring system. The adequacy of motor function for ambulation was also evaluated. Delay of analgesia was the time interval between the injection of the solution and the first painless contraction. Duration of analgesia was the time from the first painless contraction to the parturients' requests for further analgesia.

Results: Twelve parturients failed to complete the study. Eleven parturients had inadequate analgesia (four in Group Levobupivacaine, four in Group Ropivacaine and three in Group Bupivacaine; P > 0.05). Data was analysed from 34 parturients in Group Levobupivacaine, from 37 in Group Ropivacaine and from 35 in Group Bupivacaine. There were no differences in the delay of analgesia or in the number of parturients who were able to walk unaided. Levobupivacaine and ropivacaine produced more prolonged analgesia than bupivacaine (114 and 119 min, respectively, versus 89 min; P < 0.01).

Conclusions: During early labour, equipotent low concentrations of levobupivacaine, ropivacaine and bupivacaine, all with the addition of sufentanil 10 μg, produced similar pain relief and motor block, but levobupivacaine and ropivacaine produced a longer lasting analgesia. About 10% of parturients had inadequate analgesia with a single bolus of the tested solutions.

Summary

Background and objective: The study was designed to identify those factors associated with early tracheal extubation following cardiac surgery. Previous studies have tended to concentrate on surgery for coronary artery bypass or on other selected cohorts.

Methods: Sequential cohort analysis of 296 unselected adult cardiac surgery patients was performed over 3 months.

Results: In total, 39% of all patients were extubated within 6 h, 89% within 24 h and 95% within 48 h. Delayed extubation (>6 h after surgery) appeared unrelated to age, gender, body mass index, a previous pattern of angina or myocardial infarction, diabetes, preoperative atrial fibrillation, and preoperative cardiovascular assessment, as well as other factors. Delayed tracheal extubation was associated with poor left ventricular, renal and pulmonary function, a high Euroscore, as well as the type, duration and urgency of surgery. Early extubation (<6 h) was not associated with a reduced length of stay in either the intensive care unit or in hospital compared with patients who were extubated between 6 and 24 h. In these groups, it is presumed that organizational and not clinical factors appear to be responsible for a delay in discharge from intensive care. Patients who were extubated after 24 h had a longer duration of hospital stay and a greater incidence of postoperative complications. Postoperative complications were not adversely affected by early tracheal extubation.

Conclusions: In an unselected sequential cohort, both patient- and surgery-specific factors may be influential in determining the duration of postoperative ventilation of the lungs following cardiac surgery. In view of the changing nature of the surgical population, regular re-evaluation is useful in reassessing performance.