Consistency of remifentanil concentrations in propofol-Remifentanil infusions. A laboratory-based study.

BACKGROUND: There is increasing interest in two-agent single-pump intravenous infusions for anesthesia and sedation in pediatric patients. Propofol-remifentanil is one such mixture. The poor miscibility of such admixtures when remifentanil is added in very high concentrations and when the admixtures are maintained in static conditions has been demonstrated; however, these physiochemical properties have not been examined in clinically relevant concentrations or settings. AIM: To examine if propofol-remifentanil admixtures maintain consistent remifentanil delivery when mixed in clinically relevant remifentanil concentrations and subjected to the physical effects of an actively infusing, directly-engaged syringe driver system with an extension line, as occurs when propofol-remifentanil is administered to a patient. METHODS: A propofol 10 mg.ml-1 combined with remifentanil 5 mcg.ml-1 solution was run using a Paedfusor® propofol target-controlled infusion model for 10 kg and 20 kg children for 57 min at a target plasma concentration of 3 mcg.ml-1 through a 30 ml syringe, 180 cm minimum volume extension line, lever lock cannula, interlink injection site, and 22 g intravenous cannula into sample pots. Samples were taken at the completion of the loading bolus, 1 and 2 min postcompletion of loading bolus, and every 5 min thereafter. The remifentanil concentration in these samples was then assayed using chromatography. RESULTS: There was no difference in the concentration of remifentanil in the samples based on the duration of infusion to the endpoint of 1 h, or on the patient weight model used. The concentration remained 5 mcg.ml-1 +/- 0.5 mcg.ml-1 per sample. The measurement uncertainty for the assay at 0.5 mcg.ml-1 is +/- 0.2 mcg.ml-1 . CONCLUSION: The concentration of remifentanil was 5 mcg.ml-1 +/- 0.5 mcg.ml-1 and was consistent across 57 min of infusion, and two different pediatric weight profiles.

Whipple's in the valleys: a case of Whipple's with thrombocytopenia and endocarditis.

INTRODUCTION: This case report details the second described case of Whipple's disease-related thrombocytopenia in the medical literature. Whipple's disease is a rare multisystem infection caused by the actinomycete Tropheryma whipplei, first described by George Whipple in 1907. The key clinical manifestations are weight loss, diarrhoea and malabsorption, but arthralgia and endocarditis are also well described. CASE PRESENTATION: A 62-year-old Caucasian female presented with weight loss, anaemia and behavioural changes but denied any abdominal symptoms. Thrombocytopenia subsequently developed rapidly. Bone marrow examination showed abundant megakaryocytes in keeping with peripheral platelet sequestration. In addition, there was significant polyclonal plasmacytosis. She was also found to have a 1.6 cm tricuspid vegetation. The diagnosis was confirmed by presence of foamy macrophages on duodenal biopsy, positive periodic acid-Schiff staining and visualisation of T whipplei actinomycetes on electron microscopy. Tissue PCR performed mid-treatment showed traces of T whipplei DNA. The infection was treated with a 2-week intravenous course of ceftriaxone followed by 12 months of oral co-trimoxazole. The thrombocytopenia and anaemia resolved rapidly with antibiotic therapy, her behaviour returned to normal and she remains clinically well. CONCLUSIONS: This report confirms the association of thrombocytopenia with Whipple's disease, likely due to peripheral platelet sequestration, which resolves rapidly with treatment. In patients with a long history of unintended weight loss, Whipple's disease is a rare but important differential diagnosis as it is ultimately fatal if left untreated.