Potential drug sequestration during extracorporeal membrane oxygenation: results from an ex vivo experiment.

OBJECTIVE: Using an ex vivo simulation model we set out to estimate the amount of drug lost due to sequestration within the extracorporeal circuit over time. DESIGN: Simulated closed-loop extracorporeal membrane oxygenation (ECMO) circuits were prepared using a 1.5-m2 silicone membrane oxygenator. Group A consisted of heparin, dopamine, ampicillin, vancomycin, phenobarbital and fentanyl. Group B consisted of epinephrine, cefazolin, hydrocortisone, fosphenytoin and morphine. Drugs were tested in crystalloid and blood-primed circuits. After administration of a one-time dose of drugs in the priming fluid, baseline drug concentrations were obtained (P0). A simultaneous specimen was stored for stability testing at 24 h (P4). Serial post-membrane drug concentrations were then obtained at 30 min (P1), 3 h (P2) and 24 h (P3) from circuit fluid. MEASUREMENTS AND RESULTS: One hundred and one samples were analyzed. At the end of 24 h in crystalloid-primed circuits, 71.8% of ampicillin, 96.7% of epinephrine, 17.6% of fosphenytoin, 33.3% of heparin, 17.5% of morphine and 87% of fentanyl was lost. At the end of 24 h in blood-primed extracorporeal circuits, 15.4% of ampicillin, 21% of cefazolin, 71% of voriconazole, 31.4% of fosphenytoin, 53.3% of heparin and 100% of fentanyl was lost. There was a significant decrease in overall drug concentrations from 30 min to 24 h for both crystalloid-primed circuits (p = 0.023) and blood-primed circuits (p = 0.04). CONCLUSIONS: Our ex vivo study demonstrates serial losses of several drugs commonly used during ECMO therapy. Therapeutic concentrations of fentanyl, voriconazole, antimicrobials and heparin cannot be guaranteed in patients on ECMO.

Successful use of bivalirudin for cardiac transplantation in a child with heparin-induced thrombocytopenia.

Bivalirudin, a direct thrombin inhibitor, has recently emerged as a promising option for anti-coagulation during cardiopulmonary bypass in patients who cannot receive heparin. There is limited experience with the use of bivalirudin in children. We present the case of a child with heparin-induced thrombocytopenia with thrombosis (HIT Type II) who underwent successful orthotopic cardiac transplantation using bivalirudin as the primary anti-coagulant for cardiopulmonary bypass.

The first use of live continuous glucose monitoring in patients on extracorporeal life support.

BACKGROUND: Evidence suggests that glycemic control provides clinical benefit to critically ill patients. The Extracorporeal Glucose Monitoring System (EGMS), Medtronic Minimed, Northridge, CA) has been developed to measure real-time, continuous blood glucose concentrations in patients on extracorporeal bypass. This pilot study reports the first in vitro and in vivo evaluations of EGMS in an extracorporeal circuit. METHODS: In an in vitro study, three EGMS sensors were inserted in a neonatal extracorporeal circuit. Circuit blood glucose levels were altered by saline dilution and dextrose infusion. EGMS sensors were then inserted into the venous return limb of the extracorporeal circuit in a cohort of six critically ill infants on extracorporeal life support (ECLS). Continuous glucose measurements were compared with laboratory and bedside glucose values at predefined intervals. Linear regression analyses and the Clarke error grid were constructed to analyze device accuracy. RESULTS: All three in vitro EGMS sensors recorded real-time data without interruption for 48 h. EGMS glucose measurements closely correlated with reference levels (R (2) = 0.93). EGMS glucose values demonstrated an approximate 7-10 min lag while glucose concentrations were rapidly changing. Eight EGMS devices were inserted into six neonates on ECLS on day of life 6 +/- 3. EGMS correlated well with laboratory glucose (R2 = 0.61) and bedside glucose during a hyperinsulinemic euglycemic clamp (R2 = 0.78). On the Clarke error grid, 98% of readings were within zones A and B using laboratory glucose as reference, and 100% were within zones A and B using bedside glucose measurements. Blood glucose range during the in vitro study was 19-295 mg/dL and during the in vivo study was 80-257 mg/dL. CONCLUSIONS: This pilot study suggests that EGMS is a reliable tool for measuring continuous blood glucose in critically ill patients connected to an extracorporeal circuit, although important limitations exist. Potential applications of this technology include intensive glucose monitoring in patients on ECLS, cardiopulmonary bypass, and renal replacement therapy.