Multiband compression limiting for hearing-impaired listeners

Four multiband compression limiters and two linear amplification systems were compared in terms of the intelligibility of consonant-vowel-consonant (CVC) nonsense syllables for two hearing-impaired listeners over a 30 dB range of input levels. Each system incorporated one of two frequency-gain characteristics and one of three limiting characteristics (no limiting, moderate limiting, or severe limiting). The subjects were instructed to choose overall listening levels that would permit speech spanning the range of input levels to be as intelligible as possible and comfortable for long-term listening. Relative to linear amplification, the overall gain selected by the subjects increased by roughly 5 and 11 dB for the moderate and severe limiter, respectively. With linear amplification, the maximum score, 82 percent correct, was obtained at the highest input level and scores fell roughly 34 percentage points as input level was reduced. With compression limiting, although the maximum scores, 81 percent and 79 percent correct, were obtained at lower input levels, performance was comparable to that with linear amplification. Also, scores spanned a range of only 22 and 9 percentage points across the range of input levels with the moderate and severe limiter, respectively. This benefit was due to the improved scores provided by compression limiting at the low input levels. However, this advantage was offset somewhat by the disadvantage provided by compression at high input levels relative to linear amplification. Error analysis indicated that the spectral degradations introduced by independent compression of 16 frequency bands may have caused the reduced intelligibility at higher input levels.     

Removal of the endothelial layer in perfused mesenteric vascular bed of the rat.

The endothelial layer was removed from the isolated mesenteric vascular bed of the rat by perfusion with hypotonic Tyrode solution for 12.5 min. This procedure damaged more than 95% of the endothelial cells. After endothelial removal, the response to norepinephrine was significantly enhanced, whereas the relaxation induced by acetylcholine (ACh) was completely abolished. The results of this work show that perfusion with hypotonic solutions provides a reliable method of endothelial removal in isolated perfused vascular beds, allowing the study of endothelial-dependent vascular responses.     

Stroke as the first manifestation of calcific aortic stenosis

Heart valve calcifications are rarely recognized as a potential source for cerebral embolism. Previous studies have identified mitral, but not aortic, valve calcifications to be risk factors for stroke. Based on these studies, heart surgery is unlikely to be indicated in patients who present with a stroke and an 'incidental' aortic valve calcification. We report a case of a 46-year-old man presenting with acute onset of left-sided weakness and numbness. A previous smoking history was the only cardiovascular risk factor found. Head CT scan revealed a right middle cerebral artery territory infarct and an adjacent high-density lesion. CT angiography demonstrated the presence of calcific embolic material in the middle cerebral artery. A search for embolic sources revealed a calcific aortic stenosis (CAS). Initially placed on coumadin, the patient developed silent myocardial infarction 2 months later, presumed to be also embolic in origin from the CAS. After aortic valve replacement, the patient has been symptom-free during a 2-year follow-up. In conclusion, CT angiography may be the method of choice for detecting calcific cerebral emboli, and demonstration of a causal relationship between CAS and an embolic stroke by CT angiography may be an important adjunct in surgical decision-making.     

Biliary Complications in Orthotopic Liver Transplantation Using Choledochocholedochostomy with a T-tube

Despite significant advances in orthotopic liver transplantation (OLT), biliary tract reconstruction is still a major source of complications. Choledochocholedochostomy with a T-tube used to be the standard procedure for biliary reconstruction after OLT. However, many centers currently avoid use of the T-tube because of the high incidence of complications. Our aim was to study the biliary complications occurring at our center when end-to-end choledochocholedochostomy (EE-CC) over a T-tube was used as the standard procedure for biliary reconstruction. A retrospective review was conducted of all patients who underwent liver transplantation from February 1, 1996, to April 30, 2010. Only patients requiring any therapy to treat biliary complications were considered, whereas those with concomitant hepatic artery complications were excluded. The study cohort consisted of 743 patients who had EE-CC with a T-tube.Of these, 73 patients (9.8%) experienced any biliary complication. Anastomotic strictures occurred in 17 patients (2.3%), and non-anastomotic strictures in 2 (0.3%). Fifteen patients with anastomotic strictures were successfully treated by dilatation and stenting. Bile leakage was diagnosed in 39 patients (5.2%). Leakage occurred at the anastomosis in 15 patients (2%), and at the exit site of the T-tube in 24 patients (3.2%). Tube opening was the only treatment used in 30 patients with bile leakage (76.9%). Seven patients experienced leaks after elective T-tube removal (1%). Overall, repeat surgery to manage biliary complications was needed in 9 patients (1.2%). The mortality rate from biliary complications was 0.13%. In conclusion, EE-CC with a T-tube was followed by a low incidence of biliary complications. The complication rate after elective T-tube removal and the repeat surgery rate were extremely low. These results might challenge the current trend to avoid T-tube stenting in OLT.     

Calcium-sensing receptor attenuates AVP-induced aquaporin-2 expression via a calmodulin-dependent mechanism

Recent evidence suggests that arginine vasopressin (AVP)-dependent aquaporin-2 expression is modulated by the extracellular calcium-sensing receptor (CaSR) in principal cells of the collecting duct, but the signaling pathways mediating this effect are unknown. Using a mouse cortical collecting duct cell line (mpkCCD(cl4)), we found that increasing the concentration of apical extracellular calcium or treating with the CaSR agonists neomycin or Gd(3+) attenuated AVP-dependent accumulation of aquaporin-2 mRNA and protein; CaSR gene-silencing prevented this effect. Calcium reduced the AVP-induced accumulation of cAMP, but this did not occur by increased degradation of cAMP by phosphodiesterases or by direct inhibition of adenylate cyclase. Notably, the effect of extracellular calcium on AVP-dependent aquaporin-2 expression was prevented by inhibition of calmodulin. In summary, our results show that high concentrations of extracellular calcium attenuate AVP-induced aquaporin-2 expression by activating the CaSR and reducing coupling efficiency between V(2) receptor and adenylate cyclase via a calmodulin-dependent mechanism in cultured cortical collecting duct cells.     

The inflammatory response to colloids and crystalloids used for pump priming during cardiopulmonary bypass

Background: Systemic inflammatory response frequently occurs after coronary artery bypass surgery and is strongly correlated with the risk of postoperative morbidity and mortality. This study tests the hypothesis that the priming of the extracorporeal circuit with colloid solutions results in less inflammation in patients undergoing cardiac surgery than priming with crystalloid solutions. Methods: A prospective, randomized study was designed. Forty‐four patients undergoing elective coronary artery bypass grafting were randomly allocated to one of two groups: 22 patients primed with Ringer's lactate (RL) solution and 22 patients primed with gelatin‐containing solution during the surgery. Plasma levels of interleukin (IL)‐6, IL‐8, tumor necrosis factor (TNF)‐α, C‐reactive protein (CRP) and, complement 4 were measured during the surgical intervention and over the following 48 postoperative hours. Cytokine levels were measured by enzyme‐linked assays from plasma samples obtained at specific time points pre‐ and post‐operatively. Results: In both groups the serum levels of the pro‐inflammatory cytokines (IL‐6, IL‐8, TNF‐α), CRP, complement 4, and leukocytes increased significantly over the baseline, although no significant differences were observed between the two groups. The operation time, blood loss, need for inotropic support, extubation time, and length of intensive care unit stay did not differ significantly between the two groups. Conclusion: Priming with gelatin vs. RL produces no significant differences in the inflammatory response in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.     

Management of Hepatocellular Carcinoma Recurrence After Liver Transplantation

Management of patients with hepatocellular carcinoma (HCC) recurrence after liver transplantation (OLT) is not well established. We conducted a retrospective analysis of our results in the treatment of HCC recurrence after OLT Patients. The 23 HCC recurrences developed after 182 OLT performed for HCC within Milan criteria, had an average follow-up of 60 months.

Results

The median time to recurrence was 23.4 months. Surgical resection of the recurrence was possible in 11 patients, but an R-0 resection was obtained in 8 patients. Four of these 8 patients developed another recurrence, with 3 succumbing due to tumor recurrence and 1 alive at 12 months with recurrence. The other 4 patients without recurrences, include 3 who are alive at 19, 31, and 86 months and 1 who died at 32.6 months due to hepatitis C recurrence. The 3 patients with palliative resections developed recurrences. Twelve patients were rejected for surgery: 8 were treated symptomatically, 2 with systemic chemotherapy, and 2 with everolimus and sorafenib. This last treatment was also prescribed for 2 patients after R-0 surgery who are alive at 19 and 31 months and for 1 patient after R-1 surgery who is alive at 19 months. Of 15 patients who died, 13 succumbed to HCC recurrence. The average survival from transplantation was 61.7 ± 37.5 and 48 ± 34.3 months for patients without and with recurrence, respectively (P < .001). The survival from the recurrence was significantly higher among patients with R-0 surgery: 32.3 ± 21.5 versus 11.9 ± 6.9 months (P = .006).

Conclusions

HCC recurrence after OLT of patients within Milan criteria was low but had a great impact on survival. Few cases are amenable to R-0 resection, but when possible it was associated with a significantly increased survival, although with an high incidence of a new recurrence. There is a rationale for the use of sorafenib and mammalian target of rapamycin based immunosuppression, which warrants randomized studies.