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Biomedical subjects

I Macquin

Publications and source records attributed to I Macquin.

16 recordsLinked to original sources
PubMed1991

Effect of clonidine on the circulation and vasoactive hormones after aortic surgery.

After completion of abdominal aortic graft, 29 patients received an i.v. infusion of placebo (n = 16) or clonidine 7 micrograms kg-1 (n = 13) over 120 min in a double-blind study. Cardiovascular variables were measured and plasma samples obtained up to 5 h after arrival in the recovery room, for assay of noradrenaline, adrenaline, vasopressin and renin concentrations. Noradrenaline, adrenaline and vasopressin concentrations decreased in the clonidine group throughout recovery (P less than 0.001, 0.05 and 0.05, respectively, vs placebo). Heart rate was less in the clonidine group (P less than 0.01). There was no significant difference in mean arterial pressure between groups. Stroke volume was larger (P less than 0.01) and there were fewer episodes of hypertension (P less than 0.05) and tachycardia in the clonidine group. In addition, a reduction in the number of circulatory interventions (P less than 0.05) and episodes of shivering was noted in the clonidine group. Mean (SD) postoperative volume requirements were larger in the clonidine group (total postoperative input: clonidine 1462 (604) ml; placebo 1064 (348) ml (P less than 0.05]. These data are consistent with the observation that clonidine modifies endocrine and circulatory status after major surgery.

Aorta, Abdominal↗
PubMed1990

Aortic surgery: effect of clonidine on intraoperative catecholaminergic and circulatory stability.

Twenty-eight patients presenting for aortic surgery were randomly assigned in a double-blind, placebo-controlled protocol to receive placebo (n = 14) or clonidine (4.7 +/- 1.2 micrograms.kg-1 po; n = 14), in addition to flunitrazepam 120 min before induction of anesthesia. Plasma catecholamines (CA) and hemodynamic variables were determined at 7 stages during surgery. In the placebo group, plasma epinephrine (E) and norepinephrine (NE) had risen twofold at skin closure compared to baseline (E: from 109 +/- 51 pg.ml-1 to 294 +/- 161 pg.ml-1; NE: from 658 +/- 226 to 1150 +/- 494 pg.ml-1). Plasma CA were significantly lower in the clonidine group (P less than 0.001 and 0.01 vs placebo for NE and E respectively). In both groups, similar directional changes were observed for the circulatory variables, upon aortic clamping and declamping. In the clonidine group, however, mean arterial pressure was lower at most stages (P less than 0.05 vs placebo); moreover, stroke volume index was greater in the clonidine group (P less than 0.05) upon declamping. This improved stability in the clonidine group was achieved with a halving in the number of anesthetic/circulatory interventions (P less than 0.05 vs placebo). Provided intravascular volume is adequate, clonidine suppresses the increase in plasma catecholamines induced by aortic surgery and improves circulatory stability, with a reduced number of anesthetic, circulatory adjustments.

Adult↗
PubMed1985

Bronchorelaxation and plasma histamine after salbutamol inhalation.

Plasma histamine in 8 normal subjects was measured before and after inhalation of carbachol to induce a 50% fall in specific airway conductance (SGaw). The measurements were repeated 5 min after inhalation of salbutamol or placebo. No significant change in plasma histamine occurred after placebo or carbachol inhalation, despite the persistent induced bronchospasm after the latter treatment. In contrast, plasma histamine was significantly increased from 0.25 to 0.43 ng/ml after salbutamol inhalation. Simultaneously, induced bronchospasm was relieved, from 51% to 103% of baseline SGaw. Thus, the relief of carbachol-induced bronchospasm by salbutamol was associated with a rise in plasma histamine. Since salbutamol itself is a potent inhibitor of mast cell degranulation and histamine release, the present findings suggest that histamine may be released and sequestered within the lungs during carbachol-induced-bronchospasm, and also that desequestration of bronchoconstrictor mediators accumulated at the point of contact of bronchial smooth muscle may contribute to the relief of bronchospasm by salbutamol.

Adult↗
PubMed1985

A microcomputer-based system for real-time calculation of airway conductance in awake guinea pigs.

Bronchial responsiveness to various drug stimuli is currently studied by constructing cumulative dose-response curves of specific respiratory conductance (SG). Airway conductance can be measured in guinea pigs by the plethysmographic technique, during the rapid transition from expiration to inspiration (TEI). Since the drug action assigns a strict timing to the experiment, conventional methods of measuring SG prove inconvenient and often lack accuracy. A computerized data acquisition system has therefore been developed to recognize TEI and calculate SG in real time. This paper describes the significant features of the program DOREMI, and gives an illustrative example of the system in use.

Airway Resistance↗
PubMed1984

Plasma histamine and catecholamines during carbachol-induced bronchoconstriction in normal subjects.

To determine (1) whether changes in plasma histamine occurred during provoked bronchospasm and (2) if so, whether such changes could be related to variations in plasma catecholamines, venous plasma histamine and catecholamines were measured during a dose-response carbachol challenge in eight healthy volunteers. A significant rise in plasma histamine was observed, whereas induced bronchoconstriction was small, 80% +/- 4% of initial specific airway conductance. There was no further increase in plasma histamine, whereas induced bronchoconstriction became more marked (70%, 60%, and 50% of specific airway conductance initial value). Plasma catecholamines did not change throughout the study. We conclude that mast cell degranulation occurs during a carbachol challenge, and that the variations in plasma histamine are not related to changes in plasma catecholamines.

Adult↗
PubMed1983

[Use of a severity index in 8 multidisciplinary resuscitation centers].

A universal severity index for acutely ill patients was applied to 794 acute patients treated in eight medical and surgical French intensive care units located in teaching or community hospitals either in Paris or in provincial towns. Measured on the first day in hospital from objective numerical data, the index proved reliable and correlated well with hospital mortality and the sustained therapeutic efforts of the first 24 hours. It could be used in multicentre studies to compare outcomes and evaluate new treatments.

Disease↗
PubMed1983

Blood pressure and plasma norepinephrine concentrations after endogenous norepinephrine release by tyramine.

To determine whether small changes in sympathetic activity would cause detectable changes in plasma norepinephrine (NE) levels, and whether the effects of endogenously released and exogenous NE differ, we injected tyramine infusions and l-norepinephrine (l-NE), into six healthy subjects, and the changes in blood pressure (BP) and plasma NE were related. The mean increase in systolic BP was approximately 17 mm Hg with both infusions; diastolic BP increased with l-NE but did not rise significantly with tyramine. Heart rate fell more with l-NE than with tyramine infusions. The maximum increase in plasma NE levels was more than 500% during l-NE infusions but less than 200% with tyramine. There was no correlation between plasma NE and absolute levels of systolic BP when individual data were plotted for tyramine infusions, whereas mean group changes in systolic BP correlated strongly with mean group plasma NE, both during tyramine and l-NE infusions. The slope of the relationship was much steeper for tyramine than for l-NE. We conclude that the use of plasma NE to measure small differences in sympathetic activity among individuals is limited by interindividual variability, whereas changes in sympathetic activity within groups are more likely to be detected.

Adult↗
PubMed1982

Concentration effect relationships of infused histamine in normal volunteers.

Histamine was infused in six normal volunteers at rates of 16, 32, 64 and 96 ng/kg/min increasing at 5-min intervals followed by 128 ng/kg/min for 45 min. Heart rate increased, diastolic blood pressure decreased and skin temperature increased in a dose-dependent fashion. Mean heart rate increased by 15.6 +/- 5.7 beats/min, mean diastolic pressure fell by 8.8 +/- e.2 mmHg and mean skin temperature increased by 1.2 +/- 0.3 degrees C at the highest infusion rate. Mean plasma histamine rose from a basal level of 0.20 +/- 0.03 ng/ml to 1.97 +/- 0.25 ng/ml at the end of the highest infusion rate. The threshold infusion rate for physiological effects was 64-96 ng/kg/min corresponding to 0.77-0.97 ng/ml. Salivary flow was stimulated by 21% after 30 min at the highest dose infusion (P = 0.05). Plasma adrenaline increased 132% but plasma noradrenaline was unchanged. There was a linear decline in heart rate after terminating the histamine infusion with a half time of 82 sec. The half life of infused histamine in the plasma was 102 sec. The clearance of histamine from the plasma was 6.1 %/- 0.2 l/min or 83 ml/kg/min. These concentration effect relationships in normals throw doubt on some of the high endogenous plasma histamine values in the literature.

Adult↗
PubMed1982

Catecholamine neurotransmitters and the heart.

The possible role of adrenaline as a cardiac neurotransmitter was studied following its infusion in 6 healthy volunteers. After the end of the infusion, heart rate remained elevated for several hours despite a rapid fall in plasma adrenaline concentration. Stimulation of sympathetic activity by standing caused a further marked increase in heart rate, which was greater than that found on a control occasion. These effects were abolished or reduced by pretreatment with either desipramine or (in the dog) alpha-methyl-p-tyrosine, suggesting that they depend both on uptake of the adrenaline into sympathetic nerve endings during infusion and on increased release of endogenous noradrenaline. These results are consistent with stimulation of the beta-presynaptic receptor by adrenaline when re-released from sympathetic nerves.

Blood Pressure↗
PubMedDate not supplied

[Effects of histamine on the pressure-volume curve of the respiratory system in the guinea pig].

Intravenous infusion of histamine has been shown to constrict smooth muscle of alveolar ducts. In this study, we have assessed the effects of a prolonged infusion of histamine to obtain a steady state response on quasistatic pressure-volume curves (P-V curves) together with the changes in dynamic compliance (Cdyn) and conductance (G) of the respiratory system. Increasing doses of histamine were given in order to obtain the dose-response characteristics of the changes in Cdyn, G and P-V curves. In nine anesthetized guinea-pigs under mechanical ventilation, administration of histamine resulted in a fall in Cdyn and G with a decrease of 50% of initial value approximately for 150 ng X kg-1 X s-1 of histamine. Modifications of the P-V curves were characterized by a decrease in the maximal volume, and an increase in the hysteresis of the P-V loop due to the downward displacement of the inflation limb. With infusion of histamine, there was a large decrease of quasi-static compliance which appeared to account for most of the decrease in dynamic compliance. Such changes in P-V curves can be related both to a closure of alveolar ducts and to an alteration of lung distensibility. Comparison of the dose-response curves for the different parameters indicated that Cdyn and G reflect, at least in part, events occurring in the periphery of the lung.

Animals↗