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Biomedical subjects

J Feely

Publications and source records attributed to J Feely.

At least 91 records · Page 5Linked to original sources
PubMed1990

Flash visual evoked responses in the early encephalopathy of chronic liver disease.

In recent years many variants of EEG sensory evoked responses have been studied as potential diagnostic aids in the detection and quantification of hepatic encephalopathy (HE). This study assesses the value of the flash visual evoked response (VER). Twenty-six controls and 21 non-encephalopathic and 12 encephalopathic (grade 1/2), biopsy-proven, cirrhotic patients were assessed clinically, psychometrically, and electrophysiologically. Flash VER from three different leads were obtained from each patient. Data from the fronto-occipital leads gave the best differentiation between the subjects. The P2 and N3 peak latencies were significantly increased in the two liver groups and correlated with the mental state and psychometric results. The N3 latency had a 92% specificity and a 50% sensitivity in the detection of grade 1/2 HE. This study suggests that the N3 latency changes may be a good marker of early clinical HE and useful in the longitudinal assessment of individual patients.

Adult↗
PubMed1990

Altered pharmacodynamics in the elderly.

The importance of age-related changes in drug sensitivity is increasingly appreciated. More conclusive evidence is now being presented in combined kinetic and dynamic studies. The type, intensity, and duration of drug action may be affected, ranging from therapeutic failure to major drug toxicity. Alterations in physiologic and homeostatic systems, including the autonomic system, baroreceptors, thermoregulation, and balance, have been described. These may explain the propensity to postural hypotension, falls, hypothermia, and confusion, particularly following drug-induced decrements in these systems. Studies on the sensitivity to individual drugs produce a varied picture emphasizing the danger of generalizations. An increased sensitivity to many agents affecting the central nervous system, including benzodiazepines, halothane, metoclopramide, and narcotic analgesics, is becoming apparent. For the latter this may also be accompanied by an age-associated qualitative difference in toxicity. Whereas there is conclusive evidence of a reduced responsiveness to propranolol, the data are conflicting for calcium antagonists. The increased hypotensive response to ACE inhibitors is more likely due to kinetic factors. The anticoagulant response to warfarin is enhanced. Evidence is also emerging of a wide divergence in the sensitivity of different systems to the same drug--with aging the inotropic effect of theophylline is increased, but the bronchodilator response is decreased. It is becoming clear also that there is a need to separately study certain subgroups of the elderly population.

Aged↗
PubMed1989

Do subjects with stiff arteries have high blood pressure?

It has been argued that age-related increases in arterial stiffness could lead to spuriously high indirect blood pressure measurements, with consequent overdiagnosis of hypertension in older patients. To study the relationship between arterial stiffness and blood pressure, we identified patients with 'arterial stiffness', using Osler's manoeuvre, and compared their blood pressure levels with patients of a similar age. A total of 250 hospital inpatients were assessed independently by two doctors. In the 198 patients (79%) where both observers agreed on Osler's manoeuvre status, positive Osler's manoeuvre was uncommon under the age of 50 years but became more common thereafter, rising to 58% of patients aged over 75 years. However, blood pressure levels were similar in each age group, irrespective of Osler's manoeuvre status. We conclude that increased arterial stiffness as measured by Osler's manoeuvre is not necessarily associated with raised blood pressure levels in the elderly.

Adolescent↗
PubMed1987

Calcium channel blocker drugs and diabetic control.

Calcium channel blockers are now widely used and there have been case reports of hyperglycemia with nifedipine. In a double-blind, randomized, crossover study of the effects of 4 weeks of therapy, each with two dihydropyridine calcium channel blocker drugs, nifedipine and nicardipine, glucose tolerance, plasma insulin levels, and hemoglobin A1 were assessed in 20 patients with non-insulin-dependent diabetes (mean age 59 years). There was no significant difference in glucose tolerance on active therapy (AUC: control, 548.3 +/- 24.8; nifedipine, 559.3 +/- 41.0; and nicardipine, 589.3 +/- 40.3). Similarly, despite producing significant hemodynamic effects, these drugs produced no significant effect on plasma insulin and hemoglobin A1 levels. Calcium channel blocker drugs may be useful alternatives to thiazide diuretics and beta-blockers in the treatment of ischemic heart disease and hypertension, especially in patients with diabetes.

Adult↗
PubMed1987

The effect of calcium channel blockade with nifedipine on splanchnic and systemic haemodynamics in cirrhosis.

The splanchnic and systemic haemodynamic effects of a single sublingual dose of nifedipine (slow calcium channel blocker) in nine patients with cirrhosis of the liver and portal hypertension were studied. Nifedipine produced a significant reduction in the mean arterial blood pressure (98 +/- 5.3 vs. 86 +/- 5 mmHg, P less than 0.05) but did not alter the mean heart rate, portal venous pressure or total liver blood flow. The systemic antihypertensive effect of nifedipine can be achieved without altering liver blood-flow in patients with chronic liver disease and portal hypertension.

Hemodynamics↗
PubMed1987

The effects of ageing on aminopyrine and caffeine breath tests in the rat.

The influence of ageing on demethylation of 14C-aminopyrine (AP) and 14C-caffeine (Caf) in Wistar littermate rats was studied serially using the 14CO2-breath test. In both sexes, the elimination half-life (t1/2) of 14C-AP fell from a mean of approximately 75 min when weaned at 17 days to 45 min at maturity (49 days); thereafter t1/2 became prolonged, being most prolonged (82 min) in elderly male rats (210 days). Similarly, t1/2 of 14C-Caf was also prolonged with ageing. These studies using in vivo and longitudinal techniques indicate the importance of ageing on hepatic demethylation.

Aging↗
PubMed1987

Effects of chronic treatment with amiodarone on hepatic demethylation and cytochrome P450.

The effect of chronic treatment with amiodarone on hepatic oxidative metabolism using an in-vivo [14C]aminopyrine breath test and on hepatic cytochrome P450 was examined in Wistar rats. Aminopyrine demethylation was significantly impaired but returned to pretreatment values following amiodarone for 4 weeks. In contrast the levels of cytochrome P450 were significantly depressed during treatment and at 4 weeks following treatment. While an inhibitory effect on oxidative metabolism may explain the reported drug interactions with amiodarone, the discrepancy between its in-vivo effects and cytochrome P450 levels may suggest the development of 'compensatory' extra-hepatic site of drug metabolism.

Aging↗
PubMed1987

Clinical pharmacokinetics and endocrine disorders. Therapeutic implications.

Endocrine disorders are common and produce widespread changes in cellular and organ function. Alterations in the sensitivity of patients with thyroid disorders to digoxin, anticoagulants and sedatives have been recognised for many years. Many of the recently documented kinetic alterations in endocrine patients are explicable on the basis of disease-induced changes in hepatic drug metabolism, protein binding and renal function. In hyperthyroidism the rate of absorption of paracetamol, propranolol and oxazepam is increased due to increased gastrointestinal motility. The volume of distribution of propranolol and digoxin is increased and there is decreased binding of both basic and acidic drugs as a consequence of alterations in alpha 1-acid glycoprotein and albumin concentration. The rate of glucuronidation of paracetamol and oxazepam is increased in hyperthyroidism. While oxidative metabolism of antipyrine, propranolol, metoprolol and theophylline is enhanced, the clearance of a number of other agents, including diazepam, warfarin, antithyroid drugs and phenytoin, is unaltered. The systemic clearance of propranolol is enhanced as a consequence of a 50% increase in liver blood flow. The rate of elimination of a number of endogenous substances, including cortisol, thyroid hormones and insulin, also appear to be enhanced. Hyperthyroidism has a variable effect on renal function, with a possible increase in digoxin elimination, but no effect on the clearance of renally excreted beta-blockers, atenolol, sotalol and nadolol. These kinetic changes suggest that individualization and higher than normal dosage of propranolol is necessary to control hyperthyroidism, and in thyrotoxic atrial fibrillation higher doses of digoxin or additional therapy with beta-blockers, or verapamil, may be indicated. The increased sensitivity of thyrotoxic patients to warfarin suggest care with dosage and frequent monitoring of response are warranted. Less information is available concerning hypothyroidism, but there is a general trend for decreased absorption of paracetamol and propranolol. In addition, the volume of distribution of digoxin is reduced, as is renal clearance. Limited studies suggest no alteration in the glucuronidation of oxazepam, but antipyrine clearance appears to be reduced. Steady-state propranolol concentrations are elevated in hypothyroidism and there appears to be a decreased metabolism of thyroid hormones and cortisol. Preliminary information suggests the binding of propranolol is increased. Thus, in the treatment of hypothyroid patients, a lower dosage of propranolol may be required.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocrine System Diseases↗