Influence of caffeine on blood pressure and platelet aggregation.

OBJECTIVE: Studies have demonstrated that methylxanthines, such as caffeine, are A1 and A2 adenosine receptor antagonists found in the brain, heart, lungs, peripheral vessels, and platelets. Considering the high consumption of products with caffeine in their composition, in Brazil and throughout the rest of the world, the authors proposed to observe the effects of this substance on blood pressure and platelet aggregation. METHODS: Thirteen young adults, ranging from 21 to 27 years of age, participated in this study. Each individual took 750 mg/day of caffeine (250 mg tid), over a period of seven days. The effects on blood pressure were analyzed through the pressor test with handgrip, and platelet aggregation was analyzed using adenosine diphosphate, collagen, and adrenaline. RESULTS: Diastolic pressure showed a significant increase 24 hours after the first intake (p<0.05). This effect, however, disappeared in the subsequent days. The platelet aggregation tests did not reveal statistically significant alterations, at any time during the study. CONCLUSION: The data suggest that caffeine increases diastolic blood pressure at the beginning of caffeine intake. This hypertensive effect disappears with chronic use. The absence of alterations in platelet aggregation indicates the need for larger randomized studies.

Comportamento da pressão arterial em filhos de normotensos e filhos de hipertensos submetidos a estímulos pressóricos / Arterial blood pressure responses in children of normotensive and hypertensive parents submitted to pressor tests

OBJETIVO - Comparar a pressão arterial (PA) basal e as respostas a estímulos pressóricos de filhos de normotensos e filhos de hipertensos. MÉTODOS - Foram examinados 32 adolescentes, do sexo masculino, brancos, na faixa etária entre 13 e 18 anos, sendo que 16 eram filhos de hipertensos e 16 filhos de normotensos. Para cada indivíduo foi aferida a PA basal seguida da aplicaçäo de três testes pressóricos: teste do exercício isométrico com o handgrip, teste pressor ao frio e teste do exercício aritmético mental. Para a aferiçäo da PA foi utilizado um dispositivo oscilométrico, digital, previamente calibrado. Resultados - Os filhos de hipertensos exibiram valores basais de PA, tanto sistólica quanto diastólica, maiores que os filhos de normotensos (p "menor" 0,10). Quanto aos testes pressóricos, as respostas foram maiores nos filhos de hipertenso, porém somente a resposta da PA diastólica ao teste do exercício aritmético mental alcançou significância estatística (p "menor" 0,10). Conclusäo - Os resultados obtidos indicam a necessidade de atençäo especial às crianças e adolescentes com antecedentes familiares de hipertensäo.

[Blood pressure responses in children of normotensive and of hypertensive parents treated with pressor stimulus]. / Comportamento da pressão arterial em filhos de normotensos e filhos de hipertensos submetidos a estímulos pressóricos.

PURPOSE: To compare cardiovascular reactivity in adolescents with and without family history of hypertension. METHODS: Thirty two subjects, males, students, aging between 13 to 18 years old were examined. One half of them had no family history of hypertension and the other half had at least one hypertensive parent. Basal blood pressure level was obtained before the application of the following selected tests: isometric handgrip exercise test, cold pressor test and arithmetic mental stress test. The blood pressure values were obtained by a digital, oscilometric device, previously calibrated. RESULTS: The subjects with family history of hypertension exhibited higher basal levels of both systolic and diastolic blood pressure (p < 0.10). Concerning the tests applied, the subjects with family history of hypertension also exhibited higher responses, but only the responses of the diastolic blood pressure to the mental stress test was statistically significant (p < 0.10). CONCLUSION: Our findings point to the need of a special follow-up of children with a family history of hypertension.