Abstract

The project is entitled «Studies on microvascular permeability, fluid exchange and hemodynamic alterations during cardiopulmonary bypass». Within a well-established porcine model it focus different aspects of cardiopulmonary bypass (CPB). CPB was introduced in heart surgery during the 1950`s. Still, CPB is performed worldwide and the principle of extracorporeal circulation is mandatory in order to facilitate open heart surgery. Despite technological advances during these years the technique is still hampered with undesirable effects such as fluid overload, tissue edema formation and postoperative vital  organ dysfunction. Consequently, the anesthetic- and bypass-techniques is still debated. The actual porcine model aims specifically on microvascular fluid extravasation but has additionally the potential to adapt, include and investigate other parameters of clinical relevance.

In the first study we evaluated microvascular fluid exchange during 3 hours on CPB with the combined use of a non-pulsatile bypass-pump and intra-aortic balloon pump (IABP), the latter used to generate pulsatility (16 pigs; 8 pulsatile group, 8 non-pulsatile group). No significant differences i fluid extravasation rates were observed. The study was published in 2013 (J Thorac Cardiovasc Surg. 2013; 146: 1275-82).

The second study is based upon data obtained from the comprehensive first study and evaluates the impact of IABP-pulsed perfusion on hemodynamics and microvascular tissue perfusion above and beneath the IABP-balloon. During IABP-pulsed perfusion, proximal aortic pressure increased, whereas distal aortic pressure decreased. The decrease in distal aortic pressure in the pulsatile group was associated with a 75% decrease (P<0.001) of renal perfusion. During non-pulsatile perfusion, both proximal and distal aortic pressure behaved similarly and essentially without any differences during CPB. The study is in preparation for submission to The Annals of Thoracic Surgery by May 2014.

A third study is dealing with two different anesthetic protocols applied during 2 h of general anesthesia during CPB. 14 pigs received either propofol (n=7) or isoflurane anesthesia (n=7). Fluid extravasation rates before and during extracorporeal circulation was determined. Administration of isoflurane during CPB, resulted in contrast to propofol, to a significant general increase in the fluid shifts from the vascular to the interstitial space with formation of  tissue edema affecting most organ systems tested. This study was published in 2013. (Anesthesiology. 2013; 119: 861-70).

The fourth and final study is scheduled to take place in September to November 2014. During these experiments we will further elucidate the concept of pulsatility during CPB by comparing a pulsatile versus non-pulsatile roller-pump-perfusion technique. Both perfusion modes are in common, clinical use during cardiac surgery worldwide.  In addition to microvascular fluid shifts during different perfusion modes, we will investigate hemodynamic aspects of pressure and flow, tissue perfusion (microspheres), platelet function and activation and as previously, cerebral metabolism and pressure and flow differences using the two different perfusion modes.