Prophylactic incisional negative pressure wound therapy reduces the risk of surgical site infection after caesarean section in obese women: a pragmatic randomised clinical trial.

OBJECTIVE: To evaluate the reduction of surgical site infections by prophylactic incisional negative pressure wound therapy compared with standard postoperative dressings in obese women giving birth by caesarean section. DESIGN: Multicentre randomised controlled trial. SETTING: Five hospitals in Denmark. POPULATION: Obese women (prepregnancy body mass index (BMI) ≥30 kg/m2 ) undergoing elective or emergency caesarean section. METHOD: The participants were randomly assigned to incisional negative pressure wound therapy or a standard dressing after caesarean section and analysed by intention-to-treat. Blinding was not possible due to the nature of the intervention. MAIN OUTCOME MEASURES: The primary outcome was surgical site infection requiring antibiotic treatment within the first 30 days after surgery. Secondary outcomes included wound exudate, dehiscence and health-related quality of life. RESULTS: Incisional negative pressure wound therapy was applied to 432 women and 444 women had a standard dressing. Demographics were similar between groups. Surgical site infection occurred in 20 (4.6%) women treated with incisional negative pressure wound therapy and in 41 (9.2%) women treated with a standard dressing (relative risk 0.50, 95% CI 0.30-0.84; number needed to treat 22; P = 0.007). The effect remained statistically significant when adjusted for BMI and other potential risk factors. Incisional negative pressure wound therapy significantly reduced wound exudate whereas no difference was found for dehiscence and quality of life between the two groups. CONCLUSION: Prophylactic use of incisional negative pressure wound therapy reduced the risk of surgical site infection in obese women giving birth by caesarean section. TWEETABLE ABSTRACT: RCT: prophylactic incisional NPWT versus standard dressings postcaesarean in 876 women significantly reduces the risk of SSI.

Use of hyperbaric oxygen therapy and PEGylated carboxyhemoglobin bovine in a Jehovah's Witness with life-threatening anemia following postpartum hemorrhage.

We present a case of a Jehovah's Witness patient who refused blood products, with the exception of albumin and clotting factors, and underwent cesarean section under spinal anesthesia complicated by postpartum hemorrhage. She was fluid resuscitated and treated with multiple uterotonics and internal iliac artery embolization. Because of agitation she required emergency tracheal intubation. Her hemoglobin concentration dropped from a preoperative value of 12mg/dL to 3mg/dL on postoperative day one. She was acidotic, requiring vasopressors for hemodynamic stability and remained ventilated and sedated. She was treated with daily erythropoietin, iron therapy and cyanocobalamin. Because of ongoing hemorrhage, continued acidemia and vasopressor requirements she was co-treated with PEGylated carboxyhemoglobin bovine and hyperbaric oxygen therapy to reverse her oxygen debt. On postoperative day eight her hemoglobin concentration was 7mg/dL, she was hemodynamically stable and vasopressors were discontinued. She was extubated and discharged from the intensive care unit on postoperative day eight. This report highlights the multiple modalities used in treating a severely anemic patient who refused blood, the use of an investigational new drug, the process of obtaining this drug via the United States Food and Drug Administration emergency expanded access regulation for single patient clinical treatment, and ethical dilemmas faced during treatment.

Long term end-stage renal disease and death following acute renal replacement therapy in the ICU.

INTRODUCTION: In ICU the need for acute renal replacement therapy (RRT) associates with high mortality and risk of end-stage renal disease (ESRD), but there are limited long-term data. We investigated these outcomes and their risk factors. METHODS: Retrospective analysis of all adult patients admitted to a general, university hospital ICU 2005-2012, excluding chronic dialysis patients. ESRD was defined as need of RRT > 90 days or kidney transplant. RESULTS: Of 5766 patients included, 1004 (16%) received acute RRT; their 30-day mortality was 42% vs. 16% for those not requiring acute RRT (adjusted hazard ratio (HR) 1.13 (0.96-1.32)). The 90-day mortality was 55% for patients receiving acute RRT vs. 22% for those who did not (adjusted HR 1.32 (1.15-1.51)) and 1-year mortality was 63% vs. 30%, respectively, (adjusted HR 1.31 (1.16-1.48)). The 7-year risk of ESRD for ICU patients surviving 90 days was 10% for patients who received acute RRT vs. 0.5% among those who did not (adjusted HR 5.9 (2.9-12.4)). Independent risk factors for ESRD included pre-existing kidney disease, pre-existing peripheral vascular disease and use of acute RRT in ICU. CONCLUSIONS: The need of acute RRT was associated with markedly increased long term risk of death and ESRD; in contrast its use was not associated with 30-day mortality. In addition to acute RRT, decreased kidney function and peripheral vascular disease before ICU admission were risk factors for ESRD. It seems warranted offering medical follow-up to patients after acute RRT in ICU.

Ultra-short wavelength operation of a thulium fibre laser in the 1660-1750 nm wavelength band.

Ultra-short wavelength operation of a thulium fibre laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable fibre laser source operating from 1660 nm to 1720 nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium fibre lasers in this band, fixed wavelength operation at 1726 nm with output power up 12.6 W and with slope efficiency > 60% is also shown.

Laser-induced photo-polymerisation for creation of paper-based fluidic devices.

Paper-based microfluidics is a rapidly progressing inter-disciplinary technology driven by the need for low-cost alternatives to conventional point-of-care diagnostic tools. For transport of reagents/analytes, such devices often consist of interconnected hydrophilic fluid-flow channels that are demarcated by hydrophobic barrier walls that extend through the thickness of the paper. Here, we present a laser-based fabrication procedure that uses polymerisation of a photopolymer to produce the required fluidic channels in paper. Experimental results showed that the structures successfully guide the flow of fluids and allow containment of fluids in wells, and hence the technique is suitable for fabrication of paper-based microfluidic devices. The minimum width for the hydrophobic barriers that successfully prevented fluid leakage was ~120 µm and the minimum width for the fluidic channels that can be formed was ~80 µm, the smallest reported so far for paper-based fluidic patterns.

Poled-fiber source of broadband polarization-entangled photon pairs.

We demonstrate broadband polarization-entangled photon pair generation in a poled fiber phase matched for Type II downconversion in the 1.5 µm telecom band. Even with signal-idler separation greater than 100 nm, we observe fringe visibilities greater than 97% and tangle greater than 0.8. A Hong-Ou-Mandel interference experiment is also used to experimentally confirm the broadband nature of the entanglement.

100 kW peak power picosecond thulium-doped fiber amplifier system seeded by a gain-switched diode laser at 2 µm.

We report on the generation of picosecond pulses at 2 µm directly from a gain-switched discrete-mode diode laser and their amplification in a multistage thulium-doped fiber amplifier chain. The system is capable of operating at repetition rates in the range of 2 MHz-1.5 GHz without change of configuration, delivering high-quality 33 ps pulses with up to 3.5 µJ energy and 100 kW peak power, as well as up to 18 W of average power. These results represent a major technological advance and a 1 order of magnitude increase in peak power and pulse energy compared to existing picosecond sources at 2 µm.

Novel technique for mode selection in a multimode fiber laser.

A simple technique for transverse mode selection in a large-mode-area (multimode) fiber laser is described. The technique exploits the different spectral responses of feedback elements based on a fiber Bragg grating and a volume Bragg grating to achieve wavelength-dependent mode filtering. This approach has been applied to a cladding-pumped thulium-doped fiber laser with a multimode core to achieve a single-spatial-mode output beam with a beam propagation factor (M2) of 1.05 at 1923 nm. Without mode selection the free-running fiber laser has a multimode output beam with an M2 parameter of 3.3. Selective excitation of higher order modes is also possible via the technique and preliminary results for laser oscillation on the LP11 mode are also discussed along with the prospects for scaling to higher power levels.

Lactate concentrations in the rectal lumen in patients in early septic shock.

BACKGROUND: Previously, we observed that rectal luminal lactate was higher in non-survivors compared with survivors of severe sepsis or septic shock persisting >24 h. The present study was initiated to further investigate this tentative association between rectal luminal lactate and mortality in a larger population of patients in early septic shock. METHODS: A prospective observational multicentre study of 130 patients with septic shock at six general ICU's of university hospitals. Six to 24 h after the onset of septic shock, the concentration of lactate in the rectal lumen was estimated by a 4-h equilibrium dialysis. Dialysate concentrations of lactate were determined using an auto-analyser. RESULTS: The overall 30-day mortality was 32%, with age and Simplified acute physiology scores II and sequential organ failure assessment scores being significantly higher in non-survivors. In contrast, there were no differences in concentrations of lactate in the rectal lumen [2.2 (1.4-4.1) and 2.8 (1.6-5.1) mmol/l (P=0.34)] (medians and 25th-75th percentiles) or arterial blood [2.1 (1.4-4.2) and 2.0 (1.3-3.2) mmol/l (P=0.15)] between non-survivors and survivors. The rectal-arterial difference of the lactate concentration was higher in survivors. There were no differences in blood pressure, noradrenaline dose or central venous oxygen saturation between the groups. CONCLUSION: In this prospective, observational study of unselected patients with early septic shock, there was no difference in the concentration of lactate in the rectal lumen between non-survivors and survivors. TRIAL REGISTRATION: Clinicaltrials.gov (no: NCT00197938).

High-power linearly-polarized single-frequency thulium-doped fiber Master-Oscillator Power-Amplifier.

We report a high power narrow-linewidth source at approximately 2 microm based on a Tm-doped fiber distributed-feedback master-oscillator and three Tm fiber amplifier stages. The master-oscillator and first two amplifier stages were in-band pumped by Er,Yb fiber lasers operating at 1565 nm, and the final stage amplifier was cladding-pumped at 795 nm by two spatially-combined diode-stacks. The MOPA yielded 100 W of single frequency output at 1943 nm with a beam propagation factor (M(2)) of 1.25 and with a polarization extinction ratio of >94%. The output power was limited by thermally-induced damage in the final amplifier stage. The prospects for further power scaling are considered.

Time domain add-drop multiplexing scheme enhanced using a saw-tooth pulse shaper.

We experimentally demonstrate the use of saw-tooth optical pulses, which are shaped using a fiber Bragg grating, to achieve robust and high performance time-domain add-drop multiplexing in a scheme based on cross-phase (XPM) modulation in an optical fiber, with subsequent offset filtering. As compared to the use of more conventional pulse shapes, such as Gaussian pulses of a similar pulse width, the purpose-shaped saw-tooth pulses allow higher extinction ratios for the add and drop windows and significant improvements in the receiver sensitivity for the dropped and added channels.

High-power Tm-doped fiber distributed-feedback laser at 1943 nm.

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an Er/Yb fiber laser at 1565 nm. The fiber DFB laser yielded up to 875 mW of single-ended output at 1943 nm on two orthogonally polarized modes for 3.5 W of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was >3 W for a combined absorbed pump power of 8.1 W. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered.

Broadly tunable single-frequency cw mid-infrared source with milliwatt-level output based on difference-frequency generation in orientation-patterned GaAs.

A narrow-linewidth mid-IR source based on difference-frequency generation of an amplified 1.5 microm diode laser and a cw Tm-doped fiber laser in orientation-patterned (OP) GaAs has been developed and evaluated for spectroscopic applications. The source can be tuned to any frequency in the 7.6-8.2 microm range with an output power of 0.5 mW. The measured characteristics of the OP-GaAs sample demonstrate a high quality of the material.

Norepinephrine in low to moderate doses may not increase luminal concentrations of L-lactate in the gut in patients with septic shock.

AIM: To investigate the effect of different doses of norepinephrine (noradrenaline) on luminal concentrations of L-lactate in the rectum and stomach in patients with fluid-resuscitated septic shock. METHODS: This was a paired cross-over study in which the dose of norepinephrine was titrated to mean arterial blood pressures (MAPs) of 65 and 85 mmHg in random sequence. It was performed in a mixed intensive care unit at a university hospital. Eight patients with fluid-resuscitated septic shock requiring norepinephrine (>0.1 microg/kg/min) were included. Patients were treated with norepinephrine to a MAP of either 65 or 85 mmHg for 2 h. After a 'washout' period of 2 h, the dose of norepinephrine was titrated to the other endpoint of MAP for another 2 h. The concentrations of L-lactate in the rectal and gastric lumen were estimated by 1-h equilibrium dialysis during the second hour of the treatment periods. RESULTS: MAP and central venous oxygen saturation were increased by increasing the dose of norepinephrine [median (range) (microg/kg/min): 0.07 (0.00-0.60) and 0.18 (0.11-1.00) at MAPs of 65 and 85 mmHg, respectively], whereas the metabolic markers were unaffected [luminal concentrations (mmol/l) of L-lactate in the rectum of 1.9 (0.8-6.4) and 1.8 (0.9-5.7) (P =0.94) and in the stomach of 1.1 (0.1-10.0) and 1.3 (0.3-9.7) (P =0.88) at MAPs of 65 and 85 mmHg, respectively]. CONCLUSION: In this small study, luminal concentrations of L-lactate in the rectum and stomach were unaffected by norepinephrine at low to moderate doses. These data suggest that norepinephrine may not increase luminal concentrations of l-lactate in the gut in patients with fluid-resuscitated septic shock.

Effects of endotoxaemia on markers of permeability, metabolism and inflammation in the large bowel of healthy subjects.

BACKGROUND: Increased permeability and increased luminal concentrations of L-lactate have previously been shown in the large bowel in septic patients. To advance these observations, a human model of colorectal barrier failure in sepsis is desirable. Therefore, we assessed the effects of endotoxaemia on markers of permeability, metabolism and inflammation in the large bowel in healthy subjects. METHODS: Twelve healthy male subjects received intravenous endotoxin (2 ng/kg body weight) or saline in a paired cross-over design. Colorectal permeability was assessed after 3, 6, 9 and 12 h by the systemic recovery of luminally instilled (99m)Tc-diethylenetriaminepentaacetate. Luminal concentrations of L-lactate were assessed by equilibrium dialysis. Mucosal biopsies from the large bowel were sampled after 6 and 12 h, and the apoptotic ratio of the epithelium was assessed by terminal deoxynucleotidyl transferase-mediated desoxyuridinetriphosphate nick end-labelling (TUNEL) assay and the expression of inducible nitric oxide synthase (iNOS) mRNA by reverse transcriptase-polymerase chain reaction. RESULTS: Systemic effects of endotoxaemia were observed, including fever, tachycardia and strongly increased plasma values of tumour necrosis factor-alpha. By contrast, the colorectal permeability, luminal lactate concentrations, mucosal infiltration of inflammatory cells, epithelial apoptotic ratio and expression of iNOS were all unaffected by endotoxin. CONCLUSIONS: No effect of a single intravenous dose of endotoxin was observed on markers of large bowel permeability, metabolism and inflammation in healthy subjects. This suggests that this part of the gut is relatively resistant to the systemic inflammation induced by experimental endotoxaemia in humans.

High-power continuous-wave cladding-pumped Raman fiber laser.

We demonstrate a high-power single-mode cladding-pumped Raman fiber laser. The Raman fiber laser consists of a 1.2 km long germanium-doped double-clad fiber in a linear cavity, which is spliced to a single-mode fiber. The laser is end pumped by a multimode erbium-ytterbium-doped fiber, which is coupled to the inner cladding of the Raman fiber. The embedded core was designed to be single mode at the Raman Stokes wavelength, and up to 10 W of power was obtained at 1660 nm from the single-mode fiber end. The laser has a slope efficiency of 67% and a threshold of 6.5 W.

Plasma cholinesterase activity and duration of action of mivacurium in phenotypically normal patients.

BACKGROUND: The short duration of action of mivacurium is due to its rapid hydrolysis by plasma cholinesterase (pChe). In patients with normal phenotype, low pChe activity because of, for instance, disease or intake of drugs may prolong the duration of action of mivacurium. The purpose of this study was to evaluate the relationship between pChe activity and the duration of action of mivacurium 0.2 mg/kg in phenotypically normal patients. MATERIAL: Forty-three adult patients with normal pChe phenotype and low or normal pChe activity, undergoing a variety of surgical procedures were included in the study with their informed consent and Ethics Committee approval. The neuromuscular block was monitored using TOF stimulation every 12 s and mechanomyography. The time to reappearance of the first response to TOF stimulation was measured. RESULTS: The patients pChe activities ranged from 45 to 1272 U/l (normal range 660-1620 U/l) and the time to first response to TOF from 8.1 to 62.7 min. An inverse relationship between enzyme activity and duration of action of mivacurium was found. The relationship was described by the equation: log10 (time) =alpha- beta log10 (pChe), where alpha (SD) is 2.547 (0.186) and beta (SD) 0.454 (0.069). CONCLUSION: In patients with phenotypically normal pChe, prediction of the duration of action of mivacurium is possible from the patients actual pChe activity. In patients with pChe activities below the normal range, the time to reappearance of the first response to TOF stimulation may vary from 10 to 180 min Only patients with pChe activities <220 U/l had a significantly prolonged duration of action of mivacurium.

Onset and duration of action of rocuronium--from tracheal intubation, through intense block to complete recovery.

BACKGROUND: The primary objective of this study was to establish the relation between the post tetanic count (PTC) and the time to reappearance of the first response (T1) in train-of-four (TOF) nerve stimulation following rocuronium 0.6 mg/kg, 0.9 mg/kg, and 1.2 mg/kg. The secondary objective was to evaluate the intubation conditions after 1 min. METHODS: One hundred and eight patients were randomised to one of three doses of rocuronium: 0.6, 0.9 or 1.2 mg/kg. Tracheal intubation was performed at 60 s by a blinded investigator. During propofol, fentanyl, midazolam anaesthesia the neuromuscular block was monitored by mechanography using TOF stimulation every 12 s. At 6 min intervals, a tetanic stimulation (50 Hz) was applied for 5 s preceded and followed by a 30 s period of 1 Hz stimulation until the reappearance of T1. RESULTS: There was a significant difference in recovery following the high dose and the two lower doses. The relation between time (min) to reappearance of T1 (t) and PTC can be expressed as follows: t(0.6 and 0.9 mg/kg)(min)=18.8-6.46 PTC and t(1.2 mg/kg)(min)=26.1-9.12 PCT. T1 was seen at a mean PTC level of 8 or 9 in all three groups. The intubation conditions were graded as excellent or good in all patients except in two patients following the 0.6 mg/kg dose of rocuronium. CONCLUSION: The PTC method can be used to predict the time to first response to TOF nerve stimulation during intense rocuronium induced neuromuscular blockade. The relation between PTC and the time to T1 was prolonged after 1.2 mg/kg compared with 0.6 mg/kg and 0.9 mg/kg. No further improvement in intubation conditions at 60 s was evident by increasing the rocuronium dose from 0.9 mg/kg to 1.2 mg/kg.

Distributed-feedback fiber laser sensor for simultaneous strain and temperature measurements operating in the radio-frequency domain.

Radio-frequency (rf) beat frequencies between two longitudinal modes and two polarization modes of a birefringent dual-longitudinal-mode moiré distributed-feedback fiber laser are employed to measure strain and temperature simultaneously. Operating entirely in the rf domain, this approach potentially allows one to employ low-cost and precise rf measuring techniques. A strain-temperature cross sensitivity of the strain- and the thermo-optic coefficients, which can be neglected in wavelength-based grating sensors, has been observed. The achieved sensor accuracy was +/-15 microepsilon and +/-0.2 degrees C.