Observations on deliberate dural puncture with a Tuohy needle: depth measurements

Observations were made during the use of a Tuohy needle to perform deliberate dural puncture for the insertion of lumbar drains to improve operating conditions for intracranial aneurysm surgery. The most striking finding was the distance from identification of the epidural space to penetration of the dura. We postulate that this was because of tenting of the dura by the blunt Tuohy needle. This was facilitated by the absence of a negative epidural space pressure because an open system was used, which allowed time for pressure equilibration. This minimised the reactive forces across the dura. Aspiration and rotation of the Tuohy needle revealed dural puncture in some cases.     

Low-flow anaesthesia

An 8-week survey was conducted to determine whether the introduction of low-flow anaesthesia (a fresh gas flow of 4 litres/minute or less) into routine use would be acceptable to members of a representative anaesthetic department and if the consequent reduction in use of volatile anaesthetics would result in financial savings. The hourly consumption of the volatile agents was measured during anaesthesia conducted using either conventional or low fresh gas flows. Anaesthetists' acceptance of low-flow anaesthesia was assessed using a questionnaire. Data were gathered on 286 patients undergoing inhalational anaesthesia for routine operative procedures. A 54.7% reduction in the consumption of isoflurane and a 55.9% reduction in that of enflurane was found. Of the 28 anaesthetists at the hospital, 21 would use low-flow anaesthesia routinely. The routine use of low-flow anaesthesia would therefore be acceptable and could result in annual savings of 26,870 pounds at Northwick Park Hospital.     

Selective bronchial intubation for one lung anaesthesia in thoracic surgery

A new method for one lung anaesthesia in thoracic surgery is described. Separate lung ventilation is obtained with selective main bronchus intubation, by means of an appropriate cuffed tube inserted through a standard orotracheal tube. Ventilation is carried out separately through the bronchial tube on one side and the residual tracheal tube lumen on the other side. This method greatly simplifies the technique of bronchial intubation and offers many advantages over commercially available double-lumen tubes.     

Pressure generated during insertion of lumbar epidurals. A comparison with the Portex epidural injection simulator

The aim of this study was to measure pressures exerted during insertion of lumbar epidurals in obstetric patients. The pressures were compared with those obtained when the Portex epidural injection simulator was used, and were significantly greater when a saline technique was used compared to those when air was used (p less than 0.05). There were no differences between the pressures obtained with the simulator and those measured in vivo.     

A comparison of the performance of 20 pulse oximeters under conditions of poor perfusion

The performance of 20 pulse oximeters with finger probes was evaluated by comparison of their readings with directly measured arterial blood oxygen saturations. The samples were taken from patients who had undergone cardiac surgery under hypothermic cardiopulmonary bypass and had poor peripheral perfusion. The mean difference (bias, accuracy), standard deviation (precision) and drop-out rate for each pulse oximeter was determined. An overall ranking of performance of each pulse oximeter was calculated using five criteria (accuracy, precision, number of readings within 3% of standard, percentage of readings given within 3% of standard, expected overread limit in 95% of cases). Two pulse oximeters achieved a combination of accuracy and precision such that 95% of measurements would be expected to be within 4% of the co-oximeter value; these two also had the lowest drop-out rate.     

Faulty Superset plastic catheter mounts

Nine Superset (Intersurgical Ltd) single-use corrugated plastic catheter mounts were found to be faulty in a boxed batch of 75. The manufacturer's meticulous system of batch coding enabled the source of the problem to be traced quickly. Sporadic faults must be expected to occur in mass-produced disposable equipment and the unusual origin of the defect reported in these catheter mounts is testimony to the way unexpected events can prejudice the most carefully regulated quality control. It is emphasised that the user can help safeguard the community by ensuring that stock is used in strict rotation and that batch numbers are accurately reported when faults arise.     

ATB细菌鉴定仪与手工法鉴定结果比较分析

目的通过分析比较细菌鉴定仪与手工法鉴定结果，以期建立一套现实可行的仪器与手工相结合的鉴定方法。方法用ATB细菌鉴定仪与手工法分别鉴定29株来自质控及临床标本菌株。结果鉴定29株细菌其中有2株细菌仪器与手工法的鉴定结果不符。结论合理应用传统的手工法不失为仪器鉴定的一种辅助方法。手工法也可将细菌准确地鉴定到种，为没有细菌自动鉴定仪的基层医院增强了细菌鉴定的信心。     

乳腺显像装置在99Tcm-MIBI乳腺显像中的多中心应用

目的：探讨乳腺显像装置对^99Tc^m-甲氧基异丁基异腈（MIBI）乳腺显像诊断乳腺肿块的价值。方法：多医疗中心采用广东省人民医院设计的乳腺显像装置行^99Tc^m-MIBI乳腺显像，采用特殊俯卧位检查。721例受检查^99Tc^m-MIBI乳腺显像结果均与病理检查资料对照。其中行B超检查137例，红外线检查86例，针吸细胞学检查112例。结果：^99Tc^m-MIBI乳腺显像、B超、红外线检查、针吸细胞学检查对乳腺肿块诊断的灵敏度分别为92．28％、75．44％、69．44％、80．90％，特异性分别为87．0％、75．00％、54．00％、100％。结论：应用该显像装置的^99Tc^m-MIBI乳腺显像对诊断乳腺肿块有较高的灵敏度和特异性。     

Evaluation of long sampling tubes for remote monitoring by mass spectrometry

The long sampling tubes required for remote mass spectrometry alter the sampling system’s performance characterized by sample flow, residence time, and 10 to 90% response time. We searched for an easy-to-handle tube with (1) a length of 30 m, (2) sample flow less than 50 ml · min^-1, and (3) residence and response times approaching those predicted by our mathematical model. We tested tubes of various geometries and various commercially available materials by using them as inlet catheters for a quadrupole mass spectrometer (Centronic 200 MGA, Centronic Ltd, Craydon, UK). We measured their responses at 0 to 10% (on transients) and 10 to 0% (off transients) step changes in gas concentration for nitrogen, argon, nitrous oxide, oxygen, and carbon dioxide and 0 to 3% and 3 to 0% for halothane, enflurane, and isoflurane. With 5 polyethylene tubes, halothane response times were up to 38 times longer than predicted. One 30-m polyethylene tube combined a 158-ms response time for nitrogen and argon with a 2,205-ms response time for halothane. Teflon, polyvinyl chloride, and stainless steel also proved to be unsuitable because of unacceptable signal distortion: the carbon dioxide response time for a 30-m Teflon tube was 2,600 ms. A glass tube showed the least signal distortion but was hard to handle. Our requirements were fulfilled by a 29.77-m tube made from nylon with a 1.00-mm inside diameter to which a 0.23-m length of nylon with a 0.25-mm inside diameter was added at the patient end. It offers (1) sample flow equals 46 ml · min^-1, (2) residence time equals 11.1 seconds, and (3) response times approaching our theoretical predictions, that is, 159, 164, 180, 159, 188, 302, 298, and 300 ms (means of on and off transients) for nitrogen, argon, nitrous oxide, oxygen, carbon dioxide, halothane, enflurane, and isoflurane, respectively. This tube allows the accurate monitoring of breathing frequencies up to 25 and 50 breaths/min for volatile agents and gases, respectively.     

Evaluation of a small soda lime canister in a to-and-fro system

The main disadvantages of the to-and-fro system (the bulky canister and the progressive increase in apparatus deadspace) may be overcome by the use of a smaller canister. In this laboratory study, we have evaluated a 160 g canister in a low-flow to-and-fro system (fresh gas flow 1 litre/minute). Two carbon dioxide productions of 150 and 200 ml/minute were simulated. The mean times to exhaustion, defined here as a 0.5 kPa rise in end-tidal PCO2, were 112 and 79 minutes in the 150 and 200 ml/minute carbon dioxide groups respectively. Ventilation to normacapnia or hypocapnia did not affect the times to exhaustion. The soda lime absorbed 16 litres of carbon dioxide before exhaustion, and this was not affected by minute volume or carbon dioxide production. A small soda lime canister is suitable for carbon dioxide absorption in a low-flow to-and-fro system for ventilated adults.