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Biomedical subjects

J R Rigg

Publications and source records attributed to J R Rigg.

At least 19 recordsLinked to original sources
PubMed2000

Design of the multicenter Australian study of epidural anesthesia and analgesia in major surgery: the MASTER trial.

The Multicenter Australian Study of Epidural Anesthesia and Analgesia in Major Surgery (The MASTER Trial) was designed to evaluate the possible benefit of epidural block in improving outcome in high-risk patients. The trial began in 1995 and is scheduled to reach the planned sample size of 900 during 2001. This paper describes the trial design and presents data comparing 455 patients randomized in 21 institutions in Australia, Hong Kong, and Malaysia, with 237 patients from the same hospitals who were eligible but not randomized. Nine categories of high-risk patients were defined as entry criteria for the trial. Protocols for ethical review, informed consent, randomization, clinical anesthesia and analgesia, and perioperative management were determined following extensive consultation with anesthesiologists throughout Australia. Clinical and research information was collected in participating hospitals by research staff who may not have been blind to allocation. Decisions about the presence or absence of endpoints were made primarily by a computer algorithm, supplemented by blinded clinical experts. Without unblinding the trial, comparison of eligibility criteria and incidence of endpoints between randomized and nonrandomized patients showed only small differences. We conclude that there is no strong evidence of important demographic or clinical differences between randomized and nonrandomized patients eligible for the MASTER Trial. Thus, the trial results are likely to be broadly generalizable.

Aged↗
PubMed1999

Evidence-based methods to improve anaesthesia and intensive care.

This review concerns the application of the methods of clinical epidemiology to problems in anaesthesia and intensive care. It explores the quality of evidence to guide clinical decision-making and health policy provided by experimental and various non-experimental research designs. Ten recent publications in anaesthesia and intensive care are analysed to provide relevant examples.

Journal Article↗
PubMed1998

Rapid attainment of steady state plasma drug concentrations within precise limits.

We describe a method of rapidly obtaining a specified steady state plasma concentration of an intravenous drug within precise limits. The technique requires an initial bolus to raise the plasma concentration to the upper limit followed by a series of constant-rate infusions each of which is associated with a minimum plasma concentration equal to the lower limit. The infusion rate is stepped down when the plasma concentration returns to the upper limit. Computer simulation, based on the method, is used to generate plasma concentration-time curves with fluctuations of up to 10% about selected steady state concentrations of amrinone, esmolol, lidocaine, midazolam, propofol, and theophylline. The utility of this general approach to intravenous dosing and potential limitations of the method are discussed.

Computer Simulation↗
PubMed1998

Outcome after general or regional anaesthesia in high-risk patients.

This review is a critical analysis of research design for studies of outcome comparing epidural anaesthesia and analgesia with general anaesthesia and alternative postoperative analgesia regimens. If important advances in knowledge are to be made, appropriately designed multicentre randomized controlled trials are essential. These trials must incorporate strict controls on patient entry, a comprehensive range of carefully defined and clinically significant morbidity endpoints and the previous determination of sample size through a proper analysis of statistical power.

Journal Article↗
PubMed1991

Does regional block improve outcome after surgery?

Seventy-five years have elapsed since the first claim that the use of local anaesthetics improved surgical outcome. Despite extensive research, the literature provides contradictory views of the role of regional block in improving outcome. This paper attempts to reconcile these contradictions by examining biological hypotheses underlying the research question and reviewing relevant epidemiological clinical research methodology. The paper concludes with recommendations to prospective investigators for strategies in design, planning and execution of randomised trials to assess the efficacy of regional block in determining outcome after surgery.

Anesthesia, Conduction↗
PubMed1982

Control of breathing after fentanyl and Innovar anaesthesia.

Ventilation (VI), end-tidal (PCO2), mixed venous (PvCO2) and the ventilatory response to carbon dioxide were measured before surgery, and during the first 4 h of recovery in 18 adult patients who underwent elective limb surgery under fentanyl or Innovar anaesthesia. End-tidal and mixed venous PCO2 were increased significantly in the first 150 min after the last dose of drug (P less than 0.001, P less than 0.01), but had returned to control values by 4 h. Ventilation and ventilatory response to carbon dioxide were significantly depressed in all patients (P less than 0.001), but returned to near control values at 4 h. Fentanyl and Innovar anaesthesia displaced the carbon dioxide response to the right, but no correlation was found between either the magnitude of the displacement of the response curve or the alteration in slope and the control values. This suggests that patients with a low value of VI/PCO2 are not more susceptible to the ventilatory depressed action of narcotic anaesthetics. Recovery of ventilatory responsiveness towards normal during the 4 h after anaesthesia, occurred in a graded and progressive manner, there was no evidence of a biphasic pattern of recovery.

Adult↗
PubMed1981

Pulmonary atelectasis after anaesthesia: pathophysiology and management.

The pathophysiological basis of pulmonary atelectasis is reviewed and risk factors that enhance lung collapse are discussed. Management strategies to reduce or eliminate risk factors and to prevent collapse are discussed and the rational bases of these strategies are identified. Instability of lung alveoli is a consequence of surface tension and regional differences in alveolar size. The inherent tendency of alveoli to collapse is enhanced by the following risk factors; low lung volume, high closing volume, oxygen therapy, a rapid shallow ventilatory pattern, chronic lung disease, smoking, obesity, postoperative pain following abdominal or thoracic surgery, narcotic induced ventilatory depression, and neurological, neuromuscular, muscular and musculoskeletal diseases associated with mechanical impairment of respiratory function. The primary goal of perioperative respiratory management is prevention of atelectasis. Appropriate management strategies include physiotherapy and delay of elective surgery if substantial improvement in respiratory status can be achieved by specific treatments such as antibiotics, bronchodilators, steroids, and reduction of tobacco use and caloric intake. In selected cases, elective postoperative controlled ventilation may be indicated.

Analgesia↗
PubMed1981

A method for achieving rapidly steady-state blood concentrations of I.V. drugs.

The theoretical basis of a pharmacokinetic method to obtain rapidly and maintain a steady plasma concentration of an i. v. drug is described. Computer simulations of morphine disposition in man, using pharmacokinetic constants obtained from the literature, are provided as examples of steady-state dose regimens. The usefulness and potential limitations of the method are discussed.

Computers↗
PubMed1981

Steady-state plasma fentanyl in the rabbit.

Linear pharmacokinetic models were obtained for fentanyl in anaesthetized rabbits. A composite model was used to predict the bolus dose and infusion rates necessary to achieve rapidly a steady-state concentration of fentanyl in plasma. When this was tested in a further six rabbits, steady-state concentrations were greater than predicted. The most likely reasons for this are imperfect mixing between plasma and the central compartment, and substantial uptake of fentanyl by the lung. These sources of error were allowed for in modifications to the model. On further testing, a 4-h infusion set to achieve a plasma fentanyl concentration of 10 ng ml-1 yielded actual concentrations ranging from a mean low of 8.7 ng ml-1 to a mean high of 18.0 ng ml-1. The second model described more precisely the disposition of fentanyl, although a tendency to overestimate dosing requirement remained. This tendency is probably a consequence of continuing lung uptake of fentanyl. The demonstrated ability to obtain rapidly and maintain for 4h "steady" blood fentanyl concentrations suggests that the methods merits further investigation with other drugs both in animals and man.

Anesthesia, General↗
PubMed1981

Relationship of ventilatory depression to steady-state blood pethidine concentrations.

An i.v. infusion regimen was developed to permit rapid attainment of steady-state blood pethidine concentrations (Cpss). In 10 adult volunteers (12 studies) the relationship of pethidine Cpss to the ventilatory effects of the drug were examined. Mean pethidine Cpss ranged from 170 to 320 ng ml-1, with a median Cpss of 480 ng ml-1. Increased end-tidal (PE'CO2) and mixed venous (PVCO2) and decreased slope (delta VI/delta PCO2) and position (ISO-VI) of the carbon dioxide response were all significant (P less than 0.001) for Cpss (1) less than or equal to 480 and (2) greater than 480 ng ml-1. The averaged changes in PE'CO2, PVCO2, delta VI/delta PCO2, and ISO-VI expressed as a per cent of respective control variables, were shown to be linear functions of Cpss. It is concluded that, under conditions of Cpss, significant ventilatory depression occurs at blood pethidine concentrations less than those required for analgesia. The possible significance of these findings in volunteers is discussed in terms of this application to the clinical setting of postoperative pain and its management after general anaesthesia.

Adolescent↗
PubMed1981

An academic department of anaesthesia in a new Canadian medical school.

The development of an academic department of anaesthesia over its first ten years at McMaster Medical School in Hamilton, Ontario, Canada, is described. The organisation and goals of the department are described within the context of the regional organisation of health care delivery and of the functions of the faculty of health sciences. The activities of department members in various educational programmes, particularly the undergraduate and postgraduate programmes, are described in detail and the roles of the department in research and clinical anaesthesia and related clinical activities are also described. The role of an academic department of anaesthesia within a community of specialist anaesthetists is discussed.

Academic Medical Centers↗
PubMed1980

Changes in the perception of inspiratory resistive loads during partial curarization.

1. The ability of normal subjects to estimate the magnitude of resistive loads and to detect resistive loads was determined using standard psychophysical techniques. The experiments were repeated during maintained partial neuromuscular blockade with D-tubocurarine. 2. During curarization the ability to detect the presence of a small inspiratory resistive load was not significantly impaired. This finding is consistent with the view that changes in the usual breath-by-breath relation between pressure and flow mediate detection. 3. The size of resistive loads was over-estimated during partial curarization. Subjects thus placed more reliance on sensing the increased motor command required during curarization than on alternative peripheral signals related to pressure, flow or resistance. 4. The exponent for the power function relating the perceived magnitude of a resistive load to its actual size (Stevens, 1957) was reduced during partial neuromuscular blockade. 5. These results suggest that detection of resistive loads depends upon sensing apparent information arising from an unexpected pressure-flow disturbance but that estimation of the size of an added load depends, in part, on sensing the outgoing motor command.

Adult↗
PubMed1980

Paediatric outpatient surgery under general anaesthesia.

An innovative health care programme to provide anaesthesia and surgery to small children on an outpatient basis is described, together with the results of formal evaluations of the programme. It is concluded that, with attention to the education of the child and parents at a pre-anaesthetic clinic and the involvement of one parent with the induction and recovery of the child, the anaesthesia and surgery experience has negligible adverse psychological impact for the child, a positive influence on parental understanding and appreciation of the quality of anaesthesia care, in addition to a reduced incidence of cross infection and reduced cost to the health care system.

Ambulatory Surgical Procedures↗