Perfusion technique for nonhaemic cardiopulmonary bypass prime in neonates and infants under 6 kg body weight

Safety and utility of modified ultrafiltration in pediatric cardiac surgery

INTRODUCTION

Modified ultrafiltration (MUF) is employed at the termination of cardiopulmonary bypass (CPB) in pediatric and neonatal patients undergoing congenital heart surgery to reduce the accumulation of total body water thus increasing the concentration of red blood cells and the other formed elements in the circulation. Modified ultrafiltration has been reported to remove circulating pro-inflammatory mediators that result in systemic inflammatory response syndrome (SIRS) postoperatively.

METHODS

Four hundred patients undergoing cardiac surgery requiring cardiopulmonary bypass and weighing less than or equal to 12 kg were retrospectively evaluated for the effectiveness of MUF. After the termination of CPB, blood was withdrawn through the aortic cannula and passed through a hemoconcentrator attached to the blood cardioplegia set and returned to the patient through the venous cannula. The entire CPB circuit volume in addition to the patient's circulating blood volume were concentrated until the hematocrit value displayed on the CDI cuvette within the MUF circuit reached 45% or there was no more volume to safely remove. At the same time a full unit of FFP can be infused as water is being removed, thus maintaining euvolemia.

RESULTS

MUF was performed in all 400 patients with no MUF-related complications. Following the conclusion of MUF, anecdotal observations included improved surgical hemostasis, improved hemodynamic parameters, decreased transfusion requirements, and decreased ventilator times.

CONCLUSIONS

Complete MUF enables the clinician to safely raise the post-CPB hematocrit to at least 40% while potentially removing mediators that could result in SIRS. In addition a full unit of FFP can be administered while maintaining euvolemia.

Patient Blood Management in Pediatric Cardiac Surgery: A Review

Efforts to reduce blood product transfusions and adopt blood conservation strategies for infants and children undergoing cardiac surgical procedures are ongoing. Children typically receive red blood cell and coagulant blood products perioperatively for many reasons, including developmental alterations of their hemostatic system, and hemodilution and hypothermia with cardiopulmonary bypass that incites inflammation and coagulopathy and requires systemic anticoagulation. The complexity of their surgical procedures, complex cardiopulmonary interactions, and risk for inadequate oxygen delivery and postoperative bleeding further contribute to blood product utilization in this vulnerable population. Despite these challenges, safe conservative blood management practices spanning the pre-, intra-, and postoperative periods are being developed and are associated with reduced blood product transfusions. This review summarizes the available evidence regarding anemia management and blood transfusion practices in the perioperative care of these critically ill children. The evidence suggests that adoption of a comprehensive blood management approach decreases blood transfusions, but the impact on clinical outcomes is less well studied and represents an area that deserves further investigation.

Comprehensive blood conservation program in a new congenital cardiac surgical program allows bloodless surgery for the Jehovah Witness and a reduction for all patients

BACKGROUND

Cardiac surgery on Jehovah's Witnesses (JW) can be challenging, given the desire to avoid blood products. Establishment of a blood conservation program involving the pre-, intra- and post-operative stages for all patients may lead to a minimized need for blood transfusion in all patients.

METHODS

Pre-operatively, all JW patients were treated with high dose erythropoietin 500 IU/kg twice a week. JW patients were compared to matching non-JW patients from the congenital cardiac database, two per JW to serve as control. Blood use, ventilation time, bypass time, pre-operative hematocrit, first in intensive care unit (ICU) and at discharge and 24 hour chest drainage were compared. Pre-operative huddle, operating room huddle and post-operative bedside handoff were done with the congenital cardiac surgeon, perfusionist, anesthesiologist and intensive care team in all patients for goal alignment.

RESULTS

Five JW patients (mean weight 24.4 ± 25.0 Kg, range 6.3 - 60 Kg) were compared to 10 non-JW patients (weight 22.0 ± 22.8 Kg, range 6.2 - 67.8 Kg). There was no difference in bypass, cross-clamp, time to extubation (0.8 vs. 2.1 hours), peak inotrope score (2.0 vs. 2.3) or chest drainage. No JW patient received a blood product compared to 40% of non-JW. The pre-operative hematocrit (Hct) was statistically greater for the JW patients (46.1 ± 3.3% vs. 36.3 ± 4.7%, p<0.001) and both ICU and discharge Hct were higher for the JW (37 ± 1.8% vs 32.4 ± 8.0% and 41 ± 8.1% vs 34.8 ± 7.9%), but did not reach statistical significance. All patients had similar blood draws during the hospitalization (JW x 18 mL/admission vs non-JW 20 mL/admission).

CONCLUSION

The continuous application and development of blood conservation techniques across the continuum of care allowed bloodless surgery for JW and non-JW patients alike. Blood conservation is a team sport and to make significant strides requires participation and input by all care providers.

Retrospective analysis of eliminating modified ultrafiltration after pediatric cardiopulmonary bypass

Modified ultrafiltration (MUF) is a technique which is commonly used immediately post-cardiopulmonary bypass (CPB) for open heart surgery in children. There are many advantages of MUF, but there are also a number of less reported disadvantages. At our institution, after considering all of the available data, a decision was made to no longer perform MUF. The primary motivation being the simplified and miniaturized CPB circuit would reduce hemodilution, decrease our likelihood of reaching our transfusion trigger during CPB and, potentially, improve safety. This study reports the before and after data from this practice change. A total of 160 patients less than 8kg were studied over 38 months and divided into neonatal and pediatric cohorts. Parameters reported in this study include: demographics, hematocrit, blood product transfusion, hemostasis, hemodynamics and outcomes. Although retrospective, our analysis supports an advantage of preventing hemodilution (via circuit miniaturization) versus reversing hemodilution (via MUF) at our institution with the patient population we examined.

New technology increases perioperative haemoglobin levels for paediatric cardiopulmonary bypass: what is the benefit?

Increasing perioperative haemoglobin level by reducing priming volume and maintaining a safe cardiopulmonary bypass (CPB) system is the aim of every perfusionist. In this study, we have compared the two membrane oxygenators and pump systems used for paediatric bypass at the Royal Children’s Hospital on a regular basis since 1988. We looked at all patients who had the Cobe VPCML (Cobe Laboratories, Denver, CO, USA) and Terumo RX-05 (Terumo Corporation, Tokyo, Japan) oxygenators used for flows from 800 mL/min up to the maximum rated flow for the respective oxygenator from January 2002 until March 2004. The VPCML refers to using only the 0.4-m2 section of the oxygenator. The pump systems used were the Stöckert CAPS (Stöckert Instrumente GmbH, Munich, Germany) and Jostra HL 30 (Jostra AB, Lund, Sweden). Changing from the VPCML to the RX-05 resulted in a 37% reduction in priming volume. The introduction of the Jostra HL 30 with a custom-designed mast system reduced the priming volume by another 15%. This change in priming volume allowed a significant increase, from 6 to 34%, in the percentage of patients who received bloodless primes, and for those patients who received blood primes, an increase in haemoglobin (Hb) on bypass from 8.2 to 9.6 g/dL, on average.

Splitting blood and blood product packaging reduces donor exposure for patients undergoing cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass for congenital heart surgery requires packed red cells (PRBC) and fresh frozen plasma (FFP) to be available, both for priming of the circuit as well as to replace blood loss. This study examines the hypothesis that splitting one unit of packed red blood cells and one unit of fresh frozen plasma into two half units reduces blood product exposure and wastage in the Operating Room.

METHODS

Beginning August 2013, the blood bank at Children's National Medical Center began splitting one unit of packed red blood cells (PRBC) and one unit of fresh frozen plasma (FFP) for patients undergoing cardiopulmonary bypass (CPB). The 283 patients who utilized CPB during calendar year 2013 were divided into 2 study groups: before the split and after the split. The principal endpoints were blood product usage and donor exposure intra-operatively and within 72 hours post-operatively.

RESULTS

There was a significant decrease in median total donor exposures for FFP and cryoprecipitate from 5 to 4 per case (p = 0.007, Mann-Whitney U-test). However, there was no difference in the volume of blood and blood products used; in fact, there was a significant increase in the amount of FFP that was wasted with the switch to splitting the unit of FFP.

CONCLUSIONS

We found that modification of blood product packaging can decrease donor exposure. Future investigation is needed as to how to modify packaging to minimize wastage.

Recent Advances in Pediatric Cardiopulmonary Bypass

There have been numerous recent advances geared specifically toward the practice of pediatric cardiopulmonary bypass (CPB). These advances include the development of the first oxygenator intended solely for the neonatal CPB patient; pediatric oxygenators with low prime volumes and surface areas, which allow flows up to 2 L/min; pediatric oxygenators with integrated arterial filters; and miniature ultrafiltration (UF) devices, which allow for high rates of ultrafiltrate removal. When used in combination with heart lung machines with mast-mounted pumps, these advances can result in significant decreases in CPB circuit surface areas and prime volumes. This may attenuate CPB-associated hemodilution and decrease or eliminate the need for homologous red blood cells during or after CPB. In addition to these equipment-related advances, changes in myocardial protection strategies and the technique of modified UF as it relates to these advances are discussed.

Five-year experience with mini-volume priming in infants ≤5 kg: safety of significantly smaller transfusion volumes

Reducing the cardiopulmonary bypass (CPB) priming volume in congenital cardiac surgery is important because it is associated with fewer transfusions. This retrospective study was designed to compare safety and transfusion volumes between the mini-volume priming (MP) and conventional priming (CP) methods. Between 2007 and 2012, congenital heart surgery using CPB was performed on 480 infants (≤5 kg): the MP method was used in 331 infants (MP group, 69.0%), and the CP method was used in 149 infants (CP group, 31.0%). In the MP group, narrow-caliber (3/16″) tubing was used, and the pump heads were vertically aligned to shorten the tubing lengths. The smallest possible oxygenators and hemofilters were used, and vacuum drainage was applied. Ultrafiltration was vigorously applied during CPB to avoid excessive hemodilution. The mean age and body weight of the patients were 48 ± 41 (0-306) days and 3.8 ± 0.8 (1.3-5.0) kg, respectively. The total priming and transfusion volumes during CPB were lower in the MP group than in the CP group (141 ± 24 mL vs. 292 ± 50 mL, P < 0.001, and 82 ± 40 mL vs. 162 ± 82 mL, P < 0.001, respectively). In the MP group, the smallest priming volume was 110 mL. However, there was no significant difference in the lowest hematocrit level during CPB between the two groups (22 ± 3% vs. 22 ± 3%, P = 0.724). The incidence of postoperative neurological complications was not significantly different between the MP and CP groups (1.8% vs. 2.7%, P = 0.509). After adjustment for the Risk Adjustment for Congenital Heart Surgery category, body surface area, and age, MP was not an independent risk factor of postoperative neurological complications or early mortality (P = 0.213 and P = 0.467, respectively). The MP method reduced the priming volume to approximately 140 mL without increasing the risk of morbidity or mortality in infants ≤5 kg. The total transfusion volume during CPB was reduced by 50% without compromising hematocrit levels. We recommend the use of mini-volume priming, which is a safe and effective method for reducing transfusion volumes.

Use of a miniaturized cardiopulmonary bypass circuit in neonates and infants is associated with fewer blood product transfusions

Miniaturized bypass circuits, including the Kids D100 oxygenator and the D130 arterial filter, were specially designed to reduce blood transfusions in small infants undergoing cardiac surgery. This study compared the number of blood product transfusions and short-term outcome between patients younger than 1 year undergoing cardiac surgery with a conventional and a miniaturized bypass circuit, after controlling for baseline characteristics and surgical complexity by 1:1 matching. Adjusted odds ratios (ORs) and 95% confidence intervals for exposure to transfusions and to any additional transfusion were estimated from binary and polytomous regression models. Of the 804 patients enrolled retrospectively, 246 were analyzed after matching. The use of the miniaturized circuit required a lower priming volume, 265.5 vs. 432.4 mL, p < 0.001, fewer packed red blood cell (PRBC) transfusions, 1.4 vs. 2.0 U, p < 0.001, and fewer platelet transfusions on the day of surgery, 57.7% vs. 76.4%, p < 0.001. After adjustment for the use of antifibrinolytics, the ultrafiltration rate, and the year of surgery, the use of the miniaturized circuit was independently related to a reduced risk of additional PRBC transfusions, OR 0.04 (0.01, 0.13), and exposure to platelet transfusions, OR 0.78 (0.63, 0.96). Short-term outcome was similar.

Specific requirements for bloodless cardiopulmonary bypass in neonates and infants; a review

A miniaturized cardiopulmonary bypass circuit enables the safe performance, in selected pediatric patients, of bloodless open heart surgery. As the latest survival rates in neonatal and infant cardiac surgery have become satisfactory, investigators have concentrated upon the improvement of existing procedures. Institutional guidelines and multidisciplinary efforts undertaken in the pre- and postoperative periods are of great importance, concerning bloodless CPB and should be seriously pursued by all involved caregivers.

This review reflects upon the selective, most relevant requirements for success of asanguinous neonatal and infant CPB: acceptable level of hemodilution during the CPB, patient preoperative hematocrit value and volume of CPB circuit. We present an assessment of practical measures that were also adapted in our institution to achieve an asanguinous CPB for neonatal and infant patients.

Small, smaller, smallest. Steps towards bloodless neonatal and infant cardiopulmonary bypass

In open heart surgery in neonates and small children, the cardiopulmonary bypass circuit surface and the priming volume are relatively large in relation to patient size and blood volume. Therefore, the use of allogeneic blood is inevitable to maintain the optimal hematocrit level during bypass. To avoid the deleterious effects of blood transfusion, as well as to reduce the contact surface of blood with artificial materials, we stepwise reduced the bypass circuit size. Use of the commercially available minimized elements and an adjusted set-up of the system allowed us to reduce usage of allogeneic blood in the prime and during the bypass. However, other supplemental measures are needed to obtain asanguineous cardiopulmonary bypass for neonatal and infant patients.

Acute kidney injury in an infant after cardiopulmonary bypass

The infant who develops acute kidney injury (AKI) after cardiopulmonary bypass (CPB) surgery presents unique challenges and opportunities to the clinician and to the investigator interested in the study of AKI pathophysiology. Infants do not have many of the comorbid conditions that confound CPB outcome studies of adults. Because the timing of the AKI event is known in this clinical setting, collaboration between cardiology intensivists, nephrologists, and perfusion technologists is essential to minimize the impact of CPB on the kidney. Early institution of ultrafiltration in the operating room and renal replacement therapy in the postoperative period may decrease the proinflammatory milieu and its resultant systemic effects. In addition, early initiation of renal replacement therapy to prevent fluid overload may result in improved infant outcomes.

Efficacy of a miniature centrifugal rotary pump (TinyPump) for transfusion-free cardiopulmonary bypass in neonatal piglets

We have developed a miniaturized semiclosed cardiopulmonary bypass (CPB) circuit incorporating a centrifugal blood pump (TinyPump) with a volume of 5 ml. The current study was undertaken to evaluate the hemolytic performance of the TinyPump in comparison with the BioPump and to investigate the impact of different CPB circuit volumes on hemodilution, coagulation, and the inflammatory response. Twelve 1-week-old piglets (3.4 +/- 0.2 kg) were used. The circuit comprised a centrifugal pump, a membrane oxygenator, and a cardiotomy reservoir. Cardiopulmonary bypass was conducted with mild hypothermia at 150 ml/kg/min for 3 hours. Transfusion was not performed. Priming volume was 68 ml for the circuit with the TinyPump and 111 ml for the circuit with the BioPump. Although the TinyPump required higher speed, plasma free hemoglobin levels after CPB were not different between the groups. After CPB, the TinyPump group had a significantly higher hematocrit (27% +/- 3% vs. 23% +/- 3%) and lower platelet reduction rate, lower thrombin-antithrombin complex levels, and lower interleukin-6 levels. Better lung compliance with less water content was observed in the TinyPump group. The TinyPump maintained CPB with acceptable hemolysis and lower inflammatory responses. This miniaturized CPB circuit may make transfusion-free open heart surgery feasible in neonates and would help to prevent postoperative organ dysfunction.

Usefulness of low prime perfusion pediatric circuit in decreasing blood transfusion

We tested the efficiency of small prime volume in decreasing the blood requirement during pediatric cardiac surgery. This is a retrospective analysis of transfusion in 259 consecutive patients weighing <15 kg. We downsized the bypass circuit and avoided noncritical components to obtain a cardiopulmonary bypass prime volume, including a cardioplegia circuit of 140 ml for patients up to 6 kg, and of 170 ml for those weighing 6-15 kg. For intra- and postoperative care, transfusions were limited to 1 unit of packed red blood cells and 1 unit of fresh frozen plasma in 129 of the 134 patients weighing <6 kg. Seventy-six of 125 (61%) patients who were between 6 kg and 15 kg had bloodless surgery. None of the 259 patients had platelets infusion. In transfused cases, only eight patients (3%) needed more than two different donor products. In bloodless cases, hemoglobin values were 11.5 +/- 1.8 g/dl before, 9.4 +/- 1.7 g/dl during, and 10.5 +/- 1.8 g/dl after surgery. No adverse effects of this procedure were encountered. Small prime volume is efficient and safe in decreasing blood use in pediatric surgery.

The Use of a Miniaturized Circuit and Bloodless Prime To Avoid Cerebral No-Reflow After Neonatal Cardiopulmonary Bypass

BACKGROUND

Our miniaturized bloodless prime circuit for neonatal cardiopulmonary bypass (CPB) has previously been shown to elicit significantly reduced systemic inflammation. We studied the effects of this circuit on cerebral reperfusion because the pathophysiology of "no-reflow" is believed to have an inflammatory component.

METHODS

Twenty neonatal piglets were randomized to CPB with miniaturized circuitry using either blood (group 1) or bloodless (group 2) prime. At 18 degrees C, piglets underwent 60 minutes of either (A) deep hypothermic circulatory arrest (DHCA) or (B) continuous low-flow bypass (DHCLF). Analysis of cerebral blood flow (CBF) was undertaken before and after CPB in addition to quantification of circulating tumor necrosis factor-alpha (TNFalpha) and intracerebral TNFalpha messenger RNA (mRNA).

RESULTS

The final hematocrit in group 2 was 22% versus 28% (p < 0.05). The CBF fell in every animal in group 1A, but increased in every animal in group 2A (p < 0.001), despite no overall change in total cardiac output. The use of DHCLF was not associated with pronounced trends in either prime group. Final serum TNFalpha concentrations were significantly higher in group 1B (3166 +/- 843 pg/mL) than group 2B (439 +/- 192 pg/mL; p < 0.05). Irrespective of the CPB strategy used, the use of a blood prime generated significantly higher levels of intracerebral TNFalpha mRNA.

CONCLUSIONS

We attribute the hyperemic cerebrovascular response to reduced inflammation through avoiding allogeneic whole blood. The analysis of circulating and intracerebral TNFalpha in this study suggests that DHCLF in conjunction with a bloodless prime might offer advantages through avoiding ischemia, no-reflow, and in addition, resulting in a significantly reduced cerebral inflammatory response.

Use of hemoglobin vesicles during cardiopulmonary bypass priming prevents neurocognitive decline in rats

BACKGROUND

Homologous blood use is considered to be the gold standard for cardiopulmonary bypass (CPB) priming in infants despite exposure of the patient to potential cellular and humoral antigens. However, the use of hemoglobin vesicles (HbVs), artificial oxygen carriers that encapsulate a concentrated hemoglobin solution within phospholipid bilayer membranes, for CPB priming may prevent neurocognitive decline in infants. The goal of this study was to determine whether HbV use offsets hemodilution caused by patient/priming volume-mismatched CPB and thereby prevents the development of postoperative neurocognitive deficits.

METHODS AND RESULTS

CPB was established in 28 male Sprague-Dawley rats (age, 14 to 16 weeks; weight, 450 grams) after cannulation of the tail artery and right atrium. The animals were randomly assigned to 1 of 3 groups: sham surgery (n=9), HbV (-) prime (n=10), or HbV (+) prime (n=9). CPB was conducted for 90 minutes at 200 mL/kg per minute. The hematocrit during CPB was 10.0+/-1.2% in the HbV (+) prime group and 9.9+/-1.3% in the HbV (-) prime group (P=not significant). Learning and memory function were evaluated using 2 different maze tests (Maze-1 and Maze-2, in which the arrival times to the target were measured on the first, third, fifth, and seventh postoperative days). Learning and memory function were significantly better in the HbV (+) prime group than in the HbV (-) prime group (Maze-1, P=0.012; Maze-2, P=0.042); there was no difference between the HbV (+) prime and the sham surgery group.

CONCLUSIONS

The use of HbV for CPB priming may serve as a substitute for homologous blood to prevent the unacceptable hemodilution and contribute to maintenance of intact neurocognitive function.

Effects of Circuit Miniaturization in Reducing Inflammatory Response to Infant Cardiopulmonary Bypass by Elimination of Allogeneic Blood Products

Conventional neonatal cardiopulmonary bypass requires the use of large volumes of allogeneic blood to prevent unacceptable hemodilution. Evidence is accumulating to suggest that the use of blood products during cardiopulmonary bypass has a negative effect on clinical recovery through inflammatory side effects. This would suggest an advantage for eliminating blood use in infant cardiopulmonary bypass through circuit miniaturization. In this article, we review the data supporting this rationale and provide the results from studies in our laboratory that emphasize the benefits of circuit miniaturization.

Large-Dose Pretreatment with Methylprednisolone Fails to Attenuate Neuronal Injury After Deep Hypothermic Circulatory Arrest in a Neonatal Piglet Model

Conflicting results have been reported with regard to the neuroprotective effects of steroid treatment with cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA). We evaluated the mode and severity of neuronal cell injury in neonatal piglets after prolonged DHCA and the possible neuroprotective effect of systemic pretreatment (>6 h before surgery) with large-dose methylprednisolone (MP). Nineteen neonatal piglets (age, <10 days; weight, 2.1 +/- 0.5 kg) were randomly assigned to 2 groups: 7 animals were pretreated with large-dose systemic MP (30 mg/kg) 24 h before surgery, and 12 animals without pharmacological pretreatment (saline) served as control groups. All animals were connected to full-flow CPB with cooling to 15 degrees C and 120 min of DHCA. After rewarming to 38.5 degrees C with CPB, animals were weaned from CPB and survived 6 h before they were killed, and the brain was prepared for light and electron microscopy, immunohistochemistry, and TUNEL-staining. Quantitative histological studies were performed in hippocampus, cortex, cerebellum, and caudate nucleus. Systemic pretreatment with large-dose MP lead to persistent hyperglycemia but no significant changes of cerebral perfusion. Necrotic and apoptotic neuronal cell death were detected in all analyzed brain regions after 120 min of DHCA. In comparison to the control group, large-dose pretreatment with systemic MP lead to an increase of necrotic neuronal cell death and induced significant neuronal apoptosis in the dentate gyrus of the hippocampus (P = 0.001). In conclusion, systemic pretreatment with large-dose MP fails to attenuate neuronal cell injury after prolonged DHCA and induces regional neuronal apoptosis in the dentate gyrus.

Vacuum-Assisted Venous Drainage during Fetal Cardiopulmonary Bypass

We investigated a miniature magnetically levitated centrifugal blood pump intended to deliver 0.3-1.5 l/min of support to neonates and infants. The back clearance gap between the housing and large volume of the rotor, where the suspension and motor bearings are located, forms a continuous leakage flow path. Within the gap, flow demonstrates a very complex three-dimensional structure: the fluid adjacent to the rotating disk tends to accelerate by centrifugal force to flow radially outwards toward the outlet of the impeller against an unfavorable pressure gradient, which in turn forces blood to return along the stationary housing surfaces. Consequently, one or multiple vortices may be generated in the gap to block blood flow and cause the formation of a retrograde and antegrade leakage flow phenomenon at the gap outlet using an optimization process including extensive computational fluid dynamics (CFD) analysis of impeller refinements, we found that secondary blades located along the back or extended to the side surfaces of the rotor have the capacity to reduce and eliminate the retrograde flow in the back clearance gap. Flow visualization confirmed the CFD-predicted flow patterns. This work demonstrates the utility of CFD-based design optimization to optimize the fluid path of a miniature centrifugal pump.

Using a Miniaturized Circuit and an Asanguineous Prime to Reduce Neutrophil-Mediated Organ Dysfunction Following Infant Cardiopulmonary Bypass

BACKGROUND

Contemporary infant cardiopulmonary bypass circuits require a blood prime. Blood, especially when stored, generates an inflammatory response, and may contribute to organ dysfunction following cardiopulmonary bypass. We determined whether using a miniaturized circuit and an asanguineous prime attenuated the post-bypass inflammatory response, and improved right ventricular and pulmonary function.

METHODS

Sixteen infant piglets were placed into 3 groups based on prime components: group I (fresh blood), group II (stored blood), and group III (miniaturized circuit and asanguineous prime). Piglets were placed on cardiopulmonary bypass (100 mL.kg(-1).min(-1)), cooled to 18 degrees C, and underwent continuous perfusion (50 mL.kg(-1).min(-1)) for 30 minutes. They were rewarmed and separated from bypass. Serum tumor necrosis factor-alpha, right ventricular function, and pulmonary function were measured before and 30 minutes after bypass. Neutrophil priming activity in fresh and stored donor blood was also assessed.

RESULTS

Animals in group III had significantly improved cardiopulmonary function than the groups receiving blood (right ventricular cardiac index [mL.kg(-1).min(-1)]: group I [18.8 +/- 4.8], group II [21.5 +/- 6.2], and group III [81.2 +/- 11.4], p < 0.001; and pulmonary vascular resistance index [dynes.mL(-1).kg(-1)]: group I [1169 +/- 409], group II [1610 +/- 486], and group III [214 +/- 63], p = 0.03). Tumor necrosis factor-alpha (pg.mL(-1)) was lower in group III (1465 +/- 39) than in the groups receiving blood (3940 +/- 777), p = 0.002. Neutrophil priming activity (nmol.min(-1)) was also higher in stored blood (3.7 +/- 6) than in fresh blood (1.9 +/- 0.2), p = 0.02.

CONCLUSIONS

We have devised a unique miniaturized circuit that allows an asanguineous prime without hemodilution in an infant swine model. The employment of this circuit attenuates the post-bypass inflammatory response and has salutary effects on cardiopulmonary function.