Surgical management of juxtarenal aortic (JR-Ao) aneurysms and occlusive disease may include supraceliac aortic clamping, a retroperitoneal approach, or medial visceral rotation. The authors report ...their results using preferential direct suprarenal aortic clamping via a midline transperitoneal incision. Between July 1, 1992, and July 31, 2001, they treated 58 patients with JR-Ao disease (44 aneurysmal, 14 occlusive) via a midline incision without medial visceral rotation. Preferential suprarenal aortic clamping was used in 53 cases (42 proximal to both renal arteries, 11 proximal to the left renal artery only) and supraceliac or supramesenteric clamping in 5 cases when there was insufficient space for an aortic clamp between the superior mesenteric artery and renal arteries. This strategy avoided mesenteric ischemia associated with supraceliac clamping in the majority of cases and afforded better exposure of the right renal artery than obtainable with a left retroperitoneal approach or medial visceral rotation. Eleven patients underwent concomitant renal revascularization. Critical adjuncts included the following: (1) selective left renal vein (LRV) division if the vein stump pressure was <35 mm Hg (suggesting sufficient renal venous collaterals existed), (2) bilateral renal artery occlusion during aortic clamping to prevent thromboembolism, (3) flushing of aortic debris before restoring renal perfusion, and (4) routine administration of perioperative intravenous mannitol and renal-dose dopamine. Patients with type IV thoracoabdominal aneurysms, ruptured aneurysms, or JR-Ao disease approached via a retroperitoneal incision (severely obese patients, re-do aortic surgery) were excluded. No patients died or required dialysis during their hospital stay. The LRV was divided in 12 (21%) cases and reanastomosed in 2 cases (elevated stump pressures). The average suprarenal clamp time was 26 minutes (range, 10–60). Postoperative serum creatinine remained >0.5 ng/dL above baseline in 3 (5%) patients. These results support suprarenal aortic clamping with a midline transperitoneal incision as the optimal strategy for treating juxtarenal aortic aneurysms and occlusive disease. The authors believe that selective left renal vein division enhances juxtarenal aortic exposure, and routine administration of renal protective agents, along with occlusion of both renal arteries during suprarenal aortic clamping, are critical adjuncts in performing these operations.
Approximately 10 years ago, the Section of Vascular Surgery at Pennsylvania Hospital reported results of critical pathways that we developed for all major vascular operations, including carotid ...endarterectomy (CEA). After implementing these pathways, we then developed a specific five-step protocol to further improve results and decrease costs for elective CEA. With the advent of carotid artery balloon angioplasty and stenting (CABAS), CEA has come under increasing attack by endovascular interventionalists. We believe our regimen remains the gold-standard against which CABAS should be compared. Our five-step CEA protocol includes: (1) duplex ultrasonography performed in an accredited vascular laboratory as the sole diagnostic carotid preoperative study, (2) admission the day of surgery, (3) cervical block anesthesia to eliminate intraoperative electroencephalographic monitoring and other costly intraoperative monitoring tests, (4) transfer from the recovery room after a short observation period to the vascular ward, and (5) discharge the first postoperative morning. Since this 5-step protocol was implemented several years ago, we have found it to be safe and cost-effective, and now represents the standard against which CABAS should be compared.
Lidar measurements were made of the dispersion of the plume from a coastal industrial plant over three weeks between September 1996 and May 1998, 67 experimental runs were obtained, mostly of 30 min ...duration, and these were analysed to provide plume parameters (i.e. height, vertical and lateral spreads). These measurements were supplemented by local meteorological measurements at two portable meteorological stations and also by radiosonde measurements of wind, temperature and pressure profiles. The dispersion was modelled using three commercial regulatory models: ISC3 (EPA, Trinity Consultants and Lakes Environmental), UK-ADMS (CERC) and AERMOD (EPA, Lakes Environmental). Where possible, each model was run applying all choices as between urban or rural surface characteristics; wind speed measured at 10 m or 100 m; and surface corrected for topography or topography plus buildings. We have compared the range of output from each model with the Lidar measurements. In the main, the models underestimated dispersion in the near field and overestimated it beyond a few hundred m. ISC tended to show the smallest dispersion, while AERMOD gave the largest values for the lateral spread and ADMS gave the largest values of the vertical spread. Buoyant plume rise was modelled well in neutral conditions but rather erratically in unstable conditions. The models are quite sensitive to the reasonable input choices listed above: the full range of sensitivity is comparable to the difference between the median modelled value and the measured value.
The chronologies of five northern European ombrotrophic peat bogs subjected to a large ANIS C-14 dating effort (32-44 dates/site) are presented here. The results of Bayesian calibration (BCal) of ...dates with a prior assumption of chronological ordering were compared with a Bayesian wiggle-match approach (Bpeat) which assumes constant linear accumulation over sections of the peat profile. Interpolation of BCal age estimates of dense sequences of C-14 dates showed variable patterns of peat accumulation with time, with changes in accumulation occurring at intervals ranging from 20 to 50 cm. Within these intervals, peat accumulation appeared to be relatively linear. Close analysis suggests that some of the inferred variations in accumulation rate were related to the plant macrofossil composition of the peat. The wiggle-matched age-depth models had relatively high chronological uncertainty within intervals of closely spaced 14 C dates, suggesting that the premise of constant linear accumulation over large sections of the peat profile is unrealistic. Age models based on the assumption of linear accumulation over large parts of a peat core (and therefore only effective over millennial timescales), are not compatible with studies examining environmental change during the Holocene, where variability often occurs at decadal to centennial time-scales. Ideally, future wiggle-match age models should be constrained, with boundaries between sections based on the plant macrofossil composition of the peat and physical-chemical parameters such as the degree of decomposition. Strategies for the selection of material for dating should be designed so that there should be enough C-14 dates to accurately reconstruct the peat accumulation rate of each homogeneous stratigraphic unit.
Fossil pollen, stomata and charcoal were examined from a lake sedimentary sequence in the Glen Affric National Nature Reserve, one of the largest areas of remnant native pine woodland in Scotland, in ...order to assess ecosystem dynamics over the last 11 000 years. Results reveal that pinewood communities have been continuously present in East Glen Affric for the last 8300 years. Pinus sylvestris first arrived in the area around 9900 cal. BP, but occurred in only low abundance for the subsequent 1600 years. Pine populations expanded around 8300 cal. BP and remained in relatively constant abundance throughout the remainder of the Holocene. There is no evidence of a hypothesized regional mid-Holocene 'pine decline' at the site. Charcoal results reveal that pinewood communities in East Glen Affric do not appear to have been dependent on fire for either their establishment or their maintenance as has previously been suggested.
How do the predicted climatic changes (
IPCC, 2007
) for the next century compare in magnitude and rate to those that Earth has previously encountered? Are there comparable intervals of rapid rates ...of temperature change, sea-level rise and levels of atmospheric CO
2
that can be used as analogues to assess possible biotic responses to future change? Or are we stepping into the great unknown? This perspective article focuses on intervals in time in the fossil record when atmospheric CO
2
concentrations increased up to 1200 ppmv, temperatures in mid- to high-latitudes increased by greater than 4 °C within 60 years, and sea levels rose by up to 3 m higher than present. For these intervals in time, case studies of past biotic responses are presented to demonstrate the scale and impact of the magnitude and rate of such climate changes on biodiversity. We argue that although the underlying mechanisms responsible for these past changes in climate were very different (i.e. natural processes rather than anthropogenic), the rates and magnitude of climate change are similar to those predicted for the future and therefore potentially relevant to understanding future biotic response. What emerges from these past records is evidence for rapid community turnover, migrations, development of novel ecosystems and thresholds from one stable ecosystem state to another, but there is very little evidence for broad-scale extinctions due to a warming world. Based on this evidence from the fossil record, we make four recommendations for future climate-change integrated conservation strategies.
How do the predicted climatic changes (IPCC, 2007) for the next century compare in magnitude and rate to those that Earth has previously encountered? Are there comparable intervals of rapid rates of ...temperature change, sea-level rise and levels of atmospheric CO2 that can be used as analogues to assess possible biotic responses to future change? Or are we stepping into the great unknown? This perspective article focuses on intervals in time in the fossil record when atmospheric CO2 concentrations increased up to 1200 ppmv, temperatures in mid- to high-latitudes increased by greater than 4 degree C within 60 years, and sea levels rose by up to 3m higher than present. For these intervals in time, case studies of past biotic responses are presented to demonstrate the scale and impact of the magnitude and rate of such climate changes on biodiversity. We argue that although the underlying mechanisms responsible for these past changes in climate were very different (i.e. natural processes rather than anthropogenic), the rates and magnitude of climate change are similar to those predicted for the future and therefore potentially relevant to understanding future biotic response. What emerges from these past records is evidence for rapid community turnover, migrations, development of novel ecosystems and thresholds from one stable ecosystem state to another, but there is very little evidence for broad-scale extinctions due to a warming world. Based on this evidence from the fossil record, we make four recommendations for future climate-change integrated conservation strategies.
Previous reports have suggested "short" focal stenoses in peripheral vein grafts (PVGs), namely less than 2 cm long, can be successfully balloon dilated with good long-term patency rates. We ...questioned if enthusiasm for balloon angioplasty of these lesions in failing PVGs is warranted. Between August 1, 1993 and December 31, 1996, we performed balloon angioplasty of "short" stenoses in 19 PVGs in 16 patients. Bypasses included seven femoropopliteal, six femorotibial, and six popliteal-tibial or -pedal PVGs. All bypasses were originally performed for limb salvage. Single lesions were present in 13 grafts and two lesions in six grafts. Ten lesions were located at an anastomosis, 10 were located in the body of the graft, and five were peri-anastomotic. Fifteen procedures were performed percutaneously. Four angioplasties were performed using an open surgical approach because a percutaneous attempt failed in one case and three grafts were either in situ or tunneled subcutaneously making them easy to expose. Completion arteriogram documented excellent initial results in all 19 grafts. Cumulative one-year primary patency rate was 39%. The assisted primary patency rate at one year was 73%. Only five grafts remained patent 7-20 months (mean, 10 months) during follow-up without requiring further revision. One patient died with a patent graft 23 months post-balloon angioplasty. Complications included two hematomas following a percutaneous approach that required surgical repair. These results when compared to publications detailing patency following surgical revision suggest that balloon angioplasty of "short" stenoses less than 2 cm long in PVGs may be better treated by surgical revision. We reserve balloon angioplasty for "short" lesions when surgical revision is associated with inordinate difficulty such as a scarred groin wound in an obese patient.
Approximately 10 years ago, the Section of Vascular Surgery at Pennsylvania Hospital reported results of critical pathways that we developed for all major vascular operations, including carotid ...endarterectomy (CEA). After implementing these pathways, we then developed a specific five-step protocol to further improve results and decrease costs for elective CEA. With the advent of carotid artery balloon angioplasty and stenting (CABAS), CEA has come under increasing attack by endovascular interventionalists. We believe our regimen remains the gold-standard against which CABAS should be compared. Our five-step CEA protocol includes: (1) duplex ultrasonography performed in an accredited vascular laboratory as the sole diagnostic carotid preoperative study, (2) admission the day of surgery, (3) cervical block anesthesia to eliminate intraoperative electroencephalographic monitoring and other costly intraoperative monitoring tests, (4) transfer from the recovery room after a short observation period to the vascular ward, and (5) discharge the first postoperative morning. Since this 5-step protocol was implemented several years ago, we have found it to be safe and cost-effective, and now represents the standard against which CABAS should be compared.
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