Human sympathetic and vagal baroreflex responses to sequential nitroprusside and phenylephrine

L. Rudas, Alexandra A. Crossman, Carlos A. Morillo, John R. Halliwill, Kari U O Tahvanainen, Tom A. Kuusela, Dwain L. Eckberg

Research output: Contribution to journalArticle

206 Citations (Scopus)

Abstract

We evaluated a method of baroreflex testing involving sequential intravenous bolus injections of nitroprusside followed by phenylephrine and phenylephrine followed by nitroprusside in 18 healthy men and women, and we drew inferences regarding human sympathetic and vagal baroreflex mechanisms. We recorded the electrocardiogram, photoplethysmographic finger arterial pressure, and peroneal nerve muscle sympathetic activity. We then contrasted least squares linear regression slopes derived from the depressor (nitroprusside) and pressor (phenylephrine) phases with 1) slopes derived from spontaneous fluctuations of systolic arterial pressures and R-R intervals, and 2) baroreflex gain derived from cross-spectral analyses of systolic pressures and R-R intervals. We calculated sympathetic baroreflex gain from integrated muscle sympathetic nerve activity and diastolic pressures. We found that vagal baroreflex slopes are less when arterial pressures are falling than when they are rising and that this hysteresis exists over pressure ranges both below and above baseline levels. Although pharmacological and spontaneous vagal baroreflex responses correlate closely, pharmacological baroreflex slopes tend to be lower than those derived from spontaneous fluctuations. Sympathetic baroreflex slopes are similar when arterial pressure is falling and rising; however, small pressure elevations above baseline silence sympathetic motoneurons. Vagal, but not sympathetic baroreflex gains vary inversely with subjects' ages and their baseline arterial pressures. There is no correlation between sympathetic and vagal baroreflex gains. We recommend repeated sequential nitroprusside followed by phenylephrine doses as a simple, efficient-means to provoke and characterize human vagal and sympathetic baroreflex responses.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume276
Issue number5 45-5
Publication statusPublished - May 1999

Fingerprint

Baroreflex
Nitroprusside
Phenylephrine
Arterial Pressure
Blood Pressure
Accidental Falls
Pharmacology
Pressure
Muscles
Peroneal Nerve
Motor Neurons
Least-Squares Analysis
Intravenous Injections
Fingers
Linear Models
Electrocardiography

Keywords

  • Aging
  • Baroreflex gain
  • Hysteresis
  • Muscle sympathetic nerve activity

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

Rudas, L., Crossman, A. A., Morillo, C. A., Halliwill, J. R., Tahvanainen, K. U. O., Kuusela, T. A., & Eckberg, D. L. (1999). Human sympathetic and vagal baroreflex responses to sequential nitroprusside and phenylephrine. American Journal of Physiology - Heart and Circulatory Physiology, 276(5 45-5).

Human sympathetic and vagal baroreflex responses to sequential nitroprusside and phenylephrine. / Rudas, L.; Crossman, Alexandra A.; Morillo, Carlos A.; Halliwill, John R.; Tahvanainen, Kari U O; Kuusela, Tom A.; Eckberg, Dwain L.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 276, No. 5 45-5, 05.1999.

Research output: Contribution to journalArticle

Rudas, L, Crossman, AA, Morillo, CA, Halliwill, JR, Tahvanainen, KUO, Kuusela, TA & Eckberg, DL 1999, 'Human sympathetic and vagal baroreflex responses to sequential nitroprusside and phenylephrine', American Journal of Physiology - Heart and Circulatory Physiology, vol. 276, no. 5 45-5.
Rudas, L. ; Crossman, Alexandra A. ; Morillo, Carlos A. ; Halliwill, John R. ; Tahvanainen, Kari U O ; Kuusela, Tom A. ; Eckberg, Dwain L. / Human sympathetic and vagal baroreflex responses to sequential nitroprusside and phenylephrine. In: American Journal of Physiology - Heart and Circulatory Physiology. 1999 ; Vol. 276, No. 5 45-5.
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