Techniques of paediatric modified ultrafiltration: 1996 survey results

Impact of miniaturized cardiopulmonary bypass circuits on ultrafiltration during congenital heart surgery

OBJECTIVE

To investigate whether the miniaturized cardiopulmonary bypass (CPB) system decreased the usage of ultrafiltration (UF), and to explore whether the non-UF with miniaturized CPB strategy could get good clinical results during congenital heart surgery.

METHODS

We performed a retrospective analysis of all patients undergoing congenital heart surgery with CPB at Shenzhen Children's Hospital from 1 May 2015 to 30 September 2019. We classified patients to UF with miniaturized CPB group, non-UF with miniaturized CPB group, UF with conventional CPB group and non-UF with conventional CPB group.

RESULTS

Of the 2145 patients, 721 (33.6%) were in the conventional CPB group, and 1424 (66.4%) were in the miniaturized CPB group. The UF rate was significantly lower in the miniaturized CPB group compared with that in the conventional CPB group (12.5% vs. 76.8%, p < 0.001). Compared with patients in the other groups, patients in the non-UF with miniaturized CPB group had a shorter postoperative MV time (p < 0.05), and a shorter length of stay in the ICU (p < 0.001) and hospital (p < 0.001). The age of children in the UF with miniaturized CPB group was relatively younger (median: 1.5 months, IQR: 0.3-4.6 months), and the preoperative weight was relatively lower (median: 3.9 kg, IQR: 3.2-5.4 kg). Moreover, this group of children had a relatively longer postoperative MV time and length of stay in the ICU and hospital.

CONCLUSION

The miniaturized CPB system could decrease the usage of UF. Good results were achieved in children who did not use UF based on the miniaturized CPB circuit system during congenital heart surgery.

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.

Modified Ultrafiltration in Children

Pediatric cardiopulmonary bypass (CPB) results in increased total body water and capillary permeability. Ultrafiltration has been effective in removing this excess water. The con ventional method of ultrafiltration is restricted by the vol ume in the venous reservoir and therefore is inefficient in smaller children and neonates, whose blood volume is dis proportionately smaller than the circuit volume. Modified ultrafiltration, performed in the immediate post-CPB period, is more effective in these patients. Blood from the aorta is pumped through the ultrafilter, and warm concentrated blood is returned to the right atrium. This removes excess water from the patient and provides a method of salvaging volume from the circuit. Modified ultrafiltration results in consistent improvements in systolic blood pressure, cardiac index, and lung compliance, as well as a reduction in pul monary vascular resistance. Removal of various inflamma tory mediators, such as tumor necrosis factor a, interleu kin-6, and interieukin-8, has been reported after modified ultrafiltration. Other advantages include an increase in he matocrit, colloid osmotic pressure, and coagulation factors, resulting in decreased bleeding and a decreased need for transfusions. In the animal model, improvement in cerebral recovery after deep hypothermic circulatory arrest has been reported. The disadvantages of this technique include the risk of air entrapment, delay in heparin reversal, and poten tial for cooling.

Impact of Modified Ultrafiltration on Morbidity after Pediatric Cardiac Surgery

Cardiopulmonary bypass is a double-edged sword. Without it, corrective cardiac surgery would not be possible in the majority of children with congenital heart disease. However, much of the perioperative morbidity that occurs after cardiac surgery can be attributed to a large extent to pathophysiologic processes engendered by extracorporeal circulation. One of the challenges that has confronted pediatric cardiac surgeons has been to minimize the consequences of cardiopulmonary bypass. Ultrafiltration is a strategy that has been used for many years in an effort to attenuate the effects of hemodilution that occur when small children undergo surgery with cardiopulmonary bypass. Over the past several years, a modified technique of ultrafiltration, commonly known as modified ultrafiltration, has been used with increasing enthusiasm. Multiple studies have been undertaken to assess the effects of modified ultrafiltration on organ function and postoperative morbidity following repair of congenital heart defects. This review attempts to evaluate current available scientific evidence on the impact of modified ultrafiltration on organ function and morbidity after pediatric cardiac surgery.

Modified ultrafiltration during cardiopulmonary bypass and postoperative course of pediatric cardiac surgery

Context:

The use of cardiopulmonary bypass (CPB) provokes the inflammatory responses associated with ischemic/reperfusion injury, hemodilution and other agents. Exposure of blood cells to the bypass circuit surface starts a systemic inflammatory reaction that may causes post-CPB organ dysfunction, particularly in lungs, heart and brain.

Evidence Acquisition:

We investigated in the MEDLINE, PUBMED, and EMBASE databases and Google scholar for every available article in peer reviewed journals between 1987 and 2013, for related subjects to CPB with conventional or modified ultrafiltration (MUF) in pediatrics cardiac surgery patients.

Results:

MUF following separation from extracorporeal circulation (ECC) provides well known advantages in children with improvements in the hemodynamic, pulmonary, coagulation and other organs functions. Decrease in blood transfusion, reduction of total body water, and blood loss after surgery, are additional benefits of MUF.

Conclusions:

Consequently, MUF has been associated with attenuation of morbidity after pediatric cardiac surgery. In this review, we tried to evaluate the current evidence about MUF on the organ performance and its effect on post-CPB morbidity in pediatric patients.

Perfusionist strategies for blood conservation in pediatric cardiac surgery

There is increasing concern about the safety of homologous blood transfusion during cardiac surgery, and a restrictive transfusion practice is associated with improved outcome. Transfusion-free pediatric cardiac surgery is unrealistic for the vast majority of procedures in neonates or small infants; however, considerable progress has been made by using techniques that decrease the need for homologous blood products or even allow bloodless surgery in older infants and children. These techniques involve a decrease in prime volume by downsizing the bypass circuit with the help of vacuum-assisted venous drainage, microplegia, autologous blood predonation with or without infusion of recombinant (erythropoietin), cell salvaging, ultrafiltration and retrograde autologous priming. The three major techniques which are simple, safe, efficient, and cost-effective are: a prime volume as small as possible, cardioplegia with negligible hydric balance and circuit residual blood salvaged without any alteration. Furthermore, these three techniques can be used for all the patients, including emergencies and small babies. In every pediatric surgical unit, a strategy to decrease or avoid blood bank transfusion must be implemented. A strategy to minimize transfusion requirement requires a combined effort involving the entire surgical team with pre-, peri-, and postoperative planning and management.

A Simplified Circuit of Modified Ultrafiltration

A simplified circuit of modified ultrafiltration (MUF) is described. The technique described is simple, inexpensive, allows both conventional ultrafiltration (CUF) and modified ultrafiltration with minimum manipulation of the circuit, allows re-institution of cardiopulmonary bypass (CPB) in an emergency, reduces the risk of air embolism and air cavitation and can be used in adults as well as children.

Pediatric cardiopulmonary bypass devices: trends in device use for cardiopulmonary bypass and postcardiotomy support

Cardiopulmonary bypass (CPB) devices and techniques have continuously evolved. We have conducted surveys that chronicle the changes in CPB devices and techniques used at North American pediatric cardiac surgery centers since 1989. The aim of this article is to describe trends in cardiopulmonary bypass device use during cardiac surgery and changes in the devices used for extracorporeal life support (ECLS) following cardiac surgery for pediatric patients. The diffusion of innovation in pediatric cardiovascular surgery has not been solely driven by the availability of scientific evidence to support change but rather it has often been related to other factors that influence clinicians willingness to change including; tradition, ease of use, and cost related pressures. The current CPB systems used for cardiac surgery are more homogenous than in previous years. Most centers use a heparin coated or modified surface system comprised of a "hard shell" open venous reservoir, a roller pump, a hollow fiber membrane oxygenator, and arterial line filter. ECLS systems comprised of hollow fiber oxygenators and centrifugal pumps for are gradually replacing the classical ECLS circuit, servo regulated roller pumps and silicone rubber membranes. Nearly 40% of centers use these alternate components in their ECLS systems. Costs, utility, safety and measurable benefit to the patient should guide decisions related to device selection.

Critical care in cardiovascular medicine

The field of cardiac intensive care is rapidly evolving with nearly simultaneous advances in surgical techniques and adjunctive therapies, respiratory care, intensive care technology and monitoring, pharmacologic research and development, and computing and electronics. The focus of care has now shifted toward reducing morbidity and improving "quality of life" while the survival of infants and children with congenital heart defects, including those with univentricular hearts has dramatically improved during the last three decades. Despite these advances, there remains a predictable fall in cardiac output after cardiopulmonary bypass. This article focuses on early identification and aggressive treatment of the low cardiac output syndrome peculiar to these patients. The authors also briefly review the recent advances in the treatment of pulmonary hypertension, mechanical support, and neurologic surveillance after cardiac surgery.

Simple modified ultrafiltration

After reviewing all available methods of modified ultrafiltration (MUF), an attempt was made to develop a more simplified approach to this beneficial method of post-bypass fluid removal by withdrawing blood from the right atrium and reinfusing into the aortic cannula (venoarterial). The simplicity of operation, ease of setup and analysis of hemoglobin, hematocrit, total proteins and colloid osmotic pressure, and fluid removed were examined in 12 consecutive neonatal and pediatric patients undergoing cardiac surgery. Results indicate that this simplified modified ultrafiltration (SMUF) is comparable to all other methods of MUF by achieving dramatic improvements in all parameters measured. In addition, SMUF provides the perfusionist with the ability to run conventional ultrafiltration throughout the bypass procedure, using this one circuit design. As well as finding the learning curve for SMUF to be very short, this method was found to be superior in its simplicity of operation, ease of setup, reduced risk of complications and acceptance by the surgeon and anesthetist.

A circuit to perform a combined ultrafiltration procedure in pediatric open heart surgery

Cardiopulmonary bypass (CPB) induces an increased capillary permeability and tissues water content due to hemodilution and the inflammatory response, resulting in organ dysfunction. The reduction of the water accumulation and inflammatory response can be achieved by employing ultrafiltration during CPB. Recently we developed a simple CPB circuit for ultrafiltration using the aortic venting tube as an inlet line. Such a technique offers the advantages of performing a combined ultrafiltration procedure and eliminating the danger of air embolism. We employed this circuit in 12 consecutive pediatric patients undergoing open heart surgery.

Impact of modifying priming components and fluid administration using miniaturized circuitry in neonatal cardiopulmonary bypass

Following a succession of changes in circuitry and priming additives between 1993 and 1998, a comprehensive re-evaluation of neonatal cardiopulmonary bypass (CPB) practice was undertaken. Samples from 10 infants (Group 1) undergoing CPB were evaluated for osmolality, oncotic pressure, total protein, hematocrit, glucose, and electrolytes (Na+, K+, iCa2+). These samples were tested at six measurement points: (1) after priming, (2) patient pre-CPB, (3) CPB-start, (4) CPB-mid, (5) CPB-end, and (6) post-modified ultrafiltration (MUF). Prime volumes were also carefully measured as well as the type and amount of volume given during CPB. After evaluating the initial data, changes in protocol regarding mannitol, calcium correction, and oncotic strength on CPB were made. Following implementation of these protocol changes, a second set (Group 2) of 10 infants was identically evaluated. Group 1 prime osmolality was 379 +/- 44 mOsm/kg, while Group 2 prime osmolality was 324 +/- 14 mOsm/kg (p = 0.003). There were no differences in osmolality between groups during bypass and osmolality was unaffected by modified ultrafiltration. Ionized calcium levels were significantly different at the end of bypass between Group 1, 0.6 +/- 0.1 mmol/l; and Group 2, 1.17 +/- 0.24 mmol/l (p < 0.001). In Group 1, there was a 40% drop (p = 0.001) in colloid osmotic pressure (COP) levels from pre-CPB (13.3 +/- 3.4 mmHg) to CPB-end (8.8 +/- 1.2 mmHg). In Group 2, there were no differences in COP during CPB. COP levels of Group 1 and Group 2 at CPB-end were 8.8 +/- 1.2 mmHg and 14 +/- 1.9, respectively (p < 0.0001). Total volume addition during bypass for Group 1 was 363.5 +/- 148.7 ml and for Group 2 was 245.1 +/- 92.2 ml (p < 0.05). In conclusion, progressive changes in neonatal circuits and techniques can have potentially wide-ranging effects on electrolyte and osmotic/oncotic homeostasis. An audit of perfusion management through expanded laboratory tests is recommended, especially in periods of change.