A Coupled Cavity Micro Fluidic Dye Ring Laser

We present a laterally emitting, coupled cavity micro fluidic dye ring laser, suitable for integration into lab-on-a-chip micro systems. The micro-fluidic laser has been successfully designed, fabricated, characterized and modelled. The resonator is formed by a micro-fluidic channel bounded by two isosceles triangle mirrors. The micro-fluidic laser structure is defined using photo lithography in 10 microns thick SU-8 polymer on a glass substrate. The micro fluidic channel is sealed by a glass lid, using PMMA adhesive bonding. The laser is characterized using the laser dye Rhodamine 6G dissolved in ethanol or ethylene glycol as the active gain medium, which is pumped through the micro-fluidic channel and laser resonator. The dye laser is optically pumped normal to the chip plane at 532 nm by a pulsed, frequency doubled Nd:YAG laser and lasing is observed with a threshold pump pulse energy flux of around 55 micro-Joule/square-milimeter. The lasing is multi-mode, and the laser has switchable output coupling into an integrated polymer planar waveguide. Tuning of the lasing wavelength is feasible by changing the dye/solvent properties.Comment: Accepted for Microelectronic Engineerin

Factors influencing preoperative stress response in coronary artery bypass graft patients

BACKGROUND: In many studies investigating measures to attenuate the hemodynamic and humoral stress response during induction of anaesthesia, primary attention was paid to the period of endotracheal intubation since it has been shown that even short-lasting sympathetic cardiovascular stimulation may have detrimental effects on patients with coronary artery disease. The aim of this analysis was, however, to identify the influencing factors on high catecholamine levels before induction of anaesthesia. METHODS: Various potential risk factors that could impact the humoral stress response before induction of anaesthesia were recorded in 84 males undergoing coronary aortic bypass surgery, and were entered into a stepwise linear regression analysis. The plasma level of norepinephrine measured immediately after radial artery canulation was chosen as a surrogate marker for the humoral stress response, and it was used as the dependent variable in the regression model. Accordingly, the mean arterial blood pressure, heart rate and the calculated pressure-rate product were taken as parameters of the hemodynamic situation. RESULTS: Stepwise regression analysis revealed that the oral administration of low-dose clonidine (mean dose 1.75 μg·kg(-1)) on the morning of surgery was the only significant predictor (p = 0.004) of the high variation in preoperative norepinephrine plasma levels. This intervention decreased norepinephrine levels by more than 40% compared to no clonidine administration, from 1.26 to 0.75 nmol·l(-1). There was no evidence for dose-responsiveness of clonidine. All other potential predictors were removed from the model as insignificant (p > 0.05). The use of beta-blocker, ace-inhibitors, ejection fraction, and body mass index were significant determinants for the hemodynamic situation (heart rate, mean arterial pressure, pressure rate product) of the patient during the pre-induction period. CONCLUSION: The oral administration of clonidine is the only significant predictor for the observed variation of norepinephrine levels during the preoperative period. Lack of significant dose responsiveness suggests that even a low dose of the drug can attenuate the preoperative stress response and thus is recommended in cardiovascular high risk patients

Management of accidental dural puncture and post-dural puncture headache after labour: a Nordic survey

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldBACKGROUND: a major risk with epidural analgesia is accidental dural puncture (ADP), which may result in post-dural puncture headache (PDPH). This survey was conducted to explore the incidence of ADP, the policy for management of PDPH and the educational practices in epidural analgesia during labour in the Nordic countries. METHODS: a postal questionnaire was sent to the anaesthesiologist responsible for Obstetric anaesthesia service in all maternity units (n=153) with questions relating to the year 2008. RESULTS: the overall response rate was 93%. About 32% (22-47%) of parturients received epidural analgesia for labour. There were databases for registering obstetric epidural complications in 13% of Danish, 24% of Norwegian and Swedish, 43% of Finnish and 100% of hospitals in Iceland. The estimated incidence of ADP was 1% (n approximately 900). Epidural blood patch (EBP) was performed in 86% (n≈780) of the parturients. The most common time interval from diagnosis to performing EBP was 24-48 h. The success rate for EBP was >75% in 67% (62-79%) of hospitals. The use of diagnostic CT/MRI before the first or the second EBP was exceptional. No major complication was reported. Teaching of epidurals was commonest (86%) in the non-obstetric population and 53% hospitals desired a formal training programme in obstetric analgesia. CONCLUSION: we found the incidence of ADP to be approximately 1%. EBP was the commonest method used for its management, and the success rate was high in most hospitals. Formal training in epidural analgesia was absent in most countries and trainees first performed it in the non-obstetric population