Hypotension during endotoxemia in aged humans K. S. Krabbe*, H. Bruunsgaard*, J. Qvist*, C. M. Hansen*, K. Mùller*, L. Fonsmark*, P. L. Madsen*, G. Kronborg*, U. Frandsen , H. é. Andersenà, P. Skinhùj* and B. K. Pedersen* *The Department of Infectious Medicine M7721, Rigshospitalet,  Institute of Exercise and Sport Sciences, August Krogh Instituttet, àThe Department of Cardiac Catheterization, Laboratory B2014, Rigshospitalet, University of Copenhagen, Denmark Summary Background and objective The aim of this study was to determine possible age-associated differences in human blood pressure regulation during an immu- nological challenge in healthy subjects. Methods Eight healthy young volunteers (median age 24 yr) and nine healthy elderly volunteers (median age 66 yr) received an intravenous bolus injection of Eschericia coli endotoxin (2 ng kg ±1 ). Blood pressure, heart rate and core temperature were monitored during the ®rst 7 h. Plasma catecholamine concentrations were measured at hourly intervals. Results The elderly showed a signi®cantly more pronounced decrease in mean arterial pressure 4±7 h after endotoxin administration compared with the young controls (ANOVA; age ´ time; P < 0.0005). This mainly re¯ected a decrease in the systolic blood pressure in the elderly. The heart rate of both groups increased without difference between groups. Increased plasma epinephrine concentrations were found 2±3 h after endotoxin administration in both groups. Five hours after the endotoxin challenge, the epinephrine concentration had returned to control values in the elderly group only, in spite of decreased blood pressure. Conclusion In conclusion, healthy elderly subjects fail to maintain a constant mean arterial pressure in response to the immunological challenge of endo- toxemia. Keywords: HAEMODYMAMICS, blood pressure; physio- logical processes, ageing; CATECHOLAMINES, epineph- rine; VASODILATOR AGENTS, nitric oxide. Introduction Hypotension in¯uences the outcome in septic patients [1]. Also, great age has been shown to be a risk factor in bacteremia and sepsis [2±4]. Recently, we demonstrated that there is a prolonged fever and proin¯ammatory response in aged vs. young individ- uals following endotoxin administration [5]. Several studies have described the response in blood pres- sure in young humans following endotoxin adminis- tration including a signi®cant decrease in mean arterial pressure (MAP) and in systemic vascular resistance [6]. To our knowledge, no study has previously presented data on the vascular response in elderly individuals. To determine possible age-associated differences in blood pressure control in healthy humans during an immunological challenge, we applied a human endotoxemia model to a group of young and a group of elderly human beings. Methods Eight healthy young volunteers, of whom ®ve were male, median age 24 yr (range 20±27 yr), and nine healthy elderly volunteers, of whom seven were male, median age 66 yr (range 61±69 yr), were included. All subjects had a negative medical history and a normal physical examination including elec- trocardiography; the elderly also underwent an exer- cise electrocardiogram, which in all cases was found to be normal. A normal exercise electrocardiogram gives an estimated risk of coronary artery disease of maximally 3% [7]. The regional scienti®c ethical committee approved the study, and written informed Accepted January 2001 Correspondence: Dr Bente Klarlund Pedersen, Department of Infectious Medicine M7641, Rigshospitalet, Blegdamsvej 9, 2200 Copenhagen N, Denmark (e-mail: bkp@rh.dk). European Journal of Anaesthesiology 2001, 18, 572±575 572 Ó 2001 European Academy of Anaesthesiology