Measurement and modelling of air pollution and atmospheric chemistry in the U.K. West Midlands conurbation: overview of the PUMA Consortium project.

The PUMA (Pollution of the Urban Midlands Atmosphere) Consortium project involved intensive measurement campaigns in the Summer of 1999 and Winter of 1999/2000, respectively, in which a wide variety of air pollutants were measured in the UK West Midlands conurbation including detailed speciation of VOCs and major component analysis of aerosol. Measurements of the OH and HO2 free radicals by the FAGE technique demonstrated that winter concentrations of OH were approximately half of those measured during the summer despite a factor of 15 reduction in production through the photolysis of ozone. Detailed box modelling of the fast reaction chemistry revealed the decomposition of Criegee intermediates formed from ozone-alkene reactions to be responsible for the majority of the formation of hydroxyl in both the summer and winter campaigns, in contrast to earlier rural measurements in which ozone photolysis was predominant. The main sinks for hydroxyl are reactions with NO2, alkenes and oxygenates. Concentrations of the more stable hydrocarbons were found to be relatively invariant across the conurbation, but the impacts of photochemistry were evident through analyses of formaldehyde which showed the majority to be photochemical in origin as opposed to emitted from road traffic. Measurements on the upwind and downwind boundaries of the conurbation revealed substantial enhancements in NOx as a result of emissions within the conurbation, especially during westerly winds which carried relatively clean air. Using calcium as a tracer for crustal particles, it proved possible to reconstruct aerosol mass from the major chemical components with a fairly high degree of success. The organic to elemental carbon ratios showed a far greater influence of photochemistry in summer than winter, presumably resulting mainly from the greater availability of biogenic precursors during the summer campaign. Two urban airshed models were developed and applied to the conurbation, one Eulerian, the other Lagrangian. Both were able to give a good simulation of concentrations of both primary and secondary pollutants at urban background locations.

Airborne transmission of foot-and-mouth disease virus from Burnside Farm, Heddon-on-the-Wall, Northumberland, during the 2001 epidemic in the United Kingdom.

The results of a detailed assessment of the atmospheric conditions when foot-and-mouth disease (FMD) virus was released from Burnside Farm, Heddon-on-the-Wall, Northumberland at the start of the 2001 epidemic in the UK are consistent with the hypothesis that the disease was spread to seven of the 12 farms in the immediate vicinity of the source by airborne virus, and airborne infection could not be ruled out for three other premises; the remaining two premises were unlikely to have been infected by airborne virus. The distances involved ranged from less than 1 km up to 9 km. One of the farms which was most probably infected by airborne virus from Burnside Farm was Prestwick Hall Farm, which is believed to have been key to the rapid spread of the disease throughout the country. In contrast, the results of detailed atmospheric modelling, based on a combination of clinical evidence from the field and laboratory experiments have shown that by assuming a relationship between the 24-hour average virus concentrations and subsequent infection, threshold infection levels were seldom reached at the farms close to Burnside Farm. However, significant short-term fluctuations in the concentration of virus can occur, and short-lived high concentrations may have increased the probability of infection and explain this discrepancy.

Investigation of the possible spread of foot-and-mouth disease virus by the burning of animal carcases on open pyres.

An atmospheric dispersion model was used to predict the airborne spread and concentrations of foot-and-mouth disease virus within the plumes generated by 11 pyres built to burn infected carcases during the epidemic of 2001 in the UK. On the basis of assumptions about the quantity of virus emitted during the three hours after the pyres were built and the threshold concentration of virus required to cause an infection in cattle, it was concluded that none of the disease breakdowns which occurred under the plumes was due to the spread of virus from the pyres.

Patient-controlled analgesia: epidural fentanyl and i.v. morphine compared after caesarean section.

We have compared patient-controlled epidural fentanyl (PCEF) and patient-controlled i.v. morphine (PCIM) after Caesarean section in 84 patients, in a randomized, double-blind study. All patients had an epidural and an i.v. patient-controlled analgesia (PCA) device, one of which delivered normal saline. Group PCEF received epidural fentanyl 20 micrograms with a 10-min lockout. Group PCIM received i.v. morphine 1 mg with a 5-min lockout. PCA use was lower for PCEF patients (P = 0.0007). The highest pain score recorded at rest for PCEF patients was median 20 (interquartile range 10-33) mm compared with 32 (14-52) mm for PCIM patients (P = 0.02). The highest pain score recorded on coughing was 31 (21-41) mm with PCEF compared with 56 (30-71) mm for PCIM (P = 0.001). There was less nausea (P = 0.02) and drowsiness (P = 0.0003) with PCEF. There was no difference in the overall incidence and severity of pruritus (P = 0.77). However, pruritus started earlier with PCEF.

Analysis of a petrol plume over England: 18-19 January 1997.

OBJECTIVES: About 7000 tonnes of unleaded petrol were discharged into the English Channel after a tanker collision off Ostend on Saturday 18 January 1997. The petrol evaporated and the vapour plume was carried across the central part of England to Wales, resulting in reports of unidentified odours, and irritation of the eyes, skin, and upper respiratory tract. This work uses this incident to show how marine and atmospheric dispersion modelling together with routine air quality monitoring can assist in identifying hazards to the population at risk from chemical incidents. METHODS: Public health surveillance and results from environmental sampling were compared with the behaviour of the plume as predicted by computer modelling. RESULTS: The predicted plume path and dispersion were shown to correlate well with the results from surveillance and environmental analysis. CONCLUSIONS: There is a need for public health professionals to interact with medical toxicologists, atmospheric and marine scientists and engineers, and other environmental experts in managing events of this nature.

Does intrathecal fentanyl produce acute cross-tolerance to i.v. morphine?

We have examined the hypothesis that intrathecal fentanyl at operation can increase postoperative i.v. morphine requirements. We studied 60 patients undergoing Caesarean section. All received intrathecal 0.5% plain bupivacaine 2 ml combined with either fentanyl 0.5 ml (25 micrograms) (group F) (n = 30) or normal saline 0.5 ml (group S) (n = 30). In addition, 10 ml of an extradural solution (fentanyl 1 ml (50 micrograms) combined with 0.5% bupivacaine 9 ml) was administered after delivery. Extradural solution was only given before delivery if the intrathecal injection failed to produce a block above T6 or the patient required further analgesia. Postoperative analgesia was provided with i.v. morphine patient-controlled analgesia. At operation, intrathecal fentanyl reduced the need to administer extradural solution before delivery, increased the anaesthetist's satisfaction with analgesia and reduced nausea, but increased pruritus. Up to 6 h after delivery there was no difference in postoperative morphine requirements or pain scores. Between 6 h and 23 h there was a 63% increase in morphine requirements in group F. We consider the most likely explanation for this finding to be that intrathecal fentanyl induced acute spinal opioid tolerance.

Patient-controlled extradural analgesia with bupivacaine, fentanyl, or a mixture of both, after Caesarean section.

In this randomized, double-blind study of 60 patients, we have assessed the analgesic efficacy of extradural bupivacaine and extradural fentanyl, either alone or in combination, after Caesarean section. Patients received 0.1% bupivacaine (group B), fentanyl 4 micrograms ml-1 (group F) or 0.05% bupivacaine combined with fentanyl 2 micrograms ml-1 (group BF) by patient-controlled extradural analgesia (PCEA). Adding fentanyl to bupivacaine reduced the dose of bupivacaine by up to 68%, improved analgesia at rest and decreased PCEA use. Motor and sensory block were decreased, but there was more pruritus. Overall patient satisfaction was increased. Adding bupivacaine to fentanyl reduced the dose of fentanyl by up to 57% without altering pain scores or PCEA use. Sensory block increased but pruritus did not decrease. Bupivacaine 0.05% produced clinically significant leg weakness in three patients. Overall patient satisfaction was not altered. There was a significant additive analgesic effect between 0.05% bupivacaine and fentanyl but no clinical benefit was demonstrated from using the combination compared with fentanyl alone for this group of postoperative patients.

The anaesthetic management of Caesarean section for placenta praevia: a questionnaire survey.

The purpose of this study was to determine current UK anaesthetic practice regarding the use of regional anaesthesia in the management of patients with placenta praevia presenting for Caesarean section. We asked the members of the Obstetric Anaesthetists Association to complete a postal questionnaire in which a range of clinical situations involving varying degrees of placenta praevia were presented. In each case respondents were asked whether they would be willing to use regional anaesthesia. A wide variety of clinical practice was demonstrated. Anaesthetists with two or more obstetric sessions were more willing to use regional anaesthesia for Caesarean section in the presence of placenta praevia in both elective and emergency situations associated with haemorrhage.

Extradural fentanyl for postoperative analgesia: predominant spinal or systemic action?

This randomized, double-blind study of 40 patients was designed to determine if the predominant analgesic effect of extradural fentanyl is mediated by a direct spinal action or an indirect systemic one. After Caesarean section, postoperative analgesia was provided for 24 h by patient-controlled extradural analgesia (PCEA group) or by patient-controlled i.v. analgesia (PCIVA group). Both groups received a bolus dose of fentanyl 20 micrograms with a 10-min lockout interval. In the PCIVA group, nine patients stopped early (compared with none in the PCEA group) because of inadequate analgesia. Mean visual analogue pain scores (0-100 mm) at 8 and 12 h were lower for PCEA (23 (sd 13) mm at rest, 31 (23) mm on coughing) than for PCIVA (50 (25) mm at rest, 67 (24) mm on coughing) (P < 0.0005). The mean dose of fentanyl self-administered between 4 and 8 h was lower in the PCEA group (38 (sd 30) micrograms h-1) compared with the PCIVA group (59 (27) micrograms h-1) (P < 0.05). Our results support the hypothesis that the predominant analgesic effect of extradural administration of fentanyl is mediated by a direct spinal action rather than an indirect action from systemic absorption.

Mechanism of extension of spinal anaesthesia by extradural injection of local anaesthetic.

We have examined the effect of extradual injection of 0.5% bupivacaine or normal saline on the progression of spinal anaesthesia in 28 patients undergoing Caesearean section. Three groups were studied. Subarachnoid anaesthesia was established in all patients. Group A (n = 10), the control, received no extradural injection for 20 min. Group B (n = 9) received extradural bupivacaine 10 ml and group C (n = 9) received extradual saline 10 ml 5 min after the subarachnoid injection. Sensory levels were compared at 5-min intervals and extension of the block was found to be similar in groups B and C and significantly faster than the control (P < 0.05). The quality of anaesthesia and incidence of adverse effects was similar for all three groups. We conclude that the mechanism of extension of spinal anaesthesia by extradural injection of local anaesthesia is largely a volume effect.

Tonsils, obesity and obstructive sleep apnoea.

In this article the normal effects of anaesthesia on breathing are defined. Specific threats to the airway are identified and illustrated by reference to common clinical conditions.