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Ann Thorac Surg 1998;65:1105-1109
© 1998 The Society of Thoracic Surgeons

Impact of Ultrafiltration on Blood Use for Atrial Septal Defect Closure in Infants and Children

^a University of Tennessee–Memphis, Le Bonheur Children’s Medical Center, Memphis, Tennessee, USA

Address reprint requests to Dr Novick, Pediatric Cardiothoracic Surgery, The Heart Center, 777 Washington Ave, Suite 215, Memphis, TN 38105
e-mail: (ichfno{at}aol.com)

Presented at the Forty-fourth Annual Meeting of the Southern Thoracic Surgical Association, Naples, FL, Nov 6–8, 1997.

	Abstract

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Background. Infants and children undergoing open cardiac operations have a high incidence of blood product transfusion. Ultrafiltration has been shown to reverse hemodilution and improve myocardial function and hemodynamics after cardiopulmonary bypass (CPB).

Methods. The effect of ultrafiltration on the amount of blood transfusion and hospital charge in 39 consecutive patients who underwent elective atrial septal defect repair was examined. Patients in group I (n = 26) had a conventional cardiopulmonary circuit prime with blood, whereas 13 patients had bloodless prime (group II). Ultrafiltration was used immediately after weaning from CPB in group II. The patients in group I received blood products after discontinuation of CPB to achieve a hematocrit of 30%. The amount of blood product used, hematocrit immediately after CPB and on arrival in intensive care unit, postoperative hemodynamics and saturations, total operating room charge, blood charge, hospital stay, and hospital charge were compared.

Results. Mean body weight (15.8 kg in group I versus 17.5 kg in group II) and preoperative hematocrit values (35.6% in group I versus 34.2% in group II) were similar. Mean hematocrit immediately after CPB was 22% and 14% in group I and II, respectively (p < 0.0001). The mean hematocrit upon arrival to the intensive care unit was 34% in group I and 22% in group II (p < 0.0001). The amount of blood product transfusion was 32 mL/kg in group I and 3 mL/kg in group II patients (p < 0.0001). The patients in group II had significantly less blood bank charges; however, operating room charges and total hospital charges were similar between the two groups.

Conclusions. Elective atrial septal defect repair was performed with no blood product transfusion without increased morbidity or hospital stay. Ultrafiltration can be used to reverse hemodilution resulting from a bloodless CPB prime without an increase in hospital charge.

	Introduction

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Ultrafiltration removes water and low-molecular-weight solutes from blood with the help of the driving force of a roller head pump and a hollow-fiber membrane. Currently, two techniques are used: routine ultrafiltration during the cardiopulmonary bypass (CPB) run and modified ultrafiltration after CPB. When ultrafiltration was employed at the end of CPB, it has been shown to decrease total body water, increase hematocrit, and improve hemodynamic parameters [1, 2]. This technique has also decreased the postoperative bleeding and the need for blood transfusion in pediatric patients after CPB [3]. In a recent study, modified ultrafiltration decreased the postoperative blood loss and decreased the incidence of postoperative pleuropericardial effusions in a population of patients with single ventricle undergoing cavopulmonary connection [4].

Despite these benefits, modified ultrafiltration requires use of special equipment and additional operating room time after CPB that can potentially increase the hospital charges. In the era of cost-conscious health care, these additional charges can be concerning. Few data regarding the financial aspect of ultrafiltration are available [5].

	Material and methods

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We performed a retrospective review of medical records and hospital charges of 39 consecutive patients who underwent elective secundum atrial septal defect repair. The patients were divided into two groups with respect to type of CPB circuit prime and employment of ultrafiltration. Twenty-six patients (group I) had the conventional CPB prime with blood products and no ultrafiltration. Thirteen patients (group II) underwent bloodless CPB prime and modified ultrafiltration at the end of CPB.

Extracorporeal circulation was maintained with a Sarns (3M Healthcare, Ann Arbor, MI) 7000 roller pump system. A Minimax (Medtronic, Inc, Minneapolis, MN) hollow-fiber oxygenator was used for flow rates less than 2,500 mL/min, whereas a Maxima (Medtronic, Inc, Minneapolis, MN) hollow-fiber oxygenator was used when flow rates were more than 2,500 mL/min. The total bypass circuit priming volume was 600 mL for the Minimax and 1,100 mL for the Maxima oxygenator.

Packed red blood cells were added to the pump circuit in group I patients according to the following formula:

A Biofilter (Research Medical, Inc, Midvale, UT) cellulose biacetate hemoconcentrator was incorporated into the bypass circuit in patients in group II. The hemofilter was primed simultaneously with the CPB circuit. The inlet of the filter was connected to the arterial line and the venous line was connected to the filter outlet. Ultrafiltration was carried out immediately after the discontinuation of CPB as described previously by Naik and Elliot [3]. The hydrostatic pressure required was provided by the roller pump, and a transfilter gradient of 350 mm Hg was maintained. Vacuum was not used. The blood in the bypass circuit was passed through the filter, and blood substitute was added to the circuit as needed to keep the venous reservoir primed at all times until the goal ultrafiltration volume was reached. A target volume removed of 20 mL/kg was selected, and ultrafiltration was continued until this was accomplished. Charges were obtained from a review of patient bills.

The two patient groups were compared with respect to postoperative hemodynamics; hematocrit preoperatively, immediately after CPB, and postoperatively in the intensive care unit; amount of blood transfusion; operating room charges; charges due to blood and blood product preparation and administration; and total hospital charges.

Results were compared with the two-sample t test. A probability value of less than 0.05 was considered statistically significant.

	Results

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The preoperative diagnosis was isolated secundum atrial septal defect without pulmonary hypertension in all patients. Patient demographics are demonstrated in Table 1. The two patient groups were similar with respect to age, average weight, and mean preoperative hematocrit. The average volume of ultrafiltration was 19.8 mL/kg in group II patients. The average ultrafiltration time was 11 ± 5 minutes. Intraoperative and postoperative hematocrit and amount of blood transfused are depicted in Table 2. The patients in group II had significantly lower hematocrits immediately after CPB and in the intensive care unit. A significant increase in the hematocrit after ultrafiltration in group II patients (14.3% ± 5.3% versus 22.0% ± 8.6%; p < 0.0001) was seen. Patients in group II received significantly less blood transfusion than group I patients (32 ± 24 versus 3 ± 6 mL/kg; p < 0.0001). The mean operative times were 119 ± 19 and 124 ± 34 minutes in group I and group II patients, respectively. Postoperative oxygen saturations, pulse rate, intensive care unit stay, and hospital stay are demonstrated in Table 3. No significant difference in postoperative hemodynamic parameters or oxygen saturation between the two groups was present. The average postoperative chest tube outputs were 9.2 mL/kg in group I and 13.2 mL/kg in group II patients (p = 0.032). Patients who underwent ultrafiltration had a tendency for a shorter total hospital stay (2.9 days in group I versus 2.5 days in group II), but this did not reach statistical significance (p = 0.171). Blood bank charges, operating room charges, and total hospital charges are outlined in Table 4. Patients in group II had significantly lower blood bank charges ($750 ± 81 versus $529 ± 88; p < 0.004). The operating room charges and total hospital charges were similar in the two groups.

	Comment

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We accepted a hematocrit of 15% during weaning from the CPB before ultrafiltration. Hematocrit increased to 22% after ultrafiltration. However, hematocrit immediately after CPB ranged from 8% to 27% in group II and from 13% to 30% in group I. This did not result in impaired oxygen saturation or hemodynamic instability as reflected by identical transcutaneous O₂ saturations and hemodynamic parameters in the two groups. Several studies have determined the critical hematocrit for optimal oxygen transport and myocardial function. Mathru and associates [13] have found a hematocrit of 15% to be safe in anesthetized humans after coronary artery bypass grafting. A hematocrit of 20% has been well tolerated after self-limiting anemia in the pediatric population [14, 15]. Other authors have found a steep decrease in tissue oxygenation and loss of adaptation reflexes at hematocrits less than 10% in dogs [16].

Cardiac operations have been performed in the pediatric population without blood transfusion [17, 18]. This technique involves priming the CPB circuit with crystalloid or colloid solutions to obviate homologous blood transfusion. Several clinical studies have demonstrated that the degree of hemodilution rather than the amount of blood loss is the reason for blood transfusion during CPB [19]. It appears that the lower limit of safe hematocrit can be decreased further in patients who are otherwise healthy and undergo relatively simple procedures with short CPB runs. These patients usually recover well without transfusion.

Acute hemodilution due to nonblood CPB prime can cause severe total body edema that can result in organ dysfunction and derangements in the coagulation system owing to dilution of coagulation factors. Ultrafiltration after CPB has been shown to reverse hemodilution [20]. Naik and colleagues [21] have demonstrated that modified ultrafiltration elevated the blood pressure and cardiac index in children. Hemofiltration has also improved coagulation and decreased the early postoperative blood loss by reversing hemodilution and increasing the concentration of coagulation factors [22].

A detailed analysis of true costs requires prospective application of suitable systems [23] and probably represents an exercise in frustration. Hospital charges are not costs. True accounting costs can be difficult to obtain. As a first approximation and because of ease of retrieval, hospital charges were used in the two groups to make comparisons. Perhaps future efforts will help describe the cost differences between the techniques.

We also examined the financial aspect of the ultrafiltration. The charge and benefit factors have been an active area of research for congenital cardiac operations [24]. Altered practice models are being proposed to decrease the hospital cost without compromising patient care for elective secundum atrial septal defect repair [25]. Preoperative financial risk stratification models to identify the patients with potentially high hospital costs are another example of today’s cost-conscious health care [23]. We were concerned that the hemofilter device and the additional time required for the ultrafiltration process would increase the cost of the procedure. The charge of the hemofilter to the patient was about $150. The modified ultrafiltration process typically takes between 10 and 15 minutes depending on the weight of the patient. However, in this study, the operating room charges and the total hospital charges were similar between the two groups of patients. This may be because of decreased use of blood products and hence reduced blood bank charges in patients who underwent ultrafiltration.

A remarkable difference in the amount of blood transfusion in the ultrafiltration group was present. However, the differences in the blood bank charges, although statistically significant, were not as substantial between the two groups of patients. The blood bank charges were itemized. The majority of blood bank charges resulted from the typing and crossmatch process. The actual blood products contributed only 10% to 15% to blood bank charges.

	References

Top Abstract Introduction Material and methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): William M. Novick Donald C. Watson Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gurbuz, A. T. Articles by Watson, D. C. Search for Related Content PubMed PubMed Citation Articles by Gurbuz, A. T. Articles by Watson, D. C.