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.

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.

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.

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.