Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution.

Peroxyacetyl nitrate (PAN) formed in the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) is the principal tropospheric reservoir for nitrogen oxide radicals (NOx = NO + NO2). PAN enables the transport and release of NOx to the remote troposphere with major implications for the global distributions of ozone and OH, the main tropospheric oxidants. Simulation of PAN is a challenge for global models because of the dependence of PAN on vertical transport as well as complex and uncertain NMVOC sources and chemistry. Here we use an improved representation of NMVOCs in a global 3-D chemical transport model (GEOS-Chem) and show that it can simulate PAN observations from aircraft campaigns worldwide. The immediate carbonyl precursors for PAN formation include acetaldehyde (44% of the global source), methylglyoxal (30 %), acetone (7 %), and a suite of other isoprene and terpene oxidation products (19 %). A diversity of NMVOC emissions is responsible for PAN formation globally including isoprene (37 %) and alkanes (14 %). Anthropogenic sources are dominant in the extratropical Northern Hemisphere outside the growing season. Open fires appear to play little role except at high northern latitudes in spring, although results are very sensitive to plume chemistry and plume rise. Lightning NOx is the dominant contributor to the observed PAN maximum in the free troposphere over the South Atlantic.

Transfer of take-home messages in graduate ICU education.

PURPOSE: Teaching by lecture (lecture format) is widely used at congresses and in medical educational programmes. The process involves the transfer of take-home messages. The aim of this study was to assess the number of take-home messages identified by postgraduate critical care junior doctors (juniors) during lectures. METHODS: This was a prospective observational study of 13 lectures. Lecturers were not informed in advance of the study. At the end of the lecture (30 or 50 min), the lecturer (senior doctor) and juniors listed the three main take-home messages on a form. Subjective elements of the juniors' appraisal (quality of the presentation, explanation of the topic's relevance, enthusiasm of the lecturer, background, case-based, delivery and personality, comprehensibility, practical applicability of information given, prioritization, presence of raw data, references, overall satisfaction) and objective elements (length of lecture, number of take-home messages written on the slides) of the lectures were recorded. Successful knowledge transfer was assessed by matching lecturers' and juniors' take-home messages. RESULTS: In total, 367 forms completed by 367 juniors were analysed. A match equal to 3 (highest match), 2, 1 or 0 was observed in 3.8, 26.7, 48.2 and 21.2% of the forms, respectively. No single subjective or objective element of the lecture was associated with the number of identified take-home messages. CONCLUSIONS: Two-thirds of critical care junior doctors identified at best only one of the three main take-home messages of a lecture, suggesting that knowledge transfer is poor during passive format learning. These results suggest that there is a need to develop strategies to improve the performance of lecture-based learning.

Timely closure of loop ileostomy following anterior resection for rectal cancer.

The implications of constructing a temporary ileostomy as part of the primary surgery for some rectal cancers must not be underestimated and many patients are particularly keen to have their stoma closed as early as possible. Currently, there are no set protocols in place which determine when this should take place, meaning that stoma reversal can be extremely variable between hospitals in the UK. We have created a policy to give patients a provisional date for ileostomy closure at discharge from primary surgery, which takes into account any necessary adjuvant treatment. We compared time to closure of ileostomy between two adjacent centres that share common stoma-care and oncology teams to see what benefit this policy provides. Patients were recruited over a 2-year period from 2005 to 2007 from two adjacent centres. Centre 1 had a policy to provide patients with a provisional date for closure of their ileostomy. The notes were studied retrospectively to determine time to closure of the ileostomy and reasons for any delays in closure. A total of 107 patients fulfilled the inclusion criteria, of which 83 patients (72%) had their stomas closed. Thirty patients had their stomas closed within 12 weeks (37%) - more than 67% (23/34) in centre 1 against 15% (7/48) in centre 2. At 1 year, all patients in centre 1 had their ileostomy closed, while 10% (5/48) were still waiting in centre 2. The mean time to closure was 13.47 and 25.25 weeks for centres 1 and 2 respectively -P-value < 0.0001. Offering patients a date for ileostomy closure at discharge from their primary resection results in the majority of stomas being closed within 12 weeks. For those patients who are to undergo adjuvant chemotherapy, we aim to perform this surgery in between the second and third cycles of treatment.

Colorectal tubulovillous adenomas identified on fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography scans.

OBJECTIVE: The aim of this retrospective study was to assess the significance of incidental focal colonic lesions on fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG PET/CT) scans in patients undergoing staging for noncolorectal cancer. METHOD: Of the 110 patients in our PET/CT database, 10 were found to have abnormally high uptake of tracer in their large bowel. RESULTS: Seven patients who underwent further endoscopic evaluation of these abnormalities had intermediate to high-risk adenomatous polyps. CONCLUSION: Benign colonic polyps produce high-intensity focal FDG uptake in large bowel. Endoscopic evaluation is recommended before curative resectional surgery of the presenting cancer where appropriate.

Determination of atmospheric methyl bromide by cryotrapping-gas chromatography and application to soil kinetic studies using a dynamic dilution system.

Methyl bromide (CH(3)Br) is considered to be a major source of stratospheric Br, which contributes to the destruction of ozone. It is therefore necessary to understand the natural sinks of this compound and to accurately measure ambient mixing ratios. Methodology is described for the measurement of atmospheric CH(3)Br by cryotrapping-gas chromatography and its application to soil kinetics. A 2-propanol/dry ice cryotrap was used to preconcentrate CH(3)Br in standard and air samples, with subsequent detection using a gas chromatograph equipped with an O(2)-doped electron capture detector (GC-ECD). The GC-ECD cryotrapping method had a detection limit of 0.23 pmol of CH(3)Br. This is equivalent to the amount of CH(3)Br in a 500 mL sample of ambient air at the estimated northern hemisphere atmospheric mixing ratio of 11 parts per trillion by volume (pptv). A dynamic dilution system was developed to produce mixing ratios of CH(3)Br ranging between 4 and 1000 pptv. Calibrated mixing ratios of CH(3)Br produced with the dilution system were used to determine soil uptake kinetics employing a dynamic soil incubation method.

Accuracy of colonoscopy in localisation of colorectal cancer.

An audit was performed of 77 patients with a single colorectal cancer visualised and sited before surgery by colonoscopic examination. The site of the cancer described at colonoscopy was compared with the actual site found at laparotomy. Six significant errors in preoperative localisation were encountered, when a change from the preoperatively planned resection to an alternative resection was found necessary. In two of these cases, extra morbidity was encountered as a result of these siting errors. Inaccurate localisation is a potential hazard of colonoscopy, especially when the examination is incomplete.

Comparison of preoperative serum CA19-9 levels with results of diagnostic imaging modalities in patients undergoing laparotomy for suspected pancreatic or gallbladder disease.

A prospective, blinded study of CA19-9 in 2,467 patients having abdominal surgery yielded 356 patients with pancreatic, gallbladder, and biliary disease who submitted coded preoperative serum specimens. In this group, there were 84 patients with pancreatic cancer and 24 patients with gallbladder-biliary cancer; the remainder had benign lesions. The recorded imaging data and marker results were merged with the patients' demographic, clinical, and surgical data and tissue diagnoses for analysis. Receiver operator character calculation suggested that a reference value of 100 U/ml for CA19-9 was appropriate rather than the 37-40 U/ml value most frequently employed and yielded a specificity of 97% in the 467 operated patients with a sensitivity of 8.3% for all nonpancreatic-biliary cancers and 62% overall for these lesions. In the more diagnostically challenging nonicteric patients, CA19-9 sensitivity was 55%, specificity was > 99%, positive predictive value (PPV) was 97%, and negative predictive value (NPV) was 88%. When CA19-9 results were combined with those from endoscopic retrograde cholangiopancreatography, ultrasound (US), or computed tomography (CT), the PPV, and especially the NPV were increased. The addition of carcinoembryonic antigen results did not affect overall results. The addition of CA19-9 results to ambiguous or indeterminant imaging interpretation clearly improved the combined specificity, sensitivity, and PPV, but the change was less impressive, albeit positive, for NPV. The combination of CA19-9 and CT (or US) is a reasonable, cost-effective, noninvasive approach to establishing the diagnosis of pancreatic, cholangitic, or biliary cancer in nonicteric patients. Although no single procedure or combination of procedures was found to detect early, small lesions, CA19-9 is clearly a clinically useful adjunct to imaging in nonjaundiced patients suspected of having these malignancies.

Bone metastases in carcinoma of the rectum: a clinical and pathological review.

Bone metastases were confirmed in 48 patients after treatment of rectal cancer and occurred predominantly in the lumbar spine and pelvis. Most of the deposits were lytic and coexisted with widespread metastatic disease. Correspondingly, the median survival from diagnosis was only 4 months. The new prognostic classification for rectal cancer was applied to the original tumour specimens and categorized 23 of these tumours into group IV which confidently predicts a poor outcome compared with only eight by the method of Dukes.

Anal endosonography in the evaluation of perianal sepsis and fistula in ano.

Anal endosonography has been performed in 22 patients with fistula in ano and perianal sepsis and compared with the operative findings. Using a special hard cone attachment to a radial 7 MHz probe the examination was well tolerated, rapid and generally accurate, detecting two unsuspected foreign bodies and all seven complicated fistula in ano preoperatively.

Conservative proctocolectomy: a dubious option in ulcerative colitis.

Conservative proctocolectomy was performed for ulcerative colitis in 19 patients, Crohn's disease in three and familial adenomatous polyposis in one. Healing was uncomplicated in only three patients (13 per cent). Eleven developed an anal discharge and nine an infected pelvic haematoma despite peranal drainage. Fourteen patients developed pelvic sepsis and, despite surgical curettage in 11, none healed. Six of these patients have had the anal sphincter divided, with healing in only one, and the anal canal has been excised in two. Eleven patients have ultimately healed at a median time of 28 months and eight have persistent sepsis after a median period of 45 months. Two patients with sepsis have had a successful ileoanal anastomosis. Conservative proctocolectomy cannot be recommended as a definitive operation for ulcerative colitis even though it may permit a subsequent restorative procedure.

Temporary elevation of CA 125 after abdominal surgical treatment for benign disease and cancer.

Analyses of preoperative and one to seven day postoperative determinations of CA 19-9, carcinoembryonic antigen (CEA) and CA 125 levels in 873 patients indicate that postoperative CA 19-9 and CEA serum levels were within the expected technical variance of the preoperative assay values in patients who were considered to have negative findings (below the reference value) from these tests preoperatively. If the test results were preoperatively positive in patients with cancer, they decreased postoperatively to or below normal reference values, unless the operation was palliative and significant tumor removal was not possible. For patients with a preoperative positive CA 125 level (greater than 35 units per mililiter), the postoperative serum levels were comparable with the CEA and CA 19-9 result. However, when the preoperative CA 125 level was within normal limits, 62 per cent of the patients had postoperative elevations, often to levels of less than 35 units per milliliter. Sequential postoperative determinations of CA 125 in 21 patients revealed that maximum levels of CA 125 were seen about two to four hours after the operation and that elevations persisted for as long as three months. Inferential evidence suggests that postoperative increases in serum CA 125 occur from incision and healing of the peritoneum and omentum by de novo synthesis of this antigen rather than shedding from tissues. Patients with CA 125 negative results and with carcinoma of the ovary having postoperative increases of this antigen within two months of the operation may pose a difficult problem in interpretations, and such patients require further investigation.

Comparison of portal and peripheral blood levels of carcinoembryonic antigen, CA 19-9, and CA 125 tumor-associated antigens in patients with colorectal and pancreatic cancer.

Synchronous serum specimens from the systemic and portal circulations of 43 patients with gastrointestinal cancer were assayed for levels of carcinoembryonic antigen, CA 19-9, and CA 125 tumor-associated antigens. The number of patients having a mean ratio of portal to systemic levels greater than 1 and the observed quantity of tumor-associated antigens were significant for carcinoembryonic antigen and CA 125 only in patients with colorectal cancer. No correlations were noted with the surgical stage of disease or with high or low (normal) levels of the three tumor-associated antigens. These findings suggest that peripheral concentrations of these antigens are in equilibrium with shedding from tumors and that hepatic clearance of a single pass does not significantly alter peripheral concentrations.

Dysplasia of the colon after jejuno-ileal bypass.

Colonoscopic biopsies were performed on 38 patients, 10-13 years after jejuno-ileal bypass. No significant dysplasia or premalignant change was seen in 371 biopsies. In one patient two tubulovillous adenomata were found in an otherwise normal colon, which is likely to be a chance finding. Although it will take another 10-20 years to establish whether jejuno-ileal bypass is associated with an increased risk of large bowel cancer in humans, there is at present no indication for regular colonoscopic surveillance.

Changing epidemiology, diagnosis, and treatment of Clostridium difficile toxin-associated colitis.

One hundred and ninety patients with Clostridium difficile toxin-associated colitis (CTAC) or pseudomembranous colitis (PMC) were identified, from microbiology records, disease index and proctoscopy service records, and studied retrospectively. CTAC was associated with cephalosporin antibiotic administration in 70 per cent of the patients. CTAC developed postoperatively in 108 patients after all types of surgery with no preponderance for abdominal surgery. Identification of cytotoxin in stool samples was the primary diagnostic test in 81 per cent of patients but cytotoxin was isolated in 98 per cent of all patients. Pseudomembranes visible on proctoscopy established the diagnosis in 19 per cent of patients and were more commonly seen in severe colitis (71 per cent) than in mild colitis (23 per cent). CTAC responded similarly to oral vancomycin and metronidazole with a relapse rate of 20-23 per cent, respectively. With its association with cephalosporin administration, CTAC is likely to occur with increasing frequency in surgical practice. Oral metronidazole is an effective, cheap, alternative to vancomycin therapy.

Vascular complications of inflammatory bowel disease.

During an 11-year period from January 1970 to December 1980, 7,199 patients at our institution had chronic ulcerative colitis or Crohn's disease. Thromboembolic complications developed in 92 (1.3%) of these patients. An additional 4 patients had cutaneous vasculitis, and 17 had an arteritis-associated diagnosis. Of the thromboembolic complications, 61 were deep vein thromboses or pulmonary emboli. The mortality among patients with thromboembolic complications was high (25%). Sixty percent of the patients had a thrombocytosis unaffected by sulfasalazine or corticosteroid therapy. In 73% of the patients, the erythrocyte sedimentation rate was increased, and when measured, fibrinogen and factor VIII were commonly elevated. Peripheral arterial thrombosis, coronary thrombosis, and mesenteric and portal vein thrombosis were predominantly postsurgical complications, but 77% of peripheral venous thromboses occurred spontaneously. The role of anticoagulation and surgical intervention in the management of hypercoagulation in patients with inflammatory bowel disease is discussed.

Evaluation of ankle joint proprioception following injection of the anterior talofibular ligament*.

The purpose of this investigation was to measure ankle joint proprioception preceding and following injection of Xylocaine into the anterior talofibular ligament (ATFL). Previous investigators have indicated that the typical inversion ankle sprain causes decreased afferent input from the joint which results in a proprioceptive deficit at the ankle. It was hypothesized that anesthesia of the ATFL would simulate this proprioceptive deficit. Fourteen individuals were blindfolded and subjected to pre-test proprioceptive measurements on a multiaxial balance evaluator. Xylocaine was introduced into the ATFL and post-test measurements were taken. A significant increase in average time in balance was found following anesthesia of the ATFL. The unexpected results may indicate that multiple trials caused a learning effect. This supports the contention of other investigators that proprioceptive deficits can be improved with training. It is concluded that proprioceptive training should be included in the overall rehabilitation program following ankle sprains. J Orthop Sports Phys Ther 1986;8(2):70-76.