An overview of therapeutic apheresis in pediatrics.

Therapeutic apheresis in pediatrics requires selected modifications due to the child's smaller size, blood volume, and developmental age. Red blood cell priming is used to prevent dilution of the child's hematocrit from the normal saline prime. Continuous flow cell separators maintain isovolemia. Discontinuous flow machines cause alterations in the blood volume which may be poorly tolerated by small and critically ill children. Whole blood volumes are calculated on 100 cc/kg for newborns and 70 cc/kg for toddlers and children. Although peripheral access may be used in older children, the majority of pediatric patients require central venous lines preferably the stiffer apheresis or dialysis double lumen catheters. Anticoagulants include heparin, anticoagulant citrate dextrose (ACD), or a combination of both. The heparin dose is titrated to achieve activated clotting times of 180-220 seconds. Children are more sensitive to the hypocalcaemic effects of ACD especially if citrated replacement products such as fresh frozen plasma are used. Prevention or treatment of low ionized calcium levels may include decreased citrate rates, calcium addition to 5% albumin replacement, calcium gluconate infusions, intravenous boluses of calcium chloride, or a change in anticoagulant. Apheresis risks can be reduced through adequate monitoring and preventive measures. The most commonly performed treatments are plasma exchanges and peripheral blood stem cell collections. Diversional activities appropriate for the child's developmental age are provided to allay anxiety, to divert attention, and to elicit cooperation. In conclusion, size and clinical condition are not exclusionary criteria for apheresis.

Large-volume leukapheresis in pediatric patients: processing more blood diminishes the apparent magnitude of intra-apheresis recruitment.

BACKGROUND: Recruitment of progenitors during a large-volume collection, as defined by increasing relative and absolute numbers of progenitors (colony-forming units-granulocyte-macrophage [CFU-GM] of CD34+ cells), has been reported previously. STUDY DESIGN AND METHODS: To ascertain whether intra-apheresis recruitment occurs in pediatric patients who have undergone mobilization with chemotherapy and granulocyte-colony-stimulating factor (G-CSF), each hour's portion of a 4-hour leukapheresis was collected into separate bags, and assessed by complete blood count, CFU-GM, and CD34+ cell assays. Seven pediatric patients (median age, 7; range, 2-19) were studied in connection with 2 to 4 collections each, for a total of 21 collections (with hourly samples). The collections lasted for 4 hours, at an inlet rate of 1 to 3 mL per kg per minute, for daily processing totals of 5 to 12 blood volumes. (One blood volume [mL] is estimated by the patient's weight in kg x 70 mL/kg.) Smaller (younger) patients had inlet rates exceeding 2 mL per kg per minute, and larger (older) patients had rates of 1 to 1.5 mL per kg per minute. CFU-GM and CD34+ cell counts obtained each hour of the collection and divided by the first hour's value were compared by nonparametric repeated-measures ANOVA. RESULTS: Second-, third- and fourth-hour CD34+ progenitor cell counts were arithmetically higher than first-hour counts, but the trend did not reach significance (p = 0.1561). Second-hour counts were higher than first-hour counts in the overall analysis (mean +/- standard error [SE], 1.00 and 1.39 +/- 0.1, respectively; p = 0.0525) and in children older than 5 years (1.00 vs. 1.70 +/- 0.30, respectively; p = 0.0259), but not in children younger than 5 years (p = 0.8125). CFU-GM counts did not differ among the 4 hours of collection (p = 0.1717) or between the first and second hour (p = 0.9587). CONCLUSION: In larger (older) patients, from whom fewer blood volumes were collected, there is a trend toward intra-apheresis recruitment, although less than reported previously. In the smaller (younger) patients, from whom more blood volumes were collected, no trend was observed. Lack of (or submaximal) prior mobilization in previously reported studies may have facilitated intracollection recruitment. Alternatively, the larger number of blood volumes collected from the smaller (younger) patients may have masked intra-apheresis recruitment. The study documents the feasibility of large-volume, 4-hour leukapheresis in pediatric patients.

Pediatric large volume peripheral blood progenitor cell collections from patients under 25 kg: a primer.

Collection of peripheral blood progenitor cells from small pediatric patients provides many social and technical challenges not faced when collecting from adult patients. This paper provides a single institutions experience with 85 collections from 14 patients less than 25 kg of weight over a 2 year period. Specific challenges include obtaining venous access, anticoagulation, volume shifts, and obtaining patient cooperation. A systematic analysis of options for access, alternative modes of anticoagulation, and the effect of large ratios of extra-corporeal volume to patient's blood volume are discussed. Access uniformly required central venous catheters (CVC) ranging from 7-10 Fr. Anticoagulation included systemic heparinization titrating dose by activated clotting time in all cases and combined with citrate at a ratio of 1:25-1:30 in most cases. Collections were performed on a COBE Spectra, after priming with leukoreduced irradiated red cells and omitting both the initial 120cc diversion and rinse back of red cells at the end. Social challenges include issues of assent and ability to distract patients for the duration of a prolonged collection. Progenitor yields from collections from 14 patients were quantitated by CD34+ assay in all cases and CFU-GM in ten of 14 patients. A median of 4.5 x 10(6)/kg CD34+ cells were obtained for each collection. Complications, including those related to catheter access, are enumerated. In summary, large volume peripheral blood progenitor collection can be safely and efficaciously performed in small pediatric patients.

Intensive blood and plasma exchange for treatment of coagulopathy in meningococcemia.

Eight pediatric patients with fulminant meningococcemia, purpura, and disseminated intravascular cogulation who by multiple prognostic scoring systems were anticipated to have a poor outcome underwent intensive plasma exchange (IPE) or whole blood exchange (WBE) in addition to standard medical therapy. IPE/WBE was initiated shortly after admission with a mixture of both fresh frozen plasma and cryoprecipitate as the replacement solution. All IPE procedures were performed using a continuous flow system and a red cell prime. The mean fibrinogen level increased from 62 to 192 mg/dl, the prothrombin time (PT) decreased from a mean of 32.4 seconds to 15.1 seconds, and the mean activated partial thromboplastin time (APTT) decreased from 89.5 seconds to 40.1 seconds following completion of the initial IPE/WBE. There was a corresponding improvement in all coagulation factor levels but only slight improvement in antithrombin III (ATIII) and protein C levels. Seven of eight patients survived (87.5%) their initial presentation with the sole early death attributed to meningitis with cerebral edema. Mean fluid balance after the procedure was +10.8 +/- 5.87 cc/kg. There were no significant bleeding or cardiovascular complications during the procedure. There was no clinical or radiographic evidence of fluid overload after the procedure. This experience demonstrates that IPE/WBE may be conducted safely in critically ill, unstable pediatric patients and is effective in rapidly improving coagulopathy without fluid overload.