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Biomedical subjects

R A MacKenzie

Publications and source records attributed to R A MacKenzie.

12 recordsLinked to original sources
PubMed2001

The frequency of perioperative vision loss.

UNLABELLED: The frequency of perioperative vision loss, especially for spinal surgery, has been increasing recently. We undertook a retrospective study to determine the frequency of this outcome in a large surgical population receiving general or central neuraxis regional anesthesia for noncardiac procedures from 1986 to 1998. Specific criteria were used to separate cases in which the surgical procedure likely directly contributed to the vision loss. Vision loss was present if any part of the visual field was affected. Initial database screening found 405 cases of new-onset vision loss or visual changes in 410,189 patients who underwent 501,342 anesthetics and who survived at least 30 days after their final procedures. Two hundred sixteen of these patients regained full vision or acuity within 30 days. Of the 189 patients who developed vision deficits for longer than 30 days, 185 underwent ophthalmologic or neurologic procedures in which ocular or cerebral tissues were surgically damaged or resected. The remaining 4 patients (1 per 125,234 overall; 0.0008%) developed prolonged vision loss without direct surgical trauma to optic or cerebral tissues. In this large study population of noncardiac surgical patients, including those who underwent spinal surgical procedures, the frequency of perioperative vision loss persisting for longer than 30 days was very small. IMPLICATIONS: Vision loss and blindness after surgery and anesthesia is a very rare event. In this study, only one per 125,234 patients undergoing noncardiac surgery developed vision loss persisting for longer than 30 days.

Adolescent↗
PubMed1986

Hypophosphatemic osteomalacia complicating von Recklinghausen's neurofibromatosis: increase in spinal density on treatment.

A 62-year-old white male with neurofibromatosis presented with multiple fractures and bone pain. He was found to have hypophosphatemic osteomalacia secondary to a renal tubular phosphate leak and was treated with phosphate, 1,25-dihydroxycholecalciferol and calcium. With treatment, his dual photon vertebral bone density increased markedly over 12 months. Repeat iliac crest bone biopsies showed that improvement in bone histology was predominantly cortical. This suggests that dual photon absorptiometry of the spine may be markedly influenced by changes in cortical bone status.

Biopsy↗
PubMed1986

Sulphur colloid bone scan assessment of femoral head vascularity following subcapital fracture of the hip.

The study was done to determine femoral head vascularity in the immediate postfracture stage as assessed by 99m Tc-sulphur colloid bone scanning and tetracycline uptake in the excised femoral heads of 30 patients with subcapital fractures treated by primary hemiarthroplasty. Twenty-four cases were diagnosed avascular by the scan, and this was confirmed by the absence of tetracycline labelling in all 24. Two cases were vascular by the scan, and this was confirmed by tetracycline labelling. The scan was inaccurate in only four cases, where the head appeared vascular by the scan, but avascular by tetracycline labelling. Sulphur colloid is helpful in predicting femoral head vascularity in the immediate postfracture phase.

Femur Head↗
PubMed1984

Anesthesia computing applications at Mayo Clinic.

Institutional computer applications benefit from having a single identifiable group assigned overall responsibility. This results in a more unified, efficient approach to automation. This approach will facilitate compliance with developing medicolegal standards. It will produce the most usable system for the institution's money. The inherent increased efficiency and accuracy of billing procedures resulting from automation will help offset costs of these systems. Of the many computer applications at Mayo Clinic having impact on anesthesiology, three are outlined: Computerized Surgical Schedule; Computerized Anesthetic Data Acquisition System; and Respiratory Care Management System.

Anesthesia Department, Hospital↗
PubMed1981

Angiographic findings in herpes zoster arteritis.

Four adults patients who experienced an ipsilateral hemispheric deficit 6 to 8 weeks after having developed herpes zoster ophthalmicus were seen during a six-month period. All four patients underwent full-circle angiography, including study of the extracranial arteries in the three older patients. Each examination demonstrated areas of segmental constriction of arteries on the ipsilateral side; two locations that were especially affected were the A2 segment of the pericallosal artery beneath the genu of the corpus callosum and the M4 segment of the middle cerebral artery. The cerebral arteries of the opposite hemisphere and the extracranial vessels did not contain demonstrable abnormalities. Pathological studies suggest that patients with this syndrome may have a necrotizing arteritis of ipsilateral blood vessels; in patients with disseminated zoster, a granulomatous angiitis of cerebral blood vessels has been found. We propose that the pattern of angiographic abnormalities described here is characteristic of herpes zoster arteritis; furthermore, the distribution pattern of the lesions suggests that the virus may spread to these arteries via branches of the ophthalmic division of the trigeminal nerve.

Adult↗
PubMed1976

Neurophysiological aspects of peripheral neuropathies.

1. Eighty-eight intrafascicular neural recordings were obtained in 10 normal subjects, 5 patients with axonal degeneration and 11 patients with demyelinating neuropathy. 2. Stimulus levels required for perception and fibre activation were higher in neuropathic subjects. Fibres transmitting touch perception had significantly lower conduction velocities in both patient groups, but were very much lower in the group with demyelinating neuropahty than the group with axonal degeneration. Maximum electrical stimulation evoked dispersed fibre responses in the axonal degeneration group and more dispersed, slowly conducting fibre potentials in the demyelinating group. In patients with hypertrophic Charcot-Marie-Tooth disorder, usually only a small group of slowly conducting low amplitude potentials was recorded. 3. Delivery of a train of supramaximal stimuli caused prolongation of latency and dispersion of fibre potentials in all microneurographic recordings. The changes were significantly greater in the axonal neuropathy group than in normals, and recovery was slower. The demyelinating neuropathies showed significantly greater changes than both the normal and the axonal neuropathy groups, and post-tetanic conduction slowing became even more marked after limb temperature was raised. 4. Surface SAP recordings showed normal refractory period in chronic axonal neuropathy but significant latency prolongation occurred in demyelinating neuropathy. 5. It is concluded that both receptor and nerve fibre abnormalities contribute to sensory dysfunction in degenerative and demyelinating neuropathies.

Action Potentials↗
PubMed1969

Prevalence of cytomegalovirus infection in a normal urban population in Nova Scotia.

During 1967 and 1968 a seroepidemiological survey was conducted on the prevalence of CF antibodies to CMV in the normal population of the Halifax-Dartmouth metropolitan area of Nova Scotia. Samples of 550 sera, collected from all age groups, including newborns, were processed. At birth, 34% of infants possess antibodies, presumably of maternal origin, and there follows a decline until at 2 years of age only 4% of children exhibit evidence of infection. There is a gradual increase up to 16% by 20 years of age, and thereafter this is maintained until by 40+ years half the population possesses antibodies.A more detailed analysis of cord sera indicated that approximately 60% of women of childbearing age possess no antibodies and are susceptible to primary CMV infection. Among these, age and gravidity are not significant factors.These data indicate that CMV infection is fairly widespread in this community, although comparative studies suggest that it is less so than in some other areas, such as Easter Island, where a more homogeneous pattern of overcrowding and poor sacioeconomic conditions prevails.

Adolescent↗
PubMedDate not supplied

Corpus callosotomy for intractable epilepsy: seizure outcome and prognostic factors.

We reviewed the outcome of corpus callosal section in 64 adult and pediatric patients to identify factors associated with a good outcome: 48% of patients had a favorable outcome for overall seizure frequency. Improvement was noted in several seizure types and was most likely for drop attacks, particularly in the setting of a unilateral focal cerebral lesion or a true generalized epilepsy of Lennox-Gastaut type. Poor outcomes for drop attacks were more likely if there was associated severe intellectual handicap or bilateral independent spikes on interictal EEG. Complex partial seizures (CPS), most commonly of frontal lobe origin, also responded favorably. The complications of callosal section were usually mild and transient. New focal seizures occurred in only 2 patients and were not as frequent or disabling as preoperative seizures types. A worthwhile improvement in seizure outcome was achieved by completion of the callosotomy in 6 of 10 patients with unsatisfactory results from anterior callosotomy.

Adolescent↗