Effect of electron blocking layer on the efficiency of AlGaN mid-ultraviolet light emitting diodes

The performance of AlGaN-based mid and deep ultraviolet light emitting diodes (LEDs) is severely limited by electron overflow and by the poor hole injection into the device active region. We have studied the effect of various electron blocking layers on the performance of AlGaN LEDs operating at ~280 nm. It is observed that, compared to conventional p-type electron blocking layer, the incorporation of an n-type AlN/AlGaN superlattice electron blocking layer before the active region can significantly improve the device performance by reducing electron overflow without compromising hole injection. Direct on-wafer measurement showed an external quantum efficiency ~4.4% and wall-plug efficiency ~2.8% by optimizing the design of n-type AlN/AlGaN superlattice electron blocking layer, which is nearly a factor of five to ten times better than identical devices but with the incorporation of a conventional p-type electron blocking layer.

Increased B-type natriuretic peptide during liver transplantation: relationship to invasively measured hemodynamic parameters

BACKGROUND

The role of B-type natriuretic peptide (BNP) concentration in predicting cardiac dysfunction has been extensively investigated in many clinical conditions. Little is known, however, about its relationships with hemodynamic parameters from right heart catheterization in patients undergoing liver transplant surgery.

METHODS

We retrospectively evaluated 525 patients who underwent liver transplantation. Hemodynamic variables from a Swan-Ganz catheter and BNP concentrations were measured 1 hour after induction of general anesthesia. Patients were stratified by quintiles of BNP concentrations. Univariate and multivariate logistic regression analysis were used to identify hemodynamic parameters associated with BNP ≥ 135 pg/mL, a cutoff point for the 5th quintile.

RESULTS

Univariate analysis showed that factors significantly associated with BNP ≥ 135 pg/mL included model for end-stage liver disease (MELD) score, diastolic blood pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure (PCWP), cardiac index, right ventricular end-diastolic volume index (RVEDVI), systemic vascular resistance index, pulmonary vascular resistance index (PVRI), and right ventricular stroke work index. Multivariate analysis revealed that MELD score (odds ratio [OR] = 1.059, P < .001), PCWP (OR = 1.116, P = .026), RVEDVI (OR = 1.010, P = .009), and PVRI (OR = 1.009, P = .002) were independent determinants of BNP ≥ 135 pg/mL.

CONCLUSIONS

Severity of liver disease, preload dependent hemodynamic parameters, and pulmonary vascular resistance were found to be significantly associated with increased BNP concentration, reinforcing the utility of BNP as a marker of cardiac strain and ventricular volume overload in liver failure patients undergoing liver transplant surgery.

Does stroke volume variation predict intraoperative blood loss in living right donor hepatectomy?

BACKGROUND

Although stroke volume variation (SVV) is a valuable index of preload responsiveness, there is limited information about the association between low SVV and increased hepatectomy-related bleeding. We therefore evaluated whether SVV predicts blood loss during living donor hepatectomy.

METHODS

We evaluated 93 adult liver donors undergoing right hepatectomy for transplantation. Arterial blood pressure, heart rate, body temperature, central venous pressure, SVV, cardiac output, and systemic vascular resistance were measured. Logistic regression and receiver operating characteristic (ROC) curve analyses were performed to determine independent factors and optimal cutoff values of hemodynamic parameters for predicting intraoperative blood loss ≥ 700 mL.

RESULTS

Of these 93 donors, 36 (38.7%) had blood loss ≥ 700 mL. Univariate logistic regression analysis showed that factors associated with blood loss ≥ 700 mL included heart rate, SVV, cardiac output, and systemic vascular resistance. Multivariate logistic regression analysis revealed that only SVV was an independent predictor of blood loss ≥ 700 mL. ROC curve analysis showed that the optimal cutoff value for SVV predicting blood loss ≥ 700 mL was 6% (area under the curve = 0.64).

CONCLUSIONS

SVV is a significant independent predictor of blood loss ≥ 700 mL during donor hepatectomy, suggesting that low SVV may provide useful information on intraoperative bleeding in donors undergoing right hepatectomy.

Evaluation of intraoperative brain natriuretic peptide as a predictor of 1-year mortality after liver transplantation

BACKGROUND

Although brain natriuretic peptide (BNP), a marker of cardiac dysfunction, has been known to predict postoperative mortality, little is known about the postoperative prognostic ability of BNP in liver transplantation (OLT) recipients. We aimed to determine whether intraoperative BNP level can predict 1-year all-cause mortality after OLT.

METHODS

We retrospectively investigated 525 OLT recipients. BNP and hemodynamic parameters were simultaneously measured 1 hour after induction of anesthesia. Cox regression analysis and receiver operating characteristic curve analysis were performed to determine clinical predictors and optimal cutoff values of post-OLT mortality.

RESULTS

The 1-year all-cause mortality rate was 9.7% (51/525). Median BNP concentration was significantly higher in nonsurvivors than in survivors (114 vs 56 pg/mL, P < .001). Significant factors in univariate Cox regression analysis were Child-Pugh score, model for end-stage liver disease (MELD) score, logBNP, hemoglobin, creatinine, heart rate, systolic pulmonary arterial pressure, and central venous pressure. In multivariate Cox regression analysis, independent predictors of posttransplant mortality were MELD score and logBNP. However, simultaneously measured hemodynamic parameters did not remain predictors. BNP levels greater than a cutoff of 136 pg/mL (specificity = 83.5%, negative predictive value = 93.6%) were associated with increased post-OLT mortality (log-rank test P < .001).

CONCLUSIONS

Intraoperative BNP level is an independent predictor of 1-year all-cause mortality after OLT with a high negative predictive value, suggesting that its measurement appears useful in identifying patients at low risk of post-OLT mortality.

Comparison of stroke volume variations derived from radial and femoral arterial pressure waveforms during liver transplantation

BACKGROUND

Stroke volume variation (SVV) is being increasingly used to predict fluid responsiveness. Since radial arterial pressure (RAP) and femoral arterial pressure (FAP) frequently showing discrepancies during liver transplantation (LT), we sought to investigate the effect of differing arterial waveforms on SVV and cardiac output (CO) derived from the Vigileo device, by comparing SVV and CO values derived from RAP (SVV(RAP), CO(RAP)) and FAP (SVV(FAP), CO(FAP)) during LT.

METHODS

The linear associations and agreements between SVV(RAP) and SVV(FAP) and between CO(RAP) and CO(FAP) were assessed during LT. Hemodynamic variables were measured at nine predefined time points in all 32 recipients, resulting in 288 data pairs.

RESULTS

Correlations were observed between SVV(RAP) and SVV(FAP) (r = .961) and between CO(RAP) and CO(FAP) (r = .848) at all time points. These correlations between SVV(RAP) and SVV(FAP) (r = .923) and between CO(RAP) and CO(FAP) (r = .902) existed even during the period when mean RAP and FAP values differed (10 minutes after reperfusion). Bland-Altman analysis for SVV(RAP) versus SVV(FAP) and for CO(RAP) versus CO(FAP) showed weak biases (-0.2% and -0.5 L/min) and reasonable limits of agreement (-2.2 to 1.8% and -1.9 to 0.9 L/min). The percentage errors for SVV and CO values were 27.0% and 22.2%.

CONCLUSIONS

There was no significant difference between SVV(RAP) and SVV(FAP) when measured using the Vigileo device during LT. This finding indicated that SVV obtained using the Vigileo device offered relatively consistent information regardless of the catheterization site.

Thermosoftening treatment of the nasotracheal tube before intubation can reduce epistaxis and nasal damage

We evaluated whether a thermosoftening treatment with warm saline of a nasotracheal preformed tube can improve navigability through the nasal passageways and reduce epistaxis and nasal damage. A total of 150 patients were randomly allocated to three groups: Group I (untreated tube group, n = 50), Group II (35 degrees C treated tube group, n = 50), and Group III (45 degrees C treated tube group, n = 50). In Groups II and III, the tubes were softened at 35 +/- 2 degrees C and 45 +/- 2 degrees C with warm saline, respectively. In Group I the tube was prepared at room temperature (25 +/- 2 degrees C). The incidence of epistaxis and nasal damage in Groups II and III was significantly less than that of Group I (P: < 0.05). Despite the more frequent incidence of smooth passage in Group III, no statistical difference was found among the groups. Logistic regression analysis also confirmed that epistaxis was more likely to be reduced when the tube had been thermosoftened (odds ratio = 1.46, 95% confidence interval = 1.02, 2.11). We conclude that simple thermosoftening treatment of the nasotracheal tube with warm saline helps to reduce epistaxis and nasal damage.

IMPLICATIONS

Thermosoftening treatment of a nasotracheal tube with warm saline before intubation can effectively reduce epistaxis and nasal damage. This technique is safe, easy, and suitable for all types of tubes and does not require additional implements.

Cisatracurium neuromuscular block at the adductor pollicis and the laryngeal adductor muscles in humans

We have compared the dose-response relationship (n = 30) and time course of neuromuscular block (n = 20) of cisatracurium at the laryngeal adductor and the adductor pollicis muscles. ED95 values for cisatracurium were 66.8 (95% confidence interval 61.3-72.3) micrograms kg-1 at the larynx and 45.2 (42.1-48.3) micrograms kg-1 at the adductor pollicis muscle (P < 0.0001). After administration of cisatracurium 0.1 mg kg-1, onset time was 2.7 (2.2-3.2) min at the larynx and 3.9 (3.0-4.8) min at the adductor pollicis (P < 0.0001). Time to 95% recovery of the first twitch of the TOF was 26.9 (20.1-33.7) min and 45.6 (39.7-51.5) min, respectively (P < 0.0001). We found that the laryngeal adductors were more resistant to the action of cisatracurium than the adductor pollicis muscle, but onset and recovery were faster at the larynx.

Deposition of eosinophil-granule major basic protein and expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in the mucosa of the small intestine in infants with cow's milk-sensitive enteropathy

BACKGROUND

Cow's milk-sensitive enteropathy (CMSE) is an important cause of chronic diarrhea and failure to thrive in infancy. The immunopathology of the mucosal lesion associated with CMSE has not yet been described.

OBJECTIVES

This study investigated the eosinophil activation and the role of adhesion molecules in the pathogenesis of intestinal mucosal damage associated with CMSE.

METHODS

Twenty-one patients with chronic diarrhea and abnormal mucosa on duodenal biopsy specimens were included. The patients had negative responses to skin prick tests and RASTs with milk. Fourteen patients were diagnosed with CMSE by milk challenge test and were designated as the CMSE group. Seven patients with no milk intolerance were defined as the non-CMSE group. Four infants with frequent vomiting and no mucosal abnormalities were also studied as the control group. Immunohistochemical stains for eosinophil major basic protein (MBP), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 on endoscopic duodenal biopsy specimens were performed.

RESULTS

The degree of eosinophil degranulation, as evidenced by localization of extracellular MBP, was significantly greater in the CMSE group compared with the non-CMSE and control groups (P <.05). Expression of VCAM-1 on mononuclear cells was higher in the CMSE group compared with the non-CMSE and control groups (P <.05). The severity of villous atrophy was positively correlated with the deposition of MBP (r = 0.79, P <.001).

CONCLUSION

These results strongly suggest eosinophils and VCAM-1 are implicated in the pathogenesis of mucosal damage associated with CMSE.

Paroxysmal tachycardia and hypertension with or without ventricular fibrillation during laparoscopic adrenalectomy: two case reports in patients with noncatecholamine-secreting adrenocortical adenomas

We present two cases of sudden unanticipated cardiovascular complications in patients with noncatecholamine-secreting adrenocortical adenomas during laparoscopic adrenalectomy. In the first case, the patient developed paroxysmal tachycardia and hypertension followed by ventricular fibrillation shortly after clipping of the adrenal vein. In the second case, the patient suffered hypertension and bigeminy during manipulation of the adrenal gland just around the adrenal vein. Awareness of such complications during either conventional or laparoscopic adrenalectomy is important even if the operation is performed in a patient with an apparently noncatecholamine-secreting adrenocortical adenoma.

Neuromuscular interactions between mivacurium and esmolol in rabbits

We compared the dose-response relationship and the neuromuscular blocking effects of mivacurium during infusions of esmolol in 40 anaesthetised rabbits. Train-of-four stimuli were applied every 10 s to the common peroneal nerve and the force of contraction of the tibialis anterior muscle was measured. Plasma cholinesterase activity decreased by 13% after esmolol infusion. The ED95 of mivacurium increased significantly from 29 (4.8) micrograms.kg-1 with placebo to 61 (9.8) micrograms.kg-1 during esmolol 100 micrograms.kg-1.min-1, 49 (8.2) micrograms.kg-1 during esmolol 300 micrograms.kg-1.min-1 and 54 (7.3) micrograms.kg-1 during esmolol 500 micrograms.kg-1.min-1, respectively (p < 0.001). The duration of neuromuscular block with mivacurium 0.16 mg.kg-1 was prolonged by 30% with esmolol due to diminished plasma cholinesterase activity (p < 0.05). Heart rate and mean arterial blood pressure decreased by 15% with esmolol (p < 0.05). The results of this study show that, in rabbits, esmolol decreased plasma cholinesterase activity, antagonised the neuromuscular blocking potency of mivacurium and prolonged its neuromuscular blocking effect.

Influence of pig embryos on uterine growth

The influence of embryos on growth of the uterus was determined by comparing uterine length, weight and diameter between gravid and nongravid horns within unilaterally pregnant gilts. Eighty-two prepubertal gilts were ovariectomized unilaterally at 5 mo of age, and the ipsilateral uterine horn was ligated near the junction of the uterine horns. Gilts were mated and were assigned randomly for examination on either d 9, 12, 15, 18, 21, 24 or 27 of gestation. Absolute differences and ratios in length, weight and diameter between gravid and nongravid horns of unilaterally pregnant gilts were analyzed. The gravid horn was 40% longer than the nongravid horn from d 18 to 27. Uterine horns with embryos increased linearly in weight and diameter (P less than .01) between d 15 and 27. Embryos, or the signals that they might give, apparently caused increases in length, weight and diameter of the uterine horn by d 18, but not before.