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Biomedical subjects

D R Bevan

Publications and source records attributed to D R Bevan.

At least 163 records · Page 9Linked to original sources
PubMed1981

Clinical pharmacokinetics and pharmacodynamics of fazadinium in renal failure.

The pharmacokinetic behaviour and neuromuscular blockade produced by the administration of fazadinium bromide at a dose of 1 mg/kg have been studied in seven patients with end-stage renal failure. No significant differences were found in the pharmacokinetic or pharmacodynamic properties when compared with patients with normal renal function. It is suggested that fazadinium may be superior to either d-tubocurarine or pancuronium in providing muscle relaxation for patients with renal failure.

Adult↗
PubMed1981

Controlled succinylcholine infusion in a patient receiving echothiophate eye drops.

A 69 year old man receiving echothiophate eye drops for glaucoma was given a controlled infusion of succinylcholine during elective surgery for incisional hernia. Neuromuscular blockade was assessed by the measurement of the force of contraction of the adductor pollicis muscle. Only 9.5 mg succinylcholine were required for tracheal intubation and 1.1 mg/min for maintenance. When the infusion was stopped, recovery of neuromuscular transmission was rapid and uneventful. Plasma cholinesterase activity was 62 per cent below normal, but the enzyme was qualitatively normal. Thus, muscle relaxation can be achieved safely with a succinylcholine infusion in patients with decreased plasma cholinesterase activity if neuromuscular function is closely monitored.

Aged↗
PubMed1981

Anaesthesia for the morbidly obese. Experience with 110 patients.

The anaesthetic management and postoperative complications of 110 grossly obese patients undergoing weight-reducing surgery have been reviewed. The major problems were technical, related to the bulk of the patient, and respiratory, caused by alterations in pulmonary physiology. Extradural catheters were placed in 70 patients before induction of general anaesthesia. In all patients the trachea was intubated during anaesthesia and the lungs ventilated with large tidal volumes and appropriate inspired oxygen concentrations. Muscle relaxation was achieved with extradural block in 35 patients; the remainder received pancuronium i.v. Extradural analgesia with bupivacaine provided excellent analgesia after surgery and greatly facilitated nursing care.

Adult↗
PubMed1981

Mixed neuromuscular block: the effect of precurarization.

The effects of precurarisation, with small doses of pancuronium, curare or gallamine, on the neuromuscular blockade following suxamethonium, 1 mg/kg, were studied using train-of-four stimulation. The duration of the block was reduced by pretreatment with d-tubocurarine and gallamine but increased with pancuronium. The degree of competitive neuromuscular blockade, both after administration of the precurarising dose and at full recovery from suxamethonium was mild and was insufficient to be a cause of postoperative muscle weakness.

Adolescent↗
PubMed1980

Transport of a carcinogen, benzo[a]pyrene, from particulates to lipid bilayers: a model for the fate of particle-adsorbed polynuclear aromatic hydrocarbons which are retained in the lungs.

Fluorescence spectroscopic methods were used to investigate the effects of adsorption of benzo[a]pyrene to particulate matter on its rate of uptake into model membranes composed of dipalmitoyl L-alpha-phosphatidylcholine. From these experiments we conclude the following: 1. Adsorption of benzo[a]pyrene to four types of asbestos (anthophyllite, crocidolite, chrysotile, and amosite) and a variety of non-fibrous particles (hematite, silica, titanium dioxide, porous glass and talc) results in increased rates of membrane uptake when compared with aqueous suspensions of benzo[a]pyrene microcrystals. Benzo[a]pyrene was not released from carbon black. 2. Asbestos-adsorbed benzo[a]pyrene was transferred to the membranes most rapidly. 3. Adsorption of benzo[a]pyrene to the surface of the particles is necessary for its enhanced transport into membranes. That is, simple mixtures of benzo[a]pyrene microcrystals and particulates do not show enhanced transport. 4. Particle-enhanced transport of benzo[a]pyrene is not correlated with the effects of the particles on vesicle integrity, binding of vesicles to the particles, or the concentrations of either particles or vesicles. The rate limiting step for transport of benzo[a]pyrene into vesicles appears to be its rate of desorption from the surface of the particle. Following desorption, membrane uptake of benzo[a]pyrene is rapid.

Adsorption↗
PubMed1980

Mechanism of porphobilinogen synthase. Requirement of Zn2+ for enzyme activity.

The role of metal ions in the mechanism of action of bovine liver porphobilinogen synthase was investigated. Studies with chelating agents were consistent with a requirement of metal ions for enzyme activity, and the use of 8-hydroxyquinoline-5-sulfonic acid suggested that Zn2+ was present in the enzyme. The low activity detected in metal-free apoporphobilinogen synthase was attributed to adventitious metal ions. Addition of Zn2+ to the apoenzyme completely restored enzyme activity if the essential sulfhydryl groups on the enzyme were first reduced with sulfhydryl reagents. It does not follow necessarily from this observation that Zn2+ forms a bond with a sulfhydryl group in the enzyme. However, we also observed that Zn2+ did not bind to the enzyme unless the essential cysteinyl residues were reduced. We have concluded that the octameric enzyme contains 4 g atoms of Zn2+/mol from our enzyme activity measurements and binding studies. Alkylation of the enzyme resulted in a marked reduction in the binding of Zn2+ to the enzyme. These observations are consistent with the suggestion that the interaction of the Zn2+ ions with the enzyme occurs with sulfhydryl groups at the active site. It appears that Zn2+ does not participate in substrate binding nor in the maintenance of the quaternary structure of the enzyme. Possible mechanistic roles for Zn2+ in porphobilinogen synthase are discussed. It should be noted that Cd2+ was the only other element found which restored activity to the apoenzyme.

Animals↗
PubMed1980

Benzo[a]pyrene uptake into rat liver microsomes: effects of adsorption of benzo[a]pyrene to asbestos and non-fibrous mineral particulates.

The fluorescence yield of benzo[a]pyrene (BP) increases dramatically upon its transfer from the surface of particulates to rat liver microsomes. Adsorption of BP to Canadian chrysotile, anthophyllite, hematite and silica results in greatly enhanced uptake rates into microsomes when compared to uptake from a microcrystalline dispersion of BP. The fibrous minerals chrysotile and anthophyllite were more effective than silica and hematite in enhancing BP uptake. Simple mixtures of BP microcrystals and particles did not display enhanced transport, indicating that adsorption of BP to the particulate surface is necessary for enhanced microsomal uptake. BP was not released into microsomes from carbon black. We suggest that particulate-enhanced availability of BP may be of significance in the co-carcinogenesis between particulates and polynuclear aromatic hydrocarbons. However, other mechanisms are also possible, and are not excluded by our experiments. The fluorescence methodology, described in this paper provides a novel and convenient means to quantify microsomal uptake of BP and thereby investigate further the mechanisms of cocarcinogenesis.

Adsorption↗
PubMed1980

Neostigmine, pyridostigmine, and edrophonium as antagonists of pancuronium.

This study was performed to compare the effects of three anticholinesterases on rates of recovery from pancuronium-induced neuromuscular blockade. Pancuronium (3 mg/70 kg) was antagonized during nitrous oxide-oxygen-halothane anesthesia, in man, with neostigmine (2.5 or 5.0 mg/70 kg), pyridostigmine (10 or 20 mg/70 kg), or edrophonium (50 or 100 mg/70 kg). Reversal was attempted at 10 per cent spontaneous recovery of muscle twitch, which was measured by use of train-of-four stimulation. Following administration of the antagonists each patient had progressive recovery of neuromuscular function. Recurarization was not observed during the period of study. Recovery was most rapid with edrophonium and slowest with pyridostigmine. Five minutes after administration of the antagonists, mean T4, the height of the fourth twitch as a percentage of the first in each train, exceeded 50 per cent only with the larger dose of neostigmine and both doses of edrophonium. Thirty minutes after reversal there was no significant difference in recoveries among the drugs tested, and T4 exceeded 70 per cent for all patients. It is concluded that, under the conditions of this study, neostigmine, pyridostigmine, and edrophonium induce sustained antagonism of pancuronium-induced neuromuscular blockade. The antagonism produced by large doses of edrophonium is faster than that produced by neostigmine or pyridostigmine.

Adolescent↗
PubMed1980

Clinical pharmacokinetics of fazadinium.

Fazadinium was administered as an intravenous bolus of 0.5 or 1 mg/kg to nine patients during neurolept-anaesthesia. Continuous recording of neuromuscular activity and serial collection of blood samples for drug assay allowed the relationship between neuromuscular blockade and plasma fazadinium concentration to be studied. Pharmacokinetic analysis demonstrated high plasma clearances (221 and 185 ml/min), and short terminal half-lives, (30 and 50 min), for the two doses of the drug. Mean plasma concentrations at 10 and 50% recovery were 1.42 and 0.88 micrograms/ml respectively, demonstrating that the potency of fazadinium is approximately half that of tubocurarine and one eighth that of pancuronium. In addition, the relationship between plasma concentration and depression of neuromuscular activity during spontaneous recovery from the relaxant is described.

Adult↗
PubMed1980

Colloid osmotic pressure.

Technical advances have made the bedside measurement of colloid osmotic pressure (COP) a rapid and reproducible test. The principles of measurement are described and the place of COP determinations in the recognition, treatment and prophylaxis of oedematous states is discussed.

Aged↗
PubMed1979

Shy-Drager syndrome. A review and a description of the anaesthetic management.

Autonomic failure in patients with the Shy-Drager syndrome may produce cardiovascular instability during anaesthesia and surgery. The syndrome is reviewed and the anaesthetic management of a case is described. The choice between general and regional anaesthesia seems to be less important than adequate cardiovascular monitoring and the maintenance of blood pressure with intravenous fluids. Sympathomimetic drugs, if used at all, should be administered in very dilute solutions to avoid hypertension from denervation hypersensitivity. In the postoperative period, symptoms from orthostatic hypotension may be severe and their control requires prolonged postural training, by elevation of the head of the bed, and therapy with 9-alpha-fludrocortisone.

Anesthesia, General↗
PubMed1978

Fluid loading to reduce abnormalities of fetal heart rate and maternal hypotension during epidural analgesia in labour.

Fetal heart rate (FHR) was recorded and maternal blood pressure measured in 104 patients in whom lumbar epidural analgesia was induced in labour. Fifty-one patients received an intravenous load of 11 of Hartmann's solution immediately before the epidural injection. This infusion significantly reduced the incidence of abnormalities of FHR from 34% to 12% and of maternal hypotension from 28% to 2%. We did not study mothers with pre-eclampsia and hypertension, but we conclude that there is a strong case for preloading all other mothers in whom lumbar epidural analgesia is induced in labour.

Anesthesia, Epidural↗
PubMed1978

Osmolar output in the peri-operative period.

The hourly urine volume and urine concentration of seven patients undergoing major abdominal surgery were measured during the operative and postoperative periods. From these, the hourly osmolar output was calculated. The results show that the osmolar output, 700 mOsm/day, in the peri-operative period is less than that of a 70 kg man consuming a normal 2000 calorie diet. Calculation of the osmolar output might help in the differentiation of postoperative oliguria and renal dysfunction.

Abdomen↗