Factors Influencing the Formation of Nitrous Acid from Photolysis of Particulate Nitrate.

Enhanced photolysis of particulate nitrate (pNO3) to form photolabile species, such as gas-phase nitrous acid (HONO), has been proposed as a potential mechanism to recycle nitrogen oxides (NOx) in the remote boundary layer ("renoxification"). This article presents a series of laboratory experiments aimed at investigating the parameters that control the photolysis of pNO3 and the efficiency of HONO production. Filters on which artificial or ambient particles had been sampled were exposed to the light of a solar simulator, and the formation of HONO was monitored under controlled laboratory conditions. The results indicate that the photolysis of pNO3 is enhanced, compared to the photolysis of gas-phase HNO3, at low pNO3 levels, with the enhancement factor reducing at higher pNO3 levels. The presence of cations (Na+) and halides (Cl-) and photosensitive organic compounds (imidazole) also enhance pNO3 photolysis, but other organic compounds such as oxalate and succinic acid have the opposite effect. The precise role of humidity in pNO3 photolysis remains unclear. While the efficiency of photolysis is enhanced in deliquescent particles compared to dry particles, some of the experimental results suggest that this may not be the case for supersaturated particles. These experiments suggest that both the composition and the humidity of particles control the enhancement of particulate nitrate photolysis, potentially explaining the variability in results among previous laboratory and field studies. HONO observations in the remote marine boundary layer can be explained by a simple box-model that includes the photolysis of pNO3, in line with the results presented here, although more experimental work is needed in order to derive a comprehensive parametrization of this process.

Effects of a 20 year rain event: a quantitative microbial risk assessment of a case of contaminated bathing water in Copenhagen, Denmark.

Quantitative microbial risk assessments (QMRAs) often lack data on water quality leading to great uncertainty in the QMRA because of the many assumptions. The quantity of waste water contamination was estimated and included in a QMRA on an extreme rain event leading to combined sewer overflow (CSO) to bathing water where an ironman competition later took place. Two dynamic models, (1) a drainage model and (2) a 3D hydrodynamic model, estimated the dilution of waste water from source to recipient. The drainage model estimated that 2.6% of waste water was left in the system before CSO and the hydrodynamic model estimated that 4.8% of the recipient bathing water came from the CSO, so on average there was 0.13% of waste water in the bathing water during the ironman competition. The total estimated incidence rate from a conservative estimate of the pathogenic load of five reference pathogens was 42%, comparable to 55% in an epidemiological study of the case. The combination of applying dynamic models and exposure data led to an improved QMRA that included an estimate of the dilution factor. This approach has not been described previously.

High rate of revision and a high incidence of radiolucent lines around Metasul metal-on-metal total hip replacements: results from a randomised controlled trial of three bearings after seven years.

A total of 397 hips were randomised to receive Metasul metal-on-metal (MoM), metal-on-conventional polyethylene (MoP) or ceramic-on-polyethylene (CoP) bearings using a cemented triple-tapered polished femoral component (MS-30). There were 129 MoM hips in 123 patients (39 male and 84 female, mean age 63.3 years (40.7 to 72.9)), 137 MoP hips in 127 patients (39 male and 88 female, mean age 62.8 years (24.5 to 72.7)) and 131 CoP hips in 124 patients (51 male and 73 female, mean age 63.9 years (30.6 to 73.8)). All acetabular components were cemented Weber polyethylene components with the appropriate inlay for the MoM articulation. Clinical evaluation was undertaken using the Harris hip score (HHS) and radiological assessments were made at two, five and seven years. The HHS and radiological analysis were available for 341 hips after seven years. The MoM group had the lowest mean HHS (p = 0.124), a higher rate of revision (p < 0.001) and a higher incidence of radiolucent lines in unrevised hips (p < 0.001). In all, 12 revisions had been performed in 12 patients: eight in the MoM group (four for infection, four for aseptic loosening, three in the MoP group (one each of infection, dislocation and pain) and one in the CoP group (infection). Our findings reveal no advantage to the MoM bearing and identified a higher revision rate and a greater incidence of radiolucent lines than with the other articulations. We recommend that patients with a 28 mm Metasul MoM bearing be followed carefully.

Which goal for fluid therapy during colorectal surgery is followed by the best outcome: near-maximal stroke volume or zero fluid balance?

BACKGROUND: We aimed to investigate whether fluid therapy with a goal of near-maximal stroke volume (SV) guided by oesophageal Doppler (ED) monitoring result in a better outcome than that with a goal of maintaining bodyweight (BW) and zero fluid balance in patients undergoing colorectal surgery. METHODS: In a double-blinded clinical multicentre trial, 150 patients undergoing elective colorectal surgery were randomized to receive fluid therapy after either the goal of near-maximal SV guided by ED (Doppler, D group) or the goal of zero balance and normal BW (Zero balance, Z group). Stratification for laparoscopic and open surgery was performed. The postoperative fluid therapy was similar in the two groups. The primary endpoint was postoperative complications defined and divided into subgroups by protocol. Analysis was performed by intention-to-treat. The follow-up was 30 days. The trial had 85% power to show a difference between the groups. RESULTS: The number of patients undergoing laparoscopic or open surgery and the patient characteristics were similar between the groups. No significant differences between the groups were found for overall, major, minor, cardiopulmonary, or tissue-healing complications (P-values: 0.79; 0.62; 0.97; 0.48; and 0.48, respectively). One patient died in each group. No significant difference was found for the length of hospital stay [median (range) Z: 5.00 (1-61) vs D: 5.00 (2-41); P=0.206]. CONCLUSIONS: Goal-directed fluid therapy to near-maximal SV guided by ED adds no extra value to the fluid therapy using zero balance and normal BW in patients undergoing elective colorectal surgery.

The Charnley stem: clinical, radiological and survival data after 11-14 years.

BACKGROUND: The Charnley stem provides good outcome for 10 years, but several studies find deteriorating results thereafter. However, study populations, techniques and data analysis vary widely. We have studied 240 Charnley stems in a homogeneous group of patients providing clinical, radiological and survival data after 11-14 years. HYPOTHESIS: The clinical and radiological outcome of the Charnley stem is not as good than previously thought. PATIENTS AND METHODS: Five surgeons implanted 240 femoral stems in a community hospital in Norway using antibiotic impregnated cement and third generation cementing techniques. The Charnley stems were implanted with a Charnley cup in 120 cases and an uncemented hemispherical cup (Duraloc) in 120 cases. The mean age of the patients was 65.5 years and the mean Body Mass Index (BMI) was 26.8. All patients received low molecular weight heparin and antibiotic prophylaxis. Patients were assessed after 10 years by means of Harris Hip Score (HHS)and radiographic evaluation. Implant survival studies were performed after 11-14 years. RESULTS: One hundred and fifty-eight patients were available for clinical and radiographic evaluation after 10 years. HHS improved from 48.4 (95% CI: 46.6-50,2) preoperatively to 87.9 (95%CI: 86.6-89.3) after 6 months and 87.6 (95% CI: 85.3-89.8) at 10 years. Thirty-one stems had been revised, the reasons for revision were loosening (21), infection (five), instability (four) and late perisprosthetic fracture (one). Forty-one stems had one or more signs of loosening.Stem survival was 83.6% using any revisions as end point, and mean estimated stem survival was 12.7 years (12.2-13.3 years). DISCUSSION: Other studies report survival at mid-term from 83-96%. Our results are in the low-end. Even though our rate of infection was high (2%), the main cause of the poor results is aseptic loosening. We do not know the reason for this high-rate of loosening. As we believe that our technique is adequate and patient population average, we suspect that this rate of loosening is a characteristic of the implant. Results from this prospective cohort study add to the evidence that the Charnley stem should not be used hip arthroplasty unless patient life expectancy is less than 10 years.

No differences in outcomes between cemented and uncemented acetabular components after 12-14 years: results from a randomized controlled trial comparing Duraloc with Charnley cups.

BACKGROUND: Even though there are multiple studies documenting the outcome of the Charnley low-friction arthroplasty as well as abundant studies on uncemented arthroplasties, there is a dearth of comparative studies of the uncemented acetabular component and a cemented component. In this study we aimed to document the long-term clinical and radiographic outcome as well as component survival in a randomized controlled trial. MATERIALS AND METHODS: Two hundred fifteen patients (240 hips) were randomly allocated to receive a cemented Charnley cup or uncemented Duraloc 1200 cup. All patients received cemented Charnley stems and were evaluated clinically and radiographically after 6 months, and 2, 5, and 10 years. RESULTS: Harris Hip Scores improved from 48.3 [95% confidence interval (CI) 45.0-51.6] to 90.2 [95% CI 87.9-92.6] in the Charnley group and from 49.3 [95% CI 86.9-91.3] in the Duraloc group at 6 months. After 10 years, the Charnley group's Harris Hip Score was 89.8 [95% confidence interval (CI) 87.0-92.6], and the Duraloc group's score was 87.3 (95% CI 84.1-90.6). In the radiographic analysis after 10 years, there was no statistical difference in the prevalence of radiographic signs of loosening. Nine cups were revised in the Charnley group, and five cups were removed in the Duraloc group. The difference was not statistically significant. There was no statistical difference between the cups when aseptic loosening was the end-point, nor in survival analyses. CONCLUSIONS: There is no statistically significant difference in clinical or radiological outcome between the Charnley cup and the Duraloc after 10 years, and no difference in implant survival after 12-14 years. The uncemented Duraloc cup is as good as the cemented Charnley cup after 10 years.

Carbohydrate- and protein-rich diets in McArdle disease: effects on exercise capacity.

BACKGROUND: Two single case studies suggest that a protein-rich diet may be beneficial for patients with McArdle disease, based on improvements in either endurance or muscle energetics, as assessed by phosphorous MR spectroscopy. In healthy subjects, proteins contribute very little to energy metabolism during exercise, which questions the effect of protein in McArdle disease. METHODS: In a crossover, open design, we studied seven patients with McArdle disease, who were randomised to follow either a carbohydrate- or protein-rich diet for 3 days before testing. Calorific intake on each diet was identical, and was adjusted to the subject's weight, age and sex. After each diet, exercise tolerance and maximal work capacity were tested on a bicycle ergometer, using a constant workload for 15 minutes followed by an incremental workload to exhaustion. RESULTS: During the constant workload, heart rate and perceived exertion were consistently lower (p<0.0005) on the carbohydrate- versus protein-rich diet. Patients also had a 25% improvement in maximal oxidative work capacity on the carbohydrate versus the protein diet. CONCLUSIONS: This study shows that patients with McArdle disease can improve their maximal work capacity and exercise tolerance to submaximal workloads by maintaining a diet high in carbohydrate instead of protein. The carbohydrate diet not only improves tolerance to everyday activities, but will probably also help to prevent exercise-induced episodes of muscle injury in McArdle disease.

Is muscle glycogenolysis impaired in X-linked phosphorylase b kinase deficiency?

OBJECTIVE: It is unclear to what extent muscle phosphorylase b kinase (PHK) deficiency is associated with exercise-related symptoms and impaired muscle metabolism, because 1) only four patients have been characterized at the molecular level, 2) reported symptoms have been nonspecific, and 3) lactate responses to ischemic handgrip exercise have been normal. METHODS: We studied a 50-year-old man with X-linked PHK deficiency using ischemic forearm and cycle ergometry exercise tests to define the derangement of muscle metabolism. We compared our findings with those in patients with McArdle disease and in healthy subjects. RESULTS: Sequencing of PHKA1 showed a novel pathogenic mutation (c.831G>A) in exon 7. There was a normal increase of plasma lactate during forearm ischemic exercise, but lactate did not change during dynamic, submaximal exercise in contrast to the fourfold increase in healthy subjects. Constant workload elicited a second wind in all patients with McArdle disease, but not in the patient with PHK deficiency. IV glucose administration appeared to improve exercise tolerance in the patient with PHK deficiency, but not to the same extent as in the patients with McArdle disease. Lipolysis was higher in the patient with PHK deficiency than in controls. CONCLUSION: These findings demonstrate that X-linked PHK deficiency causes a mild metabolic myopathy with blunted muscle glycogen breakdown and impaired lactate production during dynamic exercise, which impairs oxidative capacity only marginally. The different response of lactate to submaximal and maximal exercise is likely related to differential activation mechanisms for myophosphorylase.

[Bacteremia in children with acute lymphoblastic leukemia]. / Bakteriaemi hos børn med akut lymfoblastaer leukaemi.

The purpose of this study was to describe the pattern of bacterial infections in children with acute lymphoblastic leukemia. Forty-six children with ALL were treated for 119 febrile episodes. Antibiotic therapy was initiated with ampicillin and gentamicin, +/- dicloxacillin and lasted for 5-8 days. Bacterial cultures were positive in 36 of 119 febrile events. At the beginning of the febrile disease there was no difference in CRP and neutrophil count between children with positive and negative blood cultures. The maximum CRP was, however, significantly higher in children with positive blood cultures. In 75% there was no need to change the initial antibiotic treatment with ampicillin and gentamicin +/- dicloxacillin. If the temperature has been normal for 2-3 days and the neutrophil count is increasing it appears safe to discontinue the antibiotic therapy after five days when blood cultures are negative and after 7-8 days when cultures are positive.

Absorption of metronidazole suppositories in patients with postoperative ileus.

Thirty-five patients with postoperative ileus were given one g metronidazole suppositories three times daily. The patients were divided into four groups according to the operative procedure. The postoperative bowel motility was assessed as the time at which bowel sounds and evacuation occurred. One group of patients differed significantly from the others with regard to the time taken for the bowel function to become normal. No significant difference existed in the serum concentrations of metronidazole between the groups. Absorption of the first suppository was slower in our patients than in normal subjects, but thereafter concentrations followed the theoretic concentration curve for healthy subjects on the same dose regimen. Steady state, indicating normal absorption, was attained before bowel function returned to normal. The reason for the slower absorption of the first suppository is probably that the patients were confined to bed.