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Biomedical subjects

I Calder

Publications and source records attributed to I Calder.

At least 55 records · Page 3Linked to original sources
PubMed1991

Intra-operative recording of motor tract potentials at the cervico-medullary junction following scalp electrical and magnetic stimulation of the motor cortex.

Activity in descending motor pathways after scalp electrical and magnetic brain stimulation of the motor cortex was recorded from the exposed cervico-medullary junction in six patients having trans-oral surgery of the upper cervical spine. Recordings during deep anaesthesia without muscle paralysis revealed an initial negative potential (D wave) at about 2 ms with electrical stimulation in five of the six patients. This was followed by a muscle potential which obscured any later waveforms. Magnetic stimulation produced clear potentials in only one patient. The earliest wave to magnetic stimulation during deep anaesthesia was 1-2 ms later than the earliest potential to electrical stimulation. Following lightening of the anaesthetic and the administration of muscle relaxants a series of later negative potentials (I waves) were more clearly seen to both electrical and magnetic stimulation. More I waves were recorded to magnetic stimulation during light anaesthesia than during deep anaesthesia. Increasing the intensity of electrical stimulation also produced an extra late I wave. At the highest intensity of magnetic stimulation the latency of the earliest potential was comparable to the D wave to electrical stimulation. The intervals between these various D and I waves corresponded to those previously described for the timing of single motor unit discharge after cortical stimulation.

Adult↗
PubMed1991

Difficult intubation and the Laryngeal Mask.

The Laryngeal Mask (LM) can be used to intubate patients in whom conventional direct laryngoscopy is difficult. Tracheal intubation can be achieved using the LM alone but the use of a fibre-optic laryngoscope increases the chances of success.

Anesthesiology↗
PubMed1990

One-stage transoral decompression and posterior fixation in rheumatoid atlanto-axial subluxation.

An operation which combined anterior transoral decompression with posterior occipitocervical fixation was used in 68 rheumatoid patients with irreducible anterior neuraxial compression at the craniocervical junction. Fibre-optic laryngoscopy with nasotracheal intubation was less hazardous than tracheostomy. The patients underwent surgery in the lateral position to allow access both to the mouth and to the back of the neck without moving the head. Specially designed instruments allowed visualisation from the front without dividing the soft palate. Posterior stabilisation was achieved by a preformed contoured loop fixed to the occiput, the atlas and the axis by sublaminar wires. The procedure allowed immediate mobilisation and had a very low morbidity in such ill patients.

Arthritis, Rheumatoid↗
PubMed1989

'Cured' myasthenia gravis and neuromuscular blockade.

A symptomless myasthenic patient who played representative squash received 0.1 mg/kg of vecuronium and enflurane as part of a general anaesthetic for elective gynaecological surgery. Neuromuscular block was prolonged. The effect of neuromuscular blocking agents and volatile anaesthetics in symptomless myasthenics is discussed. We conclude that these patients should be assumed to be sensitive to such agents.

Adult↗
PubMed1987

Dorsal column stimulation (DCS) in chronic pain: report of 31 cases.

Thirty-one patients of chronic pain treated with dorsal column stimulation (DCS) are reported. All of them had been treated previously with drugs and multiple procedures including injections and frequently several operations. After a trial of percutaneous DCS, permanent implantations were carried out. The patients have been followed for up to eight years. Overall, sixty per cent of patients had good to fair relief of pain with DCS. Some of them had a good response for five years and more.

Adult↗
PubMed1986

Anaesthesia for transoral craniocervical surgery.

Transoral surgery on lesions in the craniocervical region has been performed on 25 patients in this unit. The anaesthetic management is presented. Tracheostomy and nasotracheal intubation have both been used. Peroperative monitoring of cord compression remains an important and only partly solved problem. There were two deaths as a result of anaesthesia and surgery, and these are discussed.

Adolescent↗
PubMed1986

Anaesthesia for surgical occlusion of the basilar artery. A technique involving intra-operative awakening to allow neurological assessment.

A case is described of a giant fusiform aneurysm of the basilar artery which was treated successfully by proximal surgical occlusion of the artery. The anaesthetic management involved the intra-operative awakening of the patient in order to assess neurological function immediately after application of the clip. The difficulties involved in this type of surgery are discussed.

Adolescent↗
PubMed1986

Effect of N-hydroxyparacetamol on DNA, RNA, and protein synthesis and chromatin structure.

N-Hydroxyparacetamol treatment of lymphoblastoid cells gave rise to a dose-dependent decrease in DNA, RNA, and protein synthesis. Inhibition of DNA synthesis was less marked in medium at pH 6.5 than at pH 9.0. N-Hydroxyparacetamol appeared to inhibit DNA synthesis at least in part through alterations to chromatin structure. This compound produced a dose-dependent and time-dependent loss in the superhelix density of DNA as determined by nucleoid sedimentation analysis. Alkaline elution data as well as sucrose gradient analysis revealed that this decrease in sedimentation did not arise through single strand breakage to DNA. The structural alterations to chromatin caused by N-hydroxyparacetamol appeared to have been repaired after 6 hr. However, sedimentation of "repaired" nucleoids in the presence of ethidium bromide was markedly different from sedimentation of untreated nucleoids. These results suggested that some N-hydroxyparacetamol remained associated with nucleo-protein, thus interfering with the binding of ethidium. Furthermore, both RNA and protein synthesis were markedly inhibited by N-hydroxyparacetamol, demonstrating a major effect on cell function. The widespread effects of N-hydroxyparacetamol could be accounted for by changes to chromatin structure or by a more general effect on cellular metabolism. Either of these effects could account for the dramatic cytotoxicity of this compound. A concentration of 2.5 mM reduced cell viability by 96% after 3 days.

Acetaminophen↗