Continuous renal replacement therapy: a potential source of calories in the critically ill.

Background: Overfeeding can lead to multiple metabolic and clinical complications and has been associated with increased mortality in the critically ill. Continuous venovenous hemofiltration (CVVH) represents a potential source of calories that is poorly recognized and may contribute to overfeeding complications.Objective: We aimed to quantify the systemic caloric contribution of acid-citrate-dextrose regional anticoagulation and dextrose-containing replacement fluids in the CVVH circuit.Design: This was a prospective study in 10 critically ill adult patients who received CVVH from April 2014 to June 2014. Serial pre- and postfilter blood samples (n = 4 each) were drawn and analyzed for glucose and citrate concentrations on each of 2 consecutive days.Results: Participants included 5 men and 5 women with a mean ± SEM age of 61 ± 4 y (range: 42-84 y) and body mass index (in kg/m2) of 28 ± 2 (range: 18.3-36.2). There was generally good agreement between data on the 2 study days (CV: 7-11%). Mean ± SEM pre- and postfilter venous plasma glucose concentrations in the aggregate group were 152 ± 10 and 178 ± 9 mg/dL, respectively. Net glucose uptake from the CVVH circuit was 54 ± 5 mg/min and provided 295 ± 28 kcal/d. Prefilter plasma glucose concentrations were higher in patients with diabetes (n = 5) than in those without diabetes (168 ± 12 compared with 140 ± 14 mg/dL; P < 0.05); however, net glucose uptake was similar (46 ± 8 compared with 61 ± 6 mg/min; P = 0.15). Mean ± SEM pre- and postfilter venous plasma citrate concentrations were 1 ± 0.1 and 3.1 ± 0.2 mmol/L, respectively. Net citrate uptake from the CVVH circuit was 60 ± 2 mg/min and provided 218 ± 8 kcal/d.Conclusions: During CVVH there was a substantial net uptake of both glucose and citrate that delivered exogenous energy and provided ∼512 kcal/d. Failure to account for this source of calories in critically ill patients receiving nutrition on CVVH may result in overfeeding.

Levetiracetam Pharmacokinetics During Continuous Venovenous Hemofiltration and Acute Liver Dysfunction.

BACKGROUND: Levetiracetam clearance is dependent on renal (major) and hepatic (minor) elimination pathways. In the setting of organ dysfunction, dose reductions are recommended to prevent accumulation. Continuous venovenous hemofiltration (CVVH) has been shown to eliminate levetiracetam, but the preferred dosing regimen when a patient is on CVVH and has concomitant acute liver dysfunction is unknown. The objective of this case is to describe levetiracetam dosing and pharmacokinetics in the setting of CVVH and acute liver dysfunction. METHODS: This is a case report of a single patient. RESULTS: A 59-year-old male was admitted to the intensive care unit for acute onset multiorgan dysfunction associated with a hematologic disorder. His hospital course was complicated by persistent liver dysfunction with a model for end-stage liver disease score of 47 and renal failure which necessitated initiation of CVVH. On hospital day two, the patient developed new-onset focal seizures secondary to metabolic abnormalities that resulted in the initiation of levetiracetam 1000 mg intravenously twice daily. The peak concentration at steady state was 32.2 mcg/mL, and the trough concentration was 16.1 mcg/mL (goal 12-46 mcg/mL). The volume of distribution was 0.65 L/kg, and the elimination half-life was 11.4 h. CONCLUSION: Levetiracetam pharmacokinetics observed in this case approximated those seen in a normal healthy patient and a regimen of 1000 mg twice daily achieved serum trough concentrations at the lower limit of the target range. This case indicates that in a patient with acute liver dysfunction on CVVH, 1000 mg twice daily may be considered as an empiric levetiracetam regimen.

Polymeric plasticizer extends the lifetime of PVC-membrane ion-selective electrodes.

The nature of the plasticizer plays a pivotal role in the analytical performance of polymer membrane ion sensors. Conventional plasticizers suffer leaching or migration from the membrane and exudation, both of which could limit the lifetime of sensors based on plasticized membranes. Herein, we describe the use of polyester sebacate (PES), a model polymeric plasticizer, in the preparation of poly (vinyl chloride) (PVC) membrane ion-selective electrodes (ISEs) using valinomycin as ionophore. PVC membrane electrodes plasticized with polyester sebacate demonstrated potentiometric response characteristics that compared favorably to ones plasticized with the conventional and similarly structured plasticizer bis(2-ethylhexyl) sebacate (DOS). Increasing the content of polyester sebacate in the membrane enhanced the response and improved the selectivity of valinomycin-based ISEs toward potassium over sodium. Various methods, including electrochemical impedance spectroscopy, UV-vis spectroscopy, dark field optical microscopy, and potentiometry were employed to study the effect of plasticizer on the leaching of the membrane components and the lifetime of both DOS- and PES-plasticized membranes. PES-plasticized electrodes maintained Nernstian response and high selectivity for more than four months, an improvement over DOS-plasticized membrane electrodes. This was attributed to enhanced retention of the membrane components because of the high polymeric nature of the polyester sebacate. These characteristics suggest that polyester sebacate is a good candidate to replace the conventional plasticizers in preparing PVC membrane electrodes with longer lifetime.