TY - JOUR
T1 - Phenylephrine-induced elevations in arterial blood pressure are attenuated in heat-stressed humans
AU - Cui, Jian
AU - Wilson, Thad E.
AU - Crandall, Craig G.
PY - 2002/11/1
Y1 - 2002/11/1
N2 - To test the hypothesis that phenylephrine-induced elevations in blood pressure are attenuated in heat-stressed humans, blood pressure was elevated via steady-state infusion of three doses of phenylephrine HCl in 10 healthy subjects in both normothermic and heat stress conditions. Whole body heating significantly increased sublingual temperature by ∼0.5°C, muscle sympathetic nerve activity (MSNA), heart rate, and cardiac output and decreased total peripheral vascular resistance (TPR; all P < 0.005) but did not change mean arterial blood pressure (MAP; P > 0.05). At the highest dose of phenylephrine, the increase in MAP and TPR from predrug baselines was significantly attenuated during the heat stress [AMAP 8.4 ± 1.2 mmHg; ATPR 0.96 ± 0.85 peripheral resistance units (PRU)] compared with normothermia (ΔMAP 15.4 ± 1.4 mmHg, ΔTPR 7.13 ± 1.18 PRU; all P< 0.001). The sensitivity of baroreflex control of MSNA and heart rate, expressed as the slope of the relationship between MSNA and diastolic blood pressure, as well as the slope of the relationship between heart rate and systolic blood pressure, respectively, was similar between thermal conditions (each P > 0.05). These data suggest that phenylephrine-induced elevations in MAP are attenuated in heat-stressed humans without affecting baroreflex control of MSNA or heart rate.
AB - To test the hypothesis that phenylephrine-induced elevations in blood pressure are attenuated in heat-stressed humans, blood pressure was elevated via steady-state infusion of three doses of phenylephrine HCl in 10 healthy subjects in both normothermic and heat stress conditions. Whole body heating significantly increased sublingual temperature by ∼0.5°C, muscle sympathetic nerve activity (MSNA), heart rate, and cardiac output and decreased total peripheral vascular resistance (TPR; all P < 0.005) but did not change mean arterial blood pressure (MAP; P > 0.05). At the highest dose of phenylephrine, the increase in MAP and TPR from predrug baselines was significantly attenuated during the heat stress [AMAP 8.4 ± 1.2 mmHg; ATPR 0.96 ± 0.85 peripheral resistance units (PRU)] compared with normothermia (ΔMAP 15.4 ± 1.4 mmHg, ΔTPR 7.13 ± 1.18 PRU; all P< 0.001). The sensitivity of baroreflex control of MSNA and heart rate, expressed as the slope of the relationship between MSNA and diastolic blood pressure, as well as the slope of the relationship between heart rate and systolic blood pressure, respectively, was similar between thermal conditions (each P > 0.05). These data suggest that phenylephrine-induced elevations in MAP are attenuated in heat-stressed humans without affecting baroreflex control of MSNA or heart rate.
UR - http://www.scopus.com/inward/record.url?scp=0036838480&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036838480&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.00195.2002
DO - 10.1152/ajpregu.00195.2002
M3 - Article
C2 - 12376416
AN - SCOPUS:0036838480
SN - 0363-6119
VL - 283
SP - R1221-R1226
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 5 52-5
ER -