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Strapazzon G, Taboni A, Dietrichs ES, Luks AM, Brugger H. Avalanche burial pathophysiology - a unique combination of hypoxia, hypercapnia and hypothermia. J Physiol 2024. [PMID: 39073871 DOI: 10.1113/jp284607] [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: 09/01/2023] [Accepted: 06/17/2024] [Indexed: 07/30/2024] Open
Abstract
For often unclear reasons, the survival times of critically buried avalanche victims vary widely from minutes to hours. Individuals can survive and sustain organ function if they can breathe under the snow and maintain sufficient delivery of oxygen and efflux of carbon dioxide. We review the physiological responses of humans to critical avalanche burial, a model which shares similarities and differences with apnoea and accidental hypothermia. Within a few minutes of burial, an avalanche victim is exposed to hypoxaemia and hypercapnia, which have important effects on the respiratory and cardiovascular systems and pose a major threat to the central nervous system. As burial time increases, an avalanche victim also develops hypothermia. Despite progressively reduced metabolism, reduced oxygen and increased carbon dioxide tensions may exacerbate the pathophysiological consequences of hypothermia. Hypercapnia seems to be the main cause of cardiovascular instability, which, in turn, is the major reason for reduced cerebral oxygenation despite reductions in cerebral metabolic activity caused by hypothermia. 'Triple H syndrome' refers to the interaction of hypoxia, hypercapnia and hypothermia in a buried avalanche victim. Future studies should investigate how the respiratory gases entrapped in the porous snow structure influence the physiological responses of buried individuals and how haemoconcentration, blood viscosity and cell deformability affect blood flow and oxygen delivery. Attention should also be devoted to identifying strategies to prolong avalanche survival by either mitigating hypoxia and hypercapnia or reducing core temperature so that neuroprotection occurs before the onset of cerebral hypoxia.
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Affiliation(s)
- Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
- Department of Medicine - DIMEM, University of Padova, Padova, Italy
| | - Anna Taboni
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | | | - Andrew M Luks
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Hermann Brugger
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
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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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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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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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