A comparison of the cardiovascular and metabolic effects of incremental versus continuous dose adrenaline infusions in men and women

Abstract

The present study was designed to investigate the influence of pattern of infusion and of gender on the metabolic and haemodynamic responses to infused adrenaline. Fourteen normal weight, healthy subjects (six male) were studied on two occasions. On one visit adrenaline was infused in stepwise increments for 20 min each at 10, 25 and 50 ng/kg/min, whilst on the other visit it was infused continuously at 50 ng/kg/min for 40 min. Before and during the infusions metabolic rate (MR) and respiratory exchange ratio (RER) were calculated using indirect calorimetry, and blood glucose, plasma metabolites, heart rate, blood pressure and forearm blood flow were measured. In men the rise in MR was 4.05 J/kg/min greater in response to the 50 ng/kg/min infusion when it was part of the incremental protocol compared with the continuous protocol (P = 0.05), whilst in women this difference was only 0.29 J/kg/min (P = 0.89). For both sexes forearm flow rose by 2.5 ml/100 ml/min more during the incremental infusion (P = 0.01) and diastolic blood pressure fell by 4.5 mmHg more (P = 0.04) compared to the continuous infusion. Blood pressure responses to adrenaline were more marked in men than in women during both protocols. The changes in glucose, lactate, NEFA and beta-hydroxybutyrate were similar in both sexes. We conclude that incremental dose infusions may cause potentiation of some responses and that gender differences in response occur. Allowance should therefore be made for these factors in future studies.