Bacterial contamination of platelet concentrates: results of a prospective multicenter study comparing pooled whole blood-derived platelets and apheresis platelets

BACKGROUND: The GERMS Group initiated a prospective multicenter study to assess prevalence and nature of bacterial contamination of pooled buffy-coat platelet concentrates (PPCs) and apheresis platelet concentrates (APCs) by routine screening with a bacterial culture system. STUDY DESIGN AND METHODS: In nine centers overall, 52,243 platelet (PLT) concentrates (15,198 APCs, 37,045 PPCs) were analyzed by aerobic and anaerobic cultures (BacT/ALERT, bioMérieux). RESULTS: In 135 PLT concentrates (PCs; 0.26%), bacteria could be identified in the first culture (0.4% for APCs vs. 0.2% for PPCs; p < 0.001). In 37 (0.07%) of these PC units, the same bacteria strain could be identified in a second culture from the sample bag and/or the PC unit. The rate of confirmed-positive units did not differ significantly between APC (0.09%; 1/1169) and PPC units (0.06%; 1/1544). Bacteria from skin flora (Propionibacterium acnes, Staphylococcus epidermidis) were the most prevalent contaminants. Median times to first positive culture from start of incubation were 0.7 and 3.7 days in aerobic and anaerobic cultures for confirmed-positive units. With a "negative-to-date" issue strategy, most PC units (55%) had already been issued by time of the first positive culture. CONCLUSION: The rate of confirmed bacterial contamination of PC units was low. Nevertheless, clinicians must be aware of this risk. The risk of bacterial contamination does not warrant universal preference of APCs. It must be questioned whether routine bacterial screening by a culture method can sufficiently prevent contaminated products from being transfused due to the delay until a positive signal in the culture system and due to false-negative results.     

Subclavian Steal Syndrome with or without Arterial Stenosis: A Review

The subclavian‐vertebral artery steal syndrome (SSS) is the hemodynamic phenomenon of blood flow reversal in the vertebral artery due to significant stenosis or occlusion of the proximal subclavian artery or the innominate artery. Occasionally, SSS is diagnosed in patients not harboring arterial stenosis. With the exception of arterial congenital malformations, the limited case reports of SSS with intact subclavian artery are attributed to dialysis arteriovenous fistulas (AVFs). Interestingly, these cases are more frequently symptomatic than those with the classical atherosclerotic SSS forms. On the other hand, the disclosure of SSS due to subclavian/innominate artery atherosclerotic stenosis, even in the absence of accompanying symptoms, should prompt a thorough cardiovascular work‐up for the early detection of coexisting coronary, carotid, or peripheral artery disease. Herein, we review the incidence, clinical presentation, sonographic findings, and therapeutic interventions related to SSS with and without subclavian/innominate artery stenosis. We also review the currently available data in the literature regarding the association of SSS and dialysis AVF. In addition, we present a patient with bilateral symptomatic SSS as the result of an arteriovenous graft (AVG) that was introduced after the preexisting AVF in the contralateral arm became nonfunctional. SSS due to subclavian or innominate artery stenosis/occlusion is rarely symptomatic warranting interventional treatment. In contrast, when it is attributed to AVF, surgical correction is frequently necessary.     

Endothelin-B receptors and ventricular arrhythmogenesis in the rat model of acute myocardial infarction

The arrhythmogenic effects of endothelin-1 (ET-1) are mediated via ETA-receptors, but the role of ETB-receptors is unclear. We examined the pathophysiologic role of ETB-receptors on ventricular tachyarrhythmias (VT/VF) during myocardial infarction (MI). MI was induced by coronary ligation in two animal groups, namely in wild-type (n = 63) and in ETB-receptor-deficient (n = 61) rats. Using a telemetry recorder, VT/VF episodes were evaluated during phase I (the 1st hour) and phase II (2–24 h) post-MI, with and without prior β-blockade. Action potential duration at 90% repolarization (APD90) was measured from monophasic epicardial recordings and indices of sympathetic activation were assessed using fast-Fourier analysis of heart rate variability. Serum epinephrine and norepinephrine were measured with radioimmunoassay. MI size was similar in the two groups. There was a marked temporal variation in VT/VF duration; during phase I, it was higher (p = 0.0087) in ETB-deficient (1,519 ± 421 s) than in wild-type (190 ± 34 s) rats, but tended (p = 0.086) to be lower in ETB-deficient (4.2 ± 2.0 s) than in wild-type (27.7 ± 8.0 s) rats during phase II. Overall, the severity of VT/VF was greater in ETB-deficient rats, evidenced by higher (p = 0.0058) mortality (72.0% vs. 32.1%). There was a temporal variation in heart rate and in the ratio of low- to high-frequency spectra, being higher (<0.001) during phase I, but lower (p < 0.05) during phase II in ETB-deficient rats. Likewise, 1 h post-MI, serum epinephrine (p = 0.025) and norepinephrine (p < 0.0001) were higher in ETB-deficient (4.20 ± 0.54, 14.24 ± 1.39 ng/ml) than in wild-type (2.30 ± 0.59, 5.26 ± 0.67 ng/ml) rats, respectively. After β-blockade, VT/VF episodes and mortality were similar in the two groups. The ETB-receptor decreases sympathetic activation and arrhythmogenesis during the early phase of MI, but these effects diminish during evolving MI.     

The role of MR imaging in staging femoral head osteonecrosis

Reliability, accuracy and prognostic value of any classification system are important in evaluation and treatment of femoral head osteonecrosis. The purpose of the present study was to correlate the plain radiographs with MRI in femoral head osteonecrosis. Between 2000 and 2005, 115 hips (72 patients) were evaluated and classified according to the ARCO classification criteria with the use of plain radiographs and additional application of MRI. Classification was performed by consensus between a musculoskeletal radiologist and an orthopaedic surgeon. Sensitivity (SEN), specificity (SP), positive (PPV) and negative (NPV) predictive value of X-rays were estimated. According to MRI, 17 hips were classified as stage I, 25 as stage II, 48 as stage III and 25 as stage IV. The SEN, SP, PPV and NPV of plain radiographs were for stage II 88%, 90.5%, 78.6% and 95%; for stage III 79.2% 82%, 80.8% and 87.2%; for stage IV 76%, 100%, 100% and 90.9%, respectively. The agreement between plain radiographs and MRI was 80.6% for staging the disease, 71.2% for recording the location of the osteonecrotic lesion, 67.1% for evaluating the size of the lesion, 79.2% for the presence of collapse of the articular surface and 56.3% for the degree of collapse. In conclusion, the ARCO classification could miss important information in stages II and III, where treatment aims at preservation of the hip joint integrity. The results of the present study suggest that MRI should be incorporated in the classification of osteonecrosis (stages II and III), to add accuracy and prognostic value.