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Biomedical subjects

I Calder

Publications and source records attributed to I Calder.

At least 37 records · Page 2Linked to original sources
PubMed1995

Difficult direct laryngoscopy in patients with cervical spine disease.

Two hundred and fifty three patients were examined before surgery for cervical spine disease. The grade of glottic visibility was determined at direct laryngoscopy, using the classification proposed by Cormack and Lehane. The overall prevalence of difficulty (grades 3 and 4) was 20%. Patients with disease that includes the occipito-atlanto-axial complex have a higher prevalence of difficulty than those with disease below the axis vertebra. Occipito-atlanto-axial disease is associated with poor mandibular protrusion. The best single predictor of difficulty was reduced separation of the posterior elements of the first and second cervical vertebrae on lateral radiographs. The Mallampati examination was the best single predictor on physical examination. The Mallampati may be an indicator of poor cranio-cervical extension. Difficulty was rare in patients with class A mandibular protrusion, and invariable in patients with class C protrusion.

Adolescent↗
PubMed1995

Tropospheric ozone: respiratory effects and Australian air quality goals.

OBJECTIVE: To review the health effects of tropospheric ozone and discuss the implications for public health policy. DESIGN: Literature review and consultation with scientists in Australia and overseas. Papers in English or with English language abstracts were identified by Medline search from the international peer reviewed published reports. Those from the period 1980-93 were read systematically but selected earlier papers were also considered. Reports on ozone exposures were obtained from environmental agencies in the region. RESULTS: Exposure to ozone at concentrations below the current Australian air quality goal (0.12 ppm averaged over one hour) may cause impaired respiratory function. Inflammatory changes in the small airways and respiratory symptoms result from moderate to heavy exercise in the presence of ozone at levels of 0.08-0.12 ppm. The changes in respiratory function due to ozone are short lived, vary with the duration of exposure, may be modified by levels of other pollutants (such as sulphur dioxide and particulates), and differ appreciably between individuals. Bronchial lavage studies indicate that inflammation and other pathological changes may occur in the airways before reductions in air flow are detectable, and persist after respiratory function has returned to normal. It is not known whether exposures to ozone at low levels (0.08-0.12 ppm) cause lasting damage to the lung or, if such damage does occur, whether it is functionally significant. At present, it is not possible to identify confidently population subgroups with heightened susceptibility to ozone. People with asthma may be more susceptible to the effects of ozone than the general population but the evidence is not consistent. Recent reports suggest that ozone increases airway reactivity on subsequent challenge with allergens and other irritants. Animal studies are consistent with the findings in human populations. CONCLUSION: A new one hour air quality ozone goal of 0.08 ppm for Australia, and the introduction of a four hour goal of 0.06 ppm are recommended on health grounds.

Adaptation, Physiological↗
PubMed1994

Nystagmus and joint position sensation: their importance in posterior occipitocervical fusion in rheumatoid arthritis.

It is widely believed that brain stem dysfunction and cranial nerve palsies in patients with rheumatoid arthritis (RA) are common and related to the vertical translocation of the odontoid process. In our database of 235 patients with seropositive RA and craniocervical junction involvement, we have found a very low incidence of such problems. Long tract signs were common, but loss of proprioception (joint position sensation) as the sole neurologic deficit was rare. Nystagmus was found to be associated with the tonsillar herniation of a Chiari 1 malformation and loss of joint position sensation with severe compression of the posterior aspect of the spinal cord at the craniocervical junction. The implications for posterior occipitocervical fusion, particularly by sublaminar wiring, are discussed.

Adolescent↗
PubMed1994

Visual outcome of childhood anterior perforating eye injuries: prognostic indicators.

Ninety-six cases of anterior globe perforation in children less than 16 years old, requiring surgical repair, were reviewed. Seventy-three patients were male and 23 female, with a mean age of 9 years 4 months. Perforation involving just the cornea was associated with a good visual prognosis unless: it involved the visual axis, resulting in corneal scarring and/or significant astigmatism (> 3.0 DS); it involved greater than one-quarter of corneal diameter; or there was non-compliance with spectacles/patching in patients younger than 8 years old. Injuries involving the lens in those younger than 8 years were associated with a far worse prognosis due to the problems of correcting aphakia. Surgical delay and method of injury did not affect prognosis. Some patients fail to re-attend and greater patient/parent education prior to discharge is recommended.

Adolescent↗
PubMed1993

Hepatic peroxisome proliferation in rodents and its significance for humans.

Peroxisomes are subcellular organelles found in all eukaryotic cells. In the liver they are usually round and measure about 0.5-1.0 microns; in rodents they contain a prominent crystalloid core, but this may be absent in newly formed rodent peroxisomes as well as in human peroxisomes. A major role of the peroxisomes is the breakdown of long-chain fatty acids, thereby complementing mitochondrial fatty-acid metabolism. Many chemicals are known to increase the number of peroxisomes in rat and mouse hepatocytes. This peroxisome proliferation is accompanied by replicative DNA synthesis and liver growth. No clear structure-activity relationships are apparent. Many of these peroxisome proliferators contain acid functions that can modulate fatty acid metabolism. Two mechanisms have been proposed for the induction of peroxisome proliferation. One is based on the existence of one or several specific cytosolic receptors that bind the peroxisome proliferator, facilitating its translocation to the cell nucleus and the activation of the expression of specific genes. The second, perhaps more general, hypothesis involves chemically mediated perturbation of lipid metabolism. These two hypotheses are not mutually exclusive. Many peroxisome proliferators have been shown to induce hepatocellular tumours, despite being uniformly non-genotoxic, when administered at high dose levels to rats and mice for long periods. Three mechanisms have been proposed to explain the induction of tumours. One is based on increased production of active oxygen species due to imbalanced production of peroxisomal enzymes; it has been proposed that these reactive oxygen species cause indirect DNA damage with subsequent tumour formation. In rodents, an alternative mechanism is the promotion of endogenous lesions by sustained DNA synthesis and hyperplasia. Thirdly, it is conceivable that sustained growth stimulation may be sufficient for tumour formation. Marked species differences are apparent in response to peroxisome proliferations. Rats and mice are extremely sensitive, and hamsters show an intermediate response while guinea pigs, monkeys and humans appear to be relatively insensitive or non-responsive at dose levels that produce a marked response in rodents. These species differences may be reproduced in vitro using primary culture hepatocytes isolated from a variety of species including humans. The available experimental evidence suggests a strong association and a probable casual link between peroxisome-proliferator-elicited liver growth and the subsequent development of liver tumours in rats and mice. Since humans are insensitive or unresponsive, at therapeutic dose levels, to peroxisome-proliferator-induced hepatic effects, it is reasonable to conclude that the encountered levels of exposure to these non-genotoxic agents do not present a hepatocarcinogenic hazard to humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

A technique of awake fibreoptic intubation. Experience in patients with cervical spine disease.

We report our experience of 58 patients undergoing awake fibreoptic intubation for cervical spine surgery. Topical anaesthesia was administered using a 'spray as you go' technique. The tracheas of 57 patients were intubated successfully. The mean time from starting topical anaesthesia to intubation was 16.1 min (SEM 1.0). The procedure was associated with cardiovascular stability, a low incidence of severe cough and had a high patient acceptance. There was a low failure rate amongst trainees. The minimum mean arterial oxygen saturation was 92.9% (SEM 1.1). There was no relationship between the time taken to intubation and the episodes of desaturation or the grade of laryngeal visibility at direct laryngoscopy. This method of producing topical anaesthesia for awake fibreoptic intubation is recommended.

Adolescent↗
PubMed1993

Aetiology of perforating eye injury.

This study addresses the aetiology of perforating ocular injury in childhood and possible preventive measures. Data have been collected from the case notes of 143 patients presenting over a 10 year period to a single ophthalmic unit. Injuries occurred most often in a domestic setting (34%) or with a child at play (19%) and showed an overall four to one ratio of boys to girls. Sports injuries accounted for 15% and assault for 8% of all injuries. A changing pattern of ocular injury is evident: road traffic accidents constituted 6% of injuries, compared with 31% in a similar study published in 1976. The role of litigation is discussed, particularly with regard to firearms, which accounted for 8% of injuries. It is concluded that the most important factor in the prevention of perforating ocular trauma is parental awareness, 53% of injuries occurring with the child in a domestic setting or at play.

Accident Prevention↗
PubMed1992

Oxygen saturation and cardiovascular changes during fibreoptic intubation under general anaesthesia.

Sixty patients who required fibreoptic nasotracheal intubation were studied. Arterial oxygen saturation, arterial blood pressure and heart rate were monitored continuously during fibreoptic intubation under deep halothane anaesthesia. There were significant decreases (p less than 0.001) in arterial blood pressure and heart rate despite administration of intravenous colloid and atropine. Almost one third of the patients (18 out of 60) suffered a decrease in arterial oxygen saturation below 90% during the intubation sequence and in five patients the saturation fell below 80%. The episodes of desaturation were not related to the induction-intubation time or to the grade of laryngeal visibility at direct laryngoscopy.

Adolescent↗