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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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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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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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Jaimes R, Kuzmiak-Glancy S, Brooks DM, Swift LM, Posnack NG, Kay MW. Functional response of the isolated, perfused normoxic heart to pyruvate dehydrogenase activation by dichloroacetate and pyruvate. Pflugers Arch 2015; 468:131-142. [PMID: 26142699 DOI: 10.1007/s00424-015-1717-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 06/17/2015] [Accepted: 06/22/2015] [Indexed: 12/19/2022]
Abstract
Dichloroacetate (DCA) and pyruvate activate pyruvate dehydrogenase (PDH), a key enzyme that modulates glucose oxidation and mitochondrial NADH production. Both compounds improve recovery after ischemia in isolated hearts. However, the action of DCA and pyruvate in normoxic myocardium is incompletely understood. We measured the effect of DCA and pyruvate on contraction, mitochondrial redox state, and intracellular calcium cycling in isolated rat hearts during normoxic perfusion. Normalized epicardial NADH fluorescence (nNADH) and left ventricular developed pressure (LVDP) were measured before and after administering DCA (5 mM) or pyruvate (5 mM). Optical mapping of Rhod-2AM was used to measure cytosolic calcium kinetics. DCA maximally activated PDH, increasing the ratio of active to total PDH from 0.48 ± 0.03 to 1.03 ± 0.03. Pyruvate sub-maximally activated PDH to a ratio of 0.75 ± 0.02. DCA and pyruvate increased LVDP. When glucose was the only exogenous fuel, pyruvate increased nNADH by 21.4 ± 2.9 % while DCA reduced nNADH by 21.4 ± 6.1 % and elevated the incidence of premature ventricular contractions (PVCs). When lactate, pyruvate, and glucose were provided together as exogenous fuels, nNADH increased with DCA, indicating that PDH activation with glucose as the only exogenous fuel depletes PDH substrate. Calcium transient time-to-peak was shortened by DCA and pyruvate and SR calcium re-uptake was 30 % longer. DCA and pyruvate increased SR calcium load in myocyte monolayers. Overall, during normoxia when glucose is the only exogenous fuel, DCA elevates SR calcium, increases LVDP and contractility, and diminishes mitochondrial NADH. Administering DCA with plasma levels of lactate and pyruvate mitigates the drop in mitochondrial NADH and prevents PVCs.
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Affiliation(s)
- Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Sarah Kuzmiak-Glancy
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Daina M Brooks
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA
| | - Luther M Swift
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA
| | - Nikki G Posnack
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, GWU Science and Engineering Hall, 800 22nd Street NW, Suite 5000, Washington, DC, 20052, USA.
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, 20052, USA.
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Wold RM, Kondratiev T, Tveita T. Myocardial calcium overload during graded hypothermia and after rewarming in an in vivo rat model. Acta Physiol (Oxf) 2013; 207:460-9. [PMID: 22950548 DOI: 10.1111/apha.12003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 05/25/2012] [Accepted: 08/24/2012] [Indexed: 11/30/2022]
Abstract
AIM Mechanisms underlying cardiac contractile dysfunction during and after rewarming from hypothermia remain largely unknown. We have previously reported myocardial post-hypothermic calcium overload to be the culprit. The aim of the present study was to measure changes in myocardial [Ca(2+) ](i) during graded hypothermia and after rewarming in an anesthetized, intact rat model, using the (45) Ca(2+) technique. METHODS Rats were randomized and cooled to 15 °C. Hearts were excised and perfusion-washed to remove extracellular calcium after 0.5 h of hypothermia (n = 9), 4 h of hypothermia (n = 8), and after 4 h of hypothermia and 2 h rewarming (n = 9). A normothermic group, kept at 37 °C for 5 h, served as control (n = 6). [Ca(2+) ](i) was determined in perchloric acid extracts of heart tissue. Spontaneous cardiac electromechanic work was maintained during hypothermia without cardiac arrest or ischaemia. RESULTS Between 0.5 and 4 h at 15 °C, a six-fold increase in cardiac [Ca(2+) ](i) was observed (0.55 ± 0.10 vs. 2.93 ± 0.76 μmol (g dry wt)(-1) ). Rewarming resulted in a 33% decline in [Ca(2+) ](i) , but the actual value was significantly above the value measured in control hearts. CONCLUSION We show that calcium overload is a characteristic feature of the beating heart during deep hypothermia, which aggravates by increasing duration of exposure. The relatively low decline in [Ca(2+) ](i) during the rewarming period indicates difficulties in recovering calcium homoeostasis, which in turn may explain cardiac contractile dysfunction observed after rewarming.
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Affiliation(s)
- R. M. Wold
- Anaesthesia and Critical Care Research group; Institute of Clinical Medicine; University of Tromsø; Tromsø; Norway
| | - T. Kondratiev
- Anaesthesia and Critical Care Research group; Institute of Clinical Medicine; University of Tromsø; Tromsø; Norway
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Kondratiev TV, Wold RM, Aasum E, Tveita T. Myocardial mechanical dysfunction and calcium overload following rewarming from experimental hypothermia in vivo. Cryobiology 2008; 56:15-21. [DOI: 10.1016/j.cryobiol.2007.09.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 09/12/2007] [Accepted: 09/19/2007] [Indexed: 11/27/2022]
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Kondratiev TV, Myhre ESP, Simonsen O, Nymark TB, Tveita T. Cardiovascular effects of epinephrine during rewarming from hypothermia in an intact animal model. J Appl Physiol (1985) 2006; 100:457-64. [PMID: 16210439 DOI: 10.1152/japplphysiol.00356.2005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rewarming from accidental hypothermia is often complicated by “rewarming shock,” characterized by low cardiac output (CO) and a sudden fall in peripheral arterial pressure. In this study, we tested whether epinephrine (Epi) is able to prevent rewarming shock when given intravenously during rewarming from experimental hypothermia in doses tested to elevate CO and induce vasodilation, or lack of vasodilation, during normothermia. A rat model designed for circulatory studies during experimental hypothermia and rewarming was used. A total of six groups of animals were used: normothermic groups 1, 2, and 3 for dose-finding studies, and hypothermic groups 4, 5, and 6. At 20 and 24°C during rewarming, group 4 (low-dose Epi) and group 5 (high-dose Epi) received bolus injections of 0.1 and 1.0 μg Epi, respectively. At 28°C, Epi infusion was started in groups 4 and 5 with 0.125 and 1.25 μg/min, respectively. Group 6 served as saline control. After rewarming, both CO and stroke volume were restored in group 4, in contrast to groups 5 and 6, in which both CO and stroke volume remained significantly reduced (30%). Total peripheral resistance was significantly higher in group 5 during rewarming from 24 to 34°C, compared with groups 4 and 6. This study shows that, in contrast to normothermic conditions, Epi infused during hypothermia induces vasoconstriction rather than vasodilation combined with lack of CO elevation. The apparent dissociation between myocardial and vascular responses to Epi at low temperatures may be related to hypothermia-induced myocardial failure and changes in temperature-dependent adrenoreceptor affinity.
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Affiliation(s)
- T V Kondratiev
- Dept. of Medical Physiology, Institute of Medical Biology, Univ. of Tromsø, 9037 Tromsø, Norway.
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Aasum E, Larsen TS. Different tolerance to hypothermia and rewarming of isolated rat and guinea pig hearts. Cryobiology 1999; 38:243-9. [PMID: 10328914 DOI: 10.1006/cryo.1999.2165] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the effect of hypothermia and rewarming on myocardial function and calcium control in Langendorff-perfused hearts from rat and guinea pig. Both rat and guinea pig hearts demonstrated a rise in myocardial calcium ([Ca]total) in response to hypothermic perfusion (40 min, 10 degrees C), which was accompanied by an increase in left ventricular end diastolic pressure (LVEDP). The elevation in [Ca]total was severalfold higher in guinea pig than in rat hearts, reaching 12.9 +/- 0.8 and 3.1 +/- 0.6 micromol.g dry wt-1, respectively. The rise in LVEDP, however, was comparable in the two species: 62.5 +/- 2.5 (guinea pig) and 52.5 +/- 5.1 mm Hg (rat). Following rewarming, [Ca]total remained elevated in guinea pig, whereas a moderate decline in [Ca]total was observed in the rat (13.6 +/- 1.9 and 2.2 +/- 0.3 micromol.g dry wt-1, respectively). Posthypothermic values of LVEDP were also significantly higher in guinea pig compared to rat hearts (42.5 +/- 6.8 vs 20.5 +/- 5.1 mm Hg, P < 0.027). Furthermore, whereas rat hearts demonstrated a 78 +/- 7% recovery of left ventricular developed pressure, there was only a 15 +/- 7% recovery in guinea pig hearts. Measurements of tissue levels of high energy phosphates and glycogen utilization indicated a higher metabolic requirement in guinea pig than in rat hearts in order to oppose the hypothermia-induced calcium load. Thus, we conclude that isolated guinea pig hearts are more sensitive to a hypothermic insult than rat hearts.
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Affiliation(s)
- E Aasum
- Faculty of Medicine, University of Tromsø, Tromsø, 9037, Norway
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