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Biomedical subjects

R S Cormack

Publications and source records attributed to R S Cormack.

35 records · Page 2Linked to original sources
PubMed1988

Rate of inactivation of human and rodent hepatic methionine synthase by nitrous oxide.

The rate of inactivation of hepatic methionine synthase by nitrous oxide has been determined in 22 patients undergoing laparotomy during general anesthesia, including 70% nitrous oxide. Mean half-time of inactivation was 46 min. Metabolic consequences of nitrous oxide are, thus, critically dependent on the duration of anesthesia, and are unlikely to be significant during exposures of less than 40 min. Inactivation of methionine synthase is very much more rapid in the rat exposed to 50% nitrous oxide, with a half-time of 5.4 min.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1984

Predicting the obstetric work-load.

The daily variation in the work-load of a maternity unit during 1982 was analysed. The data fitted the Poisson distribution quite well, which suggests that future work-loads can be predicted by this method. Other clinical data of a similar kind should be amenable to the same analysis.

Delivery, Obstetric↗
PubMed1984

Difficult tracheal intubation in obstetrics.

Difficult intubation has been classified into four grades, according to the view obtainable at laryngoscopy. Frequency analysis suggests that, in obstetrics, the main cause of trouble is grade 3, in which the epiglottis can be seen, but not the cords. This group is fairly rare so that a proportion of anaesthetists will not meet the problem in their first few years and may thus be unprepared for it in obstetrics. However the problem can be simulated in routine anaesthesia, so that a drill for managing it can be practised. Laryngoscopy is carried out as usual, then the blade is lowered so that the epiglottis descends and hides the cords. Intubation has to be done blind, using the Macintosh method. This can be helpful as part of the training before starting in the maternity department, supplementing the Aberdeen drill.

Anesthesia, Obstetrical↗
PubMed1979

Awareness during surgery--a new approach.

With modern light anaesthesia the problem of awareness during surgery has defied analysis, because no physical sign reliably signals the conscious level. A test has been developed which entails direct communication with the patient at the end of surgery, noting the earliest moment after withdrawal of nitrous oxide at which he makes the appropriate response to a verbal request, the "time to correct response" (TCR). This test showed premedication with lorazepam 4 mg/70 kg to be significantly better than morphine 10 mg for ensuring unconsciousness when the main anaesthetic agent was nitrous oxide, in two groups of patients undergoing abdominal surgery (P less than 0.01). All patients who had lorazepam were able, on request, to hold up the head a few minutes after surgery. Thus the benefits of light anaesthesia were retained whilst ensuring unconsciousness.

Adult↗
PubMed1977

Respiratory effects and amnesia after premedication with morphine or lorazepam.

Lorazepam, a new benzodiazepine, was compared with morphine for premedication. Ten patients received morphine 10 mg/70 kg i.m. and 10 received lorazepam 4 mg/70 kg i.m. Respiratory effects were assessed from the change in slope (S) and intercept (B) of the carbon dioxide response line, using a development of Read's rebreathing method. Morphine depressed S by 47% (P less than 0.01), but after lorazepam S increased by 27% (P less than 0.05), neither drug altering B significantly. In two volunteers lorazepam was assessed by both the rebreathing and the steady-state methods; after lorazepam S was smaller by the steady-state than by the rebreathing technique. The findings for lorazepam are consistent with the known effects of sleep on carbon dioxide sensitivity. Amnesia lasting 4-8 h occurred in all patients who received lorazepam so that pain and nausea during this period were not recalled, but no patient who received morphine experienced amnesia. We conclude that lorazepam merits further study, particularly where sedation without respiratory depression is needed, as in obstetrics, and where amnesia for uncomfortable procedures is required.

Adolescent↗
PubMed1974

New techniques for calibrating the Lloyd-Haldane apparatus.

1. A new way of measuring the graduation error in the stem of the Lloyd-Haldane burette is described, in which a fixed mass of water is made to occupy different parts of the stem. This gave the same answer as the gravimetric method, but was much easier.2. Two independent methods of measuring the ;meniscus error' gave values of 0.006 and 0.008 ml. respectively. It is concluded that the bulb volume can be measured gravimetrically with the burette inverted, provided that the value so obtained is corrected by adding about 0.007 ml.3. Alternatively, this estimation can be made with the burette the right way up, no correction then being needed. To do this the lower end of the burette must be blocked and a method of doing this without the need to fuse on a glass tap is described.4. After calibration by the above methods analyses on fresh air for CO(2) + O(2) gave a mean value of 20.98%, which, in the authors' view, is the correct value.5. The observer error was measured and from this the theoretical maximum accuracy of gas analysis by Haldane's method was calculated. It is concluded that the calculated% should be correct to the second decimal place in about half the analyses, the rest having an error of +/- 0.01%. Results approaching this were obtained.

Air↗