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Schanche T, Han YS, Jensen CW, Arteaga GM, Tveita T, Sieck GC. β-adrenergic stimulation after rewarming does not mitigate hypothermia-induced contractile dysfunction in rat cardiomyocytes. Cryobiology 2024; 116:104927. [PMID: 38857777 DOI: 10.1016/j.cryobiol.2024.104927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 06/06/2024] [Accepted: 06/06/2024] [Indexed: 06/12/2024]
Abstract
Victims of severe accidental hypothermia are frequently treated with catecholamines to counteract the hemodynamic instability associated with hypothermia-induced cardiac contractile dysfunction. However, we previously reported that the inotropic effects of epinephrine are diminished after hypothermia and rewarming (H/R) in an intact animal model. Thus, the goal of this study was to investigate the effects of Epi treatment on excitation-contraction coupling in isolated rat cardiomyocytes after H/R. In adult male rats, cardiomyocytes isolated from the left ventricle were electrically stimulated at 0.5 Hz and evoked cytosolic [Ca2+] and contractile responses (sarcomere length shortening) were measured. In initial experiments, the effects of varying concentrations of epinephrine on evoked cytosolic [Ca2+] and contractile responses at 37 °C were measured. In a second series of experiments, cardiomyocytes were cooled from 37 °C to 15 °C, maintained at 15 °C for 2 h, then rewarmed to 37 °C (H/R protocol). Immediately after rewarming, the effects of epinephrine treatment on evoked cytosolic [Ca2+] and contractile responses of cardiomyocytes were determined. At 37 °C, epinephrine treatment increased both cytosolic [Ca2+] and contractile responses of cardiomyocytes in a concentration-dependent manner peaking at 25-50 nM. The evoked contractile response of cardiomyocytes after H/R was reduced while the cytosolic [Ca2+] response was slightly elevated. The diminished contractile response of cardiomyocytes after H/R was not mitigated by epinephrine (25 nM) and epinephrine treatment reduced the exponential time decay constant (Tau), but did not increase the cytosolic [Ca2+] response. We conclude that epinephrine treatment does not mitigate H/R-induced contractile dysfunction in cardiomyocytes.
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Affiliation(s)
- Torstein Schanche
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA; Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway
| | - Young Soo Han
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA
| | - Cole W Jensen
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA
| | - Grace M Arteaga
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA
| | - Torkjel Tveita
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA; Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway; Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, 9038, Tromsø, Norway
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic Rochester, MN, USA.
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2
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Selli AL, Ghasemi M, Watters T, Burton F, Smith G, Dietrichs ES. Proarrhythmic changes in human cardiomyocytes during hypothermia by milrinone and isoprenaline, but not levosimendan: an experimental in vitro study. Scand J Trauma Resusc Emerg Med 2023; 31:61. [PMID: 37880801 PMCID: PMC10601188 DOI: 10.1186/s13049-023-01134-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 10/15/2023] [Indexed: 10/27/2023] Open
Abstract
BACKGROUND Accidental hypothermia, recognized by core temperature below 35 °C, is a lethal condition with a mortality rate up to 25%. Hypothermia-induced cardiac dysfunction causing increased total peripheral resistance and reduced cardiac output contributes to the high mortality rate in this patient group. Recent studies, in vivo and in vitro, have suggested levosimendan, milrinone and isoprenaline as inotropic treatment strategies in this patient group. However, these drugs may pose increased risk of ventricular arrhythmias during hypothermia. Our aim was therefore to describe the effects of levosimendan, milrinone and isoprenaline on the action potential in human cardiomyocytes during hypothermia. METHODS Using an experimental in vitro-design, levosimendan, milrinone and isoprenaline were incubated with iCell2 hiPSC-derived cardiomyocytes and cellular action potential waveforms and contraction were recorded from monolayers of cultured cells. Experiments were conducted at temperatures from 37 °C down to 26 °C. One-way repeated measures ANOVA was performed to evaluate differences from baseline recordings and one-way ANOVA was performed to evaluate differences between drugs, untreated control and between drug concentrations at the specific temperatures. RESULTS Milrinone and isoprenaline both significantly increases action potential triangulation during hypothermia, and thereby the risk of ventricular arrhythmias. Levosimendan, however, does not increase triangulation and the contractile properties also remain preserved during hypothermia down to 26 °C. CONCLUSIONS Levosimendan remains a promising candidate drug for inotropic treatment of hypothermic patients as it possesses ability to treat hypothermia-induced cardiac dysfunction and no increased risk of ventricular arrhythmias is detected. Milrinone and isoprenaline, on the other hand, appears more dangerous in the hypothermic setting.
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Affiliation(s)
- Anders Lund Selli
- Experimental and Clinical Pharmacology, Department of Medical Biology, Faculty of Health Sciences, UiT - The Arctic University of Norway, Postboks 6050, 9037, Langnes, Tromsø, Norway
| | | | | | - Francis Burton
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, Scotland
- Clyde Biosciences, Newhouse, Scotland
| | - Godfrey Smith
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, Scotland
- Clyde Biosciences, Newhouse, Scotland
| | - Erik Sveberg Dietrichs
- Experimental and Clinical Pharmacology, Department of Medical Biology, Faculty of Health Sciences, UiT - The Arctic University of Norway, Postboks 6050, 9037, Langnes, Tromsø, Norway.
- Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway.
- Institute of Oral Biology, University of Oslo, Oslo, Norway.
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3
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Kuzmiszyn AK, Selli AL, Furuholmen M, Smaglyukova N, Kondratiev T, Fuskevåg OM, Sager G, Dietrichs ES. Moderate but not severe hypothermia increases intracellular cyclic AMP through preserved production and reduced elimination. Cryobiology 2023; 110:18-23. [PMID: 36649914 DOI: 10.1016/j.cryobiol.2023.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/12/2023] [Accepted: 01/12/2023] [Indexed: 01/15/2023]
Abstract
Rewarming from accidental hypothermia could be complicated by acute cardiac dysfunction but providing supportive pharmacotherapy at low core temperatures is challenging. Several pharmacological strategies aim to improve cardiovascular function by increasing cAMP in cardiomyocytes as well as cAMP and cGMP levels in vascular smooth muscle, but it is not clear what effects temperature has on cellular elimination of cAMP and cGMP. We therefore studied the effects of differential temperatures from normothermia to deep hypothermia (37 °C-20 °C) on cAMP levels in embryonic H9c2 cardiac cells and elimination of cAMP and cGMP by PDE-enzymes and ABC-transporter proteins. Our experiments showed significant elevation of intracellular cAMP in H9c2-cells at 30 °C but not 20 °C. Elimination of both cAMP and cGMP through ABC transport-proteins and PDE-enzymes showed a temperature dependent reduction. Accordingly, the increased cardiomyocyte cAMP-levels during moderate hypothermia appears an effect of preserved production and reduced elimination at 30 °C. This correlates with earlier in vivo findings of a positive inotropic effect of moderate hypothermia.
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Affiliation(s)
- Adrina Kalasho Kuzmiszyn
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway; Norwegian Air Ambulance Foundation, Research and Development Department, Oslo, Norway; Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Anders Lund Selli
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Markus Furuholmen
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Natalia Smaglyukova
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Timofei Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Ole-Martin Fuskevåg
- Department of Laboratory Medicine, Division of Diagnostic Services, University Hospital of North Norway, Tromsø, Norway
| | - Georg Sager
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway
| | - Erik Sveberg Dietrichs
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway; Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway.
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4
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McMillan M. Management of severe hypothermia and pulsus alternans in an anaesthetised cat. VETERINARY RECORD CASE REPORTS 2023. [DOI: 10.1002/vrc2.557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Matthew McMillan
- Queen Mother Hospital for Small Animals The Royal Veterinary College Hatfield UK
- The Ralph Veterinary Referral Centre Marlow UK
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5
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Selli AL, Kuzmiszyn AK, Smaglyukova N, Kondratiev T, Fuskevåg OM, Sager G, Dietrichs ES. Pharmacodynamic properties for inhibition of cAMP- and cGMP elimination by pentoxifylline remain unaltered in vitro during hypothermia. Scand J Trauma Resusc Emerg Med 2022; 30:73. [PMID: 36522632 PMCID: PMC9756503 DOI: 10.1186/s13049-022-01060-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/30/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Rewarming from hypothermia is associated with severe complications, one of which is hypothermia-induced cardiac dysfunction. This condition is characterized by decreased cardiac output accompanied by increased total peripheral resistance. This contributes to mortality rate approaching 40%. Despite this, no pharmacological interventions are recommended for these patients below 30 °C. Raising the intracellular levels of cAMP and/or cGMP, through PDE3- and PDE5-inhibitors respectively, have showed the ability to alleviate hypothermia-induced cardiac dysfunction in vivo. Drugs that raise levels of both cAMP and cGMP could therefore prove beneficial in patients suffering from hypothermia-induced cardiac dysfunction. METHODS The unselective PDE-inhibitor pentoxifylline was investigated to determine its ability to reach the intracellular space, inhibit PDE3 and PDE5 and inhibit cellular efflux of cAMP and cGMP at temperatures 37, 34, 30, 28, 24 and 20 °C. Recombinant human PDE-enzymes and human erythrocytes were used in the experiments. IC50-values were calculated at all temperatures to determine temperature-dependent changes. RESULTS At 20 °C, the IC50-value for PDE5-mediated enzymatic breakdown of cGMP was significantly increased compared to normothermia (IC50: 39.4 µM ± 10.9 µM vs. 7.70 µM ± 0.265 µM, p-value = 0.011). No other significant changes in IC50-values were observed during hypothermia. CONCLUSIONS This study shows that pentoxifylline has minimal temperature-dependent pharmacodynamic changes, and that it can inhibit elimination of both cAMP and cGMP at low temperatures. This can potentially be effective treatment of hypothermia-induced cardiac dysfunction. TRIAL REGISTRATION Not applicable.
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Affiliation(s)
- Anders Lund Selli
- grid.10919.300000000122595234Department of Medical Biology, Experimental and Clinical Pharmacology, UiT – The Arctic University of Norway, Tromsø, Norway
| | - Adrina Kalasho Kuzmiszyn
- grid.10919.300000000122595234Department of Medical Biology, Experimental and Clinical Pharmacology, UiT – The Arctic University of Norway, Tromsø, Norway ,grid.420120.50000 0004 0481 3017Research and Development Department, Norwegian Air Ambulance Foundation, Oslo, Norway ,grid.412244.50000 0004 4689 5540Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Natalia Smaglyukova
- grid.10919.300000000122595234Department of Medical Biology, Experimental and Clinical Pharmacology, UiT – The Arctic University of Norway, Tromsø, Norway
| | - Timofey Kondratiev
- grid.10919.300000000122595234Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Ole-Martin Fuskevåg
- grid.412244.50000 0004 4689 5540Division of Diagnostic Services, Department of Laboratory Medicine, University Hospital of North Norway, Tromsø, Norway
| | - Georg Sager
- grid.10919.300000000122595234Department of Medical Biology, Experimental and Clinical Pharmacology, UiT – The Arctic University of Norway, Tromsø, Norway
| | - Erik Sveberg Dietrichs
- grid.10919.300000000122595234Department of Medical Biology, Experimental and Clinical Pharmacology, UiT – The Arctic University of Norway, Tromsø, Norway ,grid.413684.c0000 0004 0512 8628Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway
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6
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Kuzmiszyn AK, Selli AL, Smaglyukova N, Kondratiev T, Fuskevåg OM, Lyså RA, Ravna AW, Tveita T, Sager G, Dietrichs ES. Treatment of Cardiovascular Dysfunction with PDE3-Inhibitors in Moderate and Severe Hypothermia—Effects on Cellular Elimination of Cyclic Adenosine Monophosphate and Cyclic Guanosine Monophosphate. Front Physiol 2022; 13:923091. [PMID: 35910566 PMCID: PMC9326216 DOI: 10.3389/fphys.2022.923091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 06/24/2022] [Indexed: 12/03/2022] Open
Abstract
Introduction: Rewarming from accidental hypothermia is often complicated by hypothermia-induced cardiovascular dysfunction, which could lead to shock. Current guidelines do not recommend any pharmacological treatment at core temperatures below 30°C, due to lack of knowledge. However, previous in vivo studies have shown promising results when using phosphodiesterase 3 (PDE3) inhibitors, which possess the combined effects of supporting cardiac function and alleviating the peripheral vascular resistance through changes in cyclic nucleotide levels. This study therefore aims to investigate whether PDE3 inhibitors milrinone, amrinone, and levosimendan are able to modulate cyclic nucleotide regulation in hypothermic settings. Materials and methods: The effect of PDE3 inhibitors were studied by using recombinant phosphodiesterase enzymes and inverted erythrocyte membranes at six different temperatures—37°C, 34°C, 32°C, 28°C, 24°C, and 20°C- in order to evaluate the degree of enzymatic degradation, as well as measuring cellular efflux of both cAMP and cGMP. The resulting dose-response curves at every temperature were used to calculate IC50 and Ki values. Results: Milrinone IC50 and Ki values for cGMP efflux were significantly lower at 24°C (IC50: 8.62 ± 2.69 µM) and 20°C (IC50: 7.35 ± 3.51 µM), compared to 37°C (IC50: 22.84 ± 1.52 µM). There were no significant changes in IC50 and Ki values for enzymatic breakdown of cAMP and cGMP. Conclusion: Milrinone, amrinone and levosimendan, were all able to suppress enzymatic degradation and inhibit extrusion of cGMP and cAMP below 30°C. Our results show that these drugs have preserved effect on their target molecules during hypothermia, indicating that they could provide an important treatment option for hypothermia-induced cardiac dysfunction.
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Affiliation(s)
- Adrina Kalasho Kuzmiszyn
- Norwegian Air Ambulance Foundation, Research and Development Department, Oslo, Norway
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
- Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Anders Lund Selli
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Natalia Smaglyukova
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Timofei Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromsø, Norway
| | - Ole-Martin Fuskevåg
- Department of Laboratory Medicine, Division of Diagnostic Services, University Hospital of North Norway, Tromsø, Norway
| | - Roy Andre Lyså
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Aina Westrheim Ravna
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Torkjel Tveita
- Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromsø, Norway
| | - Georg Sager
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
| | - Erik Sveberg Dietrichs
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT The Arctic University of Norway, Tromsø, Norway
- Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway
- *Correspondence: Erik Sveberg Dietrichs,
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7
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Bjertnæs LJ, Næsheim TO, Reierth E, Suborov EV, Kirov MY, Lebedinskii KM, Tveita T. Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update. Front Med (Lausanne) 2022; 9:824395. [PMID: 35280892 PMCID: PMC8904885 DOI: 10.3389/fmed.2022.824395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/28/2022] [Indexed: 12/01/2022] Open
Abstract
Background Accidental hypothermia (AH) is an unintended decrease in body core temperature (BCT) to below 35°C. We present an update on physiological/pathophysiological changes associated with AH and rewarming from hypothermic cardiac arrest (HCA). Temperature Regulation and Metabolism Triggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces release of Thyroid-Stimulating Hormone (TSH) and Prolactin from pituitary gland anterior lobe that stimulate thyroid generation of triiodothyronine and thyroxine (T4). The latter act together with noradrenaline to induce heat production by binding to adrenergic β3-receptors in fat cells. Exposed to cold, noradrenaline prompts degradation of triglycerides from brown adipose tissue (BAT) into free fatty acids that uncouple metabolism to heat production, rather than generating adenosine triphosphate. If BAT is lacking, AH occurs more readily. Cardiac Output Assuming a 7% drop in metabolism per °C, a BCT decrease of 10°C can reduce metabolism by 70% paralleled by a corresponding decline in CO. Consequently, it is possible to maintain adequate oxygen delivery provided correctly performed cardiopulmonary resuscitation (CPR), which might result in approximately 30% of CO generated at normal BCT. Liver and Coagulation AH promotes coagulation disturbances following trauma and acidosis by reducing coagulation and platelet functions. Mean prothrombin and partial thromboplastin times might increase by 40–60% in moderate hypothermia. Rewarming might release tissue factor from damaged tissues, that triggers disseminated intravascular coagulation. Hypothermia might inhibit platelet aggregation and coagulation. Kidneys Renal blood flow decreases due to vasoconstriction of afferent arterioles, electrolyte and fluid disturbances and increasing blood viscosity. Severely deranged renal function occurs particularly in the presence of rhabdomyolysis induced by severe AH combined with trauma. Conclusion Metabolism drops 7% per °C fall in BCT, reducing CO correspondingly. Therefore, it is possible to maintain adequate oxygen delivery after 10°C drop in BCT provided correctly performed CPR. Hypothermia may facilitate rhabdomyolysis in traumatized patients. Victims suspected of HCA should be rewarmed before being pronounced dead. Rewarming avalanche victims of HCA with serum potassium > 12 mmol/L and a burial time >30 min with no air pocket, most probably be futile.
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Affiliation(s)
- Lars J Bjertnæs
- Department of Clinical Medicine, Faculty of Health Sciences, Anesthesia and Critical Care Research Group, University of Tromsø, UiT The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Torvind O Næsheim
- Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway.,Department of Clinical Medicine, Faculty of Health Sciences, Cardiovascular Research Group, University of Tromsø, UiT The Arctic University of Norway, Tromsø, Norway
| | - Eirik Reierth
- Science and Health Library, University of Tromsø, UiT The Arctic University of Norway, Tromsø, Norway
| | - Evgeny V Suborov
- The Nikiforov Russian Center of Emergency and Radiation Medicine, St. Petersburg, Russia
| | - Mikhail Y Kirov
- Department of Anesthesiology and Intensive Care, Northern State Medical University, Arkhangelsk, Russia
| | - Konstantin M Lebedinskii
- Department of Anesthesiology and Intensive Care, North-Western State Medical University named after I.I. Mechnikov, St. Petersburg, Russia.,Federal Research and Clinical Center of Intensive Care Medicine and Rehabilitology, Moscow, Russia
| | - Torkjel Tveita
- Department of Clinical Medicine, Faculty of Health Sciences, Anesthesia and Critical Care Research Group, University of Tromsø, UiT The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
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8
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Tveita T, Sieck GC. Physiological Impact of Hypothermia: The Good, the Bad and the Ugly. Physiology (Bethesda) 2021; 37:69-87. [PMID: 34632808 DOI: 10.1152/physiol.00025.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Hypothermia is defined as a core body temperature of < 35°C, and as body temperature is reduced the impact on physiological processes can be beneficial or detrimental. The beneficial effect of hypothermia enables circulation of cooled experimental animals to be interrupted for 1-2 h without creating harmful effects, while tolerance of circulation arrest in normothermia is between 4 and 5 min. This striking difference has attracted so many investigators, experimental as well as clinical, to this field, and this discovery was fundamental for introducing therapeutic hypothermia in modern clinical medicine in the 1950's. Together with the introduction of cardiopulmonary bypass, therapeutic hypothermia has been the cornerstone in the development of modern cardiac surgery. Therapeutic hypothermia also has an undisputed role as a protective agent in organ transplantation and as a therapeutic adjuvant for cerebral protection in neonatal encephalopathy. However, the introduction of therapeutic hypothermia for organ protection during neurosurgical procedures or as a scavenger after brain and spinal trauma has been less successful. In general, the best neuroprotection seems to be obtained by avoiding hyperthermia in injured patients. Accidental hypothermia occurs when endogenous temperature control mechanisms are incapable of maintaining core body temperature within physiologic limits and core temperature becomes dependent on ambient temperature. During hypothermia spontaneous circulation is considerably reduced and with deep and/or prolonged cooling, circulatory failure may occur, which may limit safe survival of the cooled patient. Challenges that limit safe rewarming of accidental hypothermia patients include cardiac arrhythmias, uncontrolled bleeding, and "rewarming shock".
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Affiliation(s)
- Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
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9
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Selli AL, Kuzmiszyn AK, Smaglyukova N, Kondratiev TV, Fuskevåg OM, Lyså RA, Ravna AW, Tveita T, Sager G, Dietrichs ES. Treatment of Cardiovascular Dysfunction With PDE5-Inhibitors - Temperature Dependent Effects on Transport and Metabolism of cAMP and cGMP. Front Physiol 2021; 12:695779. [PMID: 34393818 PMCID: PMC8361756 DOI: 10.3389/fphys.2021.695779] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 07/09/2021] [Indexed: 01/24/2023] Open
Abstract
Introduction Cardiovascular dysfunction is a potentially lethal complication of hypothermia. Due to a knowledge gap, pharmacological interventions are not recommended at core temperatures below 30°C. Yet, further cooling is induced in surgical procedures and survival of accidental hypothermia is reported after rewarming from below 15°C, advocating a need for evidence-based treatment guidelines. In vivo studies have proposed vasodilation and afterload reduction through arteriole smooth muscle cGMP-elevation as a favorable strategy to prevent cardiovascular dysfunction in hypothermia. Further development of treatment guidelines demand information about temperature-dependent changes in pharmacological effects of clinically relevant vasodilators. Materials and Methods Human phosphodiesterase-enzymes and inverted erythrocytes were utilized to evaluate how vasodilators sildenafil and vardenafil affected cellular efflux and enzymatic breakdown of cAMP and cGMP, at 37°C, 34°C, 32°C, 28°C, 24°C, and 20°C. The ability of both drugs to reach their cytosolic site of action was assessed at the same temperatures. IC50- and Ki-values were calculated from dose–response curves at all temperatures, to evaluate temperature-dependent effects of both drugs. Results Both drugs were able to reach the intracellular space at all hypothermic temperatures, with no reduction compared to normothermia. Sildenafil IC50 and Ki-values increased during hypothermia for enzymatic breakdown of both cAMP (IC50: 122 ± 18.9 μM at 37°C vs. 269 ± 14.7 μM at 20°C, p < 0.05) and cGMP (IC50: 0.009 ± 0.000 μM at 37°C vs. 0.024 ± 0.004 μM at 32°C, p < 0.05), while no significant changes were detected for vardenafil. Neither of the drugs showed significant hypothermia-induced changes in IC50 and Ki–values for inhibition of cellular cAMP and cGMP efflux. Conclusion Sildenafil and particularly vardenafil were ableto inhibit elimination of cGMP down to 20°C. As the cellular effects of these drugs can cause afterload reduction, they show potential in treating cardiovascular dysfunction during hypothermia. As in normothermia, both drugs showed higher selectivity for inhibition of cGMP-elimination than cAMP-elimination at low core temperatures, indicating that risk for cardiotoxic side effects is not increased by hypothermia.
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Affiliation(s)
- Anders L Selli
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Adrina K Kuzmiszyn
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Natalia Smaglyukova
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Timofei V Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Ole-Martin Fuskevåg
- Department of Laboratory Medicine, Division of Diagnostic Services, University Hospital of North Norway, Tromsø, Norway
| | - Roy A Lyså
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Aina W Ravna
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Torkjel Tveita
- Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway.,Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Georg Sager
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Erik S Dietrichs
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT - The Arctic University of Norway, Tromsø, Norway.,Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway
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10
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Nilsen JH, Schanche T, Kondratiev TV, Hevrøy O, Sieck GC, Tveita T. Maintaining intravenous volume mitigates hypothermia-induced myocardial dysfunction and accumulation of intracellular Ca 2. Exp Physiol 2021; 106:1196-1207. [PMID: 33728692 DOI: 10.1113/ep089397] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 03/11/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Detailed guidelines for volume replacement to counteract hypothermia-induced intravascular fluid loss are lacking. Evidence suggests colloids might have beneficial effects compared to crystalloids. Are central haemodynamic function and level of hypothermia-induced calcium overload, as a marker of cardiac injury, restored by fluid substitution during rewarming, and are colloids favourable to crystalloids? What is the main finding and its importance? Infusion with crystalloid or dextran during rewarming abolished post-hypothermic cardiac dysfunction, and partially mitigated myocardial calcium overload. The effects of volume replacement to support haemodynamic function are comparable to those using potent cardio-active drugs. These findings underline the importance of applying intravascular volume replacement to maintain euvolaemia during rewarming. ABSTRACT Previous research exploring pathophysiological mechanisms underlying circulatory collapse after rewarming victims of severe accidental hypothermia has documented post-hypothermic cardiac dysfunction and hypothermia-induced elevation of intracellular Ca2+ concentration ([Ca2+ ]i ) in myocardial cells. The aim of the present study was to examine if maintaining euvolaemia during rewarming mitigates cardiac dysfunction and/or normalizes elevated myocardial [Ca2+ ]i . A total of 21 male Wistar rats (300 g) were surface cooled to 15°C, then maintained at 15°C for 4 h, and subsequently rewarmed to 37°C. The rats were randomly assigned to one of three groups: (1) non-intervention control (n = 7), (2) dextran treated (i.v. 12 ml/kg dextran 70; n = 7), or (3) crystalloid treated (24 ml/kg 0.9% i.v. saline; n = 7). Infusions occurred during the first 30 min of rewarming. Arterial blood pressure, stroke volume (SV), cardiac output (CO), contractility (dP/dtmax ) and blood gas changes were measured. Post-hypothermic changes in [Ca2+ ]i were measured using the method of radiolabelled Ca2+ (45 Ca2+ ). Untreated controls displayed post-hypothermic cardiac dysfunction with significantly reduced CO, SV and dP/dtmax . In contrast, rats receiving crystalloid or dextran treatment showed a return to pre-hypothermic control levels of CO and SV after rewarming, with the dextran group displaying significantly better amelioration of post-hypothermic cardiac dysfunction than the crystalloid group. Compared to the post-hypothermic increase in myocardial [Ca2+ ]i in non-treated controls, [Ca2+ ]i values with crystalloid and dextran did not increase to the same extent after rewarming. Volume replacement with crystalloid or dextran during rewarming abolishes post-hypothermic cardiac dysfunction, and partially mitigates the hypothermia-induced elevation of [Ca2+ ]i .
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Affiliation(s)
- Jan Harald Nilsen
- Anesthesia and Critical Care research group, Department of Clinical Medicine, UiT, Arctic University of Norway, Tromsø, Norway.,Department of Research and Education, Norwegian Air Ambulance Foundation, Drøbak, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
| | - Torstein Schanche
- Anesthesia and Critical Care research group, Department of Clinical Medicine, UiT, Arctic University of Norway, Tromsø, Norway.,Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Timofei V Kondratiev
- Anesthesia and Critical Care research group, Department of Clinical Medicine, UiT, Arctic University of Norway, Tromsø, Norway
| | - Olav Hevrøy
- Department of Anesthesiology and Intensive Care, Haukeland University Hospital, Bergen, Norway
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Torkjel Tveita
- Anesthesia and Critical Care research group, Department of Clinical Medicine, UiT, Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway.,Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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11
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Dietrichs ES, Selli AL, Kondratiev T, McGlynn K, Smith G, Tveita T. Resistance to ventricular fibrillation predicted by the QRS/QTc - Ratio in an intact rat model of hypothermia/rewarming. Cryobiology 2021; 98:33-38. [PMID: 33412156 DOI: 10.1016/j.cryobiol.2021.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 11/29/2020] [Accepted: 01/01/2021] [Indexed: 01/19/2023]
Abstract
Accidental hypothermia is associated with increased risk for arrhythmias. QRS/QTc is proposed as an ECG-marker, where decreasing values predict hypothermia-induced ventricular arrhythmias. If reliable it should also predict nonappearance of arrhythmias, observed in species like rat that regularly tolerate prolonged hypothermia. A rat model designed for studying cardiovascular function during cooling, hypothermia and subsequent rewarming was chosen due to species-dependent resistance to ventricular arrhythmias. ECG was recorded throughout the protocol. No ventricular arrhythmias occurred during experiments. QRS/QTc increased throughout the cooling period and remained above normothermic baseline until rewarmed. Different from the high incidence of hypothermia-induced ventricular arrhythmias in accidental hypothermia patients, where QRS/QTc ratio is decreased in moderate hypothermia; hypothermia and rewarming of rats is not associated with increased risk for ventricular fibrillation. This resistance to lethal hypothermia-induced arrhythmias was predicted by QRS/QTc.
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Affiliation(s)
- Erik Sveberg Dietrichs
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT, The Arctic University of Norway, 9037, Tromsø, Norway; Division of Diagnostic Services, University Hospital of Northern Norway, Tromsø, Norway.
| | - Anders Lund Selli
- Experimental and Clinical Pharmacology, Department of Medical Biology, UiT, The Arctic University of Norway, 9037, Tromsø, Norway
| | - Timofei Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway
| | - Karen McGlynn
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, UK
| | - Godfrey Smith
- Institute of Cardiovascular & Medical Sciences, University of Glasgow, UK
| | - Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway; Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, 9038, Tromsø, Norway
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12
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Håheim B, Kondratiev T, Dietrichs ES, Tveita T. Comparison Between Two Pharmacologic Strategies to Alleviate Rewarming Shock: Vasodilation vs. Inodilation. Front Med (Lausanne) 2020; 7:566388. [PMID: 33282886 PMCID: PMC7689197 DOI: 10.3389/fmed.2020.566388] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/05/2020] [Indexed: 11/13/2022] Open
Abstract
Rewarming from hypothermia is often challenged by coexisting cardiac dysfunction, depressed organ blood flow (OBF), and increased systemic vascular resistance. Previous research shows cardiovascular inotropic support and vasodilation during rewarming to elevate cardiac output (CO). The present study aims to compare the effects of inodilatation by levosimendan (LS) and vasodilation by nitroprusside (SNP) on OBF and global oxygen transport during rewarming from hypothermia. We used an in vivo experimental rat model of 4 h 15°C hypothermia and rewarming. A stable isotope-labeled microsphere technique was used to determine OBF. Cardiac and arterial pressures were monitored with fluid-filled pressure catheters, and CO was measured by thermodilution. Two groups were treated with either LS (n = 7) or SNP (n = 7) during the last hour of hypothermia and throughout rewarming. Two groups served as hypothermic (n = 7) and normothermic (n = 6) controls. All hypothermia groups had significantly reduced CO, oxygen delivery, and OBF after rewarming compared to their baseline values. After rewarming, LS had elevated CO significantly more than SNP (66.57 ± 5.6/+30% vs. 54.48 ± 5.2/+14%) compared to the control group (47.22 ± 3.9), but their ability to cause elevation of brain blood flow (BBF) was the same (0.554 ± 0.180/+81 vs. 0.535 ± 0.208/+75%) compared to the control group (0.305 ± 0.101). We interpret the vasodilator properties of LS and SNP to be the primary source to increase organ blood flow, superior to the increase in CO.
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Affiliation(s)
- Brage Håheim
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway
| | - Timofei Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway
| | - Erik Sveberg Dietrichs
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway.,Experimental and Clinical Pharmacology Research Group, Department of Medical Biology, UiT, The Arctic University of Norway, Tromsø, Norway
| | - Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
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13
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Tveita T, Arteaga GM, Han YS, Sieck GC. Cardiac troponin-I phosphorylation underlies myocardial contractile dysfunction induced by hypothermia rewarming. Am J Physiol Heart Circ Physiol 2019; 317:H726-H731. [PMID: 31373512 DOI: 10.1152/ajpheart.00101.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rewarming the intact heart after a period of hypothermia is associated with reduced myocardial contractility, decreased Ca2+ sensitivity, and increased cardiac troponin-I (cTnI) phosphorylation. We hypothesized that hypothermia/rewarming (H/R) induces left ventricular (LV) contractile dysfunction due to phosphorylation of cTnI at Ser23/24. To test this hypothesis, the response of wild-type mice (n = 7) to H/R was compared with transgenic (TG) mice expressing slow skeletal TnI (TG-ssTnI; n = 7) that lacks the Ser23/24 phosphorylation sites. Hypothermia was induced by surface cooling and maintained at 23-25°C for 3 h. Subsequently, the animals were rewarmed to 37°C. LV systolic and diastolic function was assessed using a 1.4 F pressure-volume Millar catheter introduced via the right carotid artery. At baseline conditions, there were no significant differences in LV systolic function between wild-type and TG-ssTnI mice, whereas measurements of diastolic function [isovolumic relaxation constant (τ) and end-diastolic pressure-volume relationship (EDPVR)] were significantly (P < 0.05) reduced in TG-ssTnI animals. Immediately after rewarming, significant differences between groups were found in cardiac output (CO; wild-type 6.6 ± 0.7 vs. TG-ssTnI 8.8 ± 0.7 mL/min), stroke work (SW; wild-type 796 ± 112 vs. TG-ssTnI 1208 ± 67 mmHg/μL), and the preload recruited stroke work (PRSW; wild-type 38.3 ± 4.9 vs. TG-ssTnI 68.8 ± 8.2 mmHg). However, EDPVR and τ returned to control levels within 1 h in both groups. We conclude that H/R-induced LV systolic dysfunction results from phosphorylation of cTnI at Ser23/24.NEW & NOTEWORTHY Rewarming following a period of accidental hypothermia leads to a form of acute cardiac failure (rewarming shock), which is in part due to reduced sensitivity to Ca2+ activation of myocardial contraction. The results of the present study support the hypothesis that rewarming shock is due to phosphorylation of cardiac troponin I.
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Affiliation(s)
- Torkjel Tveita
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota.,Anesthesia and Critical Care Research Group, Institute of Clinical Medicine, The Arctic University of Norway, Tromsø, Norway
| | - Grace M Arteaga
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Young-Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
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14
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Schanche T, Kondratiev T, Tveita T. Extracorporeal rewarming from experimental hypothermia: Effects of hydroxyethyl starch versus saline priming on fluid balance and blood flow distribution. Exp Physiol 2019; 104:1353-1362. [PMID: 31219201 DOI: 10.1113/ep087786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/18/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Mortality in accidental hypothermia patients rewarmed by extracorporeal circulation remains high. Knowledge concerning optimal fluid additions for extracorporeal rewarming is lacking, with no apparent consensus. Does colloid versus crystalloid priming have different effects on fluid balance and blood flow distribution during extracorporeal rewarming? What is the main finding and its importance? In our rat model of extracorporeal rewarming from hypothermic cardiac arrest, hydroxyethyl starch generates less tissue oedema and increases circulating blood volume and organ blood flow, compared with saline. The composition of fluid additions appears to be important during extracorporeal rewarming from hypothermia. ABSTRACT Rewarming by extracorporeal circulation (ECC) is the recommended treatment for accidental hypothermia patients with cardiac instability. Hypothermia, along with initiation of ECC, introduces major changes in fluid homeostasis and blood flow. Scientific data to recommend best practice use of ECC for rewarming these patients is lacking, and no current guidelines exist concerning the choice of priming fluid for the extracorporeal circuit. The primary aim of this study was to compare the effects of different fluid protocols on fluid balance and blood flow distribution during rewarming from deep hypothermic cardiac arrest. Sixteen anaesthetized rats were cooled to deep hypothermic cardiac arrest and rewarmed by ECC. During cooling, rats were equally randomized into two groups: an extracorporeal circuit primed with saline or primed with hydroxyethyl starch (HES). Calculations of plasma volume (PV), circulating blood volume (CBV), organ blood flow, total tissue water content, global O2 delivery and consumption were made. During and after rewarming, the pump flow rate, mean arterial pressure, PV and CBV were significantly higher in HES-treated compared with saline-treated rats. After rewarming, the HES group had significantly increased global O2 delivery and blood flow to the brain and kidneys compared with the saline group. Rats in the saline group demonstrated a significantly higher total tissue water content in the kidneys, skeletal muscle and lung. Compared with crystalloid priming, the use of an iso-oncotic colloid prime generates less tissue oedema and increases PV, CBV and organ blood flow during ECC rewarming. The composition of fluid additions appears to be an important factor during ECC rewarming from hypothermia.
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Affiliation(s)
- Torstein Schanche
- Anaesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway
| | - Timofei Kondratiev
- Anaesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway
| | - Torkjel Tveita
- Anaesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, Tromsø, Norway
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15
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Role of superoxide ion formation in hypothermia/rewarming induced contractile dysfunction in cardiomyocytes. Cryobiology 2018; 81:57-64. [PMID: 29458041 DOI: 10.1016/j.cryobiol.2018.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 01/24/2023]
Abstract
Rewarming following accidental hypothermia is associated with circulatory collapse due primarily to impaired cardiac contractile (systolic) function. Previously, we found that reduced myofilament Ca2+ sensitivity underlies hypothermia/rewarming (H/R)-induced cardiac contractile dysfunction. This reduced Ca2+ sensitivity is associated with troponin I (cTnI) phosphorylation. We hypothesize that H/R induces reactive oxygen species (ROS) formation in cardiomyocytes, which leads to cTnI phosphorylation and reduced myofilament Ca2+ sensitivity. To test this hypothesis, we exposed isolated rat cardiomyocytes to a 2-h period of severe hypothermia (15 °C) followed by rewarming (35 °C) with and without antioxidant (TEMPOL) treatment. Simultaneous measurements of cytosolic Ca2+ ([Ca2+]cyto) and contractile (sarcomere shortening) responses indicated that H/R-induced contractile dysfunction and reduced Ca2+ sensitivity was prevented in cardiomyocytes treated with TEMPOL. In addition, TEMPOL treatment blunted H/R-induced cTnI phosphorylation. These results support our overall hypothesis and suggest that H/R disrupts excitation-contraction coupling of the myocardium through a cascade of event triggered by excessive ROS formation during hypothermia. Antioxidant treatment may improve successful rescue of accidental hypothermia victims.
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16
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Dietrichs ES, Håheim B, Kondratiev T, Traasdahl E, Tveita T. Effects of hypothermia and rewarming on cardiovascular autonomic control in vivo. J Appl Physiol (1985) 2017; 124:850-859. [PMID: 29357499 DOI: 10.1152/japplphysiol.00317.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rewarming from accidental hypothermia is associated with cardiovascular dysfunction that complicates rewarming and contributes to a high mortality rate. We investigated autonomic cardiovascular control, as well as the separate effects of cooling, hypothermia, and rewarming on hemodynamic function, aiming to provide knowledge of the pathophysiology causing such complications in these patients. A rat model designed for circulatory studies during cooling, hypothermia (15°C), and rewarming was used. Spectral analysis of diastolic arterial pressure and heart rate allowed assessment of the autonomic nervous system. Hemodynamic variables were monitored using a conductance catheter in the left ventricle and a pressure transducer connected to the left femoral artery. Sympathetic cardiovascular control was reduced after rewarming. Stroke volume increased during cooling but decreased during stable hypothermia and did not normalize during rewarming. Despite autonomic dysfunction, total peripheral resistance increased during cooling and did not normalize after rewarming. The present data show that sympathetic cardiovascular control is reduced by hypothermia and rewarming. A simultaneous systolic dysfunction is seen in rewarmed animals, caused by reduced filling of the left ventricle and impaired contractile function, in the presence of normal diastolic function. These findings show that dysfunction of the efferent sympathetic nervous system could be instrumental in development of rewarming shock. NEW & NOTEWORTHY The present study shows impaired autonomic control of cardiovascular function after rewarming from severe hypothermia. In victims of accidental hypothermia, rewarming shock is a much feared and lethal complication. The pathophysiology causing such cardiovascular collapse appears complex. Our findings indicate that dysfunction of the autonomic nervous system is an important part of the pathophysiology. Thus the present study gives novel information, important for further development of treatment strategies in this patient group.
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Affiliation(s)
- Erik Sveberg Dietrichs
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway , Tromsø , Norway.,Department of Research and Education, Norwegian Air Ambulance Foundation, Drøbak, Norway.,Department of Clinical Pharmacology, Division of Diagnostic Services, University Hospital of North Norway , Tromsø , Norway
| | - Brage Håheim
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway , Tromsø , Norway
| | - Timofei Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway , Tromsø , Norway
| | - Erik Traasdahl
- PET Imaging Center, Division of Diagnostic Services, University Hospital of North Norway , Tromsø , Norway
| | - Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway , Tromsø , Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway , Tromsø , Norway
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17
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Håheim B, Kondratiev T, Dietrichs ES, Tveita T. The beneficial hemodynamic effects of afterload reduction by sodium nitroprusside during rewarming from experimental hypothermia. Cryobiology 2017; 77:75-81. [PMID: 28479295 DOI: 10.1016/j.cryobiol.2017.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 05/02/2017] [Accepted: 05/03/2017] [Indexed: 01/13/2023]
Abstract
BACKGROUND Rewarming from hypothermia is associated with depressed cardiac function, known as hypothermia-induced cardiac dysfunction (HCD), and increased systemic vascular resistance (SVR). Previous studies on pharmacological treatment of HCD have demonstrated beneficial effects when using drugs with the combined effects; cardiac inotropic support and peripheral vasodilation. The presented study aims to investigate the isolated effects of arterial dilatation on cardiac functional variables during rewarming from hypothermia using sodium nitroprusside (SNP). METHODS We utilized a rat model designed to induce HCD following 4 h at 15 °C and rewarming. To study effects on left ventricular (LV) functional variables in response to afterload reduction by SNP during rewarming a conductance catheter was used. Index of LV contractility, preload recruitable stroke work (PRSW), was obtained with inferior vena cava occlusions at 37 °C before and after hypothermia. Pressure signals from a catheter in the left femoral artery was used to pharmacologically adjust SVR. RESULTS After rewarming both animal groups showed significant reduction in both SV and CO as a manifestation of HCD. However, compared to saline controls, SV and CO in SNP-treated animals increased significantly during rewarming in response to afterload reduction displayed as reduced SVR, mean arterial- and end-systolic pressures. The cardiac contractility variable PRSW was equally reduced after rewarming in both groups. CONCLUSION When rewarming the present model of HCD a significant increase in SVR takes place. In this context, pharmacologic intervention aimed at reducing SVR show clear positive results on CO and SV. However, a reduction in SVR alone is not sufficient to fully alleviate CO during HCD, and indicate the need of additional inotropic support.
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Affiliation(s)
- Brage Håheim
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037 Tromsø, Norway.
| | - Timofey Kondratiev
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037 Tromsø, Norway.
| | - Erik Sveberg Dietrichs
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037 Tromsø, Norway; Department of Research and Education, Norwegian Air Ambulance Foundation, 1441 Drøbak, Norway.
| | - Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037 Tromsø, Norway; Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, 9038 Tromsø, Norway.
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18
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Dietrichs ES, Sager G, Tveita T. Altered pharmacological effects of adrenergic agonists during hypothermia. Scand J Trauma Resusc Emerg Med 2016; 24:143. [PMID: 27919274 PMCID: PMC5139099 DOI: 10.1186/s13049-016-0339-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 11/29/2016] [Indexed: 01/02/2023] Open
Abstract
Rewarming from accidental hypothermia is often complicated by hypothermia-induced cardiac dysfunction, calling for immediate pharmacologic intervention. Studies show that although cardiac pharmacologic support is applied when rewarming these patients, a lack of updated treatment recommendations exist. Mainly due to lack of clinical and experimental data, neither of the international guidelines includes information about pharmacologic cardiac support at temperatures below 30 °C. However, core temperature of accidental hypothermia patients is often reduced below 30 °C. Few human studies exploring effects of adrenergic drugs during hypothermia have been published, and therefore prevailing information is collected from pre-clinical studies. The most prominent finding in these studies is an apparent depressive effect of adrenaline on cardiac function when used in doses which elevate cardiac output during normothermia. Also noradrenaline and isoprenaline largely lacked positive cardiac effects during hypothermia, while dopamine is a more promising drug for supporting cardiac function during rewarming. Data and information from these studies are in support of the prevailing notion; not to use adrenergic drugs at core temperatures below 30 °C.
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Affiliation(s)
- Erik Sveberg Dietrichs
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway. .,Department of Research and Education, Norwegian Air Ambulance Foundation, 1441, Drøbak, Norway.
| | - Georg Sager
- Experimental and Clinical Pharmacology, Department of medical biology, UiT, The Arctic University of Norway, 9037, Tromsø, Norway
| | - Torkjel Tveita
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, UiT, The Arctic University of Norway, 9037, Tromsø, Norway.,Division of Surgical Medicine and Intensive Care, University Hospital of North Norway, 9038, Tromsø, Norway
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19
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Schaible N, Han YS, Hoang T, Arteaga G, Tveita T, Sieck G. Hypothermia/rewarming disrupts excitation-contraction coupling in cardiomyocytes. Am J Physiol Heart Circ Physiol 2016; 310:H1533-40. [PMID: 26993227 DOI: 10.1152/ajpheart.00840.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/16/2016] [Indexed: 12/25/2022]
Abstract
Hypothermia/rewarming (H/R) is poorly tolerated by the myocardium; however, the underlying intracellular basis of H/R-induced cardiac dysfunction remains elusive. We hypothesized that in cardiomyocytes, H/R disrupts excitation-contraction coupling by reducing myofilament Ca(2+) sensitivity due to an increase in cardiac troponin I (cTnI) phosphorylation. To test this hypothesis, isolated rat cardiomyocytes (13-15 cells from 6 rats per group) were electrically stimulated to evoke both cytosolic Ca(2+) ([Ca(2+)]cyto) and contractile (sarcomere shortening) responses that were simultaneously measured using an IonOptix system. Cardiomyocytes were divided into two groups: 1) those exposed to hypothermia (15°C for 2 h) followed by rewarming (35°C; H/R); or 2) time-matched normothermic (35°C) controls (CTL). Contractile dysfunction after H/R was indicated by reduced velocity and extent of sarcomere length (SL) shortening compared with time-matched controls. Throughout hypothermia, basal [Ca(2+)]cyto increased and the duration of evoked [Ca(2+)]cyto transients was prolonged. Phase-loop plots of [Ca(2+)]cyto vs. contraction were shifted rightward in cardiomyocytes during hypothermia compared with CTL, indicating a decrease in Ca(2+) sensitivity. Using Western blot, we found that H/R increases cTnI phosphorylation. These results support our overall hypothesis and suggest that H/R disrupts excitation-contraction coupling of cardiomyocytes due to increased cTnI phosphorylation and reduced Ca(2+) sensitivity.
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Affiliation(s)
- Niccole Schaible
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Young Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Thuy Hoang
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Grace Arteaga
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Torkjel Tveita
- Departments of Anesthesiology and Physiology, University of Tromsø-The Arctic University of Norway, Tromsø, Norway
| | - Gary Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
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