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Biomedical subjects

M Shannon

Publications and source records attributed to M Shannon.

At least 91 records · Page 5Linked to original sources
PubMed1992

Effect of acute versus chronic intoxication on clinical features of theophylline poisoning in children.

OBJECTIVES: To determine whether the method of intoxication influences the metabolic disturbances and pattern of life-threatening events that occur after theophylline intoxication in children. METHODS: Five-year prospective observational study of consecutive pediatric patients referred to a regional poison control center with a theophylline concentration (theo) greater than or equal to 30 micrograms/ml. At the time of referral, intoxication was categorized as acute (single toxic exposure), chronic (long-term toxic exposure), or acute-on-therapeutic (single toxic exposure superimposed on maintenance therapy). RESULTS: One-hundred twenty-five patients were monitored. Mean age was 12 years (range, 3 days to 20 y). Seventy-four patients (59%) had acute intoxication, 31 (25%) had chronic intoxication, and 20 (16%) had acute-on-therapeutic intoxication. Mean peak serum (theo) was 55 micrograms/ml. Life-threatening events occurred in 12 patients (10%). Patients with acute intoxication had a significantly lower serum potassium level (3.04 vs 3.80 mmol/L; p less than 0.001) and higher serum glucose level (10.8 vs 7.0 mmol/L (194 vs 127 mg/dl); p less than 0.001) than did children with chronic intoxication. Although life-threatening events (seizures or arrhythmias) occurred at a similar rate across categories, the (theo) at which these events occurred was significantly higher in patients with acute intoxication than in those with chronic intoxication (100 vs 42 micrograms/ml; p = 0.02). Among children with chronic intoxication, those who had life-threatening events had (theo) similar to those who remained well (42 vs 47 micrograms/ml) but were significantly younger (1.6 vs 8.0 years; p less than 0.001). CONCLUSIONS: These data indicate that method of intoxication has significant effects on the metabolic and clinical consequences of theophylline poisoning. Life-threatening events occur in those with acute theophylline intoxication at significantly higher (theo) than in those with chronic intoxication. After chronic intoxication, peak (theo) does not identify patients at risk for life-threatening events; young age appears to be the primary risk factor. These findings potentially complicate the management of theophylline poisoning, given the difficulty of extracorporeal drug removal in young infants.

Acute Disease↗
PubMed1992

Pharmacokinetics of drugs in overdose.

The pharmacokinetics of drugs may be altered following an overdose. The degree of absorption depends on the physical characteristics of the drug; the rate of dissolution may delay or broaden peak serum concentrations. The pathophysiological effects of a drug may also limit or augment absorption. Altered distribution of drugs in overdose results from changes in the extent of protein binding and size of the volume of distribution. Saturation of hepatic enzyme systems in overdose is manifested by delayed metabolism or elimination of many drugs; renal elimination of unchanged drug may take on greater importance in this instance. Familiarity with the toxicokinetic profile of a given drug enables the physician to exploit these principles in order to limit toxicity. Delayed or prolonged absorption allows for late decontamination. Multiple doses of activated charcoal are effective in interrupting both entero-enteric and enterohepatic recirculation. Alkalinisation-induced ion trapping enhances renal elimination of unchanged drugs which normally undergo hepatic transformation. For several drugs, chronic overdose due to altered distribution is associated with a greater severity of toxic manifestations despite relatively low serum drug concentrations. Conversely, with some drugs, induction of metabolic pathways may lead to more rapid drug elimination in chronic overdose. Knowledge of the pharmacokinetic alterations which occur in drug overdose enables the physician to predict toxicity with greater accuracy and to institute optimum therapy in a timely manner.

Absorption↗
PubMed1991

Unsuspected quinine intoxication presenting as acute deafness and mutism.

A case of unsuspected quinine overdose is reported in a 14-year-old girl. Presenting symptoms included deafness and mutism. Diagnosis was delayed for approximately 4 hours because of the absence of an accurate history. Case details, laboratory values, and hospital course are discussed. Signs of cinchonism and common ototoxins are discussed. Strategies for the management of quinine overdose are reviewed.

Adolescent↗
PubMed1991

Natural history of acoustic neuromas.

The growth rate of acoustic neuromas was studied in a series of 50 patients who underwent follow-up imaging studies, since surgery was not performed after the initial diagnostic study or only performed after the follow-up studies. In 50% of the cases the tumor did not grow during the length of the follow-up. In the other patients the growth was less than 50% of the original tumor size in all but four. No correlation was observed between tumor growth, length of the follow-up, and age of the patient. Our results suggest a change in the management of this benign tumor.

Journal Article↗
PubMed1991

Accidental and intentional poisonings with ethylene glycol in infancy: diagnostic clues and management.

Ethylene glycol has long been recognized as a potentially lethal poison and remains available today as automotive antifreeze and windshield deicer fluids. Ethylene glycol is rapidly absorbed from the gastrointestinal tract, with peak levels measured one to four hours after ingestion. Metabolism of the parent compound and the production of several organic acids are responsible for the metabolic acidosis observed in ethylene glycol poisoning. Target organ cellular damage is seen in the kidney, brain, myocardium, pancreas, and blood vessel walls. Renal tubular deposition of calcium oxalate crystals is felt to be responsible for the development of the severe renal injury which may accompany ethylene glycol ingestion. The clinical course is quite varied and includes inebriation, hematuria, cardiorespiratory compromise, and neurologic effects. Prompt diagnosis and initiation of treatment, including ethanol therapy and hemodialysis, is necessary to ameliorate the effects of ethylene glycol ingestion. Two cases of ethylene glycol poisoning, one accidental and one intentional, are reviewed.

Accidents, Home↗
PubMed1991

Ten cases of acute lead intoxication among bridge workers in Louisiana.

We report the cases of ten construction workers who developed acute lead intoxication while repairing a bridge in Louisiana. All but one patient received a five-day course of edetate calcium disodium (calcium EDTA) chelation therapy; one patient received five doses instead of five days of treatment. Calcium EDTA 25 mg/kg q12h was administered for ten consecutive doses by intravenous infusion over two hours. Each dose was diluted in NaCl 0.9% 500 mL. No adverse drug effects were observed during treatment. The posttreatment mean whole blood lead (PbB) concentration was significantly reduced compared with the pretreatment mean PbB (1.48 +/- 0.70 vs. 3.8 +/- 1.68 mumol/L; p = 0.0012, Student's paired t-test). This indicates that the body lead burden of these patients was effectively reduced with calcium EDTA. Eight patients had complaints on admission that were suggestive of lead intoxication. These included malaise, numbness of the extremities, arthralgia, myalgia, abdominal discomfort, sleep disturbance, and lower back pain. Patients had no complaints on discharge. Eight patients had mild anemia that was consistent with acute lead intoxication (mean pretreatment hemoglobin (+/- SD), 128.6(+/- 17.2 g/L), but calcium EDTA therapy did not appear to effect any change in the pretreatment hemoglobin values. The Occupational Safety and Health Administration (OSHA) lead standard requires that manufacturers provide employees at risk for occupational lead exposures with proper respirators and medical surveillance to prevent lead intoxication. The construction industry is exempted from these standards except in Maryland. We believe that amendment of the OSHA lead standards, to provide specific lead regulation of the construction industry, would be helpful in preventing similar cases of occupational lead intoxication.

Acute Disease↗
PubMed1990

Biliary cystadenoma: ultrasound, CT, and MRI.

Two cases of intrahepatic biliary cystadenoma, a rare tumor with malignant potential, are discussed. The sonographic, computed tomographic (CT), and magnetic resonance imaging (MRI) findings are presented together with clinical features of this entity and a brief review of the pertinent literature.

Bile Duct Neoplasms↗
PubMed1990

Serum magnesium concentrations after repetitive magnesium cathartic administration.

Severe hypermagnesemia has been reported by several authors after multiple doses of magnesium-containing cathartic are administered during management of a toxic ingestion. To evaluate the frequency and magnitude of serum magnesium elevations after the use of repetitive magnesium catharsis, we prospectively evaluated 102 patients who received multiple doses of magnesium citrate as a part of treatment of an overdose. Commonly ingested substances for which repetitive cathartic was administered were tricyclic antidepressants in 47%, aspirin in 17%, and phenytoin in 10%. For each case, serial electrolytes, blood urea nitrogen, creatinine, calcium and magnesium were obtained. Mean initial serum magnesium concentration was 1.8 +/- .03 mEq/L. After a mean 960 mL of magnesium citrate (9.22 g magnesium), final mean serum magnesium concentration was 2.5 +/- .05 mEq/L. Forty-seven patients (47%) developed an elevated (greater than 2.4 mEq/L) serum magnesium concentration, with 12 greater than 3.0 mEq/L. No correlation was found between total quantity of magnesium citrate administered and the increment in serum magnesium concentration. Our data indicate that serum magnesium concentrations consistently rise after repetitive magnesium citrate use. However, the magnitude of this rise appears modest. The elevation in serum magnesium concentration does not correlate with the quantity of magnesium administered. We conclude that with close monitoring, repetitive magnesium citrate can be administered without inducing severe hypermagnesemia (serum magnesium concentration greater than 5.0 mEq/L).

Adolescent↗