Left ventricular venting during extracorporeal membrane oxygenation; the effects on cardiac performance in a porcine model of critical post-cardiotomy failure.

INTRODUCTION: Left ventricular distension is a major concern with postcardiotomy veno-arterial extracorporeal membrane oxygenation (VA-ECMO) supporting a critical heart failure after cardiac surgery. This porcine study evaluates the effects of left ventricular venting on cardiac function during ECMO-supported circulation and after weaning from ECMO. METHODS: Twenty anaesthetised open-chest pigs were put on cardiopulmonary bypass with aortic cross-clamping and suboptimal cardioplegic arrest for 40 min. After declamping and defibrillation, the animals were supported by VA-ECMO for 180 min either with or without additional left ventricular venting. Continuous haemodynamic evaluations were performed at baseline and at cardiac arrest, during VA-ECMO and for 120 min after weaning from circulatory support. Left ventricular perfusion and function were evaluated with microspheres, pressure-volume loops and epicardial echocardiography at baseline and after 1 and 2 h with unsupported circulation. RESULTS: In vented animals both mean aortic and left ventricular peak systolic pressure increased at the end of the ECMO-supported period compared to those not vented and remained increased also after weaning. Both at 60 min and 120 min after weaning from circulatory support, left ventricular stroke work and pressure-volume area were increased in vented compared to not vented animals. At 120 min left ventricular stroke volume was increased in vented compared to not vented animals, myocardial perfusion did not differ. The left ventricular mechanical efficiency, defined as the ratio between pressure volume area and myocardial perfusion, was increased (53.2 ± 5 vs 36.2 ± 2.1 J/mL/g, p = 0.011) in vented- compared to not vented hearts. CONCLUSION: This experimental study demonstrate that left ventricular venting during post-cardiotomy veno-arterial ECMO for 3 h attenuates deterioration of left ventricular function and haemodynamics early after weaning from circulatory support.

Myocardial perfusion and cardiac dimensions during extracorporeal membrane oxygenation-supported circulation in a porcine model of critical post-cardiotomy failure.

INTRODUCTION: Venoarterial extracorporeal membrane oxygenation is widely used as mechanical circulatory support for severe heart failure. A major concern with this treatment modality is left ventricular distension due to inability to overcome the afterload created by the extracorporeal membrane oxygenation circuit. The present porcine study evaluates coronary circulation, myocardial perfusion and ventricular distension during venoarterial extracorporeal membrane oxygenation. METHODS: Ten anesthetized open-chest pigs were cannulated and put on cardiopulmonary bypass. Heart failure was achieved by 90 minutes of aortic cross-clamping with insufficient cardioplegic protection. After declamping, the animals were supported by venoarterial extracorporeal membrane oxygenation for 3 hours. Continuous haemodynamic measurements were performed at baseline, during cardiopulmonary bypass/aortic cross-clamping and during venoarterial extracorporeal membrane oxygenation. Fluorescent microsphere injections at baseline and after 1, 2 and 3 hours on venoarterial extracorporeal membrane oxygenation evaluated myocardial perfusion. Left ventricular function and distension were assessed by epicardial echocardiography. RESULTS: The myocardial injury caused by 90 minutes of ischaemia resulted in a poorly contracting myocardium, necessitating venoarterial extracorporeal membrane oxygenation in all animals. The circulatory support maintained the mean arterial blood pressure within a satisfactory range. A hyperaemic left anterior descending coronary artery flow while on extracorporeal membrane oxygenation was observed compared to baseline. Myocardial tissue perfusion measured by microspheres was low, especially in the subendocardium. Echocardiography revealed myocardial tissue oedema, a virtually empty left ventricle, and a left ventricular output that remained negligible throughout the extracorporeal membrane oxygenation run. CONCLUSION: Coronary artery blood flow is maintained during venoarterial extracorporeal membrane oxygenation after cardiopulmonary bypass and cardioplegic arrest despite severely affected performance of the left ventricle. Myocardial perfusion decreases, however, presumably due to rapid development of myocardial tissue oedema.

Is the use of hydroxyethyl starch as priming solution during cardiac surgery advisable? A randomized, single-center trial.

INTRODUCTION: The use of cardiopulmonary bypass (CPB) leads to increased fluid filtration and edema. The use of artificial colloids to counteract fluid extravasation during cardiac surgery is controversial. Beneficial effects on global fluid loading, leading to better cardiac performance and hemodynamics, have been claimed. However, renal function and coagulation may be adversely affected, with unfavorable impact on outcome following cardiac surgery. METHODS: Forty patients were randomly allocated to study groups receiving either acetated Ringer's solution (CT group) or hydroxyethyl starch (HES group, Tetraspan®) as CPB priming solution. Fluid balance, bleeding and hemodynamics, including cardiac output, were followed postoperatively. The occurrence of acute kidney injury was closely registered. RESULTS: Two patients were excluded from further analyzes due to surgical complications. Fluid accumulation was attenuated in the HES group (3374 (883) ml) compared with the CT group (4328 (1469) ml) (p=0.024). The reduced perioperative fluid accumulation was accompanied by an increased cardiac index immediately after surgery (2.7 (0.4) L/min/m2 in the HES group and 2.1 (0.3) L/min/m2 in the CT group (p<0.001)). No increase in bleeding could be demonstrated in the HES group. Three patients, all of them in the HES group, experienced acute kidney injury postoperatively. CONCLUSIONS: CPB priming with HES solution lowers fluid loading during bypass and improves cardiac function in the early postoperative period. The manifestation of acute kidney injury exclusively in the HES group of patients raises doubts about the use of HES products in conjunction with cardiac surgery. ( https://clinicaltrials.gov/ct2/show/NCT01511120 ).

Microvascular fluid exchange during CPB with deep hypothermia circulatory arrest or low flow.

OBJECTIVE: Use of deep hypothermic low-flow (DHLF) cardiopulmonary bypass (CPB) has been associated with higher fluid loading than the use of deep hypothermia circulatory arrest (DHCA). We evaluated whether these perfusion strategies influenced fluid extravasation rates and edema generation differently per-operatively. MATERIALS AND METHODS: Twelve anesthetized pigs, randomly allocated to DHLF (n = 6) or DHCA (n = 6), underwent 2.5 hours CPB with cooling to 20°C for 30 minutes (min), followed by 30 min arrested circulation (DHCA) or 30 min low-flow circulation (DHLF) before 90 min rewarming to normothermia. Perfusion of tissues, fluid requirements, plasma volumes, colloid osmotic pressures and total tissue water contents were recorded and fluid extravasation rates calculated. During the experiments, cerebral microdialysis was performed in both groups. RESULTS: Microvascular fluid homeostasis was similar in both groups, with no between-group differences, reflected by similar fluid extravasation rates, plasma colloid osmotic pressures and total tissue water contents. Although extravasation rates increased dramatically from 0.10 (0.11) ml/kg/min (mean with standard deviation in parentheses) and 0.16 (0.02) ml/kg/min to 1.28 (0.58) ml/kg/min and 1.06 (0.41) ml/kg/min (DHCA and DHLF, respectively) after the initiation of CPB, fluid filtrations during both cardiac arrest and low flow were modest and close to baseline values. Cerebral microdialysis indicated anaerobic metabolism and ischemic brain injury in the DHCA group. CONCLUSION: No differences in microvascular fluid exchange could be demonstrated as a direct effect of DHCA compared with DHLF. Thirty minutes of DHCA was associated with anaerobic cerebral metabolism and possible brain injury.

Isoflurane in contrast to propofol promotes fluid extravasation during cardiopulmonary bypass in pigs.

BACKGROUND: A highly positive intraoperative fluid balance should be prevented as it negatively impacts patient outcome. Analysis of volume-kinetics has identified an increase in interstitial fluid volume after crystalloid fluid loading during isoflurane anesthesia. Isoflurane has also been associated with postoperative hypoxemia and may be associated with an increase in alveolar epithelial permeability, edema formation, and hindered oxygen exchange. In this article, the authors compare fluid extravasation rates before and during cardiopulmonary bypass (CPB) with isoflurane- versus propofol-based anesthesia. METHODS: Fourteen pigs underwent 2 h of tepid CPB with propofol (P-group; n = 7) or isoflurane anesthesia (I-group; n = 7). Fluid requirements, plasma volume, colloid osmotic pressures in plasma and interstitial fluid, hematocrit levels, and total tissue water content were recorded, and fluid extravasation rates calculated. RESULTS: Fluid extravasation rates increased in the I-group from the pre-CPB level of 0.27 (0.13) to 0.92 (0.36) ml·kg·min, but remained essentially unchanged in the P-group with significant between-group differences during CPB (pb = 0.002). The results are supported by corresponding changes in interstitial colloid osmotic pressure and total tissue water content. CONCLUSIONS: During CPB, isoflurane, in contrast to propofol, significantly contributes to a general increase in fluid shifts from the intravascular to the interstitial space with edema formation and a possible negative impact on postoperative organ function.

Effects of Add-On Left Ventricular Assist Device to Extracorporeal Membrane Oxygenation During Refractory Cardiac Arrest in a Porcine Model.

This study evaluated the effects of extracorporeal membrane oxygenation (ECMO) in combination with a percutaneous adjunctive left ventricular assist device (LVAD) in a porcine model during 60 minutes of refractory cardiac arrest (CA). Twenty-four anesthetized swine were randomly allocated into three groups given different modes of circulatory assist: group 1: ECMO 72 ml/kg/min and LVAD; group 2: ECMO 36 ml/kg/min and LVAD; and group 3: ECMO 72 ml/kg/min. During CA and extracorporeal cardiopulmonary resuscitation (ECPR), mean left ventricular pressure (mLVP) was lower in group 1 (p = 0.013) and in group 2 (p = 0.003) versus group 3. Mean aortic pressure (mAP) and coronary perfusion pressure (CPP) were higher in group 1 compared with the other groups. In group 3, mean pulmonary artery flow (mPAf) was lower versus group 1 (p = 0.003) and group 2 (p = 0.039). If the return of spontaneous circulation (ROSC) was achieved after defibrillation, up to 180 minutes of unsupported observation followed. All subjects in groups 1 and 3, and 5 subjects in group 2 had ROSC. All subjects in group 1, five in group 2 and four in group 3 had sustained cardiac function after 3 hours of spontaneous circulation. Subjects that did not achieve ROSC or maintained cardiac function post-ROSC had lower mAP (p < 0.001), CPP (p = 0.002), and mPAf (p = 0.004) during CA and ECPR. Add-on LVAD may improve hemodynamics compared with ECMO alone during refractory CA but could not substitute reduced ECMO flow. Increased mAP and CPP could be related to ROSC rate and sustained cardiac function. Increased mLVP was related to poor post-ROSC cardiac function.

Balanced Biventricular Assist Versus Extracorporeal Membrane Oxygenation in Cardiac Arrest.

Mechanical assist devices in refractory cardiac arrest are increasingly employed. We compared the hemodynamics and organ perfusion during cardiac arrest with either veno-arterial extracorporeal membrane oxygenation (ECMO) or biventricular assisted circulation combining left- and right-sided impeller devices (BiPella) in an acute experimental setting. Twenty pigs were randomized in two equal groups receiving circulatory support either by ECMO or by BiPella during 40 minutes of ventricular fibrillation (VF) followed by three attempts of cardioversion, and if successful, 60 minute observation with spontaneous, unsupported circulation. Hemodynamic variables were continuously recorded. Tissue perfusion was evaluated by fluorescent microsphere injections. Cardiac function was visualized by intracardiac echocardiography. During VF device output, carotid flow, kidney perfusion, mean aortic pressure (AOPmean), and mean left ventricular pressure (LVPmean) were all significantly higher in the ECMO group, and serum-lactate values were lower compared with the BiPella group. No difference in myocardial or cerebral perfusion was observed between groups. In 15 animals with sustained cardiac function for 60 minutes after return of spontaneous circulation, left ventricular subendocardial blood flow rate averaged 0.59 ± 0.05 ml/min/gm during VF compared with 0.31 ± 0.07 ml/min/gm in five animals with circulatory collapse (p = 0.005). Corresponding values for the midmyocardium was 0.91 ± 0.06 vs. 0.65 ± 0.15 ml/min/gm (p = 0.085). Both BiPella and ECMO could sustain vital organ function. ECMO provided a more optimal systemic circulatory support related to near physiologic output. Myocardial tissue perfusion and sustained cardiac function were related to coronary perfusion pressure during VF, irrespective of mode of circulatory support.

Esmolol before 80 min of cardiac arrest with oxygenated cold blood cardioplegia alleviates systolic dysfunction. An experimental study in pigs.

OBJECTIVE: Myocardial dysfunction after reperfusion can be a clinical problem in the early postoperative phase after on-pump cardiac surgery. The aim was, in an experimental setting, to investigate if administration of the beta-adrenergic receptor blocker esmolol prior to cross-clamping for 80 min with cold oxygenated blood cardioplegia would improve myocardial protection and early postoperative function. METHODS: Twenty-four anaesthetised pigs were randomly allocated into one of two equally sized groups and put on mild hypothermic cardiopulmonary bypass. Esmolol 1 mg kg(-1) or saline was administered into the arterial line 4 min prior to aortic cross-clamp. Cardiac arrest during 80 min of cross-clamp was obtained with repeated antegrade cold oxygenated blood cardioplegia; the pigs were weaned from bypass following a standardised protocol. Left ventricular global and regional myocardial function and tissue blood flow were evaluated with conductance catheter, echocardiography and coloured microspheres at baseline and at 1, 2 and 3 h after declamping. Four animals did not fulfil the protocol and were excluded. RESULTS: No significant differences between groups could be demonstrated for left ventricular global and local function and tissue blood flow at baseline. At 1h after declamping the slope of preload recruitable stroke work (PRSW(slope)) averaged 73.7+/-12.7 mm Hg (SD) in controls and 72.7+/-11.1 mm Hg in esmolol-treated animals. In controls PRSW(slope) decreased to 62.1+/-11.0 and 58.4+/-12.7 mm Hg after 2 and 3h, respectively (p<0.005 vs 1h for both). In the esmolol-treated animals PRSW(slope) remained unchanged at 72.0+/-11.4 and 73.7+/-12.9 mm Hg at 2 and 3 h after declamp and were significantly higher (p<0.025 and <0.001) than the corresponding values in the control group. The slope of the end systolic pressure volume relationship did not differ between groups at 1 and 2 h after declamp, but were 1.85+/-0.86 and 2.51+/-0.96 mm Hg ml(-1) in controls and in esmolol-treated animals, respectively, after 3h (p<0.025). CONCLUSIONS: Esmolol administered prior to cold oxygenated cardioplegic arrest alleviates left ventricular dysfunction in the early hours after cardiopulmonary bypass.

Left Versus Biventricular Assist Devices in Cardiac Arrest.

Maintaining adequate organ perfusion during cardiac arrest remains a challenge, and various assist techniques have been evaluated. We assessed whether a right ventricular impeller assist device (RVAD) in adjunct to a left ventricular impeller assist device (LVAD) is beneficial. Twenty anesthetized pigs were randomized to maximized circulatory support by percutaneously implanted left- or biventricular assist device(s) during 30 minutes of electrically induced ventricular fibrillation followed by three attempts of cardioversion. Continuous hemodynamic variables were recorded. Cardiac output and myocardial, cerebral, renal, and ileum mucosa tissue perfusion were measured with fluorescent microspheres, and repeated blood gas analyses were obtained. With biventricular support, an increased LVAD output was found compared with left ventricular (LV) support; 3.2 ± 0.2 (SEM) vs. 2.0 ± 0. 2 L/minute just after start of ventricular fibrillation, 3.2 ± 0.1 vs. 2.0 ± 0.1 L/minute after 15 minutes, and 3.0 ± 0.1 vs. 2.1 ± 0.1 L/minute after 30 minutes of cardiac arrest (pg < 0.001). Biventricular support also increased aortic and LV pressure, in addition to end-tidal CO2. Tissue blood flow rates were increased for most organs with biventricular support. Blood gas analyses showed improved oxygenation and lower s-lactate values. However, myocardial perfusion was degraded with biventricular support and return of spontaneous circulation less frequent (5/10 vs. 10/10; p = 0.033). Biventricular support was associated with high intraventricular pressure and decreased myocardial perfusion pressure, correlating significantly with flow rates in the LV wall. A transmural flow gradient was observed for both support modes, with better maintained subepicardial than midmyocardial and subendocardial perfusion.

Does Roller Pump-Induced Pulsatile CPB Perfusion Affect Microvascular Fluid Shifts and Tissue Perfusion?

BACKGROUND: Pulsatile versus nonpulsatile cardiopulmonary bypass (CPB) perfusion remains debated. Beneficial effects on tissue perfusion, inflammation, and microvascular fluid exchange have been linked to pulsatile perfusion by some investigators and denied by others. This study evaluated fluid extravasation and tissue perfusion during nonpulsatile or pulsatile roller pump-induced CPB perfusion. METHODS: Fourteen pigs underwent roller pump-induced pulsatile (n = 7) or nonpulsatile CPB perfusion (n = 7) for 90 minutes. Fluid input/losses, colloid osmotic pressures (plasma/interstitium), hematocrit, serum electrolytes, serum proteins, tissue perfusion, and total tissue water content were measured, and plasma volume and fluid extravasation were calculated. RESULTS: Fluid additions/losses, plasma volume, and fluid extravasation changed similarly in both groups during CPB with no between-group differences. Neither was between-group differences observed for tissue perfusion and total tissue water content, with one exception. Total tissue water content of the right (3.92 ± 0.26 versus 4.32 ± 0.28 g/g dry weight) and left ventricle (4.02 ± 0.25 versus 4.33 ± 0.24 g/g dry weight) was lowered in the pulsatile group. CONCLUSIONS: No important differences were found between pulsatile and nonpulsatile CPB perfusion for microvascular fluid balance and tissue perfusion.

Intraaortic counterpulsation during cardiopulmonary bypass impairs distal organ perfusion.

BACKGROUND: Recent studies have focused on the use of fixed-rate intraaortic balloon pumping (IABP) during cardiopulmonary bypass (CPB) to achieve pulsatile flow. Because application of an IABP catheter may represent a functional obstruction within the descending aorta, we explored the effect of IABP-pulsed CPB-perfusion with special attention to perfusion above and below the IABP balloon. METHODS: Sixteen animals received an IABP catheter that remained turned off position (NP group, n = 8) or was switched to an automatic mode of 80 beats/min during CPB (PP group, n = 8). Flow-data and pressure-data were obtained above and below the IABP balloon. Tissue perfusion was evaluated by microspheres. RESULTS: IABP-pulsed CPB-perfusion, as assessed at 30 minutes on CPB, increased proximal mean aortic pressure (p < 0.05) and carotid artery blood flow (p < 0.001), but decreased distal mean aortic pressure (p < 0.001). The decrease of distal mean aortic pressure in the PP group was associated with a 75 % decrease (p < 0.001) of renal tissue perfusion. During nonpulsed perfusion the respective variables remained essentially unchanged compared with pre-CPB levels. CONCLUSIONS: Using IABP as a surrogate to achieve pulsatile perfusion during CPB contributes significantly to lowered aortic pressure in the distal portion of aorta and impaired tissue perfusion of the kidneys. The results are focusing on effects that may contribute to organ dysfunction and acute kidney injury. Consequently, assessment of perfusion pressure distal to the balloon should be addressed whenever IABP is used during CPB.

Microvascular fluid exchange during pulsatile cardiopulmonary bypass perfusion with the combined use of a nonpulsatile pump and intra-aortic balloon pump.

OBJECTIVE: To evaluate how pulsed versus nonpulsed cardiopulmonary bypass influences microvascular fluid exchange in an experimental setup combining a nonpulsatile perfusion pump and an intra-aortic balloon pump. METHODS: A total of 16 pigs were randomized to pulsatile cardiopulmonary bypass perfusion with an intra-aortic balloon pump switched to an automatic 80 beats/min mode after the start of cardiopulmonary bypass (pulsatile perfusion [PP] group, n = 8) or to nonpulsatile cardiopulmonary bypass with the pump switched to the off position (nonpulsatile [NP] group, n = 8). Normothermic cardiopulmonary bypass was initiated after 60 minutes of stabilization and continued for 3 hours. The fluid needs, plasma volume, colloid osmotic pressure in plasma, colloid osmotic pressure in interstitial fluid, hematocrit, and total tissue water content were recorded, and the protein masses and fluid extravasation rates were calculated. RESULTS: After cardiopulmonary bypass was started, the mean arterial pressure increased in the PP group and decreased in the NP group. At 180 minutes, the mean arterial pressure of the PP and NP groups was 70.9 ± 2.7 mm Hg and 55.9 ± 2.7 mm Hg, respectively (P = .004). The central venous pressure (right atrium) had decreased in the NP group (P = .002). A decreasing trend was seen in the PP group. No between-group differences were present. The hematocrit and colloid osmotic pressure in plasma and interstitial fluid had decreased similarly in both study groups during cardiopulmonary bypass. The plasma volume of the PP group had decreased initially but then returned gradually to precardiopulmonary bypass levels. In the NP group, the plasma volume remained contracted (P = .02). No significant differences in the fluid extravasation rate were obtained. The fluid extravasation rate of the PP group tended to stay slightly higher than the fluid extravasation rate of the NP group at all measurement intervals. The total tissue water content increased significantly in a number of organs compared with that in the control animals. However, differences in the total tissue water content between pulsed and nonpulsed perfusion were absent. CONCLUSIONS: No significant differences in the fluid extravasation rates were present between pulsed and nonpulsed cardiopulmonary bypass perfusion in the present experimental setup.

Multidose cold oxygenated blood is superior to a single dose of Bretschneider HTK-cardioplegia in the pig.

BACKGROUND: A single-dose strategy for cardioplegia is desired in minimal invasive approaches to valve surgery and aortic arch repairs. We hypothesized that a single infusion of Bretschneider HTK solution offers myocardial protection comparable to repeated cold oxygenated blood. METHODS: Sixteen pigs on bypass with 60 minutes of aortic cross-clamping were randomized to a single dose of Custodiol (HTK group) or repeated oxygenated blood cardioplegia (CBC group). Left ventricular function and perfusion were evaluated by conductance catheter, echocardiography, and microspheres. Myocardial injury was assessed with serum troponin-T. RESULTS: Baseline values showed no group differences. One hour after declamping cardiac index was reduced in the HTK group, 3.5 +/- 0.2 L x min(-1) x m(-2) (mean +/- standard error of the mean) compared with 4.7 +/- 0.4 L x min(-1) x m(-2) in the CBC group (p < 0.0005), decreasing to 4.0 +/- 0.2 and 3.9 +/- 0.2 L x min(-1) x m(-2) after 2 and 3 hours, respectively (p < 0.005 versus 1 hour). In the HTK group cardiac index remained low and unchanged. In the CBC group preload recruitable stroke work was 72.6 +/- 1.2 mm Hg 1 hour after declamping, decreasing to 65.2 +/- 2.5 and 60.3 +/- 3.9 mm Hg after 2 and 3 hours, respectively (p < 0.05 versus 1 hour). In the HTK group corresponding values after 1, 2, and 3 hours were low at 47.2 +/- 4.4, 48.4 +/- 4.2, and 50.7 +/- 4.3 mm Hg, respectively (p < 0.025 versus CBC for all). Subendocardial radial peak systolic strain averaged 80.5% +/- 4.8% after declamping in the CBC group versus 53.4% +/- 5.5% in the HTK group (p = 0.002). Serum troponin-T release was lower in the CBC group. CONCLUSIONS: Repeated oxygenated blood cardioplegia provides better myocardial protection and preservation of left ventricular function than a single dose of HTK during the early hours after declamping.

Fluid overload during cardiopulmonary bypass is effectively reduced by a continuous infusion of hypertonic saline/dextran (HSD).

OBJECTIVE: Cardiopulmonary bypass (CPB) is associated with fluid overload. We examined how a continuous infusion of hypertonic saline/dextran (HSD) influenced fluid shifts during CPB. MATERIALS AND METHODS: Fourteen animals were randomized to a control-group (CT-group) or a hypertonic saline/dextran-group (HSD-group). Ringer's solution was used as CPB-prime and as maintenance fluid at a rate of 5 ml/kg/h. In the HSD group, 1 ml/kg/h of the maintenance fluid was substituted with HSD. After 60 min of normothermic CPB, hypothermic CPB was initiated and continued for 90 min. Fluid was added to the CPB-circuit as needed to maintain a constant level in the venous reservoir. Fluid balance, plasma volume, total tissue water (TTW), intracranial pressure (ICP) and fluid extravasation rates (FER) were measured/calculated. RESULTS: In the HSD-group the fluid need was reduced with 60% during CPB compared with the CT-group. FER was 0.38(0.06) ml/kg/min in the HSD-group and 0.74 (0.16) ml/kg/min in the CT-group. TTW was significantly lower in the heart and some of the visceral organs in the HSD-group. In this group ICP remained stable during CPB, whereas an increase was observed in the CT-group (p<0.01). CONCLUSIONS: A continuous infusion of HSD reduced the fluid extravasation rate and total fluid gain during CPB. TTW was reduced in the heart and some visceral organs. During CPB ICP remained normal in the HSD-group, whereas an increase was present in the CT-group. No adverse effects were observed.

Mean arterial pressure about 40 mmHg during CPB is associated with cerebral ischemia in piglets.

OBJECTIVE: To investigate if a mean arterial pressure below 50 mmHg during CPB may lead to cerebral ischemia. MATERIAL AND METHODS: Piglets with low mean arterial pressure by nitroprusside (LP-group) (n=6) were compared with piglets given norepinephrine to obtain high pressure (HP-group) (n=6) during normothermic and hypothermic CPB. Intracranial pressure, flow and markers of cerebral energy metabolism (microdialysis) were recorded. RESULTS: Mean arterial pressure differed significantly between the groups and stabilized about 40-45 mmHg in the LP-group. Cerebral perfusion pressure decreased to 21.3 (7.7) mmHg in the LP-group and increased to 51.8 (11.2) mmHg in the HP-group at 150 min of CPB (P<0.001, between groups). During bypass the intracerebral glucose concentration decreased significantly in the LP-group. In this group the lactate/pyruvate ratio increased from 15.5 (5.3) to 64.5 (87.6) at 90 min and 45.0 (36.5) at 150 min (P<0.05) with no such changes in the HP-group. Similarly the cerebral glycerol concentration increased significantly in the LP-group, whereas glycerol remained stable in the HP-group. CONCLUSION: Mean arterial pressure about 40 mmHg during CPB is associated with cerebral ischemia.