The effects of beta1-adrenergic blockade on cardiovascular oxygen flow in normoxic and hypoxic humans at exercise. 2005

Guido Ferretti, and Marc J Licker, and Sara Anchisi, and Christian Moia, and Davide Susta, and Denis R Morel
Département de Physiologie, Centre Médical Universitaire, Geneva, Switzerland. guido.ferretti@medecine.unige.ch

At exercise steady state, the lower the arterial oxygen saturation (SaO(2)), the lower the O(2) return (QvO(2)). A linear relationship between these variables was demonstrated. Our conjecture is that this relationship describes a condition of predominant sympathetic activation, from which it is hypothesized that selective beta1-adrenergic blockade (BB) would reduce O(2) delivery (QaO(2)) and QvO(2). To test this hypothesis, we studied the effects of BB on QaO(2) and QvO(2) in exercising humans in normoxia and hypoxia. O(2) consumption VO(2), cardiac output Q, CO(2) rebreathing), heart rate, SaO(2) and haemoglobin concentration were measured on six subjects (age 25.5 +/- 2.4 years, mass 78.1 +/- 9.0 kg) in normoxia and hypoxia (inspired O(2) fraction of 0.11) at rest and steady-state exercises of 50, 100, and 150 W without (C) and with BB with metoprolol. Arterial O(2) concentration (CaO(2)), QaO(2) and QvO(2) were then computed. Heart rate, higher in hypoxia than in normoxia, decreased with BB. At each VO(2), Q was higher in hypoxia than in normoxia. With BB, it decreased during intense exercise in normoxia, at rest, and during light exercise in hypoxia. SaO(2) and CaO(2) were unaffected by BB. The QaO(2) changes under BB were parallel to those in Q.QvO(2) was unaffected by exercise in normoxia. In hypoxia the slope of the relationship between QaO(2) and VO(2) was lower than 1, indicating a reduction of QvO(2) with increasing workload. QvO(2) was a linear function of SaO(2) both in C and in BB. The line for BB was flatter than and below that for C. The resting QvO(2) in normoxia, lower than the corresponding exercise values, lied on the BB line. These results agree with the tested hypothesis. The two observed relationships between QvO(2) and SaO(2) apply to conditions of predominant sympathetic or vagal activation, respectively. Moving from one line to the other implies resetting of the cardiovascular regulation.

UI MeSH Term Description Entries
D008790 Metoprolol A selective adrenergic beta-1 blocking agent that is commonly used to treat ANGINA PECTORIS; HYPERTENSION; and CARDIAC ARRHYTHMIAS. Beloc-Duriles,Betaloc,Betaloc-Astra,Betalok,CGP-2175,H 93-26,Lopressor,Metoprolol CR-XL,Metoprolol Succinate,Metoprolol Tartrate,Seloken,Spesicor,Spesikor,Toprol,Toprol-XL,Beloc Duriles,Betaloc Astra,CGP 2175,CGP2175,H 93 26,H 9326,Metoprolol CR XL,Toprol XL
D010101 Oxygen Consumption The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346) Consumption, Oxygen,Consumptions, Oxygen,Oxygen Consumptions
D001785 Blood Gas Monitoring, Transcutaneous The noninvasive measurement or determination of the partial pressure (tension) of oxygen and/or carbon dioxide locally in the capillaries of a tissue by the application to the skin of a special set of electrodes. These electrodes contain photoelectric sensors capable of picking up the specific wavelengths of radiation emitted by oxygenated versus reduced hemoglobin. Carbon Dioxide Partial Pressure Determination, Transcutaneous,Cutaneous Oximetry,Oximetry, Transcutaneous,Oxygen Partial Pressure Determination, Transcutaneous,Transcutaneous Blood Gas Monitoring,Transcutaneous Capnometry,Transcutaneous Oximetry,PtcO2,TcPCO2,Capnometries, Transcutaneous,Capnometry, Transcutaneous,Cutaneous Oximetries,Oximetries, Cutaneous,Oximetries, Transcutaneous,Oximetry, Cutaneous,Transcutaneous Capnometries,Transcutaneous Oximetries
D002302 Cardiac Output The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat). Cardiac Outputs,Output, Cardiac,Outputs, Cardiac
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000319 Adrenergic beta-Antagonists Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety. Adrenergic beta-Antagonist,Adrenergic beta-Receptor Blockader,Adrenergic beta-Receptor Blockaders,beta-Adrenergic Antagonist,beta-Adrenergic Blocker,beta-Adrenergic Blocking Agent,beta-Adrenergic Blocking Agents,beta-Adrenergic Receptor Blockader,beta-Adrenergic Receptor Blockaders,beta-Adrenoceptor Antagonist,beta-Blockers, Adrenergic,beta-Adrenergic Antagonists,beta-Adrenergic Blockers,beta-Adrenoceptor Antagonists,Adrenergic beta Antagonist,Adrenergic beta Antagonists,Adrenergic beta Receptor Blockader,Adrenergic beta Receptor Blockaders,Adrenergic beta-Blockers,Agent, beta-Adrenergic Blocking,Agents, beta-Adrenergic Blocking,Antagonist, beta-Adrenergic,Antagonist, beta-Adrenoceptor,Antagonists, beta-Adrenergic,Antagonists, beta-Adrenoceptor,Blockader, Adrenergic beta-Receptor,Blockader, beta-Adrenergic Receptor,Blockaders, Adrenergic beta-Receptor,Blockaders, beta-Adrenergic Receptor,Blocker, beta-Adrenergic,Blockers, beta-Adrenergic,Blocking Agent, beta-Adrenergic,Blocking Agents, beta-Adrenergic,Receptor Blockader, beta-Adrenergic,Receptor Blockaders, beta-Adrenergic,beta Adrenergic Antagonist,beta Adrenergic Antagonists,beta Adrenergic Blocker,beta Adrenergic Blockers,beta Adrenergic Blocking Agent,beta Adrenergic Blocking Agents,beta Adrenergic Receptor Blockader,beta Adrenergic Receptor Blockaders,beta Adrenoceptor Antagonist,beta Adrenoceptor Antagonists,beta Blockers, Adrenergic,beta-Antagonist, Adrenergic,beta-Antagonists, Adrenergic,beta-Receptor Blockader, Adrenergic,beta-Receptor Blockaders, Adrenergic
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D000860 Hypoxia Sub-optimal OXYGEN levels in the ambient air of living organisms. Anoxia,Oxygen Deficiency,Anoxemia,Deficiency, Oxygen,Hypoxemia,Deficiencies, Oxygen,Oxygen Deficiencies
D013564 Sympathetic Nervous System The thoracolumbar division of the autonomic nervous system. Sympathetic preganglionic fibers originate in neurons of the intermediolateral column of the spinal cord and project to the paravertebral and prevertebral ganglia, which in turn project to target organs. The sympathetic nervous system mediates the body's response to stressful situations, i.e., the fight or flight reactions. It often acts reciprocally to the parasympathetic system. Nervous System, Sympathetic,Nervous Systems, Sympathetic,Sympathetic Nervous Systems,System, Sympathetic Nervous,Systems, Sympathetic Nervous
D015444 Exercise Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure. Aerobic Exercise,Exercise, Aerobic,Exercise, Isometric,Exercise, Physical,Isometric Exercise,Physical Activity,Acute Exercise,Exercise Training,Activities, Physical,Activity, Physical,Acute Exercises,Aerobic Exercises,Exercise Trainings,Exercise, Acute,Exercises,Exercises, Acute,Exercises, Aerobic,Exercises, Isometric,Exercises, Physical,Isometric Exercises,Physical Activities,Physical Exercise,Physical Exercises,Training, Exercise,Trainings, Exercise

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