The Journal of Vascular Access

Enterococci are gram-positive bacteria that are part of the normal human intestinal flora and can colonize the upper respiratory tract, biliary tract and vagina of otherwise healthy people. Although their virulence is relatively low, recently enterococci have emerged as significant nosocomial pathogens and are currently the 4th leading cause of hospital-acquired infections, including those associated with intravascular catheter and biliary stent implants. The frequent use of these medical devices is often associated with severe complications, including catheter-related bloodstream infections (CRBSIs) and biliary stent occlusions, because of microbial biofilm formation on the device surface.

Furthermore, other than a high level of resistance to penicillin, ampicillin and aminoglycosides, a dramatic increase in vancomycin resistance of enterococci has been recently observed in most clinical settings. Clinical strains exhibiting novel mechanisms of acquired resistance to antimicrobials are frequently isolated. In addition, enterococci have a great ability to transmit these resistance traits to other species and even to other genera. Due to their associated morbidity and mortality, enterococcal infections related to medical devices currently represent a major challenge for clinicians, especially for the management of critically ill patients, resulting in prolonged hospitalization and additional health costs.

Bloodstream infections (BSIs) are the third most common nosocomial infections. Catheters and other medical devices are the first exogenous causes of preventable infections in hospital. The estimated attributable mortality for catheter-associated BSI ranges from 1–35%, mainly depending on etiological agents and underlying disease. In considering this, it is necessary to reduce central venous catheter- (CVC)-related BSI prevalence and to obtain a rapid and accurate method for an early diagnosis. This review indicates the advantages and the disadvantages of old and new tools for the early diagnosis of CVC-related BSIs.

Measurement of vascular access flow (QVA) has been suggested as a method of choice for vascular access quality (VAQ) monitoring. Besides traditional duplex Doppler, a number of bedside methods based mostly on the Krivitski principle of QVA evaluation from recirculation at reversed needles (RX), have been developed. This work compares ultrasonic dilution (UD), taken as a reference, HD01, Transonic Systems; duplex Doppler (DD); thermodilution (TD), BTM, Fresenius; optodilutional RX measurement (ORX), Critline III, R-mode, HemaMetrics; direct optodilutional QVA evaluation from jumpwise changes in ultrafiltration rate at both normal and reversed needles connection (OABF), Critline III, ABF-mode; and direct transcutaneous optodilutional QVA evaluation (TQA), Critline III TQA.

Firstly, reproducibility of each method was assessed by duplicate measurement at unchanged conditions. This was followed by paired measurement with each method performed at controlled change in relevant measurement condition (two different extracorporeal blood flows in UD and TD, changed sensor position in TQA). Finally paired measurements by each method and the reference method performed at identical conditions were evaluated to assess accuracy of each method. The simple Krivitski formula QVA= QB(1-RX)/RX was used wherever manual QVA calculation was needed.

Very high reproducibility was seen in UD, both for measurement at the same extra corporeal blood flow (QB) (correlation coefficient of duplicate measurement r= 0.9702, n= 58) and for measurement at two different QB (r= 0.9735, n= 24), justifying its current status of a reference method in QVA evaluation. Slightly lower reproducibility of TD measurement at the same QB (r= 0.9197, n= 40) and at two different QB (r= 0.8508, n= 168) can be easily overcome by duplicate measurement with averaging. High correlation of TD vs. UD (r= 0.9543, n= 54) makes TD a viable clinical alternative in QVA evaluation. Consistently different QVA obtained at two different QB should prompt closer investigation of anatomical conditions of the access. Use of the simple Krivitski formula in TD (which measures total recirculation, i.e. sum of access recirculation and cardiopulmonary recirculation) brings about underestimation of QVA, which progressively increases from QVA of about 600 ml/min up. Good correlation, although with significant scatter (r= 0.8691, n= 27) was found between the DD- and UD-based QVA. By far the worst reproducibility at the same QB from among the investigated methods was found in ORX (0.6430, n= 23). Also the correlation of ORX vs. UD was lower than in other methods (r= 0.702, n=33) and general overestimation of QVA by about 25% was noted. Correlation of OABF vs. UD (r= 0.6957, n= 26) was slightly better than that of ORX and it gave less overestimated values. The TQA method showed very high reproducibility (r= 0.9712, n= 85), however only for unchanged sensor position. Correlation of QVA measured at two different sensor positions was much worse (r= 0.7255, n= 22). Correspondence of TQA vs. UD was satisfactory (r= 0.8077, n= 36). Skilled and experienced operators are a must with this method.

Angioaccess-induced ischemia is an infrequent but cumbersome problem, because both limb ischemia correction and access salvage should be undertaken during the same procedure. This paper reports two cases that we successfully managed with a bridge graft to a small distal artery after fistula ligation.

The Authors describe a case of spontaneous migration in the right jugular vein of a central venous catheter tip, properly positioned in the right atrium through the right subclavian vein two days before.

Prolonged venous access devices (PVADs) have become indispensable in antiblastic protocols for the treatment of cancer patients, in anti-infection protocols for acquired immunodeficiency syndrome (AIDS) patients and in the management of chronic malabsorption syndromes. Using these catheters carries the risk of several complications, and some are potentially lethal, for example, cardiac embolization of catheter fragments. Rupture is a complication almost exclusive to catheters positioned percutaneously: after using this technique, device malfunction can occur due to catheter kinking after its excessively medial introduction in the subclavian vein. The early recognition of any pinch-off sign (POS) is fundamental in preventing catheter rupture that frequently follows this complication. Other factors can be involved in early rupture, for example, excessive force on a syringe used to clear a catheter that shows early signs of malfunction, or a strength defect in the materials used in the catheter construction. This report describes an early rupture case of an initially correctly positioned catheter and reviews 20 such cases in the recent literature.