• Altered pharmacological effects of adrenergic agonists during hypothermia 

      Dietrichs, Erik Sveberg; Sager, Georg; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-05)
      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 ...
    • Autoregulation of Cerebral Blood Flow During 3-h Continuous Cardiopulmonary Resuscitation at 27°C 

      Valkov, Sergei; Nilsen, Jan Harald; Mohyuddin, Rizwan; Schanche, Torstein Lindahl; Kondratyev, Timofey; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-09)
      Introduction: Victims of accidental hypothermia in hypothermic cardiac arrest (HCA) may survive with favorable neurologic outcome if early and continuous prehospital cardiopulmonary resuscitation (CPR) is started and continued during evacuation and transport. The efficacy of cerebral autoregulation during hypothermic CPR is largely unknown and is aim of the present experiment.<p> <p>Methods: ...
    • Cardiovascular Effects of Epinephrine During Experimental Hypothermia (32°C) With Spontaneous Circulation in an Intact Porcine Model 

      Mohyuddin, Rizwan; Dietrichs, Erik Sveberg; Sundaram, Predip; Kondratiev, Timofei V.; Figenschou, Marie Fjellanger; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-06)
      <i>Aims</i>: Rewarming from accidental hypothermia and therapeutic temperature management could be complicated by cardiac dysfunction. Although pharmacologic support is often applied when rewarming these patients, updated treatment recommendations are lacking. There is an underlying deficiency of clinical and experimental data to support such interventions and this prevents the development of clinical ...
    • Comparison between two pharmacologic strategies to alleviate rewarming shock: vasodilation vs. inodilation 

      Håheim, Brage; Kondratyev, Timofey; Dietrichs, Erik Sveberg; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-12)
      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 ...
    • Continuous hemodynamic monitoring in an intact rat model of simulated diving 

      Gaustad, Svein Erik; Kondratyev, Timofey; Eftedal, Ingrid; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-13)
      Cardiovascular risk is elevated in divers, but detailed information of cardiac function during diving is missing. The aim of this study was to apply an intact rat model with continuous monitoring of cardiac left ventricular (LV) function in a simulated diving experiment. Thirteen rats were inserted with a LV pressure–volume catheter and a pressure transducer in the femoral artery to measure hemodynamic ...
    • Cooling to hypothermic circulatory arrest by immersion vs. cardiopulmonary bypass (CPB): Worse outcome after rewarming in immersion cooled pigs 

      Filseth, Ole Magnus; Hermansen, Stig Eggen; Kondratyev, Timofey; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-31)
      Introduction: Cooling by cardiopulmonary bypass (CPB) to deep hypothermic cardiac arrest (HCA) for cardiac surgical interventions, followed by CPB-rewarming is performed on a routine basis with relatively low mortality. In contrast, victims of deep accidental hypothermia rewarmed with CPB generally have a much worse prognosis. Thus, we have developed an intact pig model to compare effects on ...
    • Effects of cold decompression on hemodynamic function and DCS risk in a dry diving rat model 

      Gaustad, Svein Erik; Kondratyev, Timofey; Eftedal, Ingrid; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-03)
      Background: Diving in cold water is thought to increase the risk of decompression sickness (DCS), especially if the diver is cold during decompression. In this study, we investigated hemodynamic function and DCS risk in an animal model, where cold decompression was followed by rewarming at the surface. <p> <p>Methods: Nine female Sprague Dawley rats had pressure-volume catheters inserted into ...
    • Effects of Constant Flow vs. Constant Pressure Perfusion on Fluid Filtration in Severe Hypothermic Isolated Blood-Perfused Rat Lungs 

      Halsøy, Kathrine; Kondratyev, Timofey; Tveita, Torkjel; Bjertnæs, Lars J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-23)
      Victims of severe accidental hypothermia are prone to fluid extravasation but rarely develop lung edema. We hypothesize that combined hypothermia-induced increase in pulmonary vascular resistance (PVR) and a concomitant fall in cardiac output protect the lungs against edema development. Our aim was to explore in hypothermic- isolated blood-perfused rat lungs whether perfusion at constant ...
    • Effects of morphine or ketamine in rats with asphyxial cardiac arrest: a pilot study 

      Kuklin, Vladimir; Kondratyev, Timofey; Konkayeva, Maya; Akhatov, Nurlan; Sovershaev, Mikhail; Konkayev, Aidos; Tveita, Torkjel (Conference object; Konferansebidrag, 2017-05-06)
      Acute hypoxia results in uncontrolled release of glutamate and the consequent stimulation of N-methyl-D-aspartate (NMDA) receptors, which affects the whole ionic homeostasis and finally activates apoptosis of neurons. A potential therapeutic approach to prevent this sequence of events is a blockade of NMDA receptors. Meanwhile, in different models of acute hypoxia, activation of delta-opioid ...
    • Effects of rewarming with extracorporeal membrane oxygenation to restore oxygen transport and organ blood flow after hypothermic cardiac arrest in a porcine model 

      Nilsen, Jan Harald; Schanche, Torstein Lindahl; Valkov, Sergey; Mohyuddin, Rizwan; Håheim, Brage; Kondratyev, Timofey; Næsheim, Torvind; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-23)
      We recently documented that cardiopulmonary resuscitation (CPR) generates the same level of cardiac output (CO) and mean arterial pressure (MAP) during both normothermia (38 °C) and hypothermia (27 °C). Furthermore, continuous CPR at 27 °C provides O2 delivery (ḊO2) to support aerobic metabolism throughout a 3-h period. The aim of the present study was to investigate the effects of extracorporeal ...
    • Enhanced Blood Clotting After Rewarming From Experimental Hypothermia in an Intact Porcine Model 

      Schanche, Torstein Lindahl; Filseth, Ole Magnus; Østerud, Bjarne; Kondratyev, Timofey; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-29)
      Introduction: Due to functional alterations of blood platelets and coagulation enzymes at low temperatures, excessive bleeding is a well-recognized complication in victims of accidental hypothermia and may present a great clinical challenge. Still, it remains largely unknown if hemostatic function normalizes upon rewarming. The aim of this study was to investigate effects of hypothermia and rewarming ...
    • Extracorporeal rewarming from experimental hypothermia: Effects of hydroxyethyl starch versus saline priming on fluid balance and blood flow distribution 

      Schanche, Torstein Lindahl; Kondratyev, Timofey; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-29)
      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 ...
    • Functional recovery after accidental deep hypothermic cardiac arrest: Comparison of different cardiopulmonary bypass rewarming strategies 

      Filseth, Ole Magnus; Kondratyev, Timofey; Sieck, Gary C.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-05)
      Introduction: Using a porcine model of accidental immersion hypothermia and hypothermic cardiac arrest (HCA), the aim of the present study was to compare effects of different rewarming strategies on CPB on need for vascular fluid supply, level of cardiac restitution, and cerebral metabolism and pressures.<p> <p>Materials and Methods: Totally sixteen healthy, anesthetized castrated male pigs were ...
    • Hypothermia and cardiac electrophysiology: a systematic review of clinical and experimental data 

      Dietrichs, Erik Sveberg; Tveita, Torkjel; Smith, Godfrey L (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-13)
      Moderate therapeutic hypothermia procedures are used in post-cardiac arrest care, while in surgical procedures, lower core temperatures are often utilized to provide cerebral protection. Involuntary reduction of core body temperature takes place in accidental hypothermia and ventricular arrhythmias are recognized as a principal cause for a high mortality rate in these patients. We assessed both ...
    • The influences of morphine or ketamine pre-treatment on hemodynamic, acid-base status, biochemical markers of brain damage and early survival in rats after asphyxial cardiac arrest 

      Kuklin, Vladimir; Akhatov, Nurlan; Kondratiev, Timofei; Konkayev, Aidos; Baigenzhin, Abai K.; Konkayeva, Maiya; Karibekov, Temirlan; Barlow, Nicholas; Tveita, Torkjel; Dahl, Vegard (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-20)
      <i>Background</i> - In different models of hypoxia, blockade of opioid or N-methyl-D-aspartate (NMDA) receptors shows cardio- and neuroprotective effects with a consequent increase in animal survival. The aim of the study was to investigate effects of pre-treatment with Morphine or Ketamine on hemodynamic, acid-base status, early survival, and biochemical markers of brain damage in a rat model of ...
    • Maintaining intravenous volume mitigates hypothermia-induced myocardial dysfunction and accumulation of intracellular Ca2+ 

      Nilsen, Jan Harald; Schanche, Torstein; Kondratiev, Timofei V.; Hevrøy, Olav; Tveita, Torkjel; Sieck, Gary C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-17)
      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 Ca<sup>2+</sup> concentration ([Ca<sup>2+</sup>]<sub>i</sub>) in myocardial cells. The aim of the present study was to examine if maintaining euvolaemia ...
    • Moderate but not severe hypothermia causes pro-arrhythmic changes in cardiac electrophysiology 

      Dietrichs, Erik Sveberg; McGlynn, Karen; Allan, Andrew; Connolly, Adam; Bishop, Martin; Burton, Francis; Kettlewell, Sarah; Myles, Rachel; Tveita, Torkjel; Smith, Godfrey L (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-07)
      <i>Aims</i> - Treatment of arrhythmias evoked by hypothermia/rewarming remains challenging, and the underlying mechanisms are unclear. This <i>in vitro</i> experimental study assessed cardiac electrophysiology in isolated rabbit hearts at temperatures occurring in therapeutic and accidental hypothermia.<p><p> <i>Methods and results</i> - Detailed ECG, surface electrogram, and panoramic optical ...
    • A novel ECG-biomarker for cardiac arrest during hypothermia 

      Dietrichs, Erik Sveberg; Tveita, Torkjel; Myles, Rachel; Smith, Godfrey L (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-10)
      <i>Background</i> - Treatment of arrhythmias evoked by accidental or therapeutic hypothermia and rewarming remains challenging. We aim to find an ECG-biomarker that can predict ventricular arrhythmias at temperatures occurring in therapeutic and accidental hypothermia.<p><p> <i>Main body</i> - Evaluation of ECG-data from accidental and therapeutic hypothermia patients and experimental data on ECG ...
    • Physiological Changes in Subjects Exposed to Accidental Hypothermia: An Update 

      Bjertnaes, Lars J.; Næsheim, Torvind; Reierth, Eirik; Suborov, Evgeny; Kirov, Mikhail; Lebedinskii, Konstantin M.; Tveita, Torkjel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-23)
      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).<p> <p>Temperature Regulation and Metabolism: Triggered by falling skin temperature, Thyrotropin-Releasing Hormone (TRH) from hypothalamus induces ...
    • Physiological Impact of Hypothermia: The Good, the Bad, and the Ugly 

      Tveita, Torkjel; Sieck, Gary C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-22)
      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 ...