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Tune JD, Goodwill AG, Kiel AM, Baker HE, Bender SB, Merkus D, Duncker DJ. Disentangling the Gordian knot of local metabolic control of coronary blood flow. Am J Physiol Heart Circ Physiol 2019; 318:H11-H24. [PMID: 31702972 DOI: 10.1152/ajpheart.00325.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recognition that coronary blood flow is tightly coupled with myocardial metabolism has been appreciated for well over half a century. However, exactly how coronary microvascular resistance is tightly coupled with myocardial oxygen consumption (MV̇o2) remains one of the most highly contested mysteries of the coronary circulation to this day. Understanding the mechanisms responsible for local metabolic control of coronary blood flow has been confounded by continued debate regarding both anticipated experimental outcomes and data interpretation. For a number of years, coronary venous Po2 has been generally accepted as a measure of myocardial tissue oxygenation and thus the classically proposed error signal for the generation of vasodilator metabolites in the heart. However, interpretation of changes in coronary venous Po2 relative to MV̇o2 are quite nuanced, inherently circular in nature, and subject to confounding influences that remain largely unaccounted for. The purpose of this review is to highlight difficulties in interpreting the complex interrelationship between key coronary outcome variables and the arguments that emerge from prior studies performed during exercise, hemodilution, hypoxemia, and alterations in perfusion pressure. Furthermore, potential paths forward are proposed to help to facilitate further dialogue and study to ultimately unravel what has become the Gordian knot of the coronary circulation.
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Affiliation(s)
- Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Adam G Goodwill
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Alexander M Kiel
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
| | - Hana E Baker
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Shawn B Bender
- Biomedical Sciences, University of Missouri, Columbia, Missouri.,Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Daphne Merkus
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School Erasmus University Rotterdam, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Walter-Brendel Center of Experimental Medicine, University Hospital, Ludwig Maximilian University Munich, Munich, Germany.,German Centre for Cardiovascular Research, Partner Site Munich, Munich Heart Alliance, Munich, Germany
| | - Dirk J Duncker
- Division of Experimental Cardiology, Department of Cardiology, Thoraxcenter, Cardiovascular Research School Erasmus University Rotterdam, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Kiel AM, Goodwill AG, Noblet JN, Barnard AL, Sassoon DJ, Tune JD. Regulation of myocardial oxygen delivery in response to graded reductions in hematocrit: role of K + channels. Basic Res Cardiol 2017; 112:65. [PMID: 28965130 DOI: 10.1007/s00395-017-0654-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 09/25/2017] [Indexed: 01/10/2023]
Abstract
This study was designed to identify mechanisms responsible for coronary vasodilation in response to progressive decreases in hematocrit. Isovolemic hemodilution was produced in open-chest, anesthetized swine via concurrent removal of 500 ml of arterial blood and the addition of 500 ml of 37 °C saline or synthetic plasma expander (Hespan, 6% hetastarch in 0.9% sodium chloride). Progressive hemodilution with Hespan resulted in an increase in coronary flow from 0.39 ± 0.05 to 1.63 ± 0.16 ml/min/g (P < 0.001) as hematocrit was reduced from 32 ± 1 to 10 ± 1% (P < 0.001). Overall, coronary flow corresponded with the level of myocardial oxygen consumption, was dependent on arterial pressures ≥ ~ 60 mmHg, and occurred with little/no change in coronary venous PO2. Anemic coronary vasodilation was unaffected by the inhibition of nitric oxide synthase (L-NAME: 25 mg/kg iv; P = 0.92) or voltage-dependent K+ (K V) channels (4-aminopyridine: 0.3 mg/kg iv; P = 0.52). However, administration of the K ATP channel antagonist (glibenclamide: 3.6 mg/kg iv) resulted in an ~ 40% decrease in coronary blood flow (P < 0.001) as hematocrit was reduced to ~ 10%. These reductions in coronary blood flow corresponded with significant reductions in myocardial oxygen delivery at baseline and throughout isovolemic anemia (P < 0.001). These data indicate that vasodilator factors produced in response to isovolemic hemodilution converge on vascular smooth muscle glibenclamide-sensitive (K ATP) channels to maintain myocardial oxygen delivery and that this response is not dependent on endothelial-derived nitric oxide production or pathways that mediate dilation via K V channels.
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Affiliation(s)
- Alexander M Kiel
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA.,Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Adam G Goodwill
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Jillian N Noblet
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - April L Barnard
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Daniel J Sassoon
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Johnathan D Tune
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA.
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Crystal GJ. Regional tolerance to acute normovolemic hemodilution: evidence that the kidney may be at greatest risk. J Cardiothorac Vasc Anesth 2014; 29:320-7. [PMID: 25440629 DOI: 10.1053/j.jvca.2014.06.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To evaluate the regional tolerance to acute normovolemic hemodilution (ANH). DESIGN Prospective animal study. SETTING University research laboratory. PARTICIPANTS Nine anesthetized (isoflurane) dogs. INTERVENTIONS Hematocrit reduced in 10% decrements using dextran-for-blood exchange until cardiac insufficiency observed. MEASUREMENTS AND MAIN RESULTS Cardiac index (CI) was measured using thermodilution and regional blood flow (RBF) in myocardium, brain, spinal cord, kidney, liver, duodenum, pancreas, spleen, skeletal muscle, and skin with radioactive microspheres. Oxygen delivery (DO2) was calculated from the product of respective blood flow and arterial oxygen content. Systemic oxygen extraction (EO2) and oxygen consumption (VO2) were calculated. Increases in CI during ANH were inadequate to prevent decreases in systemic DO2; however, an increased systemic EO2 maintained VO2 during graded ANH to hematocrit<10%. In the myocardium, brain, and spinal cord, increases in RBF were sufficient to maintain DO2 across the entire range of hematocrits, but this was not the case in the other organs studied. Of note, renal DO2 first decreased at a hematocrit of 30% and was only 25% of baseline at a hematocrit of 10%. CONCLUSIONS During graded ANH, increases in RBF were sufficient to maintain DO2 in only the heart, brain, and spinal cord. The especially marked decrease in DO2 in the kidney, combined with previous physiologic studies demonstrating its inability to augment EO2, suggest that this organ may be the most at risk of hypoxic damage during ANH.
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Affiliation(s)
- George J Crystal
- Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL; Departments of Anesthesiology and of Physiology and Biophysics, University of Illinois College of Medicine, Chicago, IL.
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Hare GMT, Hu T, Mazer CD, Beattie WS. In Response. Anesth Analg 2013; 117:532-3. [DOI: 10.1213/ane.0b013e318296922b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Crystal GJ, Salem MR. The Role of the β-Adrenergic Receptors in Cerebral Vasodilation During Hemodilution. Anesth Analg 2013; 117:531-2. [DOI: 10.1213/ane.0b013e3182969207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Nozaki J, Kitahata H, Tanaka K, Kawahito S, Oshita S. The effects of acute normovolemic hemodilution on left ventricular systolic and diastolic function in the absence or presence of beta-adrenergic blockade in dogs. Anesth Analg 2002; 94:1120-6, table of contents. [PMID: 11973172 DOI: 10.1097/00000539-200205000-00011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED Acute normovolemic hemodilution (ANH) increases cardiac output because of a reduction in blood viscosity and enhancement of left ventricular (LV) contractility. The status of LV function, especially LV diastolic function during ANH, remains controversial. We therefore examined LV systolic and diastolic function during ANH. Sixteen dogs were anesthetized with isoflurane in the absence (Group 1) and presence (Group 2) of beta-adrenergic blockade (propranolol 1 mg/kg). LV contractility was quantified by the slope (M(w)) of the stroke work and end-diastolic volume relation. Diastolic function was evaluated with the time constant of LV relaxation (T), chamber stiffness constant (K(c)), peak LV diastolic filling rate during early filling (peak E) and atrial contraction (peak A), and ratio of peak E to peak A (E/A). Normovolemic exchange of blood (50 mL/kg) for 6% hydroxyethyl starch (ANH50) significantly increased M(w) in Group 1 but not in Group 2. In both groups, ANH50 significantly decreased T. ANH50 significantly increased peak E in both groups and peak A in Group 1, and it did not change the E/A ratio or K(c) in either group. ANH causes positive inotropic effects and enhances diastolic function without beta-blockade. Even after beta-adrenergic blockade, ANH improves diastolic function through the reduction of LV ejection impedance. IMPLICATIONS Acute normovolemic hemodilution enhances LV (left ventricular) diastolic function by alterations in the LV loading condition produced by hemodilution, which mainly contributes to a compensatory increase in cardiac output.
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Affiliation(s)
- Junpei Nozaki
- Department of Anesthesiology, Tokushima University School of Medicine, Tokushima, Japan.
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Habler O, Kleen M, Hutter J, Podtschaske A, Tiede M, Kemming G, Welte M, Corso C, Batra S, Keipert P, Faithfull S, Messmer K. IV perflubron emulsion versus autologous transfusion in severe normovolemic anemia: effects on left ventricular perfusion and function. RESEARCH IN EXPERIMENTAL MEDICINE. ZEITSCHRIFT FUR DIE GESAMTE EXPERIMENTELLE MEDIZIN EINSCHLIESSLICH EXPERIMENTELLER CHIRURGIE 1998; 197:301-18. [PMID: 9638793 DOI: 10.1007/s004330050079] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Intact cardiac compensatory mechanisms are necessary to maintain adequate tissue oxygenation during acute normovolemic hemodilution (ANH). Left ventricular (LV) perfusion, oxygenation and function were analyzed in an experimental whole-body model of profound ANH (Hct 9%) and effectiveness of a perfluorocarbon-based oxygen carrier in maintaining myocardial oxygenation and function was evaluated. A total of 22 anesthetized dogs were hemodiluted to Hct 20% followed by a simulated, controlled blood-loss phase in which dogs were randomized to either: (1) 1:1 exchange of lost blood with autologous red blood cells (RBC-group), (2) 1:1 exchange with a colloid (control-group) and (3) 1:1 exchange with a colloid after a single dose of 1.8 g/kg BW perflubron i.v. (PFC-group). Myocardial oxygen delivery and consumption as well as endocardial perfusion were determined using radioactive microspheres. LV myocardial contractility (LV MC) was assessed from: (1) the relationship between maximum rate of LV pressure increase (LVdp/dtmax) and LV enddiastolic volume (LVEDV) and (2) analysis of the LV endsystolic pressure volume relationship (ESPVR). LV diastolic properties were reflected by (1) minimum rate of LV pressure increase (LVdp/dtmin), (2) slope and intercept of the enddiastolic pressure-volume relationship (EDPVR) and (3) the time-constant of isovolumic LV pressure decline "tau 1/2". Full sets of LV MC data were obtained from 18 dogs (n = 6 per group). LV MC (LVdp/dtmax-LVEDV relation) increased after perflubron administration. At the lowest Hct level, all parameters reflecting LV MC as well as LVdp/dtmin were significantly higher in the PFC-group than in the control-group. After profound normovolemic hemodilution (Hct 9%) superiority of LV MC and LV diastolic properties was found, when myocardial oxygenation was supported by i.v. perflubron emulsion, a temporary O2 carrier.
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Affiliation(s)
- O Habler
- Institute for Surgical Research, Ludwig-Maximilians University, Munich, Germany.
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Abstract
Adequate organ function requires adequate provision of cells with oxygen (O2). The driving force for O2-diffusion from ambient air to its site of consumption in cell mitochondria is the oxygen partial pressure (pO2) gradient along this pathway. After uptake in the lungs, O2 transport in blood is achieved (1) through binding to haemoglobin and (2) through physical dissolution in plasma. While the sum of O2 in these two transport states defines total oxygen content of blood, the delivery of O2 to different organs is determined by cardiac output and arterial O2 content, being the product of both parameters. In the case of anaemia, intravascular volume and cardiac compensatory mechanisms determine the degree of O2 content reduction allowable prior tissue hypoxia and lactacidosis occur. When intravascular volume is preserved (e.g. normovolemic dilutional anaemia), reductions in O2 content are tolerated to a much higher degree than in hypovolemic anaemia (e.g. haemorrhagic shock).
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Affiliation(s)
- O P Habler
- Institute for Surgical Research, Ludwig Maximilians University of Munich, Germany
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Habler OP, Kleen MS, Podtschaske AH, Hutter JW, Tiede M, Kemming GI, Welte MV, Corso CO, Messmer KF. The Effect of Acute Normovolemic Hemodilution (ANH) on Myocardial Contractility in Anesthetized Dogs. Anesth Analg 1996. [DOI: 10.1213/00000539-199609000-00002] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Habler OP, Kleen MS, Podtschaske AH, Hutter JW, Tiede M, Kemming GI, Welte MV, Corso CO, Messmer KF. The effect of acute normovolemic hemodilution (ANH) on myocardial contractility in anesthetized dogs. Anesth Analg 1996; 83:451-8. [PMID: 8780262 DOI: 10.1097/00000539-199609000-00002] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The influence of severe acute normovolemic hemodilution (ANH) on myocardial contractility (MC) was investigated in 14 splenectomized, anesthetized dogs. MC was assessed by the maximum rate of left ventricular pressure increase (LVdp/dt(max)), end-systolic elastance (Ees), and preload recruitable stroke work (PRSW) (conductance catheter, left ventricular pressure-volume relationship). Measurements of myocardial perfusion and oxygenation (radioactive microsphere technique) assured comparability of the model to previously performed studies. Global and regional myocardial blood flow increased significantly upon hemodilution with preference to midmyocardium and subendocardium. This resulted in preservation of both myocardial oxygen delivery and consumption after ANH. Myocardial oxygen extraction as well as coronary venous Po2 were unaffected by ANH, while coronary venous lactate concentration decreased, indicating that myocardial oxygen need was met. LVdp/dt(max) decreased significantly after hemodilution (2278 +/- 577 vs 1884 +/- 381 mm Hg/s, P < 0.01), whereas Ees and PRSW increased significantly (1.76 +/- 0.54 vs 2.15 +/- 0.75 mm Hg/mL, P < 0.05, for Ees and 33 +/- 14 vs 45 +/- 14 mm Hg.mL, P < 0.05, for PRSW). While the decrease of LVdp/dt(max) most likely reflects ANH-induced changes of ventricular pre- and afterload, the increase of Ees and PRSW indicates a true increase of myocardial contractility during ANH in anesthetized dogs.
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Affiliation(s)
- O P Habler
- Institute for Surgical Research, Ludwig-Maximilians-University, Munich, Germany
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Shinoda T, Smith CE, Khairallah PA, Fouad-Tarazi FM, Estafanous FG. Effects of propranolol on myocardial performance during acute normovolemic hemodilution. J Cardiothorac Vasc Anesth 1991; 5:15-22. [PMID: 1714311 DOI: 10.1016/1053-0770(91)90087-a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effects of propranolol and hemodilution on myocardial performance and oxygen delivery were evaluated in 36 anesthetized rats. Oral propranolol treatment consisted of 64 mg/kg/d for 6 weeks prior to the experiments, whereas intravenous (IV) propranolol treatment consisted of 5 micrograms/kg/min for 60 minutes after hemodilution. The hematocrit was reduced to 20% by a hetastarch-for-blood exchange. Animals were divided into six equal groups as follows: (1) no oral drug (water), no hemodilution, no IV drug (saline); (2) oral water, hemodilution, IV saline; (3) oral water, no hemodilution, IV propranolol; (4) oral water, hemodilution, IV propranolol; (5) oral propranolol, no hemodilution, IV saline; and (6) oral propranolol, hemodilution, IV saline. Left ventricular (LV) pressure, maximal dP/dt, ascending aortic blood flow, and response to preload (peak cardiac and stroke volume indices) and afterload (LV-developed pressure) stress were measured. In group 2, hemodilution significantly increased cardiac index, stroke volume index, and dP/dt, and decreased blood pressure, peripheral resistance, and oxygen delivery compared with group 1. Compared with group 2, IV propranolol after hemodilution in group 4 significantly decreased cardiac index, dP/dt, LV-developed pressure, and peak cardiac index, and increased peripheral resistance. Stroke volume index and peak stroke volume index after preload stress remained elevated in group 4, despite the negative inotropic effects of IV propranolol. Oral propranolol in group 6 did not prevent the hemodilution-induced increase in stroke volume index and peak stroke volume index in response to preload stress, although it did decrease cardiac index and dP/dt compared with group 2. Oxygen delivery was reduced in the hemodiluted animals in proportion to the decrease in hemoglobin, regardless of propranolol treatment. It is concluded that reduced myocardial contractility and cardiac performance by nonselective pharmacological beta-adrenoceptor blockade does not interfere with the compensatory increase in stroke volume index after hemodilution.
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Affiliation(s)
- T Shinoda
- Department of Cardiothoracic Anesthesia, Cleveland Clinic Foundation, OH 44106
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Estafanous FG, Smith CE, Selim WM, Tarazi RC. Cardiovascular effects of acute normovolemic hemodilution in rats with disopyramide-induced myocardial depression. Basic Res Cardiol 1990; 85:227-36. [PMID: 2383217 DOI: 10.1007/bf01907111] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effect of myocardial depression on the circulatory response to acute normovolemic hemodilution (hematocrit 23%) with hetastarch was evaluated in 28 anesthetized Sprague-Dawley rats. Cardiac output was recorded using an electromagnetic flow probe. Mild, moderate, and severe myocardial depression were achieved by infusing disopyramide 50, 75, and 85 mg/kg. This resulted in a dose-dependent decrease in cardiac output (r = -0.73, p less than 0.05) and mean arterial pressure (r = -0.65, p less than 0.05), and an increase in left ventricular end-diastolic pressure (r = 0.77, p less than 0.05) and total peripheral resistance (r = 0.46, p less than 0.05). Following hemodilution, cardiac output and mean arterial pressure were significantly lower and total peripheral resistance significantly higher in animals with myocardial depression compared with saline anemic controls. These differences were dose-dependent for cardiac output (r = -0.83, p less than 0.05), mean arterial pressure (r = -0.68, p less than 0.05), and total peripheral resistance (r = 0.51, p less than 0.05). Although control animals were able to significantly increase their cardiac output and stroke volume after hemodilution compared with baseline, animals with severe myocardial depression were unable to do so. This resulted in marked hypotension after hemodilution in controls compared with severely depressed animals. The results suggest a diminished ability of the pharmacologically depressed heart to tolerate acute normovolemic hemodilution.
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Affiliation(s)
- F G Estafanous
- Department of Cardiothoracic Anesthesiology, Cleveland Clinic Foundation, Ohio
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