RESUMO
This study was undertaken to compare the influence of different regimens for induced hypotension down to Power a limit of 80 mmHg (systolic) on sympatho-adrenergic responses in 10 volunteers. Volunteers were investigated in five batteries of tests using glyceryl trinitrate (10 micrograms/kg BW/min), sodium nitroprusside (10 micrograms/kg BW/min maximal dosage), nifedipine (0.35 micrograms/kg BW/min) and urapidil (bolus injections of 25, 25 and 50 mg, followed by an infusion of 180 ml/h) and placebo. Catecholamines in plasma were detected by HPLC/ECD within a period of 1 h of hypotension and 1 h of recovery at 11 measuring points. Using sodium nitroprusside and glyceryl trinitrate, a significant hypotension was achieved. Urapidil was less potent. No hypotension was observed during or after treatment with nifedipine. Heart rate increased during treatment with sodium nitroprusside and glyceryl trinitrate. Sodium nitroprusside, glyceryl trinitrate and urapidil caused significant rises in noradrenaline levels. With nifedipine, noradrenaline increased within the normal range. Adrenaline left the normal range only during urapidil treatment. MAP, HR, and levels of noradrenaline and adrenaline returned to the initial values 5 min after discontinuation of the sodium nitroprusside infusion. After treatment with glyceryl trinitrate and urapidil, MAP was still low even 60 min after discontinuation of treatment. Urapidil caused marked increases in noradrenaline and adrenaline, which persisted even into the recovery phase. With regard to clinical management and sympatho-adrenergic responses, sodium nitroprusside is the most useful of these compounds for the reduction of hypotension. Having similar potency and active metabolites, glyceryl trinitrate has a longer duration of action.(ABSTRACT TRUNCATED AT 250 WORDS)