| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
Interact CardioVasc Thorac Surg 2009;8:512-516. doi:10.1510/icvts.2008.198283 © 2009 European Association of Cardio-Thoracic Surgery
Risk factors for low colloid osmotic pressure during infant cardiopulmonary bypass with a colloidal primeDepartment of Cardiothoracic Surgery, Erasmus MC, University Medical Center Rotterdam, 's Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands Received 8 November 2008; received in revised form 30 December 2008; accepted 7 January 2009
*Corresponding author. Bd 467, Erasmus MC, 's Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. Tel.: +31 10 7035208.
Extensive variations of colloid osmotic pressure (COP) measured in the priming as well as during infant cardiopulmonary bypass motivated us to audit clinical and laboratory data to identify the risk factors for low COP at the end of bypass. Data of 73 consecutive infant patients with body weight <10 kg, who underwent elective, first time open-heart surgery between March 2005 and December 2006 were examined. The following variables were analyzed: COP, blood loss, transfusion requirements and hematological data. Univariate and multivariate analysis of risk factors for low COP (<15 mmHg) was performed. Forty-eight percent of patients had COP <15 mmHg at the end of bypass. Those patients had significantly lower COP before start of bypass, during, and at the end of the operation. Significant univariate predictors of low COP at the end of bypass were: lower patient weight; lower COP before start of bypass, lower priming COP and larger volume of cardioplegia received into the circulation. After multivariable analysis, lower patient COP before bypass remained the only significant predictor for low COP at the end of bypass. Pre-bypass crystalloid dilution during induction should be avoided, as this is the most important cause of low COP during the bypass. Priming COP and COP management strategy should be adapted to the individual patient demand.
Key Words: Cardiopulmonary bypass; Infant; Colloid osmotic pressure
Despite the latest minimalization of extracorporeal circuit for infant cardiopulmonary bypass (CPB) and reduction of its priming volume, severe hemodilution with dilution of plasma proteins may occur. Decrease of plasma colloid osmotic pressure (COP) favors a fluid shift from the intravascular space into the interstitial space that consequently augments total body water and enhances the risk of multiple organ failure [1]. During the perioperative period, any estimation of the COP from the total plasma protein or albumin level would be altered by infusion therapy [2–4]. Therefore, the importance of direct measurement of COP during open-heart surgery in children is widely acknowledged [5]. Still, the effects of colloidal or crystalloid priming solutions are predominantly studied in adult patients [6, 7] and remarkably few data address this issue in pediatric patients [8, 9]. In our institution, priming of infant CPB circuit constituted of different colloidal solutions and the COP values were routinely measured. According to the pediatric protocol, human albumin solution was administrated during the bypass to manage COP at an appropriate level. Extensive variations of COP values measured in the priming as well as during the infant CPB motivated us to audit all clinical and laboratory data. The primary objective was to recognize patients prone to low COP at the end of bypass. Secondarily, we validated the existing protocol to propose the future adjustments of infant priming composition and COP regulation during the bypass.
An audit of clinical and laboratory data of consecutive infant patients with body weight (BW) <10 kg was conducted. All patients underwent elective, first time cardiac operation with CPB between March 2005 and December 2006. Patients with known clotting disorders (n=0) and procedures that required deep hypothermic circulatory arrest (n=6) were excluded from the study. Patients with COP measured at the end of CPB lower than 15 mmHg were appointed to Group Low COP, whereas all other patients were assigned to Group High COP. The same surgical, anesthesia and perfusion team performed all the operations. Collection and audit of the data was performed in compliance with the Hospital Data Protection Policy. 2.1. Infant CPB, anesthesia and anticoagulatin Infant CPB circuits consisted of a Capiox Baby Rx hollow-fiber oxygenator with hard-shell reservoir (Terumo, Tokyo, Japan), a roller pump and arterial filter. Tubing internal diameter was inch. The circuits were not coated. Circuit prime volume was 330 ml and contained homologous red blood cells (RBCs), fresh-frozen plasma (FFP) and Gelofusine (B. Braun, Melsungen, Germany). The amount of RBCs in the priming was calculated to achieve a hematocrit of 0.28 l/l during CPB. The prime was always completed with 0.5 g/kg BW mannitol, 0.5 g/kg BW human albumin 20% solution (Sanquin, Amsterdam, The Netherlands), 4.2 IU heparine/ml priming volume and 2–5 ml NaHCO3 8.4%.
Administration of RBCs, FFP, crystalloids or colloids during CPB was based upon the system working volumes and target values for hematocrit (not lower than 0.28 l/l for acyanotic as well as cyanotic patients). Human albumin was added to maintain the COP
All patients received standard general anesthesia. Activated clotting time was monitored during the bypass and maintained above 480 s. Non-pulsatile CPB, with mild hypothermia of 28–32° C, was performed with blood flow rates between 1.8 l/min/m2 to 3.2 l/min/m2 to maintain venous oxygen saturation above 70% and mean arterial pressure between 40 to 60 mmHg. During CPB COP measurements were taken from the CPB circuit before the start of bypass, after 5 min on bypass and at the end of the CPB. Additionally, patient's COP was measured at the start and at the end of the operation. Plasma COP was determined by the commercially available membrane osmometer Osmomat 050 (Gonotec, Berlin, Germany) using a membrane with molecular mass cut-off at 20 kDa. Blood loss, urine production and volume of perioperatively transfused blood products were recorded. Continuous data are presented as a mean±S.D.; categorical data – as proportions. Continuous independent data were compared with unpaired t-test and one-way analysis of variance ANOVA (in case of normally distributed data) or Mann–Whitney test (in case of non-normally distributed data). Repeated measures of continuous variables were compared using repeated measures ANOVA. Categorical data were compared with the 2-test. The Cox proportional hazards regression analysis (uni- and multivariate) was used to evaluate variables as predictors for low COP at the end of bypass. All tests were two-sided and a P<0.05 was considered statistically significant. All statistical analyses were performed using SPSS 13.0 statistical software (SPSS, Chicago, IL).
Data from 73 infants were evaluated in the study. Patient characteristics and CPB data are presented in Table 1. There were no postoperative re-explorations and all patients survived.
Thirty-five patients had COP lower than 15 mmHg at the end of CPB and were therefore assigned to Group Low COP. Group Low COP had significantly lower value of COP before the bypass, during the CPB and at the end of the operation. Additionally, value of the priming COP in this group was also significantly lower than in Group High COP (Table 2).
Absolute amount of priming used in both groups was not significantly different, Group Low COP: 349±15 ml vs. Group High COP: 342±16 ml, P=0.09. The relative amount (ml/kg BW) of priming components and fluids added into the circulation during CPB are presented in Table 3. Group Low COP received significantly more priming volume per kg BW than Group High COP. Volume of human albumin used during the bypass in Group Low COP was also significantly bigger than in Group High COP.
Fig. 1 presents total blood loss and transfusion requirements after termination of CPB. Group Low COP received after the cessation of bypass significantly more FFP transfusion than Group High COP (33±18 ml/kg BW vs. 24±15 ml/kg BW, P=0.03).
Urine output after CPB until 24 h postoperatively was not significantly different between the groups (Group Low COP: 7 ml/kg BW/h vs. Group High COP: 6 ml/kg BW/h, P=0.08).
Figs. 2–4
Significant univariate predictors of the COP value lower than 15 mmHg at the end of bypass were patient weight and COP before start of CPB, priming COP, volume of human albumin added into the circulation during CPB and volume of cardioplegia received into the circulation during CPB. After multivariate analysis, patient COP before CPB remained the only significant predictor of lower COP at the end of CPB (Table 4).
Our results show that despite colloidal prime and volume replacement therapy, guided by COP measurements, the desired level of COP was not always achieved at the end of bypass. The significant risk factor for low COP at the end of bypass was low level of patient's COP measured before the start of CPB. Although the impact of the priming components and priming volume can have significant effect on neonates and infants, there is no consensus about the choice of the priming solution and intravascular volume replacement regime as well as the optimal level of COP. Meta-analysis of control adult trials by Russell et al. [7] concluded that albumin prime favorably influenced COP, on-bypass positive fluid balance, postoperative weight gain, and colloid usage, than crystalloid priming. Eising et al. established that hyperoncotic CPB prime (COP=48 mmHg) prevented long water accumulation in the early post-pump period, while pulmonary function was unchanged [6]. Haneda et al. advocated addition of colloids to the prime in the pediatric patients [5]. Their retrospective study suggested that maintaining COP during CPB around 19 mmHg by using colloid hemodilution prime reduced significantly fluid balance at the end of CPB compared to crystalloid hemodilution. A more recent study of Aukerman et al. [11] provided information that albumin in the prime resulted in less weight gain in children after bypass. Riegger et al. [8] presented the same conclusions concerning weight gain after pediatric CPB, but they associated albumin prime with an increased transfusion rate (RBCs). The optimal COP level during bypass remains equivocal. An animal model suggested that COP of 16 mmHg is optimal [10]. Ekblad et al. [12] also concluded in their study that infants with a COP of umbilical cord plasma 16 mmHg are unlikely to develop respiratory distress syndrome. In our institution, COP target value during bypass was agreed at 15 mmHg based upon the results from the literature studies [13]. Still, forty-eight percent of patients from the study population had at the end of bypass COP of 14±1 mmHg. Those patients had already, before the start of bypass, significantly lower COP than the others (15±2 mmHg vs. 18±3 mmHg, P<0.001), presumptively due to the crystalloid infusion during induction. Since that was the only significant risk factor for low COP at the end of bypass (multivariate analysis OR=0.71, P=0.02), it is advisable to replace the crystalloids by colloidal solutions to avoid this unwanted dilution effect. All patients received colloidal prime, but prime COP in Group Low COP was significantly lower than in Group High COP (22±4 mmHg vs. 24±6 mmHg, P=0.027). Prime components were routinely calculated to target required hematocrit, with no specific regard to the achieved level of COP. In consequence, our colloidal priming was not able to counterbalance for patient's low COP before the bypass. During the CPB, Group Low COP received significantly more human albumin than the other group (Table 3). Even so, the COP level in this group significantly dropped at the end of bypass (from 15±2 mmHg to 14±1 mmHg, P=0.04). Transfusion of albumin solution during CPB to increase COP level was not effective (multivariate analysis OR=0.96, P=0.95) and therefore the COP management strategy during the bypass should be reconsidered. On the other hand, the amount of cardioplegic solution returned to the circulation during the bypass showed tendency for association with low COP level (OR=1.06, P=0.12) and should be avoided. Clinical relevance of low COP during the bypass was less evident, as both groups showed no significant differences in postoperative blood loss, urine production and length of stay in the ICU. Postoperative transfusion requirements with the exception of FFP were also not significantly different. Group Low COP received in postoperative period significantly more FFP than Group High COP (33±18 ml/kg BW vs. 24±15 ml/kg BW, P=0.03), which could be related to the extravasation of fluids caused by low levels of COP. The main limitation of this single-center study was the retrospective character and the lack of definite study endpoints related to changes of COP. A prospective, randomized study with clinical endpoints as; body weight gain, perioperative plasma albumin concentration and fluid balance, is scheduled to evaluate new composition of colloid prime and volume replacement therapy during CPB to achieve COP not lower than 18 mmHg at the end of bypass.4.2. Conclusions and recommendations Results of our study demonstrated that it is advisable to evaluate the customary protocol and identified existing risk factors in regard to protocol adjustments. Pre-bypass crystalloid dilution during induction should be avoided as well as return of the crystalloid cardioplegic solution into the circulation. Priming COP and COP management strategy during bypass should be tailored to individual patient demand.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
Top
Abstract
1. Introduction
15 mmHg. In accordance with protocol no modified ultrafiltration and no antifibrinolitic medication was used. 
–stat regulation was used. Myocardial protection was achieved with crystalloid cardioplegia. Cardioplegic solution was preferably sucked into the cell-saving (CS) device. Perioperative blood loss was collected and processed by CS device, together with residual volume of the CPB circuit. After the CPB, acyanotic as well as cyanotic patients received RBC transfusions to maintain hematocrit above 0.30 l/l and the CS product was always considered first line blood replacement therapy. Transfusion of FFP was administrated in case of enhanced blood loss and prothrombin time ratio >1.5. Platelet concentrate was administrated if the platelet count at the end of CPB was <100x109/l. 
