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Anesthesiology Nov 1993Propofol has been used for the maintenance of anesthesia. The effects of propofol infusion on splanchnic hemodynamics and liver oxygen consumption, however, have not...
BACKGROUND
Propofol has been used for the maintenance of anesthesia. The effects of propofol infusion on splanchnic hemodynamics and liver oxygen consumption, however, have not been reported. In the current investigation, the authors studied the effects of a continuous infusion of propofol on systemic and splanchnic hemodynamics using a new method to measure liver oxygen consumption in awake control and anesthetized rats.
METHODS
Cannulas were inserted into the left ventricle, femoral artery, portal vein, and hepatic vein during ether anesthesia, and the rats were allowed to awaken and recover for 3-4 h before study. Animals were infused for 30 min with either saline (controls) or propofol at a rate of 300, 600, 900, or 1,200 micrograms.kg-1 x min-1. Cardiac output and organ blood flows were measured using radiolabelled microspheres, and blood samples from the femoral artery, portal vein, and hepatic vein were used to determine liver oxygen consumption.
RESULTS
Mean arterial pressure decreased in a dose-dependent manner with a 25% reduction at the highest infusion rate. Systemic vascular resistance similarly decreased, whereas cardiac output remained unchanged at all the infusion rates. Hepatic arterial blood flow increased in a dose-dependent fashion over the dose range studied, to a maximum increase of 120%. Portal tributary blood flow increased by 30% at the highest infusion rate. Total liver blood flow increased in a dose-dependent manner to a maximum of 38%. Total oxygen delivery to the liver by the hepatic artery and portal vein increased in a dose-dependent fashion. Liver oxygen consumption increased in a dose-dependent fashion to a maximum increase of 51% at an infusion rate of 1,200 micrograms.kg-1 x min-1. The percent of oxygen extracted by the liver was not altered by propofol infusion, and hepatic venous oxygen saturation did not decrease at any dose studied. Coronary and renal blood flows were not altered. Arterial PaCO2, increased from 31 +/- 2 mmHg in awake control rats to 41 +/- 2 mmHg in spontaneously breathing rats infused with 1,200 micrograms.kg-1 x min-1 propofol.
CONCLUSIONS
The maintenance of anesthesia using an infusion of propofol resulted in an increase in liver oxygen consumption that was fully compensated for by an increase in oxygen delivery to the liver. Splanchnic hemodynamics and liver oxygenation are not adversely affected during maintenance of anesthesia with propofol in the normal rat.
Topics: Animals; Dose-Response Relationship, Drug; Hemodynamics; Infusions, Intravenous; Liver; Male; Oxygen Consumption; Propofol; Rats; Rats, Sprague-Dawley; Splanchnic Circulation
PubMed: 8238982
DOI: 10.1097/00000542-199311000-00024 -
British Journal of Anaesthesia Oct 2010
Topics: Anesthesia, General; Animals; Epinephrine; Gastrointestinal Tract; Humans; Microcirculation; Norepinephrine; Oxygen Consumption; Vasoconstrictor Agents
PubMed: 20837720
DOI: 10.1093/bja/aeq236 -
Anaesthesia Mar 2017
Topics: Oxygen; Oxygen Consumption
PubMed: 28176314
DOI: 10.1111/anae.13819 -
International Journal of Sports... Jul 2022To investigate the validity of a treadmill speed incline conversion chart using physiological and subjective measures.
PURPOSE
To investigate the validity of a treadmill speed incline conversion chart using physiological and subjective measures.
METHODS
Two groups of experienced runners (SLOW and FAST: divided based on their easy run pace) ran 6 speed incline combinations for 5 minutes each. Stages were equivalent according to the HillRunner.com chart, and stage order was randomized. Due to limitations of the chart, SLOW (n = 11) ran at inclines up to 4%, while FAST (n = 22) ran at inclines up 10%. Oxygen consumption (VO2), respiratory exchange ratio, heart rate, blood lactate, overall rating of perceived exertion (RPE), and leg RPE were measured for each stage. VO2 was compared against the VO2 predicted by the American College of Sports Medicine (ACSM) equation (ACSM VO2). Repeated-measures analysis of variance was used to detect differences between stages and inclines, and Hedges g was used as a measure of effect size.
RESULTS
Pooled results (0%-4%, N = 33) showed no incline effect on VO2, respiratory exchange ratio, heart rate, blood lactate, or RPE (P > .05; ηp2=.198), validating the chart at these inclines. At or above 6%, meaningful and significant increases occur in VO2 (g > 0.9, P < .05), with increases in heart rate, blood lactate, and leg RPE at higher inclines. ACSM VO2 underestimated oxygen consumption at all inclines up to 8% (P < .05) but not at 10% (45.9 [4.0] vs 46.7 [2.4] mL·kg-1·min-1; P = .186).
CONCLUSION
The HillRunner.com chart is only valid at or below 4%. At higher inclines, supposedly equivalent stages result in increased exercise intensity. ACSM VO2 underestimates VO2 in trained runners at inclines up to 8%.
Topics: Exercise Test; Heart Rate; Humans; Lactates; Oxygen Consumption; Physical Exertion
PubMed: 35299154
DOI: 10.1123/ijspp.2021-0021 -
Annals of Transplantation 2002Ischaemia--reperfusion damage causes injury of all heart cells. Loss of endothelium function and biologically active substances secreted by it can be essential to...
BACKGROUND
Ischaemia--reperfusion damage causes injury of all heart cells. Loss of endothelium function and biologically active substances secreted by it can be essential to development of the damage. Ischaemia and reperfusion decreases the release of nitric oxide, which influences postischaemic coronary flow and return of ventricular function. Administration of L-arginine to cardioplegic and reperfusion solution can improve protection of heart and cause the return of left ventricular function after hypothermic ischaemia through preservation of endothelial cell functions and increase of release of nitric oxide.
OBJECTIVE
How addition of L-arginine to cardioplegic solution influences oxygen consumption by myocardium and its postischaemic haemodynamic function.
METHODS
The research was conducted on isolated heart model of 56 rats, divided into seven equal groups. The hearts were prepared with modified Neely method and were perfused with the use of apparatus in accordance with modified Langendorf method. The research was carried out in the following order: initial perfusion of the non-working and working heart, perfusion with cardioplegic solution, cold cardioplegic arrest and reperfusion of the non-working heart.
RESULTS
During initial perfusion, oxygen consumption was comparable in all groups. During cardioplegic perfusion, oxygen consumption was reduced in every group. At the time of reperfusion of non-working heart model, consumption of oxygen was increased. During reperfusion of the working heart, the lowest oxygen consumption was noted in group P, the highest in group DI. The decrease in cardiac output during postischaemic period was noted in control group and groups where L-arginine was added to reperfusion solution.
CONCLUSION
Addition of L-arginine to cardioplegic solution significantly decreases oxygen consumption by myocardium. L-arginine added to cardioplegic solution improves postischaemic haemodynamic function of heart.
Topics: Animals; Arginine; Cardioplegic Solutions; Heart; Hemodynamics; In Vitro Techniques; Ischemia; Models, Animal; Oxygen Consumption; Rats; Rats, Wistar; Reperfusion
PubMed: 12416469
DOI: No ID Found -
British Journal of Anaesthesia Sep 1987The effects of propranolol on whole body oxygen consumption and blood oxygen content were measured in the dog during extreme hypoxic conditions. At 9% inspired oxygen...
The effects of propranolol on whole body oxygen consumption and blood oxygen content were measured in the dog during extreme hypoxic conditions. At 9% inspired oxygen four of eight control animals died within 40 min. An identical second group was pretreated with propranolol and none died during the same hypoxic stress. Hypoxia decreased oxygen consumption in both groups, but the decrease was less in the propranolol-pretreated dogs. A second set of 16 dogs was ventilated with 10% oxygen and all animals survived. A similar, although less pronounced, effect on oxygen consumption was noted and propranolol once again lessened the hypoxia-induced decrease in oxygen consumption. With hypoxaemia, metabolic acidosis developed in all animals and the arterio-venous oxygen content difference decreased; however, propranolol lessened the acidosis and the decrease in arterio-venous oxygen content difference. We conclude that, during hypoxia, propranolol increases oxygen utilization by the tissues and this might account for better survival.
Topics: Animals; Dogs; Hemodynamics; Hypoxia; Oxygen; Oxygen Consumption; Propranolol
PubMed: 3663438
DOI: 10.1093/bja/59.9.1171 -
The Mount Sinai Journal of Medicine,... 2012Anemia is common in critically ill patients. Although the goal of transfusion of red blood cells is to increase oxygen-carrying capacity, there are contradictory results... (Review)
Review
Anemia is common in critically ill patients. Although the goal of transfusion of red blood cells is to increase oxygen-carrying capacity, there are contradictory results about whether red blood cell transfusion to treat moderate anemia (e.g., hemoglobin 7-10 g/dL) improves tissue oxygenation or changes outcomes. Whereas increasing levels of anemia eventually lead to a level of critical oxygen delivery, increased cardiac output and oxygen extraction are homeostatic mechanisms the body uses to prevent a state of dysoxia in the setting of diminished oxygen delivery due to anemia. In order for cardiac output to increase in the face of anemia, normovolemia must be maintained. Transfusion of red blood cells increases blood viscosity, which may actually decrease cardiac output (barring a state of hypovolemia prior to transfusion). Studies have generally shown that transfusion of red blood cells fails to increase oxygen uptake unless oxygen uptake/oxygen delivery dependency exists (e.g., severe anemia or strenuous exercise). Recently, near-infrared spectroscopy, which approximates the hemoglobin saturation of venous blood, has been used to investigate whether transfusion of red blood cells increases tissue oxygenation in regional tissue beds (e.g., brain, peripheral skeletal muscle). These studies have generally shown increases in near-infrared spectroscopy derived measurements of tissue oxygenation following transfusion. Studies evaluating the effect of transfusion on the microcirculation have shown that transfusion increases the functional capillary density. This article will review fundamental aspects of oxygen delivery and extraction, and the effects of red blood cell transfusion on tissue oxygenation as well as the microcirculation.
Topics: Anemia; Critical Illness; Erythrocyte Transfusion; Humans; Oxygen Consumption
PubMed: 22238040
DOI: 10.1002/msj.21284 -
Basic Research in Cardiology Jul 2009Nitric oxide (NO) has influence on various cellular functions. Little is known of the influence of NO on myocardial energetics. In the present study oxygen consumption...
Nitric oxide (NO) has influence on various cellular functions. Little is known of the influence of NO on myocardial energetics. In the present study oxygen consumption and mechanical parameters of isometrically contracting rabbit papillary muscles (1 Hz stimulation frequency) were investigated at varying interventions while maintaining physiological conditions (37 degrees C; 2.5 mM Ca(2+)) to study the effects of NO on energetics. The NO donor sodium nitroprusside (SNP) showed a negative inotropic effect. SNP decreased the maximal force in normal rabbit muscle strips by 30%, the force time integral (FTI) by 40% and the relaxation time by 20%. In addition the oxygen consumption decreased by 60%, a notably disproportional decrease compared to the mechanical parameters. Consequently, the economy as a ratio of FTI and oxygen consumption is significantly increased by SNP. In contrast the negative inotropic effect due to a reduction in extracellular Calcium (Ca(2+)) from 2.5 to 1.25 mM reduced FTI and oxygen consumption proportionally by 40% and did not change economy. The effect of NO on force and oxygen consumption could be reproduced by the application of the cyclic guanosine monophosphate (cGMP) analogue 8-bromo-cGMP. In summary, NO increased the economy of isometrically contracting papillary muscles. The improvement in contraction economy under NO seems to be mediated by cGMP as the secondary messenger and maybe due to alterations of the crossbridge cycle.
Topics: Animals; Cyclic GMP; Muscle Contraction; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Oxygen Consumption; Papillary Muscles; Rabbits
PubMed: 19190952
DOI: 10.1007/s00395-009-0777-9 -
PloS One 2014Despite its huge ecological importance, microbial oxygen respiration in pelagic waters is little studied, primarily due to methodological difficulties. Respiration...
Despite its huge ecological importance, microbial oxygen respiration in pelagic waters is little studied, primarily due to methodological difficulties. Respiration measurements are challenging because of the required high resolution of oxygen concentration measurements. Recent improvements in oxygen sensing techniques bear great potential to overcome these limitations. Here we compare 3 different methods to measure oxygen consumption rates at low oxygen concentrations, utilizing amperometric Clark type sensors (STOX), optical sensors (optodes), and mass spectrometry in combination with (18-18)O2 labeling. Oxygen concentrations and consumption rates agreed well between the different methods when applied in the same experimental setting. Oxygen consumption rates between 30 and 400 nmol L(-1) h(-1) were measured with high precision and relative standard errors of less than 3%. Rate detection limits in the range of 1 nmol L(-1) h(-1) were suitable for rate determinations in open ocean water and were lowest at the lowest applied O2 concentration.
Topics: Electrochemistry; Kinetics; Mass Spectrometry; Oceans and Seas; Oxygen Consumption; Oxygen Isotopes; Seawater
PubMed: 24586724
DOI: 10.1371/journal.pone.0089369 -
Concepts of Lactate Metabolic Clearance Rate and Lactate Clamp for Metabolic Inquiry: A Mini-Review.Nutrients Jul 2023Lactate is known to play a central role in the link between glycolytic and mitochondrial oxidative metabolism, as well as to serve as a primary gluconeogenic precursor.... (Review)
Review
Lactate is known to play a central role in the link between glycolytic and mitochondrial oxidative metabolism, as well as to serve as a primary gluconeogenic precursor. Blood lactate concentration is sensitive to the metabolic state of tissues and organs as lactate rates of appearance and disposal/disappearance in the circulation rise and fall in response to physical exercise and other metabolic disturbances. The highest lactate flux rates have been measured during moderate intensity exercise in endurance-trained individuals who exhibit muscular and metabolic adaptations lending to superior oxidative capacity. In contrast, a diminished ability to utilize lactate is associated with poor metabolic fitness. Given these widespread implications in exercise performance and health, we discuss the concept of lactate metabolic clearance rate, which increases at the onset of exercise and, unlike flux rates, reaches a peak just below the power output associated with the maximal lactate steady state. The metabolic clearance rate is determined by both disposal rate and blood concentration, two parameters that are mutually interdependent and thus difficult to parse during steady state exercise studies. We review the evolution of the in vivo lactate clamp methodology to control blood lactate concentration and discuss its application in the investigation of whole-body lactate disposal capacities. In conclusion, we assert that the lactate clamp is a useful research methodology for examining lactate flux, in particular the factors that drive metabolic clearance rate.
Topics: Humans; Lactic Acid; Oxygen Consumption; Metabolic Clearance Rate; Anaerobic Threshold; Exercise; Exercise Test; Physical Endurance
PubMed: 37513631
DOI: 10.3390/nu15143213