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Biomedical subjects

G Antezana

Publications and source records attributed to G Antezana.

At least 19 recordsLinked to original sources
PubMed1998

Pulmonary hypertension in high-altitude chronic hypoxia: response to nifedipine.

Permanent residents at high altitude may develop excessive polycythaemia (H-Hb) and pulmonary hypertension, which often leads to cardiac failure. Inhibitors of calcium channels have been shown to reverse pulmonary hypertension in respiratory diseases and in primary pulmonary hypertension, but their efficiency has not been evaluated in high-altitude-induced pulmonary hypertension. Systolic pulmonary arterial pressure (Ppa) was studied by Doppler echocardiography, at rest and after sublingual nifedipine, in 31 asymptomatic residents at 3,600 m. Individuals were separated into two groups according to resting Ppa: a group with low Ppa (< or =4.7 kPa, n=17) and a group with high Ppa (>4.7 kPa, n=14). Individuals were also split into two groups according to haemoglobin (Hb) concentration: a normocythaemic (L-Hb) group ([Hb] < or =180 g.L(-1), n=17) and a H-Hb group ([Hb] >180 g.L.(-1), n=14). No significant difference in Ppa was observed between the L-Hb and H-Hb groups. There was no correlation between [Hb] and Ppa. Nifedipine induced a decrease of >20% in Ppa in two-thirds of the subjects. This response was correlated with higher levels of basal Ppa (p<0.001) and was inversely correlated with age in the L-Hb group (p<0.05). Pulmonary vasoreactivity to nifedipine was independent of the degree of H-Hb. Pulmonary hypertension secondary to chronic altitude hypoxia may be reversible, despite a possible remodelling of the pulmonary arterioles.

Adolescent↗
PubMed1995

Hormonal changes in normal and polycythemic high-altitude natives.

Acute and chronic exposure to high-altitude (HA) hypoxia inhibits the renin-angiotensin-aldosterone system and may modify the release of atrial natriuretic peptide (ANP) in sea-level (SL) natives. In HA natives, the release of these hormones could be influenced by changes in blood volume or pulmonary arterial pressure. Twenty-four men residing in La Paz, Bolivia, at 3,600 m were separated into two groups: one normocythemic (HAN; with hematocrit < 57%; n = 13) and the other polycythemic (HAP; with hematocrit > 57%; n = 11). A control group of 9 SL residents was studied in normoxia (SLN) as well as after 4 days spent at 4,350 m (SLH). The groups were tested for plasma active renin (PAR), plasma aldosterone concentration, ANP, and potassium and norepineprine concentrations at rest and after a maximal exercise. Pulmonary arterial systolic pressure was assessed by a Doppler technique. It was observed that PAR and plasma aldosterone concentration at rest and after exercise were lower in the SLH than in the SLN group. PAR and norepineprine concentration were higher among highlanders than in the SLN group. Renin response to exercise was normal among the HAN group and slightly decreased among the HAP group, and an exercise-induced increase in aldosterone was attenuated in both HA groups. Aldosterone response to renin was maintained among the SLH group but was attenuated in the HA groups, possibly owing to a protective mechanism against salt and water retention. Resting and exercise ANP was lower in the HA groups than in the SLN group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Adrenergic system in high altitude residents.

Heart rate (HR) response to isoproterenol (ISO) infusion (IP) is decreased in normal sea level (SL) natives exposed to high altitude (HA). Since norepinephrine plasma concentration is higher in HA hypoxia, a downregulation of beta-adrenoceptors (beta AR) was evoked. We explored this phenomenon at 3600 m in a HA normal population (HAN) and in polycythemic subjects (HAP). Results are compared to SL natives in normoxia (SLN), and during chronic hypoxia at 4800 m (SLH) (J Appl Physiol 65:1957-1961, 1988). ISO dose required to raise HR by 25 min-1 (I 25) is not different in HAN or HAP group when compared to SLN. Density of beta AR on lymphocytes was 39% and 25% lower in HAN and HAP than in SLN group, respectively. Chronotropic response to IP is similar in SL and HA subjects under their usual environmental conditions, while SL natives show a blunted response under hypoxia, probably due to a decrease in beta AR density. No adrenergic desensitization was found in highlanders. Lower beta AR density in HA groups could be an adaptive mechanism to chronic hypoxia. Polycythemia does not affect this responsiveness.

Adult↗
PubMed1986

Bioenergetic and cardiovascular responses to exercise in residents at 2.850 m, with asymptomatic Chagas' disease.

Cardiovascular and energetic responses at rest, during 30 min of exercise (mechanical output: 125 watts) and for a subsequent recovery period of 5 min were compared in two groups, each comprising 21 residents at an altitude of 2.850 m. One group was in the asymptomatic phase of Chagas' disease with positive serological tests for T. cruzi, whereas the other was without Chagas' disease (negative serological tests). The two groups were similar as regards age, weight-for-height, blood parameters, nutritional status and heart and lung functions, including heart rate and frontal plane QRS axis determinations. At rest, they differed in that maximal and minimal arterial blood pressures were slightly but significantly lower in the group with Chagas' positive serological tests than in the controls. During exercise and recovery, the only differences between them and the controls were that their minimal diastolic arterial blood pressure was significantly lower. In absolute values, the rises in arterial pressure due to exercise were exactly the same in the two groups. Maximal O2 uptake was identical in both groups, as was exercise steady state VO2. These findings indicate that the asymptomatic subjects with Chagas' disease had a normal work capacity and were not affected by high altitude.

Adult↗
PubMed1985

[Preliminary results suggesting a tenuous or nonexistent relation between clinical forms of Chagas disease and isoenzyme strains of Trypanosoma cruzi].

Trypanosoma cruzi strains obtained by xenodiagnosis carried out on 23 Bolivian patients whose pathology was known, were analysed by enzymic typing. 3 patients were infected with mixed strains of both isozymic groups 1 and 2; Isozymic strains of groups 1 and 2 were both associated with cardiac pathology as well as digestive one. Any of the strains present a special relation with a cardiac pathology.

Chagas Cardiomyopathy↗
PubMed1985

[Acute altitude-induced edema of the lung].

High-altitude pulmonary edema has the following clinical features: it occurs in young healthy subjects exposed to altitudes usually above 3,000 m; it is favored by rapid ascent, exercise, cold, and sleep; it can give a deceptive clinical picture because of the patchy distribution of the edema. Hemodynamically, severe pulmonary arterial hypertension (PAH) occurs without increase in wedge pressure or left atrial pressure. Under treatment (rest, oxygen, diuretics), the condition rapidly improves. The physiopathological mechanism of this non-cardiogenic edema is complex and not yet fully defined: PAH essentially stems from hyperreactivity of the pulmonary circulation towards hypoxic arteriolar vasoconstriction, increase in pulmonary blood volume, and pulmonary microthrombosis. Postulated mechanisms involving mixed intra-alveolar edema with high pressure and increased permeability are based on transarterial leakage, over perfusion with endothelial injury, and an increase of permeability in relation to histamine and vasoactive polypeptides. Prevention relies, for a large part, on the identification of HAPE-prone subjects, slow ascent to high altitude, moderate physical activity, warm clothing, and prior administration of acetazolamide.

Acute Disease↗
PubMed1977

Splanchnic blood flow, O2 consumption, removal of lactate, and output of glucose in highlanders.

An impairment of gluconeogenesis has been proposed to explain the low arterial blood glucose of highlanders. Therefore, we studied splanchnic blood flow, splanchnic uptake of oxygen and lactate, and output of glucose in nine normal and six anemic highlanders at an altitude of 3,750 m. Splanchnic blood flow, arteriovenous difference for oxygen, and oxygen consumption were comparable at rest in both groups and in lowlanders from the literature, whereas splanchnic output of glucose, and uptake of lactate were approximately twice those in lowlanders. After 10 min of mild exercise in 12 subjects (7 normals, 5 anemic), no significant changes in splanchnic hemodynamics and metabolism were found. During 29% oxygen breathing in 8 subjects (5 normals, 3 anemics), arterial lactate, splanchnic uptake of lactate and output of glucose fell to normal sea-level values. We concluded that splanchnic hemodynamics are similar in adapted highlanders and in lowlanders, and that there is no evidence of an impaired gluconeogenesis at the altitude of the present study.

Adaptation, Physiological↗
PubMed1976

Pressure-flow-volume relationships in pulmonary circulation of normal highlanders.

Pulmonary vascular pressures and blood flow were measured with and without unilateral pulmonary arterial occlusion (UPAO) at rest and during exercise in 10 normal highlanders at La Paz, Bolivia (altitude, 3,750 m). In 6 other highlanders at rest and during exercise, pulmonary pressures, flow, and blood volume were measured during air breathing (PIO2 congruent to 100 Torr) and 29-30% oxygen (PIO2 congruent to 150 Torr). During air breathing, pulmonary vascular resistance was elevated at rest and did not change with exercise. Pulmonary arterial pressure rose less at rest with UPAO than during exercise without UPAO, and pulmonary vascular resistance was less in the former. Raising PaO2 to normal sea-level values had no effects on the pulmonary circulation at rest but prevented to a large extent the rise in pulmonary arterial pressure during exercise. Hence pulmonary vascular resistance during exercise was lower with oxygen than without. Thus, hypoxic vasoconstriction contributed to the pulmonary hypertension during exercise in normal highlanders. Circumstantial evidence suggests that this is related to the profound mixed venous hypoxemia caused by exercise in a hypoxic environment.

Adolescent↗
PubMedDate not supplied

Electrocardiographic alterations during treatment of mucocutaneous leishmaniasis with meglumine antimoniate and allopurinol.

The electrocardiographic (ECG) changes in Bolivian patients with mucocutaneous leishmaniasis, treated with meglumine antimoniate and allopurinol, were evaluated. Electric changes due to the antimonial compound appeared in 45% of the patients, and consisted of repolarization alteration, principally affecting the T wave and the S-T segment. The changes disappeared within 2 months following the end of the antimonial treatment. In patients with associated Chagas disease and leishmaniasis, antimonial therapy did not aggravate the ECG changes characteristic of Chagasic cardiopathy.

Adolescent↗