bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of baricity on the haemodynamic effects of intrathecal bupivacaine 0.5%
Authors: Critchley L. A. H. , Morley A. P. , Derrick J.
Published: March 2003

This study compared the haemodynamic effects of subarachnoid block with plain bupivacaine 0.5% (dextrose‐free), heavy bupivacaine 0.5% (in dextrose 8%) and a mixture of these two solutions, i.e. bupivacaine 0.5% in dextrose 4%. Thirty‐six male patients, aged 55–89 years, undergoing transurethral surgery were recruited. Invasive systolic arterial and central venous pressures were recorded at 5‐s intervals after the block was initiated using a computerised data‐collection system. The height of sensory blockade was recorded at 5‐min intervals. No preload was given and episodes of hypotension were treated with colloid (8 ml.kg−1) and, if this was ineffective, a metaraminol infusion. Systolic arterial and central venous pressures decreased in all three groups following block (p < 0.05). These decreases were more rapid in onset in the heavy bupivacaine group compared with plain bupivacaine group (p < 0.005). Patients in the heavy bupivacaine group also had a greater requirement for early treatment of hypotension (< 10 min) and treatment with metaraminol (p < 0.05). The onset of sensory blockade was more rapid in the heavy group compared with the mixed group, although final sensory levels were similar. The onset of haemodynamic and sensory changes are more rapid when using heavy bupivacaine intrathecally. This leads to a higher and earlier incidence of hypotension and requirement for treatment.
Patient‐controlled analgesia using remifentanil in the parturient with thrombocytopaenia
Authors: Jones R. , Pegrum A. , Stacey R. G. W.
Published: March 2003

Patient‐controlled intravenous remifentanil was used to provide analgesia in labour for three thrombocytopaenic women. The most successful regimen comprised a patient‐demand bolus of 0.5 μg.kg−1 with a lockout period of 2–3 min, allowing for a successful demand with each contraction. There was an initial period during which the patient learned to anticipate the next contraction and to deliver a bolus about 30 s beforehand; subsequently the remifentanil provided excellent analgesia, with a range of consumption of 426–1050 μg.h−1. Apart from one episode of maternal sedation and fetal heart rate decelerations resulting from an excessive demand bolus, mothers and neonates tolerated the remifentanil without sequelae. Owing to rapid metabolism by tissue esterase, the use of remifentanil allows adequate doses of opioid to be administered to the mother to achieve good analgesia, without its accumulation in the fetus.
The use of a blood conservation pressure transducer system in critically ill patients
Authors: Thorpe S. , Thomas A. N.
Published: March 2003

We tried to determine if a blood conservation pressure transducer system reduced blood transfusions, increased haemoglobin concentration or reduced line infections in critically ill patients. One hundred patients were randomly allocated to conventional or blood conserving systems attached to systemic and pulmonary arterial catheters. Intravascular lines were cultured after removal. There were no significant differences in transfusions or haemoglobin concentration. Blood conservation: median units transfused, 2 (range 0–19); mean haemoglobin at 7 days, 11.2 g.dl−1 (SD, 1.0). Conventional: median units, 2 (range 0–34); mean haemoglobin at 7 days, 11.1 g.dl−1 (SD 1.0). Thirty‐seven of 99 arterial lines were colonised in the controls compared with 29 of 96 in the blood conservation group. Patients who required haemofiltration in both groups had significantly increased transfusion requirements. Haemofiltration: median 6 units (range 0–34) vs. non‐haemofiltered: median 1 (range 0–14; p < 0.001). There were no significant differences in transfusions, haemoglobin concentration or line colonisation with the blood conservation system. There is considerable potential for blood conservation during haemofiltration.
The bacterial and viral filtration performance of breathing system filters*
Authors: Wilkes A. R. , Benbough J. E. , Speight S. E. , Harmer M.
Published: March 2003

The bacterial and viral filtration performance of 12 breathing system filters was determined using test methods specified in the draft European standard for breathing system filters, BS EN 13328‐1. All the filters were of two types, either pleated hydrophobic or electrostatic, and these two types differed in their filtration performance. The filtration performance is expressed in terms of the microbial penetration value, defined as the number of microbes passing through the filter per 10 million microbes in the challenge. The geometric mean (95% confidence limits) microbial penetration value was 1.0 (0.5, 3.5) and 2390 (617, 10 000) for the pleated hydrophobic and electrostatic filters, respectively, for the bacterial challenge, and 87 (48, 212) and 32 600 (10 900, 84 900), respectively, for the viral challenge. In general, there was little change in the microbial penetration values following 24 h simulated use. It is concluded that results from the tests specified in the draft standard will allow comparisons to be made between different manufacturers’ products enabling an informed choice to be made.
Difficult airway equipment in English emergency departments
Authors: Morton T. , Brady S. , Clancy M.
Published: March 2003

The need for tracheal intubation in the emergency department is often unpredictable and precipitous in nature. When compared with the operating room, a higher incidence of difficult intubation is observed. There are currently no accepted guidelines with respect to the stocking of difficult airway equipment in the emergency department. We have conducted a telephone survey to determine the availability of equipment for the management of the difficult airway in English emergency departments. Overall, the majority of units held a curved laryngoscope blade (100%), gum elastic bougie (99%) and surgical airway device (98%). Of alternative devices for ventilation, a laryngeal mask airway was kept by 65% of departments, a needle cricothyroidostomy kit by 63% and an oesophageal‐tracheal twin‐lumen airway (Combitube) by 18%. Of alternative devices for intubation, fewer than 10% held a retrograde intubating kit, intubating laryngeal mask, bronchoscope or lighted stylet. Seventy‐four per cent of departments held an end‐tidal carbon dioxide detector.
Protective effects of plasma replacement fluids on erythrocytes exposed to mechanical stress
Authors: Sümpelmann R. , Schürholz T. , Marx G. , Zander R.
Published: March 2003

Haemoglobin release from 40 suspensions of packed red blood cells in modified fluid gelatin, 4% albumin solution, 6% hydroxyethyl starch and normal saline was investigated in vitro during circulation with a roller pump from a heart–lung machine for 120 min at a flow rate of 2.5 l.min−1 at room temperature. The lowest haemoglobin release was obtained with erythrocytes in modified fluid gelatin, whereas free haemoglobin concentrations became progressively higher with albumin, hydroxyethyl starch and normal saline [median free haemoglobin (interquartile range) after 120 min circulation: gelatin 493 (360–601) mg.l−1, albumin 692 (590–1111) mg.l−1, hydroxyethyl starch 1121 (692–1518) mg.l−1, normal saline 1178 (881–1757) mg.l−1, p < 0.001]. Modified fluid gelatin appears to have potent erythrocyte protective properties similar to those of albumin. This effect could decrease mechanical haemolysis during extracorporeal circulation or cell saver autotransfusion if modified fluid gelatin is used as part of a priming solution or as an additive in wash solutions.
Failed tracheal intubation in obstetrics: a 6‐year review in a UK region
Authors: Barnardo P. D. , Jenkins J. G.
Published: March 2003

In the South Thames (West) region of the United Kingdom, during a 6‐year period from 1993 to 1998, there was a significant increase in the Caesarean section rate accompanied by a significant decrease in the use of general anaesthesia for operative delivery. During this time, there were 36 failed tracheal intubations occurring in 8970 obstetric general anaesthetics (incidence 1/249). There was no significant difference in the incidence of failed tracheal intubation in each of the six years. In 24 of the 26 cases for which the patients' notes could be examined, there was either no recording of pre‐operative assessment, a failure to follow an accepted protocol for failed tracheal intubation, or no follow‐up.
Determination of sevoflurane alveolar concentration for tracheal intubation with remifentanil, and no muscle relaxant
Authors: Cros A. M. , Lopez C. , Kandel T. , Sztark F.
Published: March 2003

The sevoflurane alveolar concentration needed for tracheal intubation with remifentanil was studied in 26 adult patients premedicated with 100 mg hydroxyzine. Anaesthesia was induced with sevoflurane in oxygen. The concentration was determined by Dixon's up‐and‐down method. The first patient was tested at 4.5%. One minute after obtaining the preselected value, remifentanil 1 µg.kg−1 was injected for 60 s followed by an infusion of 0.25 µg.kg−1.min−1. Ventilation was then manually assisted for 2 min and tracheal intubation was attempted. Tracheal intubation conditions and responses to intubation were noted. Heart rate and mean arterial pressure were recorded before induction, before remifentanil injection, and before and 3 min after tracheal intubation. The concentration for acceptable intubating conditions was 2.5 ± 0.7%. From logistic regression, ED50 and ED95 were 2.0% (95% CI 1.3–2.5) and 3.2% (95% CI 2.6–5.6), respectively. With sevoflurane 2.5%, heart rate and mean arterial pressure decreased by 18% and 15%, respectively, after remifentanil administration and increased slightly after tracheal intubation.
Isoflurane, desflurane and sevoflurane for carotid endarterectomy
Authors: Umbrain V. , Keeris J. , D'Haese J. , Verborgh C. , Debing E. , Van den Brande P. , Camu F.
Published: March 2003

After carotid endarterectomy under general anaesthesia, the rapid elimination of desflurane and sevoflurane may allow earlier postoperative neurological assessment than after the use of isoflurane. However, desflurane may be associated with tachycardia and hypertension and may therefore increase cardiovascular risk. We investigated haemodynamic and recovery characteristics in patients scheduled for carotid endarterectomy who were anaesthetised with isoflurane, sevoflurane or desflurane. No significant peri‐operative differences were noted in cardiac index or ST segment analysis. The times to extubation, movement on command and consciousness were shorter after desflurane and sevoflurane than after isoflurane anaesthesia. Postoperative pain, nausea, vomiting and shivering were similar in the three study groups.
Compliance with postoperative instructions: a telephone survey of 750 day surgery patients
Authors: Correa R. , Menezes R. B. , Wong J. , Yogendran S. , Jenkins K. , Chung F.
Published: March 2003

Patients undergoing day surgical procedures are given postoperative instructions not to drink alcohol, drive vehicles or make important decisions for 24 h. They are also advised to have a responsible adult stay with them at home overnight. Seven hundred and fifty patients were telephoned at 24 h postoperatively to determine their compliance with these instructions. Four per cent of patients drove vehicles, 1.8% consumed alcohol, while one patient made an important decision. A higher proportion of patients (5%) drove after general anaesthesia than regional anaesthesia or intravenous sedation (2.4%). The percentage of patients consuming alcohol was similar in both groups (1.8% vs. 1.9%). Four per cent of patients had no one staying with them overnight despite being accompanied out of the hospital. Patient compliance with instructions to not drink alcohol, drive or make important decisions may be improved by physician reinforcement of instructions and patient education.
The effect of nitrous oxide on the inhibition of somatosensory evoked potentials by sevoflurane in children
Authors: Vieira da Costa V. , Saraiva R. A. , Cardozo de Almeida A. , Rodrigues M. R. , Nunes L. G. N. , Ferreira J. C. D.
Published: March 2003

Inhalational anaesthetics inhibit somatosensory evoked potentials. The present study examined the effect of nitrous oxide in anaesthetic mixture with sevoflurane on the somatosensory evoked potential in children. Forty‐five patients aged between 6 months and 6 years undergoing club foot surgery were studied to verify the influence of sevoflurane alone (21 patients) and sevoflurane with nitrous oxide (24 patients) on the somatosensory evoked potential. Fractional inspired concentration of nitrous oxide and fractional end‐tidal (alveolar) sevoflurane were measured to estimate the multiples and submultiples of the minimal alveolar concentration (age corrected). The somatosensory evoked potential signals were obtained by stimulation of the median nerve. Nitrous oxide (FI = 0.63 ± 2.5) with sevoflurane caused more reduction in the amplitude of somatosensory evoked potential waves and a greater increase in the latency of somatosensory evoked potential waves in comparison with sevoflurane alone. The results show that it is possible to obtain the inhibition of somatosensory evoked potential with smaller concentrations of sevoflurane, when it is used with nitrous oxide.
The effects of ropivacaine hydrochloride on platelet function: an assessment using the platelet function analyser (PFA‐100)
Authors: Porter J. M. , Crowe B. , Cahill M. , Shorten G. D.
Published: March 2003

Amide local anaesthetics impair blood clotting in a concentration‐dependent manner by inhibition of platelet function and enhanced fibrinolysis. We hypothesised that the presence of ropivacaine in the epidural space could decrease the efficacy of an epidural blood patch, as this technique requires that the injected blood can clot in order to be effective. Ropivacaine is an aminoamide local anaesthetic used increasingly for epidural analgesia during labour. The concentration of local anaesthetic in blood achieved in the epidural space during the performance of an epidural blood patch is likely to be the greatest which occurs (intentionally) in any clinical setting. This study was undertaken to investigate whether concentrations of ropivacaine in blood, which could occur: (i) clinically in the epidural space and (ii) in plasma during an epidural infusion of ropivacaine, alter platelet function. A platelet function analyser (Dade PFA‐100, Miami) was employed to assess the effects of ropivacaine‐treated blood on platelet function. The greater concentrations of ropivacaine studied (3.75 and 1.88 mg.ml−1), which correspond to those which could occur in the epidural space, produced significant inhibition of platelet aggregation. We conclude that the presence of ropivacaine in the epidural space may decrease the efficacy of an early or prophylactic epidural blood patch.
High‐dose intrathecal diamorphine for analgesia after Caesarean section
Authors: Stacey R. G. W. , Jones R. , Kar G. , Poon A.
Published: March 2003

Forty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric 0.5% bupivacaine were randomly allocated to receive either 0.5 mg or 1 mg intrathecal diamorphine. All women received diclofenac 100 mg at the end of surgery and morphine via a patient‐controlled analgesia system. Oral analgesics were not used. Postoperative analgesia was more prolonged and more reliable in the 1‐mg group. Mean time to first analgesia was 10.2 h in the 1‐mg group and 6.9 h in the 0.5‐mg group, and 45% in the 1‐mg group used no morphine, compared with 10% in the 0.5‐mg group. Mean morphine consumption over 24 h was 5.2 mg in the 1‐mg group and 10.6 mg in the 0.5‐mg group. Pain scores all tended to be lower in the 1‐mg group but this was only significant at 4 h. There were no serious side‐effects. Minor side‐effects were common but well tolerated, and the incidence did not differ between the groups. If intrathecal diamorphine is used in combination with rectal diclofenac and without oral analgesia, then 1 mg provides superior analgesia to 0.5 mg without any worsening of the side‐effects.
Evaluation of the disposable Vital View™ laryngoscope
Authors: Asai T. , Uchiyama Y. , Yamamoto K. , Johmura S. , Shingu K.
Published: March 2003

The Vital View™ laryngoscope (Vital Signs, NJ, USA) consists of a plastic disposable blade containing a fibrelight and a non‐disposable handle; there is therefore no need to sterilise the blade and no concern about disintegration of the fibrelight. In a random cross‐over design, we compared the Vital View laryngoscope with a conventional metal fibrelight laryngoscope (Welch Allyn, NY, USA) in 100 patients. The Vital View laryngoscope produced a brighter field than the metal laryngoscope (p < 0.001), whereas there was no significant difference in the view of the glottis or the success rate of tracheal intubation. In no patient did any problem occur, such as damage to the laryngoscope blade or loss of light during laryngoscopy. In another 10 patients, prevention of light emission from the side of the laryngoscope blade reduced the brightness (p < 0. 01). This indicated that the brightness of the Vital View laryngoscope is produced by light emission not only from the tip of the blade but also from the side of the blade. Therefore, the disposable Vital View laryngoscope can be used as effectively as a conventional non‐disposable laryngoscope.
False‐positive epidural catheter aspiration tests in needle through needle combined spinal−epidural anaesthesia
Authors: Isaac R. , Coe A. J. , Hornsby V. P. L.
Published: March 2003

We describe two separate episodes of free aspiration of clear fluid through epidural catheters during needle‐through‐needle combined spinal−epidural anaesthesia in the lateral position. Although both catheters were assumed to have been located intrathecally, both subsequently gave negative test doses and were used as epidural catheters. In the second patient, the position of the catheter was investigated using contrast spiral computerised tomography scanning, which showed epidural contrast spread only. This is the first time such an occurrence has been recognised, and we consider its significance for catheter site confirmation testing in combined spinal−epidural anaesthesia.
Peri‐operative silent myocardial ischaemia and long‐term adverse outcomes in non‐cardiac surgical patients*
Authors: Higham H. , Sear J. W. , Neill F. , Sear Y. M. , Foëx P.
Published: March 2003

Two hundred and seventy‐five non‐cardiac surgical patients were recruited to determine risk factors associated with the development of postoperative cardiovascular complications during the first year after surgery. Patients underwent ambulatory electrocardiography pre‐ and postoperatively. There were 34 adverse events over the whole study period. Twenty‐four occurred within 6 months and the remaining 10 occurred between 6 and 12 months postoperatively. Silent myocardial ischaemia was associated with adverse outcome over both the first 6 months [OR 4.44 (95% CI 1.77–11.13)] and the whole study period [OR 2.81 (1.26–6.07)]. Other risk factors were: vascular surgery [OR 17.09 (2.67–351.44)], history of angina [OR 6.29 (2.21–17.62)], concurrent treatment with calcium entry blockers [OR 2.68 (1.03–6.93)] and smoking [OR 4.93 (2.00–12.02)]. None of these was a useful predictor of long‐term outcome (between 6 and 12 months postsurgery). These results are at variance with other published data, but we conclude that monitoring for peri‐operative silent myocardial ischaemia does not aid the prediction of long‐term cardiovascular complications.
Minimum local analgesic dose of plain ropivacaine vs. ropivacaine combined with sufentanil during epidural analgesia for labour
Authors: Palm S. , Gertzen W. , Ledowski T. , Gleim M. , Wulf H.
Published: March 2003

We have used the up‐and‐down allocation technique to assess the relative analgesic potencies of epidural ropivacaine alone and ropivacaine combined with sufentanil 0.75 µg.ml−1 in 42 women requesting epidural analgesia in the first stage of labour. Parturients were randomly allocated to one of the two epidural solutions in a double‐blind manner. The concentration of local anaesthetic was determined by the response of the previous parturient: an effective concentration (pain ≤ 10 mm on a 10‐cm visual analogue pain score within 30 min) resulted in a 0.01% decrease in the concentration of ropivacaine for the next parturient, an ineffective concentration resulted in a 0.01% increase. Minimum local analgesic concentration of ropivacaine alone was 0.13% (95% CI 0.12–0.13%) compared with 0.09% (95% CI 0.08–0.1%) for ropivacaine with sufentanil (p < 0.00001).
Prevention and management of hypotension during spinal anaesthesia for elective Caesarean section: a survey of practice
Authors: Burns S. M. , Cowan C. M. , Wilkes R. G.
Published: March 2003

Hypotension during obstetric spinal anaesthesia has traditionally been managed by such measures as fluid preloading, positioning of the patient and the use of vasoconstrictors. However, studies and reports have regularly appeared in the literature disputing the value of conventional management, in particular, the fluid preload. With this in mind, we surveyed UK consultant obstetric anaesthetists to determine current practice in this area. Of the 558 respondents, 486 (87.1%) stated that they routinely give a fluid preload. The fluid chosen by 405 (83.3%) of the preloaders was Hartmann's solution and the usual volume, chosen by 194 (39.9%), was 1000 ml. A simple left lateral position was preferred by 221 respondents (39.6%) overall and in the treatment of hypotension, ephedrine was the sole vasoconstrictor selected by 531 (95.2%). Heavy bupivacaine 0.5% was the local anaesthetic chosen by 545 (97.7%) and 407 (72.9%) respondents indicated the use of additional spinal drugs.
Matrix metalloproteinase‐9 concentrations in critically ill patients
Authors: Yassen K. A. , Galley H. F. , Webster N. R.
Published: March 2003

Matrix metalloproteinase‐9 is involved in the processing of cytokines during sepsis. We studied 10 critically ill patients within 12 h of fulfilling the American Consensus Conference criteria for severe sepsis and compared the results with 12 critically ill non‐septic control patients and eight healthy subjects. Total matrix metalloproteinase‐9 concentrations were measured on days 1, 2 and 3. The median admission Acute Physiological and Chronic Health Evaluation II score was 19.5 (range 13–27) in the septic patients and 20.5 (range 7–28) in the non‐septic patients. Four patients from each group died within 28 days. Matrix metalloproteinase‐9 concentrations were elevated significantly in both groups of patients compared with healthy subjects (p = 0.0004) but there was no difference between patients with and without sepsis. Matrix metalloproteinase‐9 levels did not change with time, and there was no difference between survivors and those who died. We conclude that matrix metalloproteinase‐9 represents a non‐specific marker of systemic inflammation.
Effects of propofol and nitrous oxide on middle cerebral artery flow velocity and cerebral autoregulation
Authors: Harrison J. M. , Girling K. J. , Mahajan R. P.
Published: March 2003

We studied the effects of adding 50% nitrous oxide to propofol anaesthesia administered by target‐controlled infusion on middle cerebral artery flow velocity and autoregulatory indices derived from transient hyperaemic response tests. Nine healthy (ASA 1) adult patients scheduled to undergo elective surgery were recruited. A standardised anaesthetic comprising alfentanil 10 µg.kg−1, propofol via a target‐controlled infusion pump and vecuronium 0.1 mg.kg−1 was used. Transcranial Doppler ultrasonography was used to measure middle cerebral artery (MCA) blood flow velocity and the transient hyperaemic response test was used to assess cerebral autoregulation. These measurements were performed while awake and then at an ‘induction’ target concentration of propofol (the target at which consciousness was lost, mean 6.2 (SD 1.1) µg.ml−1). The measurements were repeated after the addition of 50% nitrous oxide to the breathing gas mixture. Propofol caused a significant decrease in MCA flow velocity and a significant increase in the strength of autoregulation. The addition of nitrous oxide had no significant effect on MCA flow velocity or cerebral autoregulation. These results suggest that addition of 50% nitrous oxide does not influence propofol‐induced changes in cerebral haemodynamics.
Effect of videotape feedback on anaesthetists' performance while managing simulated anaesthetic crises: a multicentre study
Authors: Byrne A. J. , Sellen A. J. , Jones J. G. , Aitkenhead A. R. , Hussain S. , Gilder F. , Smith H. L. , Ribes P.
Published: March 2003

The aim of this study was to examine the performance of anaesthetists while managing simulated anaesthetic crises and to see whether their performance was improved by reviewing their own performances recorded on videotape. Thirty‐two subjects from four hospitals were allocated randomly to one of two groups, with each subject completing five simulations in a single session. Individuals in the first group completed five simulations with only a short discussion between each simulation. Those in the second group were allowed to review their own performance on videotape between each of the simulations. Performance was measured by both ‘time to solve the problem’ and mental workload, using anaesthetic chart error as a secondary task. Those trainees exposed to videotape feedback had a shorter median ‘time to solve’ and a smaller decrease in chart error when compared to those not exposed to video feedback. However, the differences were not statistically significant, confirming the difficulties encountered by other groups in designing valid tests of the performance of anaesthetists.
Sir Humphry Davy; his researches in respiratory physiology and his debt to Antoine Lavoisier
Authors: Sprigge J. S.
Published: March 2003

Summary This article shows how the original works of the French scientist Antoine Lavoisier were developed by Humphry Davy, a trainee surgeon from Cornwall, while he was working as a physiologist. Antoine Lavoisier had worked out how oxidation involved the consumption of oxygen and the release of energy. Davy's book, Researches Chemical and Philosophical, Chiefly Concerning Nitrous Oxide, published in 1799, describes the measurement of his own lung volumes, including the first recorded measurement of the residual volume. He measured his own rates of oxygen consumption and carbon dioxide production. He is famous for his investigations into nitrous oxide, but he also investigated the effects of breathing nitric oxide and carbon monoxide. He made these observations with a gasometer and analysis of his expired air, and his work anticipates the invention of blood gas analysis.
Measurement of systemic oxygen uptake during low‐flow anaesthesia with a standard technique vs. a novel method
Authors: Leonard I. E. , Weitkamp B. , Jones K. , Aittomaki J. , Myles P. S.
Published: March 2003

Summary We assessed agreement between measurement of systemic oxygen uptake using the Fick‐derived method, and a novel method described by Biro, based on the difference in oxygen concentrations of the delivered fresh gas and the gas circulating in the circle system. Twenty‐nine patients undergoing elective cardiac surgery were studied during stable haemodynamic and ventilatory conditions. Systemic oxygen uptake was measured using the two methods in each patient before and after cardiopulmonary bypass. Limits of agreement were found to be wide (−162 to 311 ml.min−1 before bypass, and −257 to 401 ml.min−1 after bypass), indicating poor agreement between the methods. No significant difference was found between the pre‐ and post cardiopulmonary bypass values for each method. We conclude that the Biro method, although attractive in terms of its simplicity, is an unreliable measure of systemic oxygen uptake under these conditions.
Tracheal intubating conditions using propofol and remifentanil target‐controlled infusions
Authors: Troy A. M. , Hutchinson R. C. , Easy W. R. , Kenny G. N.
Published: March 2003

Summary Using target‐controlled infusions (TCI) we aimed to determine the most appropriate dose of remifentanil required for intubation, using a steady effect‐site concentration of propofol and without the use of neuromuscular blocking drugs. Sixty ASA I−II patients presenting for elective surgery were randomly allocated to one of three groups. Anaesthesia was induced in all patients using a target‐controlled infusion of propofol 6.5 µg.ml−1. This was reduced to 3 µg.ml−1 after 1 min. Each group received a different TCI of remifentanil, 19, 15 or 11 ng.ml−1, which was reduced to 10, 8 or 6 ng.ml−1, respectively, after 1 min. Laryngoscopy and intubation were attempted at 4 min. Laryngoscopy and ease of intubation were assessed using a standard scoring system. Intubation was considered satisfactory in 75% of patients in groups 1 and 2 and 35% of patients in group 3. Intubation was successful in 20/20, 19/20 and 15/20 patients in groups 1, 2 and 3, respectively. Pulse oximetry, heart rate and noninvasive arterial pressure were measured pre‐induction, and at intervals until after laryngoscopy and intubation. Mean arterial pressure (MAP) and heart rate decreased following induction of anaesthesia in all groups, which was statistically significant. Following laryngoscopy, MAP and heart rate increased, but were significantly less than the corresponding baseline values.
A randomised, controlled, crossover trial of oral midazolam and nitrous oxide for paediatric dental sedation
Authors: Wilson K. E. , Welbury R. R. , Girdler N. M.
Published: March 2003

Summary A randomised, controlled, crossover trial was designed to assess the safety and effectiveness of oral midazolam sedation for orthodontic extractions. Forty‐six ASA physical status I children aged 10–16 years were recruited. Each child required two treatment sessions. Sedation with either oral midazolam 0.5 mg.kg−1 or nitrous oxide in oxygen was used at the first visit, the alternative being used at the second visit. Blood pressure, heart rate, arterial oxygen saturation, and sedation and behavioural scores were recorded every 5 min. Anxiety levels and postoperative satisfaction were also recorded. Blood pressure, heart rate and arterial oxygen saturation in both groups were similar and within acceptable clinical limits. The median [range] lowest arterial oxygen saturation levels for subjects in the midazolam and nitrous oxide groups were 95 [90–100]% and 98 [93–100]%, respectively. The median [range] time to the maximum level of sedation in the midazolam group was 20 [5–65] min compared with 5 [5–10] min in the nitrous oxide group (p < 0.001). The median [range] duration of treatment was similar in both groups (midazolam group: 10 [5–30] min, nitrous oxide group: 10 [5−25] min). Seventy‐four per cent of subjects were prepared to have oral midazolam sedation again, 54% preferring it. Oral midazolam appears to be a safe and acceptable form of sedation for 10–16‐year‐old paediatric dental patients.
A randomised, controlled trial of cognitive and psychomotor recovery from midazolam sedation following reversal with oral flumazenil
Authors: Girdler N. M. , Lyne J. P. , Wallace R. , Neave N. , Scholey A. , Wesnes K. A. , Herman C.
Published: March 2003

Summary Flumazenil is traditionally administered intravenously to reverse the adverse effects of over sedation with benzodiazepines. The aim of this study was to test postoperative cognitive and psychomotor recovery from midazolam conscious sedation, following reversal with orally administered flumazenil. It was hypothesised that when administered by the oral route, flumazenil may enhance recovery over a prolonged period, thus increasing safety. Eighteen patients requiring intravenous midazolam sedation for dental treatment completed a randomised, double‐blind, crossover trial. Following treatment the patients' sedation was reversed using either flumazenil or saline (asplacebo), administered orally, on alternate appointments. Assessment of mood and cognitive function were undertaken using ClinPhone.cdr®, a highly sensitive and specific computerised battery of cognitive tests administered by telephone prior to sedation and every hour for seven hours post reversal. Results indicate that within 20 min of administration, oral flumazenil is capable of partially reversing some cognitive and psychomotor impairments but the attentional and stimulus discrimination effects of midazolam sedation still remain.
Recovery room incidents: a review of 419 reports from the Anaesthetic Incident Monitoring Study (AIMS)
Authors: Kluger M. T. , Bullock M. F. M.
Published: March 2003

Summary Four hundred and nineteen incidents that occurred in the recovery room were extracted from the Anaesthetic Incident Monitoring Study database, representing 5% of the total database of 8372 reports. Incidents were reported mainly in daylight hours, with over 50% occurring in ASA 1–2 patients. The most common presenting problems related to respiratory/airway issues (183; 43%), cardiovascular problems (99; 24%) and drug errors (44; 11%). One hundred and twenty‐two events (29%) led to a major physiological disturbance and required management in the High Dependency Unit or Intensive Care Unit. Contributing factors cited included error of judgement (77; 18%), communication failure (57; 14%) and inadequate pre‐operative preparation (29; 7%), whilst factors minimising the incident included previous experience (97; 23%), detection by monitoring (72; 17%) and skilled assistance (54; 13%). Staffing and infrastructure of the recovery room needs to be supported, with ongoing education and quality assurance programmes developed to ensure that such events can be reduced in the future.
Measurement of tracheal tube cuff pressure in critical care
Authors: Vyas D. , Inweregbu K. , Pittard A.
Published: March 2003

We conducted an observational study to measure tracheal tube cuff pressures in the critical care environment, where prolonged intubation is common. Thirty‐two patients were studied. Sixty‐two per cent of all tracheal cuffs had intracuff pressures above the recommended value. We also conducted a telephone survey of 24 intensive care units within the Northern and Yorkshire Region, which showed that 75% of the intensive care units never checked tracheal tube cuff pressures. Critically ill patients are particularly vulnerable to tracheal injury due to prolonged intubation. We suggest that cuff pressures should be measured regularly.
Postanaesthetic shivering ‐ a new look at tramadol
Authors: Mathews S. , Al Mulla A. , Varghese P. K. , Radim K. , Mumtaz S.
Published: March 2003

Summary We studied whether tramadol administered at the time of wound closure can prevent  postanaesthetic shivering. One hundred and fifty patients scheduled for general anaesthesia and surgery were randomly allocated and tramadol was administered intravenously at a dose of

 2 mg.kg−1 in the high‐dose group, 1 mg.kg−1 in the low‐dose group and 0.9% saline in the control group. In the high‐dose group, 2% of patients had postanaesthetic shivering, compared to 4% in the low‐dose group and 48% in the control group (p < 0.001 vs. tramadol groups). There was no delay in tracheal extubation after reversal of neuromuscular blockade. The incidence of adverse side‐effects such as sedation and vomiting did not differ statistically and were clinically not significant. This study strongly supports the use of tramadol at wound closure for prevention of postanaesthetic shivering.
Survey of use of end‐tidal carbon dioxide for confirming tracheal tube placement in intensive care units in the UK*
Authors: Kannan S. , Manji M.
Published: March 2003

Summary The use of end‐tidal carbon dioxide monitoring to confirm the correct placement of a tracheal tube immediately after intubation is mandatory in the operating theatre. Tracheal intubation in critically ill patients can be challenging. Quick and accurate confirmation of tracheal tube placement is essential to minimise complications. This survey explored the use of end‐tidal carbon dioxide monitoring to confirm tracheal tube placement in intensive care units in the UK. Questionnaires were sent to either the lead clinician or clinical director of randomly selected general adult intensive care units. One hundred and twenty‐seven replies were received from the 215 questionnaires sent (response rate 59%). Twenty per cent of the units did not have an end‐tidal carbon dioxide monitor, 20% had one end‐tidal carbon dioxide monitor per bed and 60% had one end‐tidal carbon dioxide monitor between several beds. Only 50% of the units having an end‐tidal carbon dioxide monitor use it to confirm correct tracheal tube placement. Of these 50%, only about a third use it for every intubation. Seventy‐two per cent of respondents felt that end‐tidal carbon dioxide is well suited to confirm correct placement of tracheal tube in critically ill patients, but 50% did not think that confirmation using end‐tidal carbon dioxide should be mandatory for intubations outside the operating theatre. Half of the units not having end‐tidal a carbon dioxide monitor cited lack of resources as a reason. In summary, although four in every five intensive care units surveyed have end‐tidal carbon dioxide monitors, only a small proportion use them to confirm correct placement of tracheal tube after intubation.
The effect of neuromuscular blockade on the efficiency of mask ventilation of the lungs*
Authors: Goodwin M. W. P. , Pandit J. J. , Hames K. , Popat M. , Yentis S. M.
Published: March 2003

Summary We conducted a two‐part study to assess the practice of withholding neuromuscular blockade until the ability to ventilate the lungs using a bag and face mask (mask ventilation) has been established following induction of anaesthesia. The first part of the study consisted of a postal survey (71% response rate) of 188 anaesthetists in the Oxford region to assess their current practice. Thirty per cent of respondents always checked mask ventilation before administering a neuromuscular blocking drug, whereas 39% of respondents (all them consultants) never did this. A further 31% only did so in the case of known or anticipated difficulty with the airway. In the second part of the study, we measured inspired (VTI) and expired (VTE) tidal volumes before and after neuromuscular blockade in 30 patients undergoing general anaesthesia. The ratio VTE/VTI was used as a measure of the efficiency of ventilation. There was no difference in VTE/VTI before [mean (SD) 0.47 (0.13)] and after [0.45 (0.13)] neuromuscular blockade. We conclude that neuromuscular blockade does not affect the efficiency of mask ventilation in patients with normal airways.
The effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with desflurane*
Authors: Karsli C. , Luginbuehl I. A. , Bissonnette B.
Published: March 2003

Summary The aim of this study was to determine the effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with desflurane. Eighteen healthy children scheduled for elective surgery were enrolled into the study. Anaesthesia was induced using sevoflurane, and a caudal block was performed following tracheal intubation. Anaesthesia was maintained with 1 age‐adjusted MAC desflurane. A transcranial Doppler probe was used to measure middle cerebral artery blood flow velocity. Each patient was randomised to receive a sequence of either air/nitrous oxide/air or nitrous oxide/air/nitrous oxide in 30% oxygen. Fifteen minutes after each change in the nitrous oxide concentration, three measurements of cerebral blood flow velocity, blood pressure and heart rate were recorded. Neither the addition nor removal of nitrous oxide caused any significant changes in middle cerebral artery blood flow velocity, heart rate or blood pressure. This may be due to a more potent cerebral vasodilatory effect of desflurane in children.
Testing models of rift basins: structure and stratigraphy of an Eocene–Oligocene supradetachment basin, Muddy Creek half graben, south‐west Montana
Authors: Janecke  , McIntosh  , Good
Published: March 2003

We examine the basin geometry and sedimentary patterns in the Muddy Creek half graben of south‐west Montana by integrating geological mapping, structural and basin analysis, 40Ar/39Ar geochronology, biostratigraphy and reflection seismic data. The half graben formed in late Middle Eocene to early Oligocene (?) time at the breakaway of a regional, WSW‐dipping detachment system. Although the structure of the half graben is that of a supradetachment basin, facies patterns and basin architecture do not conform to a recent model for extensional basins above detachment faults. The border fault, the Muddy Creek fault system, consists of three en echelon, left‐stepping normal faults separated by two relay ramps. The fault steepens southward toward each en echelon step, ranges in dip from 8 to 60° near the surface, but flattens at depths between 0 and 3 km. A broad ENE‐plunging displacement‐gradient syncline defines the central part of the half graben and is flanked by narrow SE‐and NE‐plunging anticlines to the north and south. Fine‐grained deposits of the syntectonic basin‐fill are thickest in the central syncline and interfinger with footwall‐derived conglomerate near the adjacent anticlines. These facies patterns suggest that folding was coeval with extension and sedimentation in the half graben. Pre‐extensional volcanic rocks and interbedded conglomerate filled a major ESE‐trending palaeovalley along the future axis of the Muddy Creek half graben. Synextensional sedimentary deposits include lacustrine and paludal shale, mudstone and sandstone ponded in the centre of the half graben, and a narrow (typically <1.5 km wide) fringe of coarse alluvial‐fan and fan‐delta conglomerate and sandstone derived from the footwall. Angular unconformities and rock‐slide deposits occur only locally within the syntectonic sequence. These facies patterns agree well with the half‐graben depositional model of Leeder & Gawthorpe but not with a more recent supradetachment basin model of Friedmann & Burbank despite the demonstrably low dip‐angle of the basin‐bounding normal fault. These data show that it may not be possible to differentiate between supradetachment basins and half graben with steeper border faults using the architecture of the associated basin‐fill deposits.
Modelling rates and distribution of subsidence due to dynamic topography over subducting slabs: is it possible to identify dynamic topography from ancient strata?
Authors: Burgess  , Moresi
Published: March 2003

Dynamic topography formed over subducting oceanic lithosphere has been proposed as a mechanism to explain certain otherwise anomalous long‐wavelength patterns of subsidence inferred from ancient strata. Forward modelling of mantle flow in response to a subducting slab predicts amplitudes and distributions of dynamic topography that may occur due to various subducting slab geometries and histories. Plotting calculated dynamic topographies at a point against time produces tectonic subsidence curves. These subsidence curves show features such as evolution from convex to concave shape, amplitudes up to ~2000 m, subsidence rates up to ~220 m Myr−1, and a general decrease in subsidence amplitude away from the subduction zone, over a distance of ~2000 km. On many convergent continental margins, dynamic topography is likely to be superimposed on other subsidence mechanisms. In back‐arc basins, subsidence due to dynamic topography should be distinguishable from that due to extensional tectonics based simply on the temporal subsidence evolution expressed in the subsidence curve shapes. In a foreland basin setting, comparing dynamic topography models with forward models of flexural loading suggest the two processes can generate similar temporal subsidence patterns, but that dynamic topography causes subsidence over significantly greater wavelengths. Matches between calculated subsidence due to dynamic topography and backstripped subsidence patterns from Upper Cretaceous strata of the Western Interior Basin, USA, support the hypothesis that a long‐wavelength ‘background subsidence’ was caused by dynamic topography.
Thermal history during Mesozoic extension and Tertiary uplift in the Cameros Basin, northern Spain
Authors: Mata M. P. , Casas A. M. , Canals A. , Gil A. , Pocovi A.
Published: March 2003

Detailed structural cross‐sections, analysis of extensional structures and palaeotemperatures obtained from primary fluid inclusions in quartz and calcite veins from the extensional Cameros Basin (N Spain) allow an interpretation of its thermal evolution and its geometric reconstruction to be constrained. The Cameros Basin underwent an extensional stage during the Late Jurassic to Early Cretaceous, with a maximum preserved thickness of Mesozoic deposits of about 9000 m. During the Tertiary, the basin was inverted, allowing a large part of the sedimentary sequence to be exposed. Extensional deformation in individual beds created N120E‐striking tension gashes in the synrift sequence, parallel to the master normal faults limiting the basin and dipping perpendicular to bedding. The extensional strain calculated from tension gashes varies between 4 and 12%. The number and thickness of veins increases the lower their position in the stratigraphic section. Palaeotemperatures were obtained from samples along a stratigraphic section comprising a thickness of 4000 m synrift deposits. Homogenization temperatures range from 107 to 225 °C. Palaeothermometric data and geometric reconstruction give a geothermal gradient of 27–41 °C km−1 during the extensional stage and allow an eroded section of at least 1500 m to be inferred. Low‐grade metamorphic assemblages in lutitic rocks of the deepest part of the basin presently exposed at surface imply P–T conditions of 350–400 °C and less than 2 kbar, which implies a geothermal gradient of about 70 °C km−1. Since the metamorphic thermal peak is dated at 100 Ma, the P–T path indicates a heating event during the late Albian, probably linked to the reaching of thermal equilibrium of the continental crust after extension. The results obtained support the hypothesis of a synclinal basin geometry, with vertical superposition of Lower Cretaceous sedimentary units rather than a model of laterally juxtaposed bodies onlapping the prerift sequence.
Chemostratigraphic correlation of carbonate successions in the Gariep and Saldania Belts, Namibia and South Africa
Authors: Fölling P. G. , Frimmel H. E.
Published: March 2003

ABSTRACT Inter‐ and intrabasinal correlation of Neoproterozoic carbonate successions and associated glaciogenic deposits from the Pan‐African Gariep Belt and the Kango inlier in the Saldania Belt (Namibia and South Africa) is proposed on the basis of new δ13CCarb and 87Sr/86SrI data. Highly positive δ13CCarb values (as much as + 8.65‰) and low 87Sr/86SrI ratios (0.7071–0.7077) were obtained on carbonate successions of the Hilda Subgroup between an older and a younger diamictite in the Port Nolloth Group (Gariep Belt). These results are in agreement with data elsewhere that suggest deposition between the global ∼ 750 Ma Sturtian and ∼ 580 Ma Marinoan glaciations. Considerably lower, positive δ13CCarb values (up to + 1.01‰) and higher 87Sr/86SrI ratios (0.7082–0.7085) mark the carbonates (Bloeddrif Member, Holgat Formation) on top of the Numees Formation diamictite and support a correlation of this diamictite with the Marinoan glaciation.

In the southern extension of the Gariep Belt, correlation of the Widouw Formation limestone (Gifberg Group) with the Bloeddrif Member carbonates is proposed based on similar isotopic characteristics. In the Kango inlier of the Saldania Belt, two carbonate‐bearing members exist in the Matjies River Formation. The lower one of these two (Nooitgedacht Member) compares well with the Hilda Subgroup, whereas the upper one (Kombuis Member) shows strong similarities to the Bloeddrif Member carbonates. This implies that all younger stratigraphic units of the Kango inlier are not correlatives of the Port Nolloth Group, as previously assumed, but syn‐ to post‐orogenic with respect to the 540–580 Ma Pan‐African orogeny.