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Siebenmann C, Rasmussen P, Sørensen H, Bonne TC, Zaar M, Aachmann-Andersen NJ, Nordsborg NB, Secher NH, Lundby C. Hypoxia increases exercise heart rate despite combined inhibition of β-adrenergic and muscarinic receptors. Am J Physiol Heart Circ Physiol 2015; 308:H1540-6. [DOI: 10.1152/ajpheart.00861.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/15/2015] [Indexed: 11/22/2022]
Abstract
Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of β-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions ( P < 0.001) but was always higher at a given workload in hypoxia than normoxia ( P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 ± 13.8 beats/min during Cont and similar (17.2 ± 7.7 beats/min, P = 0.95) during Prop but smaller ( P < 0.001) during Glyc and Prop + Glyc (9.8 ± 9.6 and 8.1 ± 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia ( P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 ± 1.9, 1.7 ± 1.8, and 2.3 ± 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 ± 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than β-adrenergic transmission. A potential candidate is α-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined β-adrenergic and muscarinic receptor inhibition.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - P. Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - H. Sørensen
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - T. C. Bonne
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - M. Zaar
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - N. B. Nordsborg
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - N. H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
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Siebenmann C, Rasmussen P, Sørensen H, Zaar M, Hvidtfeldt M, Pichon A, Secher NH, Lundby C. Cardiac output during exercise: A comparison of four methods. Scand J Med Sci Sports 2014; 25:e20-7. [DOI: 10.1111/sms.12201] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2014] [Indexed: 12/21/2022]
Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - P. Rasmussen
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - H. Sørensen
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Zaar
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Hvidtfeldt
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - A. Pichon
- Laboratoire Réponses Cellulaires et Fonctionnelles à l'Hypoxie; Université Paris 13; Bobigny France
| | - N. H. Secher
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - C. Lundby
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
- Food & Nutrition & Sport Science; Gothenburg University; Gothenburg Sweden
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Zaar M, Secher NH, Johansson PI, Vainer B, Ezban M, Agersø H, Madsen PL, Lomholt N, Hermit MB, Lauritzen B. Effects of a recombinant FVIIa analogue, NN1731, on blood loss and survival after liver trauma in the pig. Br J Anaesth 2009; 103:840-7. [PMID: 19808774 DOI: 10.1093/bja/aep274] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND We considered whether haemorrhage after a liver trauma would be reduced by early administration of a pro-haemostatic agent and evaluated the effect of i.v. vs i.m. administration of the coagulation factor VIIa analogue NN1731 on haemorrhage after a liver trauma in the pig. METHODS The pharmacokinetics of i.v. and i.m. NN1731 was evaluated in eight minipigs, and the effects of dose and administration route of NN1731 (i.v. 180 microg kg(-1), n=6; i.m. 540 microg kg(-1), n=4, or 2000 microg kg(-1), n=6) vs vehicle (n=16) were studied on a liver laceration injury in pigs. To simulate a pre-hospital setting, the administration of NN1731 was delayed by 1 min for i.m. administration and 7 min for i.v. administration, at which time fluid resuscitation also began. RESULTS In the minipigs, NN1731 exposure was similar after i.v. 180 microg kg(-1) and i.m. 540 microg kg(-1), with a bioavailability of approximately 35%. The injury and blood loss at 7 min was comparable between the four groups of pigs; however, after 60 min, the blood loss was lower in the i.v. treated animals: 1.3 (0.3) (i.v.) vs 2.2 (0.8) litres (i.m.(540), i.m.(2000), and vehicle) (P<0.001). Also, the survival time was increased: 117 (14) (i.v.) vs 84 (28) min (i.m.(540), i.m.(2000), and vehicle) (P<0.001). CONCLUSIONS After a liver trauma in the pig, i.v. administration of NN1731 reduced the bleeding and increased the survival time. In contrast, i.m. administration had no effect, presumably because reduced muscle perfusion during haemorrhage reduced the uptake of NN1731.
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Affiliation(s)
- M Zaar
- Department of Anaesthesia, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Denmark.
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Zaar M, Johansson PI, Nielsen LB, Crandall CG, Shibasaki M, Hilsted L, Secher NH. Early activation of the coagulation system during lower body negative pressure. Clin Physiol Funct Imaging 2009; 29:427-30. [PMID: 19656165 DOI: 10.1111/j.1475-097x.2009.00890.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We considered that a moderate reduction of the central blood volume (CBV) may activate the coagulation system. Lower body negative pressure (LBNP) is a non-invasive means of reducing CBV and, thereby, simulates haemorrhage. We tested the hypothesis that coagulation markers would increase following moderate hypovolemia by exposing 10 healthy male volunteers to 10 min of 30 mmHg LBNP. Thoracic electrical impedance increased during LBNP (by 2.6 +/- 0.7 Omega, mean +/- SD; P < 0.001), signifying a reduced CBV. Heart rate was unchanged during LBNP, while mean arterial pressure decreased (84 +/- 5 to 80 +/- 6 mmHg; P < 0.001) along with stroke volume (114 +/- 22 to 96 +/- 19 ml min(-1); P < 0.001) and cardiac output (6.4 +/- 2.0 to 5.5 +/- 1.7 l min(-1); P < 0.01). Plasma thrombin-antithrombin III complexes increased (TAT, 5 +/- 6 to 19 +/- 20 microg l(-1); P < 0.05), indicating that LBNP activated the thrombin generating part of the coagulation system, while plasma D-dimer was unchanged, signifying that the increased thrombin generation did not cause further intravascular clot formation. The plasma pancreatic polypeptide level decreased (13 +/- 11 to 6 +/- 8 pmol l(-1); P < 0.05), reflecting reduced vagal activity. In conclusion, thrombin generation was activated by a modest decrease in CBV by LBNP in healthy humans independent of the vagal activity.
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Affiliation(s)
- M Zaar
- Department of Anesthesia, Rigshospitalet, University of Copenhagen, Denmark.
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Zaar M, Lauritzen B, Secher N, Krantz T, Nielsen H, Madsen P, Johansson P. Initial administration of hydroxyethyl starch vs lactated Ringer after liver trauma in the pig. Br J Anaesth 2009; 102:221-6. [DOI: 10.1093/bja/aen350] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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