Fluid balance, oxygen transport and tissue perfusion during extracorporeal rewarming of pigs from deep hypothermic circulatory arrest.
In accordance with current domestic and international guidelines, hypothermic patients with cardiac instability is rewarmed by use of extracorporeal circulation (ECC). Although advocated by guidelines, scientific data on how to manage hypothermic patients on ECC is scarce. Both hypothermia per se, as well as the introduction of ECC give rise to major changes in blood flow and circulatory physiology. Through several mechanisms, hypothermia leads to a centralization of blood flow to vital organs and reduction of plasma- and blood volume at low temperatures. When initiating ECC on the hypothermic patient, this may lead to inadequate venous drainage and thereby difficulties in obtaining a sufficient blood flow during rewarming. The remedy for a low venous drainage is supplementary fluid additions to the extracorporeal circuit, which in turn can exacerbate fluid extravasation and lead to a fluid overload associated with organ dysfunction and adverse patient outcome.
Most traditional ECC-circuits are using a non-pulsatile, centrifugal pump, generating a non-phyisological continuous blood flow. Several recent studies have demonstrated beneficial effects on hemodynamics and systemic microcirculation using novel pumps generating a pulsatile blood flow.
A recent, unpublished study in our group comparing crystalloid and colloid priming solutions during extracorporeal rewarming of deep hypothermic rats, yielded interesting results concerning different effects on fluid balance and blood flow to vital organs during ECC. We intend to investigate these differences further, in a refined pig model of immersion cooling and extracorporeal rewarming.
All procedures in the planned experiment will be performed on pigs in surgical anaesthesia and the animals will be euthanized while still in anaesthesia. As it is not ethically possible to carry out these experiments on humans, other methods have to be used. Cell cultures or isolated in vitro methods are not suitable as this is an in vivo study looking at complex physiological mechanisms in the intact organism. Our research group have extensive experience doing similar research protocols on fully anesthetized animals. For this experimental protocol we apply for up to 48 pigs as described in detail in this application.
As our main objective is improved survival in victims of severe accidental hypothermia, the ambitions for this experimental study is:
1. Assess the effects of different fluid regimes on hemodynamics, fluid balance and oxygen transport during and after extracorporeal rewarming.
2. Assess the effects of different fluid regimes during and after ECC on microcirculation and tissue perfusion to vital organs.
3. Analyze the effect of pulsatile vs non-pulsatile pump flow during ECC on microcirculation and hemodynamics during rewarming
Thus, we intend to investigate the effects of different flow patterns and fluid regimes on fluid balance, microcirculation, oxygen transport and tissue perfusion during extracorporeal rewarming from deep hypothermic circulatory arrest (DHCA) in anaesthetised pigs.
Most traditional ECC-circuits are using a non-pulsatile, centrifugal pump, generating a non-phyisological continuous blood flow. Several recent studies have demonstrated beneficial effects on hemodynamics and systemic microcirculation using novel pumps generating a pulsatile blood flow.
A recent, unpublished study in our group comparing crystalloid and colloid priming solutions during extracorporeal rewarming of deep hypothermic rats, yielded interesting results concerning different effects on fluid balance and blood flow to vital organs during ECC. We intend to investigate these differences further, in a refined pig model of immersion cooling and extracorporeal rewarming.
All procedures in the planned experiment will be performed on pigs in surgical anaesthesia and the animals will be euthanized while still in anaesthesia. As it is not ethically possible to carry out these experiments on humans, other methods have to be used. Cell cultures or isolated in vitro methods are not suitable as this is an in vivo study looking at complex physiological mechanisms in the intact organism. Our research group have extensive experience doing similar research protocols on fully anesthetized animals. For this experimental protocol we apply for up to 48 pigs as described in detail in this application.
As our main objective is improved survival in victims of severe accidental hypothermia, the ambitions for this experimental study is:
1. Assess the effects of different fluid regimes on hemodynamics, fluid balance and oxygen transport during and after extracorporeal rewarming.
2. Assess the effects of different fluid regimes during and after ECC on microcirculation and tissue perfusion to vital organs.
3. Analyze the effect of pulsatile vs non-pulsatile pump flow during ECC on microcirculation and hemodynamics during rewarming
Thus, we intend to investigate the effects of different flow patterns and fluid regimes on fluid balance, microcirculation, oxygen transport and tissue perfusion during extracorporeal rewarming from deep hypothermic circulatory arrest (DHCA) in anaesthetised pigs.