Optimizing management of replacement fluids for therapeutic plasma exchange: Use of an automated mathematical model to predict post-procedure fibrinogen and antithrombin levels in high-risk patients.

BACKGROUND: Therapeutic plasma exchange (TPE) utilizes an extracorporeal circuit to remove pathologic proteins causing serious illness. When processing a patient's entire blood volume through an extracorporeal circuit, proteins responsible for maintaining hemostatic system homeostasis can reach critically low levels if replacement fluid types and volumes are not carefully titrated, which may increase complications. METHODS: The charts from 27 patients undergoing 46 TPE procedures were reviewed to evaluate the accuracy of our predictive mathematical model, utilizing the following patient information: weight, hematocrit, pre- and post-TPE factor levels (fibrinogen, n = 46, and antithrombin, n = 23), process volume and volumes of fluids (eg, plasma, albumin, and normal saline) administered during TPE and adverse events during and after TPE. RESULTS: Altogether, 25% of patients experienced minor adverse events that resolved spontaneously or with management. There were no bleeding or thrombotic complications. The mean difference between predicted and measured post-TPE fibrinogen concentrations was -0.29 mg/dL (SD ±23.0, range -59 to 37), while percent difference between measured and predicted fibrinogen concentration was 0.94% (SD ±10.8, range of -22 to 19). The mean difference between predicted and measured post-TPE antithrombin concentrations were 0.89% activity (SD ±10.0, range -23 to 14), while mean percent difference between predicted and measured antithrombin concentrations was 3.87% (SD ±14.5, range -25 to 38). CONCLUSIONS: Our model reliably predicts post-TPE fibrinogen and antithrombin concentrations, and may help optimize patient management and attenuate complications.

An ex vivo comparison of vascular access devices used in extracorporeal photopheresis.

BACKGROUND: Central venous access devices are commonly used in extracorporeal photopheresis, but their performance has not been systematically evaluated. The primary objective of this study was to compare pressures at various flow rates for central venous access devices in an ex vivo simulation of photopheresis. STUDY DESIGN AND METHODS: Diluted, heparinized red blood cells were circulated through central access devices in series with a photopheresis system, and pressures at several flow rates were recorded. The devices tested were the Trifusion catheter (Hickman), the Vortex single-lumen and dual-lumen ports (Angiodynamics), and the TidalPort device (Norfolk). Flow rates were also compared for silicone and polyurethane catheters and for different catheter internal diameters. RESULTS: The Vortex dual-lumen port generated pressure alarms above flow rates of 60 mL/minute. Throughout flow rates from 5 to 100 mL/minute, the Trifusion catheter and the TidalPort device operated at lower pressures than the Vortex ports. Within typical clinical flow rates, neither catheter material nor internal diameter substantially affected pressure. CONCLUSION: Central venous access devices show large differences in pressure within flow rates used routinely in clinical settings. These differences cannot be fully attributed to catheter material composition or catheter internal diameter.

Platelet recovery rate during plasma exchange predicts early and late responses in patients with thrombotic thrombocytopenic purpura.

BACKGROUND: Therapeutic plasma exchange (TPE) is the first-line therapy for patients with thrombotic thrombocytopenic purpura (TTP). However, therapeutic response to TPE and late prognosis vary among different patients, and predictors of these outcomes may help customize treatments to individual patients. STUDY DESIGN AND METHODS: We retrospectively examined the platelet (PLT) recovery rate (PRR) in 64 consecutive patients with initial episode of TTP who received TPE in our institution between 2003 and 2010. PRRs were calculated by linear regression of the PLT counts at the start and during the first few days of TPE treatment. Its relationship with remission in response to TPE, exacerbation and relapse, and survival was analyzed by univariate and multivariate analysis. RESULTS: With multivariate analysis, which included ADAMTS13 activities, patients with a PRR by Day 3 (PRR3) of 5 × 10(9) /L per 24 hours or above were 18 times more likely to achieve remission in response to TPE than those with a lower PRR3 (p < 0.001). In addition, short-term exacerbations and relapses beyond 1 month of remission occurred almost exclusively in patients with a PRR3 of 5 × 10(9) /L per 24 hours or above. Survival was significantly better in these patients than in patients with PRR3 below the cutoff (p < 0.001), and the hazard ratio adjusted for ADAMTS13 and age was 23.2 (p < 0.005). CONCLUSION: PRR3 with a cutoff of 5 × 10(9) /L per 24 hours provides a practical approach to risk stratify TTP patients receiving TPE early in their treatment and may guide the decision making both at initial encounters and during the long-term follow-up.

Linear relationship between lymphocyte counts in peripheral blood and buffy coat collected during extracorporeal photopheresis.

BACKGROUND: Extracorporeal photopheresis (ECP) is commonly used to treat patients with graft-versus-host disease (GVHD) and lung transplant rejection (LTR) in our institution. The quantitative relationship between the number of white blood cells treated during ECP and the cell count in peripheral blood is unclear. STUDY DESIGN AND METHODS: Patients with GVHD and LTR receiving ECP with either UVAR XTS or CELLEX (Therakos) were prospectively recruited for this study. A complete cell count with differential was performed on preprocedural peripheral blood and samples from the collected buffy coats. Correlation analysis and linear regression were performed between cell counts in peripheral blood and buffy coat. Collection efficiency was compared between UVAR XTS and CELLEX. RESULTS: In all 52 patients, lymphocyte counts in buffy coat and peripheral blood showed strong correlation (r values were 0.85 and 0.983 for UVAR XTS and CELLEX, respectively; p < 0.001) with slopes of 2 and 5.1 for UVAR XTS and CELLEX, respectively (p < 0.001). The quantitative relationship remained robust in patients stratified by diagnoses. Monocytes also showed consistent correlation and linearity, but not neutrophils or combined white blood cells, red blood cells, or platelets. CELLEX enriched approximately twice as many lymphocytes and monocytes than UVAR XTS per procedure (p < 0.001). CONCLUSION: The preprocedural peripheral lymphocyte count can predict the number of lymphocytes within the buffy coat collected during ECP, which may justify the use of peripheral lymphocyte count as a surrogate for the cell dose treated per procedure. Peripheral monocyte counts may serve as an alternative. CELLEX is more efficient in collecting lymphocytes and monocytes than UVAR XTS under conditions tested.