Low loss CMOS-compatible silicon nitride photonics utilizing reactive sputtered thin films.

Low temperature deposition of low loss silicon nitride (SiN) thin-films is very attractive as it opens opportunities for realization of multi-layer photonic chips and hybrid integration of optical waveguides with temperature sensitive platforms such as processed CMOS silicon electronics or lithium niobate on insulator. So far, the most common low-temperature deposition technique for SiN is plasma enhanced chemical vapor deposition (PECVD), however such SiN thin-films can suffer from significant losses at C-band wavelengths due to unwanted hydrogen bonds. In this contribution we present a back end of line (< 400°C), low loss SiN platform based on reactive sputtering for telecommunication applications. Waveguide losses of 0.8 dB/cm at 1550 nm and as low as 0.6 dB/cm at 1580 nm have been achieved for moderate confined waveguides which appear to be limited by patterning rather than material. These findings show that reactive sputtered SiN thin-films can have lower optical losses compared to PECVD SiN thin-films, and thus show promise for future hybrid integration platforms for applications such as high Q resonators, optical filters and delay lines for optical signal processing.

Possible Impact of Spinal Anesthesia and Phenylephrine on Sublingual Microcirculation of Cesarean Delivery Patients.

BACKGROUND: This study was a proof of concept of a novel means to evaluate microcirculatory changes during spinal anesthesia for cesarean delivery. It sought to examine the distributive circulatory effects of spinal anesthesia and evaluate the impact of phenylephrine administration on the microcirculation of these women. METHODS: After Research Ethics Board approval, healthy, non-laboring pregnant women with singleton, term pregnancies scheduled for elective cesarean delivery were recruited. Participants were randomly assigned to receive either phenylephrine infusion or phenylephrine bolus. Spinal anesthesia was standardized. A sidestream dark-field (SDF) MicroScan® video microscope was applied to the sublingual mucosa to obtain microcirculation videos in five different visual fields. Videos were made before and after spinal anesthesia. The resultant videos were analyzed randomly and blindly. The mean microvascular flow index (MFI) values were compared before and after spinal anesthesia. The difference in MFI following spinal anesthesia was compared between phenylephrine infusion and bolus groups. RESULTS: Thirty-two patients were recruited for the study; 22 patients had complete video sets for analysis. Baseline characteristics were similar between the two groups, including preoperative hemodynamics. There were no significant differences between pre- and post-spinal MFI. The post-spinal MFI within the infusion group (mean ± standard deviation: 2.74 ± 0.21) was not significantly different from the bolus group (2.56 ± 0.42, P = 0.22). CONCLUSION: Despite theoretical physiological implications of spinal anesthesia and phenylephrine on the microcirculation, significant alteration of the MFI was not observed between pre- and post-spinal anesthesia (within group). Additionally, despite an eight-fold larger phenylephrine dose for continuous infusion prophylaxis used in this group of women, this did not result in a significant alteration of the microcirculation compared to those who received phenylephrine treatment for hypotension (between groups).

Analysis of microcirculation measurements by novice users trained by a standardized interactive tutorial: An inter-observer variability study.

Excessive time for analysis may impede microcirculatory studies with large amounts of video data. Engaging more personnel in the analyses seems to be a rational approach in that scenario and could shorten the time-interval between capturing images and obtaining results. Our hypothesis was that novice users would be able to determine standard microcirculatory parameters using a semi-automated software with an acceptable degree of variability after participating in a standardized interactive training session. 14 volunteers were included in the study. All volunteers analyzed separately the same sample video after the training. The kappa statistic was calculated for the primary outcome parameter microvascular flow index (MFI) within small and large vessels and indicated a fair level of agreement in the results of the novice users. A standardized interactive tutorial can be useful to teach microcirculatory analysis in previously untrained subjects.

[Continuing peripheral nerve blocks - benefit for orthopedic patients with diabetes mellitus?]. / Pokracující periferní nervové blokády - prínos pro ortopedické pacienty s diabetes mellitus?

There is increasing incidence of diabetes mellitus in population of developed countries. And there is also, together with this fact, an increasing frequency of surgical not only orthopedic procedures for diabetic complications or for other reasons. However, thanks to modern sophisticated perioperative approaches, diabetes itself is no longer main risk factor for worsening of perioperative morbidity and mortality. The organ complications of diabetes still remain the crucial for patients outcome. The individual approach to each patient is important when we are plann-ing anesthesiological perioperative strategy. Assessment of long term diabetes compensation before elective surgical procedures, assessment and optimization of organ functions with searching for possible secondary complications of diabetes is also crucial. Generally, it is necessary to maintain compensation of diabetes through the whole perioperative period, avoid episodes of hypotension and tissue hypoperfusion and all anesthesiological interventions have to be targeted to rapid recovery (chronic medication, oral feeding and early rehabilitation). Technics of regional anesthesia and peripheral nerve blocks particularly, may be very useful for the objective especially for ortho-pedic patients.Key words: anesthesia - diabetes mellitus - perioperative period - peripheral nerve blocks.

Effects of hypertonic saline and mannitol on cortical cerebral microcirculation in a rabbit craniotomy model.

BACKGROUND: Hyperosmolar solutions have been used in neurosurgery to modify brain bulk and prevent neurological deterioration. The aim of this animal study was to compare the short-term effects of equivolemic, equiosmolar solutions of mannitol and hypertonic saline (HTS) on cerebral cortical microcirculation in a rabbit craniotomy model. METHODS: Rabbits (weight, 2.0-3.0 kg) were anesthetized, ventilated mechanically, and subjected to a craniotomy. The animals were allocated randomly to receive a 3.75 ml/kg intravenous infusion of either 3.2% HTS (group HTS, n = 8) or 20% mannitol (group MTL, n = 8). Microcirculation in the cerebral cortex was evaluated using sidestream dark-field (SDF) imaging before and 20 min after the end of the 15-min HTS infusion. Global hemodynamic data were recorded, and blood samples for laboratory analysis were obtained at the time of SDF image recording. RESULTS: No differences in the microcirculatory parameters were observed between the groups before the use of osmotherapy. After osmotherapy, lower proportions of perfused small vessel density (P = 0.0474), perfused vessel density (P = 0.0457), and microvascular flow index (P = 0.0207) were observed in the MTL group compared with those in the HTS group. CONCLUSIONS: Our findings suggest that an equivolemic, equiosmolar HTS solution better preserves perfusion of cortical brain microcirculation compared to MTL in a rabbit craniotomy model.

Physostigmine reverses disturbances of the intestinal microcirculation during experimental endotoxemia.

Intestinal microcirculatory disturbances play an important role in the pathophysiology of sepsis. A neural anti-inflammatory pathway has been suggested as a potential target for therapy that may dampen systemic inflammation. The aim of this study is to investigate the effects of physostigmine, a cholinesterase inhibitor, on the intestinal microcirculation and vascular contractility in experimental endotoxemia. Endotoxemia was induced in Lewis rats by intravenous lipopolysaccharide (LPS) administration. Animals were treated with either physostigmine or saline (control) following LPS challenge. The intestinal microcirculation, including leukocyte-endothelial interaction, functional capillary density (FCD) and non-perfused capillary density (NCD), was examined by intravital microscopy (IVM) 2 hours after LPS administration. The impact of physostigmine on vascular contractility of rat aortic rings was examined by in vitro myography. Physostigmine significantly reduced the number of adhering leukocytes in intestinal submucosal venules (V1 venules: -61%, V3 venules: -36%) of LPS animals. FCD was significantly increased by physostigmine treatment (circular muscle layer: +180%, longitudinal muscle layer: +162%, mucosa: +149%). Low concentrations of physostigmine produced significant contraction of aortic ring preparations, whereas high concentrations produced relaxation. In conclusion, physostigmine treatment significantly improved the intestinal microcirculation in experimental endotoxemia by reducing leukocyte adhesion and increasing FCD.

Microcirculation diagnostics and applied studies in circulatory shock - research from the bench to the bedside.

Macrohemodynamic targets such as mean arterial pressure, cardiac output, and mixed or central venous oxygen saturation have been used to guide treatment of patients presenting circulatory shock. However, it has been shown that despite of improvement of macrocirculatory parameters there is persisting microcirculatory dysfunction. The restoration of microvascular perfusion in order to improve oxygenation, prevent tissue hypoxia, and maintain organ function represents the main aim of hemodynamic resuscitation. Therefore, microcirculatory targets may represent the most important endpoints to optimize therapy of circulatory shock.