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Biomedical subjects

P Larmignat

Publications and source records attributed to P Larmignat.

At least 19 recordsLinked to original sources
PubMed1992

Haemostasis at high altitude.

Haemostasis has been studied by several authors during exposure to altitude hypoxia. On acute induction to hypoxia, platelet count, platelet aggregability and bleeding time are normal; an increase of thromboxane released from platelets and of prostacyclin, released from endothelial cells is observed; coagulation factors are unchanged except of F. VIII which is increased; modified antithrombin III (ATm) are normal; fibrinopeptide A is increased in subjects with pulmonary edema and fibrinolytic activity after venous occlusion is normal. In chronic hypoxia, during a stay at 6542 m (Mt. Sajama), we found in 7 subjects an important increase in D. Dimer (p < 0.001) that seems to correspond to an activation of coagulation and a decrease of F. VIII R. Cof/F. VIII R. Ag ratio which suggests an endothelial cell damage.

Altitude Sickness↗
PubMed1992

Detection of high-risk subjects for high altitude diseases.

The variability in sensitivity to acute mountain sickness among individuals is a phenomenon well known to physicians and high altitude alpinists. The measurement of cardiac and respiratory responses to hypoxia (FIO2 = 0.115) at rest and during exercise (50% VO2max) allows the detection of those subjects who are more liable to suffer from high altitude diseases. In a retrospective study performed on 288 subjects evaluated with a hypoxic test during a Mountain medicine consultation, we found that the most clinically susceptible subjects had at least one abnormal response to the hypoxic tests, especially during exercise. The observation of one or several abnormal values in cardiac or respiratory responses to hypoxia leads us to advise a modification in the alpine or trekking objective, an increase in the acclimatization time and/or prevention by acetazolamide.

Altitude Sickness↗
PubMed1991

Plasma prostaglandins, leukotrienes and thromboxane in acute high altitude hypoxia.

To explore the hypothesis that acute exposure to altitude hypoxia and acute mountain sickness (AMS) are associated with the release of vasoactive eicosanoids, 10 adult subjects were studied at sea-level and after 1-8 days (H1-H8) of exposure to an altitude of 4350 m (Observatoire Vallot). Plasma concentrations of 6 eicosanoids were determined in peripheral venous blood samples by radioimmunoassay after extraction with cooled ethanol and chromatographic separation by HPLC. All subjects experienced symptoms of AMS. Maximal clinical scores were observed at H1 or H2. Symptoms were no longer noted at H8. Hypoxia induced a very large increase in plasma concentration of most eicosanoids; thromboxane B2 (TxB2) and leukotriene B4 (LTB4) were maximum at H1 and H2 (about 5 times the normoxic value); prostaglandins PGE2, 6-keto-PGF1 alpha and PGF2 alpha were maximum at H3 or H4 (about 2.5-5 times of normoxic value). All eicosanoids returned almost to normoxic values by H8. Vasoconstricting mediators were released mostly at the initial phase (H1, H2), vasodilating mediators becoming predominant thereafter (H3, H4). The time pattern of appearance in blood of mediators acting on vascular permeability was strikingly parallel to the clinical score of AMS. In conclusion, exposure to acute hypoxia induced a large increase in plasma concentration of eicosanoids, the variation with time of which is compatible with a hydrostatic-permeability hypothesis of AMS pathophysiology.

Adult↗
PubMed1991

[Influence of the risk factors of atherosclerosis on the onset of early peri-operative complications in peripheral arterial surgery].

The influence of classical atherosclerosis risk factors (male sex, smoking, hypercholesterolemia, diabetes, overweight and hypertension on peri-hospital mortality and morbidity were studied in 83 patients (68 men and 15 women) aged 63 +/- 13 years and undergoing peripheral arterial surgery. None of these factors was statistically correlated with peri-operative complications with the exception of hypertension but the correlation was slight (0.5 less than p less than 0.10). In contrast, there was a powerful statistical (p less than 0.0003) link between age and morbidity and mortality associated with this type of surgery.

Aged↗
PubMed1990

Saliva flow and composition in humans exposed to acute altitude hypoxia.

The effects of acute hypoxia (2 days at 4350 m) on whole saliva flow and composition were studied on 12 sea-level natives, at rest and following a maximal exercise. Exercise, performed in normoxia and hypoxia, did not induce variations in saliva flow rate, saliva potassium or alpha-amylase concentrations. In contrast, acute hypoxia did lead to an increase in mean saliva flow rate both at rest (0.63 ml.min-1 to 0.93 ml.min-1, P less than 0.01) and after exercise (0.56 ml.min-1 to 1.06 ml.min-1, P less than 0.05) and a decrease in mean saliva potassium concentration at rest (20.8 mmol.l-1 to 14.7 mmol.l-1, P less than 0.01) as well as after exercise (21.7 mmol.l-1 to 16.5 mmol.l-1, P less than 0.05). This effect might be the consequence of a hypoxia-induced stimulation of the parasympathetic nervous system.

Adult↗
PubMed1989

Effect of beta-adrenoceptor blockade on renin-aldosterone and alpha-ANF during exercise at altitude.

The renin-aldosterone system may be depressed in subjects exercising at high altitude, thereby preventing excessive angiotensin I (ANG I) and aldosterone levels, which could favor the onset of acute mountain sickness. The role of beta-adrenoceptors in hormonal responses to hypoxia was investigated in 12 subjects treated with a nonselective beta-blocker, pindolol. The subjects performed a standardized maximal bicycle ergometer exercise with (P) and without (C) acute pindolol treatment (15 mg/day) at sea level, as well as during a 5-day period at high altitude (4,350 m, barometric pressure 450 mmHg). During sea-level exercise, pindolol caused a reduction in plasma renin activity (PRA, 2.83 +/- 0.35 vs. 5.13 +/- 0.7 ng ANG I.ml-1.h-1, P less than 0.01), an increase in plasma alpha-atrial natriuretic factor (alpha-ANF) level (23.1 +/- 2.9 (P) vs. 10.4 +/- 1.5 (C) pmol/1, P less than 0.01), and no change in plasma aldosterone concentration [0.50 +/- 0.04 (P) vs. 0.53 +/- 0.03 (C) nmol/1]. Compared with sea-level values, PRA (3.45 +/- 0.7 ng ANG I.ml-1.h-1) and PA (0.39 +/- 0.03 nmol/1) were significantly lower (P less than 0.05) during exercise at high altitude. alpha-ANF was not affected by hypoxia. When beta-blockade was achieved at high altitude, exercise-induced elevation in PRA was completely abolished, but no additional decline in PA occurred. Plasma norepinephrine and epinephrine concentrations tended to be lower during maximal exercise at altitude; however, these differences were not statistically significant. Our results provide further evidence that hypoxia has a suppressive effect on the renin-aldosterone system. However, beta-adrenergic mechanisms do not appear to be responsible for inhibition of renin secretion at high altitude.

Adult↗
PubMed1989

[Cardiac response to hypoxia and susceptibility to mountain sickness].

Exercising in high altitude is impeded during the first days of exposure to altitude hypoxia by the symptoms of Acute Mountain Sickness (AMS). Susceptibility to AMS is independent of endurance training and determined by the sensitivity of carotid chemoreceptors to hypoxemia and induced hyperventilation and tachycardia. Cardiac response to hypoxia is not as well known as ventilatory response, especially at exercise. A group of 138 male alpinists has been explored before their departure to a high altitude expedition using an hypoxic gas mixture (equivalent altitude = 4.800 m), at rest and at exercise (5 minutes at 50 p. 100 maximal O2 consumption). Cardiac response to hypoxia was assessed by the ratio DFc/DSaO2: variation in heart rate (hypoxia - normoxia)/variation in arterial O2 saturation, at rest (r) and during exercise (e). After the expedition, subjects were classified in AMS+ or AMS- group if they suffered or not from severe AMS, and also following their climbing skill. Cardiac response to hypoxia at rest is lower in AMS+ subjects (DFc/DSaO2 = - 0.86 +/- 0.40 nn - 1.% - 1) than in AMS- subjects (-1.12 +/- 0.69, p less than 0.05), but is not linked to the climbing skill. Similar differences were observed at exercise: DFc/DSaO2e = - 0.88 +/- 0.32 (AMS+) and - 1.05 +/- 0.50 (AMS-) (p less than 0.05). Associated with the respiratory response to hypoxia, the cardiac response allows the detection of AMS high-risk subjects and may be used in an much less than aptitude to altitude much greater than test.

Adolescent↗
PubMed1988

[Photoplethysmography and laser Doppler velocimetry in the study of cutaneous vasomotility at high altitudes].

During the second French scientific medical expedition to the Himalaya (ARPE, Annapurna IV, 1985), modifications of cutaneous circulation in hypoxia were studied. Two techniques were used for the first time to evaluate cutaneous vasoactivity under such conditions: laser Doppler velocimetry and photoplethysmography. Measurements were performed on the pulp of the third and fourth fingers of the right hand in 6 subjects native of sea-level countries: first at sea level, then in hypoxia after 15 days at 4,800 m before and after ingestion of a vasodilator drug (nicardipine 20 mg). Cutaneous circulation was explored under three thermal conditions: baseline (ambient temperature); after vasodilation obtained by immersion of the hand in hot water (40 degrees C), and after immersion of the hand in cold water (12 degrees C). In prolonged hypoxia a reduction in vasoconstriction at 12 degrees C was observed with both techniques. No significant change was observed at 40 degrees C. After dosing with nicardipine, the results differed according to the exploratory technique: a slight increase of the laser Doppler signal (NS) and a decrease of the photoplethysmographic signal were recorded. Acclimatization to cold and to hypoxia may concur to determine this response of cutaneous circulation. The action of vasodilating agents on cutaneous microcirculation in prolonged hypoxia is not clear and deserves further investigation. These drugs must be used with caution in the prevention and treatment of frostbite.

Adult↗
PubMed1988

[Periodic respiration during sleep at high altitude. Effects of a hypnotic benzodiazepine, loprazolam].

Sleep and respiration studies were carried out in 12 subjects (9 males, 3 females) at an altitude of 4,800 metres, during effect of a French expedition in the Himalayas. The effect of loprazolam, a hypnotic benzodiazepine, was investigated in a double-blind, 2 parallel group, 1 mg loprazolam versus placebo trial. Sleep was evaluated by means of electroencephalographic recordings and questionnaires. The effects of altitude in each subject were intercurrent wakefulness increase, slow wave sleep and paradoxical sleep decrease and nocturnal periodic breathing. The mean duration of sleep apnea episodes was 12 seconds with a maximum of 24 seconds. These episodes occurred during stages 1 or 2 of sleep and during paradoxical sleep. Female subjects exhibited less periodic breathing than males. Acclimatization to high altitude increased total sleep time, stage 3 duration and percentage of paradoxical sleep. Loprazolam tended to decrease stage 2 latency and did not worsen slow wave sleep depression or episodes of apnea. Normal amounts of slow wave sleep and intrasleep wakefulness appeared in the loprazolam group after acclimatization.

Acclimatization↗
PubMed1988

Decreased cardiac response to isoproterenol infusion in acute and chronic hypoxia.

The hypothesis of a blunted chronotropic response of cardiac beta-adrenergic receptors in altitude hypoxia was tested in nine subjects at sea level (SL) by infusion of isoproterenol. Observations were made at SL, in acute hypoxia (2 days at 4,350 m, condition H1), in more prolonged hypoxia [13 days between 850 and 4,800 m, condition H2] and in chronic hypoxia [21 days at 4,800 m, condition H3]. Resting heart rate was higher in all hypoxic conditions. Resting norepinephrine concentrations were found to be significantly higher in conditions H2 (1.64 +/- 0.59) and H3 (1.74 +/- 0.76) than at SL (0.77 +/- 0.18 ng/ml). Isoproterenol, diluted in saline, was infused at increasing doses of 0.0, 0.02, 0.04, and 0.06 micrograms.kg-1.min-1. For the highest dose, there was a significantly smaller increase in heart rate in conditions H1 (35 +/- 9), H2 (33 +/- 11), and H3 (31 +/- 11) than at SL (45 +/- 8 min-1). The increase in pulse (systolic/diastolic) pressure, considered as the vascular response to isoproterenol infusion, was smaller in condition H3 (29 +/- 16) than at SL (51 +/- 24 mmHg). There was a significant increase in the dose of isoproterenol required to increase heart rate by 25 min-1 and decrease in slope of heart rate increase vs. log(dose) relationship in conditions H2 and H3. Thus an hypoxia-related attenuated response of beta-adrenergic receptors to exogenous stimulation was found in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

Assessment by dipyridamole-thallium-201 myocardial scintigraphy of coronary risk before peripheral vascular surgery.

From October 1983 to January 1985, 46 patients (38 men and 8 women; average age, 60 years; range, 37 to 83 years) underwent peripheral vascular surgery of either the internal carotid artery or the arteries of the lower limbs. Each patient had a thorough clinical examination, an ECG, and a dipyridamole-thallium-201 myocardial scan before operation. On the basis of results, they were divided into two groups: 20 patients with and 26 patients without chronic ischemic heart disease. Three major cardiac events were noted during or after a period of 1 month after surgery: There were two deaths due to cardiac ischemic events and one patient had postoperative unstable angina pectoris. These three patients were classified in the coronary group (NS). When the patients were classified on the basis of whether or not there was thallium redistribution on serial images after infusion of dipyridamole, 14 with redistribution and 32 without redistribution were noted. The three patients who had major cardiac events were in the former group (p less than 0.04). Our data suggest that patients in whom redistribution occurs have a high incidence of postoperative ischemic events. These patients should be considered for particular preoperative coronary care to avoid major postoperative cardiac events and to increase chances of survival.

Adult↗
PubMed1987

[Evaluation by myocardial thallium-201 scintigraphy using dipyridamole of the coronary risk in peripheral vascular surgery].

From October 1983 to January 1985, 46 patients (38 men and 8 women; mean age 60 years, range 37-83) underwent peripheral vascular surgery either of the internal carotid artery or of arteries of the lower limbs. All patients had thorough clinical examination, ECG and thallium dipyridamole myocardial scanning before operation, as a result of which they were divided into 20 with, and 26 without chronic ischemic heart disease. Three major cardiac events were noted during or following a period of one month after surgery: two deaths due to a cardiac ischemic event and one post-operative unstable angina pectoris. The three patients with these complications were classified in the coronary group (NS). When the patients were reclassified according to the presence or absence of thallium redistribution on serial images after dipyridamole, 14 had redistribution and 32 had no redistribution. The three major cardiac events were found to have occurred in the group with redistribution (P less than 0.04). Our study suggests that patients with redistribution have a high incidence of postoperative ischemic events. They should be considered for a particular pre-operative coronary management to avoid post-operative major cardiac events and to improve survival.

Adult↗
PubMed1985

[Computerized report of anesthesia in real time].

The computerized report of anesthesia (C.R.A.) is an equivalent of the document filled out by the anesthesiologist, linked to a multicriteria research program giving the opportunity to study connections between different performances of anesthesia. To obtain these results, the authors are introducing a microcomputerized system in real time, including a microcomputer (capacity 64 kO), a visual display monitor (80 column format), two floppy disks controllers and a printer. Through a "menu", there is an access to the following functions: identity, patient story, drug prescriptions, anesthetics used, chronology of administration, monitoring of parameters, incidents/accidents, multicriteria research, editing of the C.R.A. The operational realisation shows that this computerized system offers storage capacity and allows a retrospective analysis of anesthesia. As it is inexpensive and easy to use, it may become a very important device in every-day practice.

Anesthesia, General↗