Con el propósito de determinar la concentración sérica de óxido nítrico (ON) en pacientes con crisis hipertensiva (CH) se diseñó un estudio prospectivo en el que participaron 10 pacientes normotensos y/o prehipertensos (grupo A), 9 con Hipertensión Arterial (HTA) estadíos 1 y/o 2 (grupo B), 9 con CH tipo urgencia hipertensiva (grupo C). Se registró presión arterial (PA) diastólica y sistólica y se midió el ON por el método de Diazotización en todos los individuos. Se encontraron niveles de ON significativamente bajos con respecto al grupo A en los grupo B y C (p<0.001), pero al compararse estos últimos no hubo diferencias estadísticamente significativas (p>0.05). Los valores de ON se correlacionaron negativamente con la presión arterial sistólica y diastólica, corroborándose que el nivel de ON fue bajo en aquellos individuos con hipertensión arterial. La sobreproducción repentina de vasoconstrictores podría explicar el aumento súbito de PA en CH.A prospective clinical study was designed with the purpose to measure nitric oxide (NO), in patients with hypertensive crises (HC). Blood samples were collected from 10 normotense and/or pre-hypertensive individuals (group A), 9 with hypertension (AHT) stages 1 and/or 2 (group B), and 9 with HC but with hypertensive urgency (group C). Systolic and diastolic blood pressure (BP) was recorded by Dynamap and NO was measured by diazotization assay. NO values in group B and C were lower than A group (p<0.001), however, when B and C groups were compared, there was no significant differences between both groups. NO levels were negative correlated with systolic and diastolic BP. We concluded that NO is low in hypertension and HC, but the association between NO and HC with respect to AHT stages 1and 2 was not corroborated. Further researches are needed to identify vasoconstrictor factors that may lead the suddenly elevation of BP levels founded in HC
