Anthony H. Ilsley

The effect of fentanyl administered epidurally by patient-controlled analgesia, continuous infusion, or a combined technique of oxyhaemoglobin saturation after abdominal surgery.

The aims of this study were to determine the effect of three different modes of epidural administration of fentanyl on oxyhaemoglobin saturation and pain control. Forty‐three patients undergoing elective abdominal surgery were randomly allocated to the following groups: (1) continuous infusion of fentanyl at a rate of 50 μg.h−1 with additional epidural boluses (25 μg.Ug) as required; (2) patient‐controlled analgesia using a 25 fig epidural bolus of fentanyl with a 15 min lockout period; (3) a combination of patient‐controlled analgesia and continuous infusion. Oxyhaemoglobin saturation was measured by continuous computerised pulse oximetry for 48 h after operation together with pain and sedation scores. In the first 24 h after surgery patients in the continuous infusion group spent a significantly greater proportion of time below oxygen saturations of 94% and 85% than those in the other two groups. On day 2 all oxygen saturation measurements were worse than during day 1, but differences between groups were not significant. Those patients receding patient‐controlled analgesia required significantly less fentanyl than patients in either of the other groups (p < 0.05). However, the mean pain and sedation scores did not differ significantly between the three treatment groups. There was no association between total fentanyl dose and oxygen saturation values. Overall, self‐administered fentanyl appeared to cause less oxyhaemoglobin desaturation than nurse‐administered analgesia without any loss of analgesic effect.

Oxyhaemoglobin saturation following elective abdominal surgery in patients receiving continuous intravenous infusion or intramuscular morphine analgesia.

Oxygen saturation was continuously measured using computerised pulse oximetry for 8 h overnight pre‐operatively and for the first 24 h postoperatively in 40 patients receiving intermittent intramuscular morphine or continuous infusion of morphine following elective upper abdominal surgery. The proportion of time with an oxygen saturation less than 94% was used as an index of desaturation. Patients receiving continuous infusion analgesia received a larger morphine dose and achieved better analgesia than the intramuscular group. Postoperatively, the duration of desaturation increased 10‐fold over pre‐operative values, ‘intramuscular’ patients spending 39.0% (SD, 37.0%) and ‘continuous infusion’ patients 40.0% (SD, 37.5%) of the time below 94% saturation. Although newer therapies (e.g. epidural analgesia and patient‐controlled analgesia) are currently receiving greater attention, the sequelae of these more traditional analgesic techniques warrant further study.

Identification of movement artefact by the Nellcor N-200 and N-3000 pulse oximeters

Objectives. The Nellcor N-3000 pulse oximeter is designed to be ableto identify signal artefact related to movement of the body part to which theprobe is attached. It may therefore provide a reliable means of monitoringarterial oxyhemoglobin saturation (SpO2) in awake, movingpatients. This study compared the Nellcor N-3000 and N-200 pulse oximeters interms of their ability to identify readings associated with movement, in agroup of volunteers making standardized movements. Methods. Thirty-sixvolunteers were studied. Volunteers breathed room air throughout the study.SpO2 of each volunteer was monitored by both a Nellcor N-200and a Nellcor N-3000 simultaneously on both hands. Volunteers made a seriesof five standardized movements, each lasting one minute, with each hand duringthe monitoring session, while SpO2 and oximeter status wererecorded from all four oximeters. The mean SpO2 reading wascalculated during each movement. SpO2 readings which theoximeter identified as being associated with movement, pulse search notlocked, sensor not attached, or break in communications were excluded fromanalysis. Results. The N-3000 rejected from 17 to 78% of readings takenduring movement, compared to 0 to 2% with the N-200. Although the remainingreadings of both types of oximeters were subject to some movement artefact,which led to spuriously low SpO2, this was significantly lesswith the N-3000. Conclusions. The Nellcor N-3000 pulse oximeter is able,to some extent, to identify movement artefact. It should offer an advantageover the N-200 when monitoring moving patients.

An automated system for testing the accuracy of patient‐controlled analgesia devices

A system was developed to test the accuracy of patient‐controlled analgesia devices in situations simulating clinical use. Bolus requests are made automatically at predetermined intervals, and the infusate delivered is measured and recorded without the need for operator presence. To ensure clinical relevance, the bolus request times used in this study corresponded to a pattern typical of those requested by patients on the ward. Graseby, Abbott Provider 5500 and IVAC patient‐controlled analgesia devices were tested and found to deliver reasonably accurately over a 24 h period. However, when an infusion was started in an unprimed system or after a period of no bolus requests in a bolus‐only mode the Graseby and IVAC machines under‐delivered. This system provides a means of testing patient‐controlled analgesia devices operating in any delivery mode.

Use of artificial sweeteners to promote alcohol consumption by rats

Summary Cirrhosis may be reliably produced in rats by exposing them intermittently to low levels of carbon tetrachloride vapour while feeding alcohol in the Lieber‐DeCarli liquid diet. Providing the alcohol in drinking water that has been sweetened with sucrose is a cheaper and more convenient method but it does not yield reliable results. This study aimed to determine whether alcohol in drinking water sweetened with artificial sweeteners would give adequate alcohol intake to achieve the desired hepatic effects. Rats were fed alcohol (8% v/v) in drinking water sweetened with sucrose (5% w/v) (n = 12), or with one of the artificial sweeteners aspartame (0.025%), saccharin (0.025%) or cyclamate (0.05%) (n = 8 per agent). During the alcohol treatment the animals were exposed to carbon tetrachloride vapour, 40 ppm, six hours per night for five nights per week, over a period of 14 weeks. All groups achieved good alcohol intakes of 5–6 g/kg/day. Only one rat, in the aspartame group, became cirrhotic; all the others had varying degrees of fibrosis which did not differ significantly among the treatments. Although it was not effective in reliably achieving cirrhosis, sweetening the alcohol solution with artificial sweeteners led to reasonable alcohol intakes with resultant hepatic fibrosis, and without the high carbohydrate intake which occurs when sucrose is used.

Pulse oximetry in pulseless patients

The timely paper by Ridley and colleagues (Anaesthesia 1991; 4 6 523-30) confirms other work on the cost of intensive therapy.’-3 In 1988, our average cost per patient day was &550,2 which has now risen to E7.58 for the current financial year (1991/1992), with an average cost of E2653 per patient. The cost can be broken down under four budget headings and includes staff costs (57%), consummables (19%), equipment (3%) and hidden costs (21 YO). Clearly the equipment budget is starved of resource, but traditionally this has provided the Health Authority with an item to squeeze to balance the financial books. Hidden costs are an intriguing item, which represents El95 700 out of a total budget of 5928 874 (1991/1992). It includes National Insurance contributions at 4% (521 200), VAT on equipment and disposables at 17.5% (&34 500) and the fixed hospital overhead costs, e.g. rates, heat, light etc, which is calculated at f400 per patient (El40 000). Sheill et ~ 1 . ~ have also looked at the cost per survivor for selected diagnosis, which bear comparison with the costs in Canada4 and N ~ r w a y , ~ but not of course the USA.6 Shiell et aL’s study had five patients (5%) costing more than El0 000 and a further nine (1 3%) between 55000 and E9999. The next step must be to try to expand this work; it is not dissimilar from knowing the cost of dialysis or a heart transplant. We are then in a position to look at the way resources are being used in intensive care and match treatment strategy, clinical diagnostic group and outcome. A multicentre study to achieve this very basic knowledge is long overdue.

A system for standardized evaluation of patient-controlled analgesia devices: Design, construction, and engineering aspects

Objective. Our objective was to design, construct, and assess an automated system to perform standardized evaluation of patient-controlled analgesia (PCA) devices.Methods. We developed a computer-controlled test station. The computer activates the PCA device under test through a purpose-built serial interface device. The dose delivered is weighed on an electronic balance; then, at a predetermined interval, the computer interrogates the balance via the serial interface device to determine the weight gain. A robotic digit simulates patient button presses for four commonly used demand mechanisms. Software programs were written to test three types of patient-demand profile.Results. The automated system is sufficiently accurate for evaluating PCA devices and has been successfully used to perform and evaluate several thousand demands on six different models of PCA device.Conclusions. The test station has proved to be simple to use and extremely reliable, and has enabled the successful evaluation of several types of PCA device.RésuméObjectifs. Concevoir, construire et évaluer un systéme automatisé pour pratiquer une évaluation standardisée des dispositifs d’analgésie contrôlée par le patient (PCA). ’ethodes. Nous avons développé une station de test controlée par ordinateur. L’ordinateur actionne le dispositif de PCA à tester à traver une interface spécifique. La dose délivrée est pesée sur une balance électronique; ensuite à des intervalles préprogramméd, l’ordinateur interroge la balance à travers l’interface pour connaître le gain de poids. Un robot simule le patient et appuie 4 fois sur le mecanisme de déclenchement habituellement utilisé. Un programme a été fait pour tester, trois types de profil de demande.Résultats. Le système automatise est suffisamment précis pour révaluation des dispositifs de PCA et a ete utilise avec succes pour evaluer plusieurs milliers de demandes sur 6 differents modeles de PCA.Conclusions. La station de test a prouve sa simplicite ä l’usage, son extreme fiabilite et a ete capable d’evaluer avec succes plusieurs types de dispositifs de PCA.AbstractZiel. Entwicklung, Aufbau und Bewertung eines automatischen Systems zur standardisierten Evaluierung von Geräten zur patientenkontrollierten Analgesie.Methoden. Wir entwickelten einen Computer-kontrollierten Versuchs-stand. Der Computer aktiviert das zu untersuchende PCA-Gerat mit Hilfe einer zu diesem Zweck angepaβten seriellen Schnittstelle. Die verabreichte Dosis wird auf einer elektron-ischen Waage gewogen. Dann fragt nach einem vorbestimm-ten Intervall der Computer über die serielle Schnittstelle die Waage ab, um das gewonnene Gewicht zu bestimmen. Ein künstlicher Finger simuliert Knopfdrücke des Patienten für vier gebräuchliche Anforderungsmechanismen. Programme wurden fur die Prufung von drei Typen von Anforderungs-profilen des Patienten geschrieben.Ergebnisse. Das automatische System ist ausreichend genau fur die Evaluierung von PCA-Geräten und wurde erfolgreich fur die Durchführung und Messung einiger tausend Anforderungen bei sechs unterschiedlichen PCA-Geraten eingesetzt.Schluβfolger-ungen. Der Versuchsstand zeigte, daβ er einfach zu benutzen und extrem zuverlässig war. Er hat die erfolgreiche Evaluierung einiger Typen von PCA-Geraten ermoglicht.ResumenObjetivos. Diseñar, construir y evaluar un sistema automático para realizar evaluatión estandarizada de dispos-itivos de analgesia controlada por paciente.Métodos. Desar-rollamos una estaciön de pruebas controlada por computador. El computador activa el dispositivo de analgesia controlada por paciente a través de un dispositivo de interfaz construido con este propösito. La dosis proporcionada es pesada en una balanza electrónica; a intervalos preprogramados el computador interroga a la balanza mediante la interfaz serial para determinar el aumento de peso. Un dedo robótico simula las presiones del botón efectuadas por el paciente se’un cuatro mecanismos de demanda comúnmente usados. Se escribó programas computacionales para evaluar tres tipos de perfil de demanda de paciente.Resultados. El sistema automatico es suficientemente preciso para evaluar dispositivos de analgesia controlada por paciente y ha sido usado con éxito para realizar y evaluar varios miles de demandas en seis diferentes modelos de dispositivos de analgesia controlada por paciente.Conclusiones. La estación de pruebas probó ser simple de usar, estremadamente confiable e hizo posible la evaluatión exitosa de varios tipos de dispositivos de analgesia controlada por paciente.

Hepatic Injury in Rats Due to Prolonged Sub-anaesthetic Halothane Exposure

Fischer-344 rats of both sexes were exposed to halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) at a concentration of 50 p.p.m. for twelve weeks. During the course of the experiment, weight gain of both sexes was depressed and serum alanine aminotransferase activities were elevated, compared to control animals. The temporal pattern of alanine aminotransferase elevation differed between the sexes. After 12 weeks of exposure, liver/body weight ratio was increased in both sexes, and pathological changes were observed in their livers. Livers of all halothane-exposed animals showed focal liver cell necrosis, considerable lobular disarray and occasional mitoses. Many liver cells showed fatty change. None of these changes were observed in any control animals. These results indicate that prolonged exposure to a low concentration of halothane caused mild liver damage with regeneration. This finding may be of significance to humans occupationally exposed to halothane.