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Biomedical subjects

J F Ryan

Publications and source records attributed to J F Ryan.

At least 19 recordsLinked to original sources
PubMed1992

EU 4093 decreases intracellular [Ca2+] in skeletal muscle fibers from control and malignant hyperthermia-susceptible swine.

The mechanisms causing the malignant hyperthermia (MH) syndrome are related to a malfunction of intracellular Ca2+ homeostasis and can be prevented or reversed by dantrolene. EU 4093 (Azumolene, 1-[[[5-(4-bromophenyl)-2-oxyzolyl] methylene]amino]-2-4- imidazolidinedione) is a 30-fold more water-soluble analogue of dantrolene that is believed to have the same effects as dantrolene on the intracellular free Ca2+ concentration [( Ca2+]i) in skeletal muscle and that should have similar efficacy in treating and preventing the clinical manifestations of MH in response to a halothane/succinylcholine challenge. To test this hypothesis, experiments were carried out in four controls (Yorkshire) and eight MH-susceptible crossbreed swine (Poland China X Pietrain). The resting [Ca2+]i in normal muscle fibers measured by Ca(2+)-selective microelectrodes was 111 +/- 12 nM (mean +/- standard deviation, n = 30), whereas in the MH muscles the resting [Ca2+]i was 395 +/- 36 nM, (n = 28) (P = 0.0001). EU 4093 decreased [Ca2+]i in MH-susceptible skeletal muscle in a dose-related fashion from 207 to 38 nM after 0.5 to 2.0 mg/kg, respectively, and had a similar effect in control skeletal muscle (58 to 30 nM) after the same doses. In MH-susceptible swine, a dose of 2.0 mg/kg was successful in preventing any clinical signs of the MH syndrome during a subsequent halothane/succinylcholine challenge. A dose of 0.5 mg/kg was able to attenuate but not reverse the clinical signs of the MH syndrome after a halothane challenge, whereas a dose of 1.0 mg/kg was completely successful in reversing this effect in all subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A single-blind study of combined pulse oximetry and capnography in children.

This single-blind study examined four levels of monitoring in 402 pediatric cases. Patients were randomly assigned to one of four groups: 1) oximeter and capnograph; 2) only oximeter; 3) only capnograph; or 4) neither oximeter nor capnograph data available to the anesthesia team. An anesthesiologist, not involved in patient care, observed all cases and continuously recorded hemoglobin oxygen saturation (Spo2), ECG, expired CO2, and the oximeter plethysmographic output. Mean age, weight, ASA physical status, airway management (mask or endotracheal tube), and anesthetic technique were similar in each group. Two-hundred sixty problems were documented in 153 patients. Fifty-nine events in 43 patients resulted in "major" desaturation (Spo2 less than or equal to 85% for greater than or equal to 30 s). Fifteen "major" capnograph events (esophageal intubation, disconnection, accidental extubation, or obstructed endotracheal tube) were observed in 11 patients; 8 of these also developed varying degrees of desaturation. One-hundred thirty "minor" desaturation events (Spo2 less than or equal to 95% for greater than 60 s) and 79 "minor" desaturation events (hypercarbaria or hypocarbia) were observed. A number of problems fulfilled criteria in multiple categories. Infants less than or equal to 6 months of age had the highest incidence of major desaturation events (18 of 65 [27%]) compared to toddlers 7-24 months of age or children greater than 24 months of age (P less than 0.001). Blinding the oximeter data increased the number of patients (12 vs. 31) experiencing major desaturation events (P = 0.003); blinding the capnograph data altered neither the frequency of desaturation events nor the incidence of major capnograph events.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1990

The effects of extracellular magnesium on myoplasmic [Ca2+] in malignant hyperthermia susceptible swine.

It is now well established that the pathophysiology of the malignant hyperthermia (MH) syndrome is related to a malfunction of intracellular calcium homeostasis. Magnesium plays important roles in the basic contractile properties of muscle, and many of its actions are antagonistic to those of calcium. The aim of this study was to determine the effectiveness of magnesium sulphate to prevent the MH episode in susceptible animals and correlate this with its effects on the intracellular free calcium [( Ca2+]i). The experiments were carried out using six control (Yorkshire) and ten MH-susceptible crossbred swine (Poland China X Pietrain). After determination of resting concentrations of [Ca2+]i and [Mg2+]i, each animal was given either two iv bolus doses of 50 mg/kg or one iv bolus of 100 mg/kg of MgSO4. The resting [Ca2+]i and [Mg2+]i were determined by means of ion-selective microelectrodes. The resting [Ca2+]i in normal muscle fibers was 0.11 +/- 0.01 microM (mean +/- SEM), whereas in the MH muscles the resting [Ca2+]i was 0.36 +/- 0.01 microM. In neither group was the resting [Ca2+]i modified by MgSO4. This cumulative dose of MgSO4 (100 mg/kg) was not able to prevent the induction of an MH episode by 2% halothane. Although MgSO4 did not directly decrease [Ca2+]i, it did attenuate the increase in [Ca2+]i associated with the syndrome from 7.29 +/- 0.43 microM in untreated animals to 0.84 +/- 0.03 microM in MgSO4 pretreated swine. In addition, the limb rigidity that accompanies this increase in calcium was prevented by MgSO4 pretreatment. Baseline measurements of [Mg2+]i were not different in control and MH-susceptible muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Parosteal osteogenic sarcoma of the hand.

Osteosarcomas of the tubular bones of the hands and feet are rare tumours and the initial biopsies are frequently misdiagnosed. We report a case of parosteal osteosarcoma arising in the metacarpal of a female patient aged 53 at first presentation. The tumour recurred three times over two decades and eventually metastasized to the lungs. The differential diagnosis includes florid reactive mesenchymal proliferation and bizarre parosteal osteochondromatous proliferations of the tubular bones of the hand.

Bone Neoplasms↗
PubMed1989

Ketamine does not trigger malignant hyperthermia in susceptible swine.

The use of ketamine in individuals susceptible to malignant hyperthermia (MH) is controversial. We describe our experience with ketamine used for induction and/or maintenance of anesthesia in our herd of swine inbred for susceptibility to MH. A total of 76 MH-susceptible swine were given a total of 112 general anesthetics using ketamine as the induction drug. In 34 of these anesthetics, anesthesia was also maintained with ketamine. Signs of MH did not develop in response to ketamine in any of the pigs.

Animals↗
PubMed1988

A single-blind study of pulse oximetry in children.

Oxygen saturation determined by pulse oximetry was monitored in 152 pediatric surgical patients divided into two groups. In one group, the oximeter data and alarms were available (N = 76) to the anesthesia team, and, in the other group, these data were unavailable (N = 76). A trained observer recorded all intraoperative hypoxic episodes and informed the anesthesia team of all major events (i.e., oxygen saturation less than or equal to 85% for greater than or equal to 30 s) (PaO2 approximately 52 mmHg). Thirty-five major events occurred: 24 in the unavailable group, and 11 in the available group (P = 0.021). A greater number of major events occurred in children less than or equal to 2 yr of age (P = 0.013). Hypoxic events diagnosed by the oximeter, but not by the anesthesiologist, were more frequent in the unavailable group (13) than in the available group (5) (P = 0.0495). ASA Physical Status 3 and 4 patients were more likely to suffer a major event (P = 0.009 available, 0.006 unavailable). The pulse oximeter diagnosed hypoxemia before the signs and symptoms of hypoxemia were apparent (i.e., prior to observed cyanosis or bradycardia). Major hypoxic events were unrelated to duration of anesthesia. Major events were evenly distributed among induction, maintenance, and awakening from anesthesia; a greater number of hypoxic events occurred during induction in the unavailable group (P = 0.031). No morbidity was documented in any patient who suffered an hypoxic event.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Case mix of public patients in skilled nursing facilities in Connecticut.

The case mix of publicly funded residents in 73 skilled nursing facilities (SNFs) in two Connecticut counties was examined. Data collected in 1980-1981 for utilization review by a professional standards review organization were used for the analysis. The findings indicate that considerable variation exists in case mix across the SNFs. Medicaid per diem rates, which are based on historic costs, have a low and negative correlation with case mix. Case mix indices are significantly higher for rural facilities, with a for-profit type of ownership, and with less than 75% of the bed days devoted to Medicaid residents.

Connecticut↗
PubMed1986

Malignant hyperthermia.

The increasing use of intravenous and inhalation sedation in the dental office has the potential of increasing the incidence of malignant hyperthermia (MH) in susceptible subjects. The object of this article is to present two cases of MH and to discuss its pathophysiology, its clinical picture, and its management in the light of the current literature. Stringent screening procedures should be adopted and maintained in order to channel suspected cases to appropriate centers for expert consultation and management. It is further advocated that a program of education for patients and their families be instituted, as it is an essential prerequisite of effective prophylaxis.

Child↗
PubMed1986

Malignant eccrine poroma: report of three cases.

The characteristic clinical and histological features of three cases of malignant eccrine poroma are discussed, in addition to the metastatic disease that had occurred in two cases. These cases were compared with previously reported cases of malignant eccrine poroma that had metastasised, and it is suggested that a strict classification of malignant eccrine sweat gland tumours should be made.

Adenoma, Sweat Gland↗
PubMed1986

Immunohistochemical analysis of mononuclear cell subsets in inflammatory and non-inflammatory myopathies.

Immunohistochemical procedures were used to analyse the subpopulations of mononuclear cells in muscle biopsies from 24 patients with polymyositis. The character of the cellular infiltrate was similar at the perivascular, perimysial, and endomysial sites, with cytotoxic-suppressor T lymphocytes (T8+) and macrophages being the dominant elements. Helper T lymphocytes (T4+) and B lymphocytes were present in smaller numbers. A control series of 17 muscle biopsies from normal subjects and patients with non-inflammatory myopathies and neurogenic conditions was also studied: the numbers of mononuclear cells present were much smaller than in polymyositis, but the ratio of T4:T8 lymphocytes was similar to that found in biopsies affected by polymyositis. We conclude that both cytotoxic-suppressor T lymphocytes and macrophages are important in the pathogenesis of inflammatory myopathy.

Adolescent↗