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Biomedical subjects

M D Vickers

Publications and source records attributed to M D Vickers.

At least 19 recordsLinked to original sources
PubMed1992

Tramadol: pain relief by an opioid without depression of respiration.

Two independent clinical trials were conducted simultaneously. In one, tramadol and pethidine were compared in 30 patients by patient-controlled analgesia during the first 24 h following abdominal surgery. The mean 24 h consumption of tramadol and pethidine was 642 mg and 606 mg respectively, giving a potency estimate of tramadol relative to pethidine of 0.94 (95% confidence interval 0.72-1.17). In the second trial, the effect on respiration of three doses of tramadol (0.5, 1.0, and 2.0 mg.kg-1) was compared with that of morphine sulphate (0.143 mg.kg-1) by intravenous injection during stable halothane anaesthesia. At approximately 1.5 times the equipotent dose, as estimated from the first trial, tramadol transiently depressed the rate of respiration but had no effect on end-tidal carbon dioxide tension. Morphine caused apnoea or considerable depression of ventilation. The results suggest that mechanisms other than opioid receptor activity play a significant role in the analgesia produced by tramadol.

Abdomen↗
PubMed1992

A comparison of the effects of codeine and tramadol on laryngeal reactivity.

The effect of tramadol on laryngeal reflex activity was assessed in a double-blind cross-over study in six volunteers receiving single oral doses of either codeine 50 mg, tramadol 50 mg or tramadol 100 mg. Laryngeal reactivity was measured by the response to the inhalation of dilute ammonia vapour. The minimum ammonia concentration required to induce a glottic stop was recorded prior to drug administration, and at 15, 30, 45, 60, 90, 120, 150 and 180 min thereafter. Psychometric tests were performed at 0, 45 and 105 min to detect any relationship between central sedation and changes in laryngeal reflex activity. The concentration of ammonia required to induce a glottic stop increased in all treatment groups, but more so in the tramadol groups. The time course suggested that the codeine effect peaked early, and had returned to normal within 2 h. For tramadol 100 mg, laryngeal depression appeared to be still increasing at the end of the 3-h study period. No correlation was found between laryngeal and sedative effects. Tramadol is produced as a racemic mixture, in which one isomer acts through an opioid receptor pathway whilst the other affects noradrenergic and serotonergic mechanisms. Both of these routes of action may be involved in the suppression of the response to experimentally induced cough.

Adult↗
PubMed1991

Effect of low concentrations of nitrous oxide and isoflurane on peak velocity of saccadic eye movements.

Peak velocity of saccadic eye movements was studied in six healthy volunteers who were each given, on separate days, 5% and 10% MAC of nitrous oxide (5% and 10% end-tidal) or of isoflurane (0.06% and 0.12% end-tidal) or air, each gas for 25 min. Subjective assessment following each treatment was also undertaken. No significant difference was found between air and either 5% or 10% nitrous oxide. However, significant differences occurred at 15 and 25 min after 0.06% isoflurane compared with air (P less than 0.05) and highly significant differences were present 5, 15 and 25 min after 0.12% isoflurane when compared with air and nitrous oxide (P less than 0.01). In contrast, there was little difference between the three gases by subjective assessment.

Adult↗
PubMed1991

Comparison of arterial and arterialized venous concentrations of propofol during infusion of propofol.

Seven patients received a series of low-dose propofol infusions designed to produce three successive pseudo-steady states of arterial blood concentration: 0.06, 0.17 and 0.43 micrograms ml-1. Arterial and arterialized venous blood samples were obtained simultaneously at the end of each infusion. The results indicate that 95% of the arterialized venous concentrations may be expected to lie within 1 +/- 43% of the corresponding arterial concentration, or -5 +/- 35% if one set of measurements with poor agreement between duplicate aliquots is omitted.

Arteries↗
PubMed1991

Effects of low concentrations of cyclopropane and halothane on peak velocity of saccadic eye movements.

We have investigated the effect of 4.7 and 8.8% MAC of cyclopropane, and 5.3 and 9.3% MAC of halothane on the peak velocity of saccadic eye movements (PSV) in six healthy volunteers. Both concentrations of cyclopropane and halothane significantly depressed PSV (P less than 0.01) compared with air, in a dose-related fashion. Halothane depressed PSV significantly more than cyclopropane (P less than 0.05). PSV returned to baseline within 5 min after discontinuation of the agents. There was no significant difference between cyclopropane, halothane and air in subjective assessment of sedation.

Adult↗
PubMed1991

The European Academy of Anaesthesiology--1992 and beyond.

The European Academy of Anaesthesiology was founded in 1978 as a means of meeting the challenges resulting from the introduction of the Medical Directives permitting the free movement of doctors within the European Community. The Academy is a scientific forum for anaesthetists throughout Europe--not just the EC countries--and has established its own English-language journal and multi-lingual Diploma examination. It is now embarking on a system of hospital recognition linked to intraining examinations. With the help of industry and a professional communications organization, it is also exploring the production of multi-lingual educational packages. It is believed that for effective evolution of hospital practice in Europe, medical specialties need to have their own academic organizations which will develop specialist training and which are in a position to provide appropriate advice to relevant national and European bodies.

Anesthesiology↗
PubMed1991

Effect of sub-anaesthetic infusions of propofol on peak velocity of saccadic eye movements.

Peak velocity of saccadic eye movements was studied in six healthy volunteers who received either 0.9% sodium chloride (as a control) or a stepwise rising propofol infusion regime of 0.24, 0.6 and 1.5 mg kg-1 h-1, which produced arterialized venous concentrations equivalent to 1%, 6% and 13% of the estimated EC50 for propofol. The infusion lasted for 75 min (25 min at each infusion rate) and was followed by a 2-h post-infusion recovery period. Peak saccadic velocity was highly significantly depressed during the 15-25-min period after the start of the second and third propofol infusions compared with saline. The relationship between arterialized venous blood concentration and peak saccadic velocity was similar during recovery when concentrations were falling to that during increasing blood propofol concentrations. Peak saccadic velocity decreased linearly with increasing log10 propofol concentration in the range of 25-800 ng ml-1 (14% of control per decade). Measured arterialized venous-blood propofol concentrations were variable, and systematically greater than computer predictions at the two higher infusion rates. In only half the subjects were the subjective assessments significantly correlated with log10 propofol concentrations or with percentage reduction in peak saccadic velocity.

Adult↗
PubMed1990

Comparison of the respiratory effects of i.v. infusions of morphine and regional analgesia by extradural block.

The incidence of postoperative respiratory apnoea was compared between five patients receiving a continuous i.v. infusion of morphine (mean 73.6 mg) and five patients receiving a continuous extradural infusion of 0.25% bupivacaine (mean 192 mg) in the 24-h period following upper abdominal surgery. Monitoring consisted of airflow detection by a carbon dioxide analyser, chest wall movement detected by pneumatic capsules, and continuous electrocardiograph recorded with a Holter ambulatory monitor. Both obstructive (P less than 0.05) and central apnoea (P less than 0.05) occurred more frequently in patients who had a morphine infusion. There was also a higher incidence of tachyarrhythmias (P less than 0.05) and ventricular ectopic beats (P less than 0.05) in the morphine infusion group.

Abdomen↗