Studies on Muscle-Tone, With Special Reference to Anaesthesia and Specific Relaxant Drugs

Brown, Robert Cecil (1954) Studies on Muscle-Tone, With Special Reference to Anaesthesia and Specific Relaxant Drugs. MD thesis, University of Glasgow.

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A brief historical survey of the concept of muscle-tone is given. Muscle-tone is defined as: "the capacity of a muscle to resist extension," An instrument, the Tonometer, working on the "hardness" principle, is described and assessed. It is shown to provide an effective measure of differences in muscle-tone. It is further shown that measures of tone based on "hardness" and based on "resistance to extension" may, under limited conditions, give equivalent results. Clinical work is described in which the effect on muscle-tone of ether anaesthesia and of resaxants is assessed by the Tonometer. It is found that the increase in tone common in second stage anaesthesia may persist into the first plane of the third stage. No decrease in tone below the level in the relaxed conscious patient was shown to occur with anaesthesia. (Objects (1) and (3), page 1). No decrease in tone below the level found in the relaxed, conscious patient was shown to occur with relaxants. (Objects (2) and (3), page 1). It is concluded that the purpose both of anaesthesia and of relaxant drugs is, not the obtaining of muscular relaxation, but its maintenance by preventing reflex increases in tone. Part 2 of the thesis is devoted to a consideration of the effects of relaxants and the way in which reflex increases in tone are prevented. This is an expansion of object (2). As relaxants produce no decrease in muscle-tone beyond that found in the relaxed conscious patient, the activity of the drugs was judged by the effect on the tendon-jerks; the effect on the response to stimulation of peripheral nerves; and by the presence or absence of conditions satisfactory for upper abdominal surgery. It is shown that tendon-jerks are gradually abolished under the influence of relaxants. When d-tubocurarine or gallamine are used, abdominal protective reflexes may be abolished while the tendon-jerks are still present. (stage of Bremer). This is not true in the case of decamethoniura. Relaxation satisfactory for upper abdominal surgery may begin while the threshold for response to stimulation of the ulnar nerve is unaltered, or is even temporarily lowered, and while both hand and abdominal muscles can still maintain an imposed tetanus. It is concluded that the peripheral blocking action of d-tubocurarine and gallamine is not sufficient to explain the abolishing of protective reflexes by these drugs, but no site is assigned for any central action which might be responsible for this effect.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Keywords: Medicine, Pharmacology
Date of Award: 1954
Depositing User: Enlighten Team
Unique ID: glathesis:1954-78955
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09

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