Entangled photon pairs from semiconductor quantum dots.

Tomographic analysis demonstrates that the polarization state of pairs of photons emitted from a biexciton decay cascade becomes entangled when spectral filtering is applied. The measured density matrix of the photon pair satisfies the Peres criterion for entanglement by more than 3 standard deviations of the experimental uncertainty and violates Bell's inequality. We show that the spectral filtering erases the "which path" information contained in the photons' color and that the remanent information in the quantum dot degrees of freedom is negligible.

Adiabatic mode multiplexer for evanescent-coupling-insensitive optical switching.

A novel adiabatic mode multiplexer enables a 2 x 2 optical switch whose operation does not depend on accumulated phase due to evanescent coupling between waveguides. The adiabatic mode multiplexer has a negligible insertion loss over C+L bands and modal cross talk better than -40 dB for any polarization state. Mode multiplexing is achieved by adiabatic transition from the fundamental mode of the single-mode waveguide to the higher mode of the multimode waveguide. Experimental measurement results for a device realized in silica-on-silicon technology are presented. By directly measuring the nonadiabatic transition probability, we show that the adiabatic mode multiplexer operates in the Landau-Zener regime.

Ultrasound-guided thrombin injection for the treatment of iatrogenic pseudoaneurysm of the femoral artery.

BACKGROUND: Pseudoaneurysm occurring after catheterization of the femoral artery is associated with significant morbidity. Percutaneous ultrasound-guided thrombin injection has recently emerged as a potential first-line therapy. OBJECTIVES: To evaluate the efficacy of this treatment in eight patients with iatrogenic femoral artery pseudoaneurysm. METHODS: After attempted treatment with external compression had failed, eight patients with iatrogenic femoral artery pseudoaneurysm were treated with thrombin injection. Treatment performed between 2 and 9 days following arterial puncture. The study group comprised seven males and one female ranging in age from 23 to 89 years (median 70). Seven had undergone cardiac catheterization with or without intervention, and five were receiving antiplatelet and/or anticoagulant drugs. Arterial pseudoaneurysm resulted from femoral vein catheterization in one patient. Using a sterile technique and real-time Doppler ultrasound guidance, a dilute solution of bovine thrombin (average dose 250 units, range 100-600), was slowly injected directly into the pseudoaneurysm until cessation of flow was seen. Patients were allowed to walk within 2 hours of the procedure and were followed up clinically and by color Doppler ultrasound during the admission. RESULTS: Cardiac catheterization had been inadvertently performed via the superficial or profunda femoris arteries in four of the eight patients. Thrombin injection was initially successful in all eight patients without complication. Thrombosis occurred immediately in every case. Early recanalization of pseudoaneurysm occurred in one patient despite repeat thrombin injection and attempted ultrasound-guided compression. He eventually required surgical repair. The final success rate was 87.5% (7/8). CONCLUSION: Faulty puncture technique is an important risk factor for the development of post-catheterization femoral artery pseudoaneurysm. Ultrasound-guided thrombin injection is a safe, rapid, well-tolerated, inexpensive and successful therapy. If initial external compression with a sandbag fails to result in thrombosis of the pseudoaneurysm then thrombin injection should be considered as first-line therapy. If unsuccessful, it does not preclude the use of alternative treatment modalities. Further study is necessary to assess the long-term effects of thrombin injection.

Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depression-type ischemia.

OBJECTIVES: The goal of this study was to investigate the nature of the association between silent ischemia and postoperative myocardial infarction (PMI). BACKGROUND: Silent ischemia predicts cardiac morbidity and mortality in both ambulatory and postoperative patients. Whether silent stress-induced ischemia is merely a marker of extensive coronary artery disease or has a closer association with infarction has not been determined. METHODS: In 185 consecutive patients undergoing vascular surgery, we correlated ischemia duration, as detected on a continuous 12-lead ST-trend monitoring during the period 48 h to 72 h after surgery, with cardiac troponin-I (cTn-I) measured in the first three postoperative days and with postoperative cardiac outcome. Postoperative myocardial infarction was defined as cTn-I >3.1 ng/ml accompanied by either typical symptoms or new ischemic electrocardiogram (ECG) findings. RESULTS: During 11,132 patient-hours of monitoring, 38 patients (20.5%) had 66 transient ischemic events, all but one denoted by ST-segment depression. Twelve patients (6.5%) sustained PMI; one of those patients died. All infarctions were non-Q-wave and were detected by a rise in cTn-I during or immediately after prolonged, ST depression-type ischemia. The average duration ofischemia in patients with PMI was 226+/-164 min (range: 29 to 625), compared with 38+/-26 min (p = 0.0000) in 26 patients with ischemia but not infarction. Peak cTn-I strongly correlated with the longest, as well as cumulative, ischemia duration (r = 0.83 and r = 0.78, respectively). Ischemic ECG changes were completely reversible in all but one patient who had persistent new T wave inversion. All ischemic events culminating in PMI were preceded by an increase in heart rate (delta heart rate = 32+/-15 beats/min), and most (67%) of them began at the end of surgery and emergence from anesthesia. CONCLUSIONS: Prolonged, ST depression-type ischemia progresses to MI and is strongly associated with the majority of cardiac complications after vascular surgery.

Preoperative dipyridamole-thallium scanning, selective coronary revascularization and long-term survival in patients with critical lower limb ischemia.

BACKGROUND: A large proportion of patients with critical limb ischemia have advanced, often asymptomatic coronary artery disease which is associated with increased perioperative risk and decreased long-term survival. METHODS: We evaluated retrospectively the short and long-term effect of routine dipyridamole-thallium cardiac scanning (DTS) and selective coronary revascularization in 113 consecutive patients who were scheduled for revascularization of the lower extremity. RESULTS: DTS was abnormal in 60 (53.1%) patients and demonstrated a moderate-severe reversible defect in 26 (23.0%) patients. On the basis of DTS and clinical evaluation 33 (29.2%) patients were referred for coronary catheterization. Of these, 9 underwent PTCA and 4 underwent coronary artery bypass, without complications. Surgical revascularization of the limbs was performed in all but two patients. Two (1.8%) patients died postoperatively, three (2.7%) sustained nonfatal postoperative myocardial infarctions. None of the patients who underwent preoperative coronary revascularization suffered a cardiac complication after the peripheral vascular operation. During mean follow-up of 31.7 months, 30 (28.0%) patients died. A moderate-severe reversible defect on DTS was the strongest predictor for shortened survival (Exp(b)=0.61, CI 95%=0.42-0.88; p=0.006). Patients who underwent preoperative coronary revascularization followed a survival curve approaching those without a reversible defect on DTS (mean survival 61+/-8 vs 63+/-4 months; NS) which was significantly better than those with such a defect who did not undergo coronary revascularization (mean survival 34+/-5 months; p=0.03). CONCLUSIONS: While the perioperative benefits of routine preoperative DTS screening in patients with critical limb ischemia, remain debatable, it provides an opportunity for identification and treatment of life-limiting coronary artery disease and improving survival.

Regulation of ROMK and channel-inducing factor (CHIF) in acute renal failure due to ischemic reperfusion injury.

BACKGROUND: Acute renal failure caused by ischemia followed by reperfusion is often associated with severe hyperkalemia. The present study was undertaken to characterize the effects of renal ischemia and reperfusion on plasma potassium (K) and on the gene expression of channel-inducing factor (CHIF), a putative K channel regulator, and of ROMK, the distal nephron secretory K channel. METHODS: The following groups of rats were studied: (1) sham operated (sham); (2) after one hour of ischemia by bilateral renal artery clamping (I), and after one hour of ischemia; (3) one hour of reperfusion (I-R 1 h); (4) 24 hours of reperfusion (I-R 24 h); (5) 48 hours of reperfusion (I-R 48 h); and (6) 72 hours reperfusion (I-R 72 h). The expression of CHIF and ROMK was examined by Northern blot hybridization in renal cortex, medulla, and papilla and in the colon. The abundance of ROMK protein was determined in the renal cortex and medulla by immunoblotting. RESULTS: Maximal plasma creatinine and potassium levels after ischemia and reperfusion were 470 +/- 16 micromol/L, P < 0.0001 versus sham, and 9.65 +/- 0.33 mmol/L, P < 0.0001 versus sham, respectively. The expression of CHIF was significantly down-regulated in the medulla and papilla, with a maximal decrease of 80% at 48 to 72 hours. In contrast, a most significant increase in CHIF mRNA expression (250% of baseline) was noted in the colon after 24 to 48 hours of reperfusion. ROMK expression was reduced in the cortex and was completely abolished in the medulla at 48 to 72 hours of reperfusion. Ischemia and reperfusion injury significantly decreased ROMK protein abundance to 10% of control in the medullary fractions. CONCLUSIONS: These results suggest that down-regulation of renal CHIF and ROMK may contribute at least partly to the hyperkalemia of acute renal failure after ischemia and reperfusion, while CHIF up-regulation in the colon may act as a compensatory mechanism of maintaining K balance via increased K secretion.

Computer assisted physiologic monitoring and stability assessment in vascular surgical patients undergoing general anesthesia--preliminary data.

BACKGROUND: Physiologic monitors present an influx of numerical data that can be overwhelming to the clinician. We combined several parameters in an effort to reduce the amount of information that must be continuously monitored including oxyhemoglobin saturation by pulse oximetry, end-tidal CO2 concentration, arterial blood pressure, and heart rate into an integrated measure--the health stability magnitude (HSM). The HSM is computed for a predetermined basal period, the reference HSM (RHSM), and recalculated continuously for comparison with the baseline value. In this study we present the HSM concept and examine changes in the HSM during abdominal aortic aneurysm surgery. MATERIALS AND METHODS: After IRB approval, nine patients were studied. The anesthesiologist recorded all significant intra-operative events. Within a defined time interval, data were recorded and used to calculate a combined parameter, the HSM. The baseline or reference value of this index (RHSM) was calculated after the induction of anesthesia. Individual HSM values were repeatedly calculated for ten second periods after the RHSM value was established. A > 30% deviation of the HSM from the RHSM was considered significant. Deviations in the HSM were compared with events recorded by the anesthesiologist on a paper record and with the record from an electronic record-keeping system. The deviation observed between two consecutive HSMs, called dHSM, was plotted against HSM to construct a contour diagram of data from all patients to which individual cases could be compared. RESULTS: The plot showed that dHSM vs. HSM values were tightly clustered. The inner contour on the distribution plot contained 90% of values. Individual patient's time course, projected on this diagram, revealed deviations form "normal" physiology. Fifty-nine events led to > 30% deviations in the HSM; 27 were anticipated events and 32 were unanticipated. CONCLUSION: The correlation between HSM and dHSM depicts changes in multiple monitored parameters that can be viewed using a single graphical representation. Projection of individual cases on the contour diagram may help the clinician to distinguish relative intraoperative stability from important events. Data reduction in this manner may guide clinical decision-making in response to unanticipated or unrecognized events.

Amputated lower limbs as a bank of organs for other organ salvage.

Aggressive modern technologies have made it possible to attempt limb salvage in even the most extreme cases. However, it is imperative to remember that prolonged salvage attempts may lead to devastating complications. The decision-making is more problematic in patients with bilateral severely injured mangled lower limbs. In such a case, protocols like the MESS are no longer valid because of the implications of bilateral amputation. In these rare cases, we use a multi-team approach and modern micro-surgical reconstructive techniques in attempting to salvage at least one of the lower limbs. We present here our experience in six patients with bilateral mangled lower limbs where an amputated limb was the source of "spare parts" for the salvage of the contralateral limb. In each of the cases, after evaluation and planning, the harvesting of the required tissues (including skin, muscle, bone, nerve and blood vessels) from the amputated leg was performed and simultaneously, a reconstruction of the contralateral severely injured limb was done. These cases emphasize the importance of modern trauma care, not only the ability to treat multiply traumatized patients, but also the capability to execute sophisticated techniques during the acute phase of treatment with maximal cooperation between teams from different disciplines.

Preoperative thallium scanning, selective coronary revascularization, and long-term survival after carotid endarterectomy.

BACKGROUND AND PURPOSE: Long-term survival in patients after carotid endarterectomy (CEA) is determined mainly by their concomitant cardiac disease. We tested to determine whether preoperative thallium scanning (PTS) and subsequent selective coronary revascularization (CR), by either percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG), improve long-term survival after CEA. METHODS: Two hundred twenty-six of 255 consecutive patients (88%) undergoing CEA from 1990 to 1996 had PTS. Those with significant reversible defects on PTS were referred for coronary angiography and possible CR. Patients who had undergone PTS were divided into the following 4 groups: group 1, normal or mild defects on PTS; group 2, moderate-severe fixed and/or reversible defects in patients who did not undergo CR; group 3, patients who had CR secondary to their PTS results; and group 4, patients who had CR in the past that was not related to the PTS. Perioperative data were prospectively recorded, and data on long-term survival and cardiac and neurological complications were collected. RESULTS: Seventy-seven patients (34%) had preoperative coronary angiography, and 42 (19%) had subsequent CR: preoperative PTCA or CABG in 24, combined CEA+CABG in 10, and post-CEA CABG in 8 patients. No deaths resulted from the coronary angiography, CR, or CEA. Six patients had perioperative nonfatal myocardial infarction and 8 had stroke. During the follow-up (40+/-23 months), 47 patients (18%) died, 31 (66%) from cardiac disease and 4 (8.5%) from stroke. Independent predictors of long-term overall mortality were diabetes mellitus, preoperative T-wave inversion on ECG, lower-extremity arterial disease, and history of neurological symptoms [exp(beta)=3. 5, 3.4, 2.5, and 2.4; P=0.0003, 0.0004, 0.01, and 0.04, respectively]. In addition, preoperative moderate-severe thallium defect without CR (group 2) independently predicted long-term cardiac mortality [exp(beta)=2.8; P=0.04]. Patients with preoperative CR (group 3) had long-term survival rate similar to that of group 1 and significantly better than that of group 2 (P=0. 02). CONCLUSIONS: PTS predicts long-term survival, and selective CR based on the thallium results improves the survival rate of patients undergoing CEA.

Results of reconstruction in major pelvic and extremity venous injuries.

PURPOSE: Outcome and venous patency after reconstruction in major pelvic and extremity venous injuries was studied. METHODS: We retrospectively reviewed 46 patients with 47 venous injuries. RESULTS: Injuries were caused by penetrating trauma in 37 extremities, blunt trauma in 6 patients, and were iatrogenic in 4 patients. Pelvic veins were injured in 4 patients, lower-extremity veins were injured in 39 limbs in 38 patients, and upper-extremity veins were injured in 4 patients. Concomitant arterial injuries occurred in 37 patients. Venous repairs were mostly of the complex type and included spiral or panel grafts in 15 (32%) reconstructions, interposition grafts or patch venoplasty in 19 (40%) reconstructions, end-to-end and lateral repair in 11 patients, and ligation in 2 patients. Two patients underwent early amputation. Early transient limb edema occurred in 2 patients, and postoperative venous occlusions were documented in 4 patients. Full function was regained in 39 (81%) extremities. No variable, including 4 retrospectively applied extremity injury scores (mangled extremity severity score [MESS], limb salvage index [LSI], mangled extremity syndrome index [MESI], predictive salvage index [PSI]), correlated with outcome. High values on all 4 scores were significantly associated with reexplorations (P <.02), which were done in 8 patients for debridement (5), arrest of bleeding (2), and repair of a missed arterial injury (1). Follow-up of 28 +/- 6 months on 27 patients (57%; duplex scan in 18, continuous-wave Doppler and plethysmography in 9, and venography in 3) showed 1 occlusion 6 weeks after the injury and patency of all other venous reconstructions. CONCLUSION: Reconstructions of major venous injuries with a high rate of complex repairs result in a large proportion of fully functional limbs and a high patency rate. A high extremity injury score predicts the need for reexploration of the extremity. Mostocclusions occur within weeks of injury, and the subsequent delayed occlusion rate is very low.

Placement of a peritoneal dialysis catheter with routine omentectomy--does it prevent obstruction of the catheter?

OBJECTIVE: To find out if routine omentectomy reduced the incidence of obstruction and other complications of catheters inserted for continuous ambulatory peritoneal dialysis (CAPD). DESIGN: Retrospective study. SETTING: Teaching hospital, Israel. SUBJECTS: 60 patients with end stage renal failure who needed catheters for CAPD. INTERVENTION: Routine omentectomy during insertion of the catheter, usually under local anaesthesia. MAIN OUTCOME MEASURES: Short and long term morbidity, and mortality. RESULTS: No patient died as a result of the procedure. The catheter obstructed in only one patient (2%) during a mean follow-up period of 28 months (range 2-108), and 90% of the catheters survived one year. CONCLUSIONS: Routine omentectomy during insertion of a catheter for CAPD under local anaesthesia is safe and the incidence of obstruction is low. Prospective randomised studies are needed before it can be recommended as the procedure of choice.

Step baroreflex response in awake patients undergoing carotid surgery: time- and frequency-domain analysis.

Step baroreceptor stimulation can provide an insight into the baroreflex control mechanism, yet this has never been done in humans. During carotid surgery under regional anesthesia, a step increase in baroreceptor stimulation occurs at carotid declamping immediately after removal of the intra-arterial atheromatous plaque. In 10 patients, the R-R interval and systolic and diastolic blood pressures (BP) were continuously recorded, and signals obtained within the time window from 10 min before until 10 min after carotid declamping were analyzed. Mean +/- SD time signals, power spectra, and transfer and coherence functions before and after declamping were calculated. Immediately after carotid declamping, both heart rate (HR) and BP declined in an exponential-like manner lasting 10.3 +/- 5.9 min, and their power spectra increased in the entire frequency range. Transfer function magnitude and coherence functions between BP and HR increased predominantly in the midfrequency region (approximately 0.1 Hz), with no change in phase function. Thus, in carotid endarterectomy patients, step increase in baroreceptor gain elicits a prolonged decline in HR and BP. Frequency analyses support the notion that the baroreflex control mechanism generates the midfrequency HR and BP variability, although other frequency regions are also affected.

Cavoatrial shunt: a graft salvage procedure for suprahepatic caval anastomosis obstruction after liver transplantation.

A liver transplant recipient developed the Budd-Chiari syndrome because of an obstruction of the suprahepatic inferior vena cava anastomosis. Percutaneous balloon dilatation angioplasty was not feasible. On exploration, dense retrohepatic fibrotic reaction was observed. The patient underwent successful retrohepatic cavoatrial shunt placement by means of a 16-mm, ring-enforced polytetrafluoroethylene graft. We conclude that this shunt should be considered an additional graft salvage procedure for this complication.

Mesenteric bypass for chronic mesenteric ischaemia.

Chronic mesenteric ischaemia is an uncommon disease that requires treatment to relieve the symptoms of abdominal angina and to prevent intestinal infarction. Over a period of 3 years, 12 patients with visceral artery stenosis or occlusion were referred to the authors' service and 10 underwent mesenteric bypass grafting. Both the coeliac and the superior mesenteric arteries were revascularized in four patients, and the superior mesenteric artery alone in six patients, using a variety of grafts and graft configurations. This was done in conjunction with aortic graft placement in four cases and with renal bypass in three. All patients survived the procedure. At a mean follow-up of 28 months, one patient died of myocardial infarction 42 months after surgery, while all survivors are symptom-free. Chronic mesenteric ischaemia can be treated safely and effectively. The variation in the pattern of mesenteric occlusions and the frequent association with aortic and renovascular disease does not allow for a single 'best' technical solution but requires the surgical procedure to be individually tailored.