Cardiac Arrhythmias Resulting from a Peripherally Inserted Central Catheter: Two Cases and a Review of the Literature.

We present two cases of patients being treated for diabetic ketoacidosis in the intensive care unit who experienced cardiac arrhythmia secondary to peripherally inserted central catheters (PICCs). In one instance, the patient became bradycardic and experienced related loss of consciousness, ultimately requiring cardiopulmonary resuscitation. In the second case, the patient experienced an episode of nonsustained ventricular tachycardia. We explore the various types of arrhythmias that have been reported secondary to central venous catheters, as well as factors that place patients at an increased risk for arrhythmia while undergoing PICC insertion. Furthermore, we look at the literature for methods to improve the insertion of PICC lines by decreasing the risk of catheter over-insertion as well as the effects of training for PICC placement.

Role of bilayer characteristics on the structural fate of aß(1-40) and aß(25-40).

The ß-amyloid (Aß) peptide is derived from the transmembrane (TM) helix of the amyloid precursor protein (APP) and has been shown to interact with membrane surfaces. To understand better the role of peptide-membrane interactions in cell death and ultimately in Alzheimer's disease, a better understanding of how membrane characteristics affect the binding, solvation, and secondary structure of Aß is needed. Employing a combination of circular dichroism and deep-UV resonance Raman spectroscopies, Aß(25-40) was found to fold spontaneously upon association with anionic lipid bilayers. The hydrophobic portion of the disease-related Aß(1-40) peptide, Aß(25-40), has often been used as a model for how its legacy TM region may behave structurally in aqueous solvents and during membrane encounters. The structure of the membrane-associated Aß(25-40) peptide was found to depend on both the hydrophobic thickness of the bilayer and the duration of incubation. Similarly, the disease-related Aß(1-40) peptide also spontaneously associates with anionic liposomes, where it initially adopts mixtures of disordered and helical structures. The partially disordered helical structures then convert to ß-sheet structures over longer time frames. ß-Sheet structure is formed prior to helical unwinding, implying a model in which ß-sheet structure, formed initially from disordered regions, prompts the unwinding and destabilization of membrane-stabilized helical structure. A model is proposed to describe the mechanism of escape of Aß(1-40) from the membrane surfaces following its formation by cleavage of APP within the membrane.