BLOOD-PRESSURE, PLASMA-CATECHOLAMINE AND RENIN RESPONSES TO CAFFEINE IN ELDERLY HYPERTENSIVES

In young hypertensive patients, after a short period of abstention, ca ffeine ingestion has a significant pressor effect, although the acute cardiovascular responses have not been reported in elderly hypertensiv es. This study assessed the acute changes in BP, pulse rate, plasma re nin activity (PRA) and arterialised plasma catecholamines after 250 mg of caffeine and matching placebo following 12 and 48 hours of caffein e abstention. After 48 hours caffeine abstention supine SBP was higher over the 120 minute study period following acute caffeine loading tha n following placebo (10 mmHg; 95% Cl 3-17 mmHg, P = 0.016) although th e overall post-caffeine rise from baseline values was small (2 mmHg; - 3 to 8 mmHg, P = 0.30). Similar differences were seen for supine DBP a nd standing SBP and DBP although pulse rate was unchanged throughout. After 12 hours abstention no acute pressor effect of caffeine was seen , in fact SBP fell over the study period (-5 mmHg; -10 to 0 mmHg, P = 0.05), and there was no difference between the caffeine and placebo ph ases. No change in plasma catecholamines or PRA values was found durin g any of the phases. These results suggest that in elderly hypertensiv es the pressor effect of caffeine (the equivalent of two to three cups of coffee) is small even after prolonged abstention. After the shorte r abstention period, of the duration likely to be seen in clinical pra ctice, no pressor response to caffeine was demonstrated. It is unlikel y that acute caffeine ingestion has a significant effect on clinic BP measurements in elderly hypertensives who are regular caffeine consume rs.