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Biomedical subjects

R J Cook

Publications and source records attributed to R J Cook.

At least 127 records · Page 7Linked to original sources
PubMed1991

Does combined epidural lignocaine and fentanyl provide better anaesthesia for ESWL than lignocaine alone?

The efficacy of epidural fentanyl combined with lignocaine 1.5% with adrenaline 1:200,000 was studied in a randomised, double-blind, controlled trial of two hundred patients undergoing extracorporeal shock wave lithotripsy with or without ancillary procedures. The quality of anaesthesia was assessed using linear analogue pain scores, the patient's impression, and the rate of intra-operative intervention by the anaesthetist. Postoperative symptomatology was also recorded. The only significant difference lay postoperatively in that the fentanyl-ancillary procedure sub-group had less pain approximately one hour postoperatively (P = 0.01). In the context of this study and in the presence of an adequate autonomic and somatic local anaesthetic blockade, the addition of epidural fentanyl does not appear to confer any significant advantage other than to enhance postoperative analgesia.

Anesthesia, Epidural↗
PubMed1991

A comparison of several point estimators of the odds ratio in a single 2 x 2 contingency table.

The relative performance of the unconditioned maximum likelihood estimators (UMLEs), conditional MLEs (CMLEs), and Jewell-type estimators of the odds ratio (OR) and its logarithm were investigated in sets of single 2 x 2 contingency tables. The tables were generated by complete enumeration of all possible cell frequencies consistent with a single fixed margin. The bias, mean squared error (MSE), and average absolute error (AAE) were computed for all estimators using the individual table probabilities as weights. The results showed that, for the OR, Jewell's estimator usually had smaller bias, MSE, and AAE than either of the MLEs. While the differences were often slight for MSE and AAE, for bias it was sometimes substantial. For the log(OR), the UMLE usually had the lowest bias, and its MSE and AAE were only slightly greater than those for the other estimators. Overall, we recommend estimation on the log scale using the UMLE. If OR is to be estimated, Jewell's method had strong merit, although it is nonsymmetric with respect to the table orientation. In view of this, the UMLE may again be favoured in some situations.

Bias↗
PubMed1991

The estimation of sensitivity and specificity in colorectal cancer screening methods.

The sensitivity and specificity of three screening tests for colorectal cancer were evaluated using latent class analysis. This type of analysis is useful in situations where screening tests are performed on each person and follow-up diagnostic test results are not available for individuals with negative test results. Traditional methods of evaluation, which assume these individuals to be disease free, may be biased under these circumstances. In addition to providing the parameter estimates, the latent class technique gives standard errors and permits significance tests for differences in sensitivity and specificity. It was found that the radial immunodiffusion technique was significantly more sensitive (p less than 0.001) than either the rehydrated or nonrehydrated Hemoccult II tests for detecting occult blood in patients with cancer or adenoma. While comparable to the rehydrated Hemoccult II test in terms of specificity, the radial immunodiffusion technique was significantly less specific (p less than 0.01) than the nonrehydrated Hemoccult test. Similar results were observed when restricting the analysis to cancer only.

Canada↗
PubMed1990

A double-blind assessment of segmental sensory changes with epidural fentanyl versus epidural saline in patients undergoing extracorporeal shock-wave lithotripsy.

Segmental changes to pin prick and cold stimuli were tested in a double-blind manner in pain-free patients scheduled for extracorporeal shockwave lithotripsy (ESWL). Fifty patients were randomly allocated to receive either epidural fentanyl (100 micrograms in 10 ml normal saline) or 10 ml epidural normal saline. In a further 25 patients an epidural catheter was inserted but no solution injected. In contrast to this latter group, epidural fentanyl and normal saline both produced segmental sensory changes. There were no significant differences between fentanyl and normal saline groups in the number of patients reporting sensory changes to pin prick, rate of onset of these changes, or segmental level. For cold stimuli, more patients in the fentanyl group than in the normal saline group reported a change (16 vs. 8; P = 0.02) but the segmental level was similar. The effect of normal saline as a diluent in epidurally administered opioids may be of clinical importance.

Anesthesia, Epidural↗
PubMed1989

Effect of nitrous oxide inactivation of vitamin B12-dependent methionine synthetase on the subcellular distribution of folate coenzymes in rat liver.

The effects of nitrous oxide inactivation of the vitamin B12-dependent enzyme, methionine synthetase (EC 2.1.1.13), on the subcellular distribution of hepatic folate coenzymes was determined. In controls, cytosolic folates were 5-methyltetrahydrofolate (45%), 5- and 10-formyltetrahydrofolate (9 and 19%, respectively), and tetrahydrofolate (27%). Exposure of rats to an atmosphere containing 80% nitrous oxide for 18 h resulted in a marked shift in this distribution pattern to 5-methyltetrahydrofolate, 84%; 5- and 10-formyltetrahydrofolate, 2.1 and 9.1%, respectively; and tetrahydrofolate, 4.7%. Activity of the cytosolic enzyme, methionine synthetase, was reduced by about 84% as compared to that of air breathing controls. In controls, mitochondrial folates were 5-methyltetrahydrofolate (7.3%), 5- and 10-formyltetrahydrofolate (11.5 and 33.1%, respectively), and tetrahydrofolate (48.1%). This distribution did not change after exposure to nitrous oxide. These results show that the effects of nitrous oxide inactivation of vitamin B12 are confined to the cytosol, at least in the short term, and suggest that there is little, if any, transport of free folates between the cytosolic and mitochondrial compartments.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1989

Abortion laws and policies: challenges and opportunities.

An analysis of abortion law reform in all regions of the world in the past 20 years shows that countries have turned from a concentration upon criminality to a concern with women's health and family well-being. Pragmatic approaches to achieve liberalization of abortion laws are described. Where legal reform is unlikely, specification of professional medical standards, clarification of laws and the scope of allowable action, as well as supportive statements by government officials, can facilitate services and may ultimately have a positive influence on legal reform.

Abortion, Illegal↗
PubMed1989

Effect of dietary methyl group deficiency on one-carbon metabolism in rats.

Amino acid-defined diets deficient in methyl groups have been shown to result in a very high incidence of hepatocellular carcinoma. It has been suggested that this is a result of decreased levels of S-adenosylmethionine and the undermethylation of DNA. Accordingly, the enzyme glycine N-methyltransferase (GNMT, EC 2.1.1.20) may play a major role in maintaining the levels of S-adenosylmethionine in liver in response to changes in dietary methionine. The effect of methyl-deficient, amino acid-defined diets on GNMT activity and S-adenosylmethionine levels in rat liver was therefore investigated. When rats were fed a defined amino acid diet containing no choline in which homocysteine was substituted for the methionine of the control diet at an equimolar level, there was a rapid and marked decrease in growth rate in spite of the fact that the rats consumed 85% of the food eaten by control rats fed a nutritionally adequate, defined amino acid diet. The GNMT activity in livers of methyl-deficient rats decreased rapidly, but there was no difference in amount of GNMT protein as measured immunologically. In methyl-deficient rats, the levels of S-adenosylmethionine were maintained but the levels of S-adenosylhomocysteine were rapidly elevated compared to control values. These changes are consistent with the postulated role of GNMT in regulating methyl group metabolism.

Amino Acids↗
PubMed1989

Effect of dietary methyl group deficiency on folate metabolism in rats.

The carcinogenic effects of methyl-deficient, amino acid-defined diets have been attributed to alterations in cellular methylation reactions. These diets contain no choline, and methionine is replaced by homocysteine. Hence, all methyl groups needed for methionine biosynthesis with subsequent formation of S-adenosylmethionine and polyamines must be formed de novo utilizing folate-dependent reduction of one-carbon units. In rats fed the methyl-deficient diet, there was a marked decrease in total liver folate levels. This decrease was apparent in the levels of the individual forms of folate: 10-HCO-H4folate, 5-HCO-H4folate, 5-CH3-H4folate and H4folate. The percent of the total folate pool made up by 5-CH3-H4folate did not change, however, until after the rats had been fed the methyl-deficient diet for 4 wk, and then an increase was seen. After the methyl-deficient rats were switched to a nutritionally adequate control diet containing methionine and choline, all values rapidly reversed. Increased use of folate for methyl group biosynthesis may be responsible for the loss of folates from the liver.

Amino Acids↗
PubMed1988

Outcome prediction in extradural haematomas.

Extradural haematoma (EDH) is generally a condition of young adult males. It represents only a small percentage of the total number of head injuries admitted to a neurosurgical service, but it must be differentiated from simple concussion, and this means that it is considered in a large number of patients. EDH has the potential for a low mortality rate because of its extraaxial location, but in practice it is approximately 10%. Our results show that about 40% of EDH present with vomiting or nausea and no focal neurological signs. Skull X-ray does not aid in the diagnosis as approximately 35% are reported as being normal. There is a place for conservative treatment of EDH but only if the shift of the midline is minimal (less than 5 mm). A score has been developed to predict accurately a patient's outcome after suffering an EDH. This score includes the Glasgow Coma Scale, pupillary reaction and initial CT scan appearance, and has an accuracy of 88%.

Adolescent↗
PubMed1988

The management of injuries--a review of deaths in hospital.

A prospective review was undertaken of the management of 111 consecutive patients who died in hospital after admission for treatment of injuries. A standard set of data relating to each patient was reviewed by each member of a trauma death audit committee and then by the whole committee. Autopsy reports were available on all patients. Conclusions were drawn concerning defective aspects of patient management and possible avoidance of each death. Injury severity was assessed using the Trauma Score (TS) and Injury Severity Score (ISS). The possibly avoidable death (PAD) rate was 17%. The most common defects in management were related to inadequate fluid resuscitation and delays in definitive management. The greatest contributions to the PAD rate were from inadequate fluid resuscitation, delays and inadequate perception of the severity of injuries or significance of clinical deterioration. Increasing age was related to a higher frequency of PAD. PAD rate in the presence of severe head injury was 8%, but was 63% in the absence of a severe head injury. It is concluded that review of all trauma deaths is an achievable, beneficial and essential part of a hospital-based integrated trauma service. TS and ISS are not sufficiently sensitive to justify their use in selecting deaths for review. Improved blood volume replacement, earlier and more direct management and supervision by senior specialist staff, and elimination of causes of delay in patient management should all decrease the death rate from injuries particularly in patients without severe head injury.

Adolescent↗
PubMed1988

International developments in abortion laws: 1977-88.

During the period between 1977 and the first quarter of 1988, 35 countries liberalized their abortion laws and four countries limited grounds for the procedure. Most legislation has extended abortion eligibility through traditional indications such as danger to maternal health or fetal handicap, but a number of other indications have been created such as adolescence, advanced maternal age, family circumstances, and AIDS or HIV infection. A number of countries have redesigned their abortion laws as part of a comprehensive package to facilitate access to and delivery of contraception, voluntary sterilization, and abortion services. Abortion litigation has increased and stimulated the liberalization of abortion provisions and the support of women's autonomous choice within the law. In Canada, the entire criminal prohibition of abortion was held unconstitutional for violating women's integrity and security. In contrast, Latin American and other constitutional developments may limit legal abortion to instances of danger to women's lives.

Abortion, Induced↗
PubMed1988

Cervical cord extradural haematoma with familial cutaneous haemangiomas.

This case report confirms the link between familial cutaneous haemangiomas and haemangiomas of the spinal extradural space. Haemorrhage from a cervical extradural haemangioma may cause a haematoma resulting in an anterior cord syndrome. Recovery is possible with early diagnosis and surgical decompression at the involved level. If the diagnosis is not made the patient may die from this extradural cervical compression. Diagnosis involves myelography with spinal angiography to confirm the site and extent of both haemangioma and extradural haematoma.

Adolescent↗
PubMed1987

A 16 year old boy with poor vision and nasal obstruction.

A 16 year old boy presented with visual deterioration and nasal obstruction. Investigations revealed a destructive pituitary tumour with extension into his skull base and nasopharynx. This unusual prolactin-secreting adenoma was treated by both surgery and bromocriptine.

Adenoma↗