Fluid filtration and vascular compliance during cardiopulmonary bypass: effects of two volatile anesthetics.

BACKGROUND: As intraoperative fluid accumulation may negatively impact post-operative organ function, strategies minimizing edema generation should be sought for. During general anesthesia, isoflurane in contrast to sevoflurane has been associated with increased fluid extravasation and edema generation. In this study, we tested sevoflurane against isoflurane with focus on vascular compliance and fluid shifts in an experimental cardiopulmonary bypass (CPB) model. METHODS: Sixteen pigs underwent 120 min of cardiopulmonary bypass with isoflurane or sevoflurane anesthesia. Net fluid balance, plasma volume, serum-electrolytes, serum-albumin, serum-protein, colloid osmotic pressures in plasma and interstitial fluid, hematocrit levels, and total tissue water content were recorded. Intra-abdominal and intracranial pressures were measured directly, and fluid extravasation rates were calculated. RESULTS: Fluid extravasation rate increased dramatically in both groups during initiation of cardiopulmonary bypass, with no group differences. The animals of the sevoflurane group needed significantly more fluid supplementation to maintain a constant reservoir volume in the CPB circuit during bypass. Plasma volumes prior to bypass were 56.5 ± 7.9 ml/kg (mean ± SD) and 58.7 ± 3.8 ml/kg in the isoflurane group and sevoflurane group, respectively. During bypass, plasma volumes in the isoflurane group decreased about 25%, and remained significantly lowered when compared to the sevoflurane group, where the values remained stable. CONCLUSIONS: No differences in fluid extravasation rates were observed between sevoflurane and isoflurane. The increased net fluid balance in the sevoflurane group during cardiopulmonary bypass was not associated with edema generation. Plasma volume was retained in the sevoflurane group, in contrast to the isoflurane group.

Does ß2-adrenergic stimulation attenuate fluid extravasation during hypothermic cardiopulmonary bypass? An experimental study in pigs.

OBJECTIVES: Hypothermic cardiopulmonary bypass (CPB) is associated with increased fluid filtration, edema formation and, occasionally, organ dysfunction. Cold-induced reduction in endothelial barrier function may play a role. ß(2)-adrenergic activation elevates cellular cyclic adenosine monophosphate (cAMP) which maintains endothelial barrier properties. In this study, we tested whether ß-adrenergic stimulation could influence the increase in fluid extravasation observed during hypothermic CPB. MATERIALS AND METHODS: Fourteen pigs randomly received terbutaline infusion (T-group) (n=7) or a control infusion (C-group) (n=7). All animals were given 60 min of normothermic CPB, followed by 90 min of hypothermic CPB. Fluid input and losses, plasma volume, colloid osmotic pressures (plasma, interstitial fluid), hematocrit, serum proteins and total tissue water content were measured and the fluid extravasation rates (FER) calculated. STATISTICS: by SPSS. Values presented as mean ± SD. Repeated measure analysis of variance was performed and a t-test used when appropriate. RESULTS: The commencement of normothermic CPB resulted in a 20% hemodilution, with an abrupt increase in fluid requirements during the first 10 min. FER increased from 0.18 (0.06) pre-bypass to 0.78 (0.27) ml/kg/min (T-group) (p=0.002) and from 0.16 (0.05) to 0.93 (0.26) ml/kg/min (C-group) (p<0.001) with no between-group differences. Thereafter, FER stabilized at a level of 0.32 (0.13) and 0.27 (0.14) ml/kg/min in the T-group and C-group, respectively. After the start of cooling, FER increased in the T-group to 0.55 (0.12) ml/kg/min (P=0.046) and in the C-group to 0.54 (0.13) ml/kg/min (P=0.006), with no between-group differences (P=0.738). CONCLUSION: In the present experimental study, we were unable to demonstrate any clinically relevant modulating effect of terbutaline on fluid extravasation during hypothermic cardiopulmonary bypass.

Infusion of hypertonic saline/starch during cardiopulmonary bypass reduces fluid overload and may impact cardiac function.

OBJECTIVE: Peri-operative fluid accumulation resulting in myocardial and pulmonary tissue edema is one possible mechanism behind post-operative cardiopulmonary dysfunction. This study aimed to confirm an improvement of cardiopulmonary function by reducing fluid loading during an open-heart surgery. MATERIALS AND METHODS: Forty-nine elective CABG patients were randomized to an intraoperative infusion of hypertonic saline/hydroxyethyl starch (HSH group) or Ringer's solution (CT group). Both groups received 1 ml/kg/h of the study solution for 4 h after baseline values were obtained (PICCO transpulmonary thermodilution technique). Net fluid balance (NFB), hemodynamic and laboratory parameters were measured. RESULTS: NFB was four times higher in the CT group compared with the HSH group during the first 6 h post-operatively. The total fluid gain until the next morning was lower in the HSH group, 2993.9 (938.6) ml, compared with the CT group, 4298.7 (1059.3) ml (P<0.001). Normalized values (i.e., %-changes from the baseline) of the cardiac index and the global end diastolic volume index increased post-operatively in both groups. Both parameters were significantly higher at 6 h in the HSH group compared with CT group (P=0.002 and 0.005, respectively). Normalized values of the intrathoracic blood volume index were lower in the HSH group at 6 h post-operatively when compared with the CT group. The PaO(2)/FiO(2) ratio decreased similarly in both groups early post-operatively, but recovery tended to be more rapid in the HSH group. Although serum-sodium and serum-chloride levels were significantly higher in the HSH group, the acid-base parameters remained similar and within the normal range. CONCLUSIONS: An intraoperative infusion of HSH during cardiac surgery contributes to reduced fluid loading and an improvement in the post-operative cardiac performance. No adverse effects of the HSH infusion were observed.

A hyperosmolar-colloidal additive to the CPB-priming solution reduces fluid load and fluid extravasation during tepid CPB.

Cardiopulmonary bypass(CPB) is associated with fluid overload. We hypothesized that fluid gain during CPB could be reduced by substituting parts of a crystalloid prime with 7.2% hypertonic saline and 6% poly (O-2-hydroxyethyl) starch solution (HyperHaes). 14 animals were randomized to a control group (Group C) or to Group H. CPB-prime in Group C was Ringer's solution. In group H, 4 ml/kg of Ringer's solution was replaced by the hypertonic saline/hydroxyethyl starch solution. After 60 min stabilization, CPB was initiated and continued for 120 min. All animals were allowed drifting of normal temperature (39.0 degrees C) to about 35.0 degrees C. Fluid was added to the CPB circuit as needed to maintain a 300-ml level in the venous reservoir. Blood chemistry, hemodynamic parameters, fluid balance, plasma volume, fluid extravasation rate (FER), tissue water content and acid-base parameters were measured/calculated. Total fluid need during 120 min CPB was reduced by 60% when hypertonic saline/hydroxyethyl starch solution was added to the CPB prime (p < 0.01). The reduction was related to a lowered FER. The effect was most pronounced during the first 30 min on CPB, with 0.6 (0.43) (Group H) compared with 1.5 (0.40) ml/kg/min (Group C) (p < 0.01). Hemodynamics and laboratory parameters were similar in both groups. Serum concentrations of sodium and chloride increased to maximum levels of 148 (1.5) and 112 (1.6) mmol/l in Group H. To conclude: addition of 7.2% hypertonic saline and 6% poly (O-2-hydroxyethyl) starch solution to crystalloid CPB prime reduces fluid needs and FER during tepid CPB.

Reduced fluid gain during cardiopulmonary bypass in piglets using a continuous infusion of a hyperosmolar/hyperoncotic solution.

BACKGROUND: The aim of this study was to evaluate how a continuous infusion of a hyperosmolar/hyperoncotic solution influences fluid shifts and intracranial pressure during cardiopulmonary bypass in piglets. METHODS: Fourteen animals, randomized to the control (CT) group or the hypertonic saline/hydroxyethyl starch (HyperHaes) (HSH) group, received acetated Ringer's solution as prime and supplemental fluid. The HSH group received, in addition, HyperHaes 1 ml/kg/h. After 1 h of normothermic cardiopulmonary bypass, hypothermic cardiopulmonary bypass (28 degrees C) was initiated and continued for 90 min. Fluid balance, plasma volume, tissue water content, acid-base parameters and intracranial pressure were recorded, and protein masses and fluid extravasation rates were calculated. RESULTS: At the start of normothermic cardiopulmonary bypass, the fluid extravasation rates (ml/kg/min) increased from 0.19 (0.06) to 1.57 (0.71) and 0.19 (0.09) to 0.82 (0.14) in the CT and HSH groups, respectively, with no between-group differences (P = 0.081) During hypothermic cardiopulmonary bypass, the fluid extravasation rates (ml/kg/min) increased from 0.19 (0.14) to 0.51 (0.10) (P < 0.01) and 0.15 (0.08) to 0.33 (0.08) (P < 0.05), respectively, with significantly lower extravasation rates in the HSH group (P < 0.01). In the HSH group, the total fluid gain during cardiopulmonary bypass decreased by about 50% (P < 0.05) and the tissue water content was significantly lower in the left and right heart as well as in the lungs. The intracranial pressure remained stable in the HSH group, but increased in the CT group. CONCLUSIONS: A continuous infusion of HSH (HyperHaes) during cardiopulmonary bypass reduced the fluid extravasation rate and the total fluid gain during bypass. No electrolyte or acid-base disturbances were present. The intracranial pressure remained stable in the HSH group.

Low arterial pressure during cardiopulmonary bypass in piglets does not decrease fluid leakage.

BACKGROUND: Cardiopulmonary bypass (CPB) is associated with increased fluid filtration occasionally leading to post-operative organ dysfunction. One of the factors determining fluid filtration is the capillary hydrostatic pressure which depends on arterial pressure, venous pressure and pre- to post-capillary resistance ratio. The purpose of this study was to assess whether lowering of the mean arterial pressure and/or the central venous pressure could reduce fluid extravasation during normothermic and hypothermic CPB. METHODS: Seven piglets were given nitroprusside to a mean arterial pressure of 35-40 mmHg during 60 min of normothermic and 90 min of hypothermic CPB (LP group). They were compared with a control group (C group, n = 7) without blood pressure interventions. Blood chemistry, net fluid balance, plasma volume, colloid osmotic pressure in plasma and interstitial fluid, intravascular protein masses, fluid extravasation rate and total tissue water content were measured or calculated. RESULTS: Mean arterial pressure was significantly lower in the LP group than in the C group during CPB. Plasma volume tended to increase in the LP group (P > 0.05), but remained essentially unchanged in the C group. Net fluid balance in the LP group was more positive than in the C group 30 min after CPB start [1.02 (0.15) vs. 0.56 (0.13) ml/kg/min (Mean (SEM) P < 0.05)]. Fluid extravasation rate tended to be higher in the LP group and total tissue water content of the gastrointestinal tract, left myocardium and skin was significantly elevated compared with the C group. CONCLUSION: During CPB, lowering of the mean arterial pressure using nitroprusside did not reduce fluid extravasation. On the contrary, the data may implicate an increase in edema formation during low pressure CPB.