Continuous in vivo monitoring in diabetes: the subcutaneous glucose concentration

The most advanced glucose sensors are measuring amperometrically the hydrogen peroxide generated in a stoichiometric relation to the prevailing glucose concentration during glucose oxidase-mediated glucose oxidation. They proved useful in commercially available glucose analysers and in experimental subcutaneous (sc) monitoring. Here it is shown (a) that under steady state conditions the sc. glucose concentration is nearly identical to that in blood, (b) that sc. inserted glucose electrodes do mirror the intracorporal glucose concentration both under hypo-, normo-, and hyperglycaemic conditions with a clinically relevant accuracy, (c) that automated feedback control of intracorporal glucose concentration is possible applying the output of sc. glucose sensor as an input to the computer that controls the insulin pump, and (d) that stable function of sc. sensor may be accomplished over intervals up to one day; in some cases applications over up to ten days have been reported. The underlying problem consists in an insufficient functional biostability which is a function of biocompatibility and size of the sensor, of its sterility, and of the permanent skin penetration. The latter is still required to get the device in place, to keep it in function, and to make use of the data under any condition. At this time, sc. glucose electrodes to be employed as hypoglycaemia-warning systems over one day are considered clinically important and technically achievable.     

Clinical Aspects of Tricyclic Antidepressant Poisoning

ABSTRACT Self-poisoning with antidepressant drugs was studied retrospectively in 225 patients admitted to an intensive care unit. Amitriptyline accounted for the overwhelming majority of cases (70%); 106 patients (47%) had taken two or more drugs, in 81 patients (36%) ethanol was found in the blood. Four patients (2%) died. On admission, 111 patients (49%) were unconscious (grade III). A further 30 patients (13%) were in grade IV coma, and of these 27 had taken amitriptyline. Twenty-four hours after admission, 22 patients (10%) remained in coma. Thirty-six patients (16%) required assisted ventilation. Nineteen patients (8%) had convulsions and 6 (3%) aspired stomach contents. Sixty-one patients (27%) had a widened QRS interval exceeding 100 msec, 18 (30%) of them required assisted ventilation, 21 (34%) were in stage IV coma and 15 (25%) had convulsions. This relationship between a widened QRS interval and the severity of intoxication should be considered in the initial assessment of patients with tricyclic antidepressant poisoning.     

Reciprocal metabolic inhibition of toluene and trichloroethylene in vivo and in vitro

Summary Administration of trichloroethylene to rats in addition to toluene suppressed the urinary excretion of hippuric acid, a main metabolite of the aromatic compound. Reversely, when co-administered with trichloroethylene, toluene reduced the amount of urinary total trichloro-compounds, the metabolites of the chlorinated ethylene. Kinetic approach in vitro to this reciprocal metabolic suppression revealed that trichloroethylene is a non-competitive inhibitor of side-chain hydroxylation of p-nitrotoluene, a substrate analogue of toluene, and toluene, in turn, inhibits oxidation of trichloroethylene non-competitively. Toxicological significance of this observation as well as circumspection in biological monitoring of organic solvent exposure in relation to metabolic suppression are briefly discussed.This work was supported in part by a research grant from the Fujiwara Memorial Foundation.     

Ornithine carbamoyl transferase deficiency: A neuropathological study

A detailed autopsy study of three children with ornithine carbamoyl transferase (OCT) deficiency is presented. Although variable in extent, a basic pattern of neuropathological lesions is discernible. Case 1 shows gross cerebral atrophy, cases 2 and 3 milder lesions in the basal nuclei but also multiple cerebellar heterotopias and delayed myelination. We suggest that the findings may provide evidence that OCT deficiency can have a teratogenic effect in utero and suggest that there is a need to monitor the pregnancies of carriers of this disorder.     

Biological monitoring of occupational exposure to methyl ethyl ketone by means of urinalysis for methyl ethyl ketone itself

Summary Head space gas chromatography (GC) was applied to measure methyl ethyl ketone (MEK) in urine from 62 MEK-exposed male workers, whose individual intensity of exposure to MEK was monitored utilizing the carbon felt dosimeter. The urinary MEK level increased rapidly to reach a plateau in the first quarter of the daily 8-h work, while very little MEK was detected in the preshift urine. When the MEK levels in the urine at the end of the shift were compared with the afternoon MEK-TWA values, the uncorrected MEK in urine correlated best with MEK in air (r=0.774, n=62), while correction for creatinine gave a comparable result and the correlation was poorer when corrected for a specific gravity of urine or for the lapse of time after preceding passage of urine. Balance of MEK absorption via inhalation and MEK excretion into urine revealed that only 0.1% of MEK absorbed will be excreted unchanged into urine. Wider application of head space GC is discussed for the analysis of unmetabolized solvents in urine.     

A comparison of two methods for the computer analysis of arterial blood pressure waveforms

Two different methods, one analogue and one digital, for the analysis of the arterial blood pressure waveform are described and compared. Little difference was found in the systolic and diastolic pressures determined by the two methods.     

Online respiratory-waveform analysis using a digital desk calculator

A system for acquiring airway pressure, flow (from a pneumotachometer) and O₂ and CO₂ concentration (from a mass spectrometer) waveforms is described. Analogue signals from these sources, as well as from gas and pneumotachometer case-temperature circuits, are interfaced with a programmable digital desk calculator. The patient-read program, in five blocks, is described in detail. Major features are: a zero-flow and gas-calibration block, which automatically switches the strain gauges to ambient air and the mass spectrometer to calibration gas; a data-acquisition block which matches flow and gas signals in time, acquires mechanics and gas-exchange data for inspiratory and expiratory cycles separately, acquires mechanics data alone in the absence of a gas waveform, and records data at the onset of the CO₂ ‘plateau’ during expiration; a data-calculation block which averages data for the number of respiratory cycles read, corrects flow readings for gas viscosity and temperature, and calculates mechanics and gas-exchange data; and a printout block which prints only data falling within arbitrary limits. A flow-calibration program using a valveless piston pump is also described. The total system is portable, relatively inexpensive and, since most of it functions automatically, may be used by untrained personnel.     

Influence of exposure to electromagnetic field on the cardiovascular system

1 We examined whether extremely low frequency electromagnetic fields (ELF-EMF) affect the basal level of cardiovascular parameters and influence of drugs acting on the sympathetic nervous system. 2 Male rats were exposed to sham control and EMF (60 Hz, 20 G) for 1 (MF-1) or 5 days (MF-5). We evaluated the alterations of blood pressure (BP), pulse pressure (PP), heart rate (HR), and the PR interval, QRS interval and QT interval on the electrocardiogram and dysrhythmic ratio in basal level and dysrhythmia induced by beta-adrenoceptor agonists. 3 In terms of the basal levels, there were no statistically significant differences among control, MF-1 and MF-5 in PR interval, QRS interval, mean BP, HR and PP. However, the QT interval, representing ventricular repolarization, was significantly reduced by MF-1 (P < 0.05). 4 (-)-Dobutamine (beta1-adrenoceptor-selective agonist)-induced tachycardia was significantly suppressed by ELF-EMF exposure in MF-1 for the increase in HR (DeltaHR), the decrease in QRS interval (DeltaQRS) and the decrease in QT (DeltaQT) interval. Adrenaline (nonselective beta-receptor agonist)-induced dysrhythmia was also significantly suppressed by ELF-EMF in MF-1 for the number of missing beats, the dysrhythmic ratio, and the increase in BP and PP. 5 These results indicated that 1-day exposure to ELF-EMF (60 Hz, 20 G) could suppress the increase in HR by affecting ventricular repolarization and may have a down-regulatory effect on responses of the cardiovascular system induced by sympathetic agonists.