benzofurans and Coma

This technique proposes a new approach to correlate intra- and extracellular variations of the ionic concentrations in vivo by means of tapered optical waveguides coupled to standard electrophysiological electrodes to monitor in vivo simultaneously the intracellular and extracellular K(+) concentration as well as the neighboring field potential. The optical fibers were tapered to a final diameter of approximately 10 μm and were used to guide the excitation light deep into the tissue and to collect the fluorescence emanating from the intracellular milieu. This fiber was coupled to a double barrel ion-sensitive electrode forming a micro-optrode with a final diameter around 15 μm. The method was successfully used to record the intracellular K(+) evolution with the fluorescent indicator PBFI during three states: normal sleep-like patterns, paroxysmal seizures, and coma. While we could not disclose any phasic fluctuations of the intracellular K(+) during normal sleep patterns, they were clearly present during seizures and coma. In the majority of cases (58%), paroxysmal discharges were associated with positive variations of the intracellular fluorescence of 62±5% corresponding to extracellular K(+) increases of 2.04±0.4 mM. In the remaining cases (42%) intracellular K(+) dropped by 44.4±12% for an extracellular K(+) increase of 2.62±0.47 mM. We suggest that this differential behavior might reflect different cellular populations (glia vs. neurons, respectively). Comatose states were accompanied by an extracellular drop of K(+) of 1.31±0.13 mM, which was reflected, in all cases, by an intracellular K(+) increase of 39±4%.

Topics: Animals; Benzofurans; Brain; Cats; Coma; Databases, Factual; Electroencephalography; Ethers, Cyclic; Extracellular Fluid; Fiber Optic Technology; Glial Fibrillary Acidic Protein; Intracellular Fluid; Ion-Selective Electrodes; Neurons; Potassium; Reproducibility of Results; Seizures; Sleep

Amiodarone is a potent new antiarrhythmic drug that has multiple effects on thyroid function, including inhibition of extrathyroidal triiodothyronine production and rarely, iodine-induced hypothyroidism. This report describes a man with recurrent ventricular tachycardia in whom hypothyroidism developed during amiodarone therapy and who died of probable myxedema coma. Parenteral and oral thyroxine therapy promptly reduced serum thyroid-stimulating hormone concentrations without increasing the patient's very low serum triiodothyronine concentration. This response to thyroxine suggests that thyroxine itself may have biologic activity and participate directly in regulation of thyrotropin secretion. Because amiodarone-induced hypothyroidism may be life-threatening, thyroid function should be monitored before and during amiodarone therapy, and the drug discontinued or appropriate therapy instituted if hypothyroidism develops.

Topics: Aged; Amiodarone; Benzofurans; Coma; Humans; Male; Myxedema; Tachycardia; Thyroid Gland; Thyrotropin; Thyroxine; Time Factors; Triiodothyronine