Developing environment-specific water quality guidelines for suspended particulate matter.

It is generally well recognised that suspended particulate matter (SPM), from nano-scale particles to sand-sized sediments, can cause serious degradation of aquatic ecosystems. However, at present there is a poor understanding of the SPM conditions that water quality managers should aim to achieve in contrasting environments in order to support good ecological status. In this article, we analyse long-term SPM data collected from a wide range of reference-condition temperate environments in the UK (638 stream/river sites comprising 42 different ecosystem-types). One-way analysis of variance reveals that there is a statistically significant difference (p < 0.001) between the background SPM concentrations observed in contrasting ecosystems that are in reference condition (minimal anthropogenic disturbance). One of the 42 ecosystems studied had mean background concentrations of SPM in excess of the current European Union (EU) water quality guideline, despite being in reference condition. The implications of this finding are that the EU's current blanket water quality guideline (25 mg L(-1) for all environments) is inappropriate for this specific ecosystem-type which will be non-compliant with the guideline regardless of the intensity of land-use. The other 41 ecosystems studied had mean concentrations below the current EU water quality guideline. However, this does not necessarily mean that the guideline is appropriate for these ecosystems, as previous research has demonstrated that detrimental impacts can be experienced by some freshwater organisms, of all trophic levels, when exposed to concentrations below 25 mg L(-1). Therefore, it is suggested here that it is likely that some ecosystems, particularly those with mean concentrations in the 0.00-5.99 mg L(-1) range, require much lower guideline values in order to be effectively protected. We propose a model for predicting environment-specific water quality guidelines for SPM. In order to develop this model, the 638 reference condition sites were first classified into one of five mean background SPM ranges (0.00-5.99, 6.00-11.99, 12.00-17.99, 18.00-23.99 and >24.00 mg L(-1)). Stepwise Multiple Discriminant Analysis (MDA) of these ranges showed that a site's SPM range can be predicted as a function of: mean annual air temperature, mean annual precipitation, mean altitude of upstream catchment, distance from source, slope to source, channel width and depth, the percentage of catchment area comprised of clay, chalk, and hard rock solid geology, and the percentage of the catchment area comprised of blown sand as the surface (drift) material. The MDA technique, with cross-validation (Wilks-Lambda 0.358, p 0.000), can predict the correct or the next closest SPM range of a site in 90% of cases. This technique can also predict SPM range membership in a probabilistic manner, allowing for an estimate of uncertainty to be made in the allocation of a site to an environment-specific SPM range.

St. Anthony's fire (ergotamine induced leg ischemia)--a case report and review of the literature.

Ergotism, once an epidemic disease, is now a rare disorder. The most common manifestation is acute peripheral ischemia due to vasospasm, with an incidence of 0.001%. We report a case of a middle-age woman who presented with ergotamine-induced leg ischemia, due to chronic use of ergotamine-containing medications for migraine headaches. The diagnosis was confirmed with arteriography results, and she responded well to vasodilator therapy. The pharmacology, clinical presentation, diagnostic approach, and therapy of ergotism are reviewed.

Carotid endarterectomy in the elderly.

BACKGROUND AND PURPOSE: Increasing life expectancy has resulted in an increasing number of elderly. As the elderly population grows, the incidence of stroke will increase. Many such strokes result from carotid stenosis (CS). In view of the benefits of carotid endarterectomy (CEA) shown in recent clinical trials, it would seem prudent that surgery for CS be considered for prevention of stroke in this population. Traditionally, members of the geriatric population have often been viewed, perhaps arbitrarily, as inappropriate candidates for CEA because of perceived greater operative risks. The purpose of this study was to assess the safety of performing CEA in geriatric patients. PATIENTS AND METHODS: A total of 175 patients who underwent CEA between January 1994 and June 1996 were evaluated retrospectively. The patients were divided into the nongeriatric group (NGG <75 years of age) and the geriatric group (GG >75 years of age). There were 90 (51%) patients in the NGG and 85 (49%) in the GG. The two groups were compared for the following: rationale for surgery (symptomatic vs. asymptomatic), risk factor profile, preoperative imaging studies (noninvasive vs. invasive), and complications of surgery. RESULTS: Both groups were generally comparable in terms of their risk factors, rationale for surgery, and preoperative cardiac risk. Noninvasive imaging alone was used in 56% of NGG and 60% of GG patients, whereas 44% of NGG and 40% of GG underwent invasive cerebral angiography in addition to other noninvasive studies. There were 4(4.4%) postoperative neurological complications, including two strokes and two transient ischemic attacks (TIAs), in the NGG and 1(1%) stroke in the GG. One patient died in the NGG from a stroke. Although one patient in the GG experienced a postoperative myocardial infarction, there was no mortality in this group. CONCLUSION: CEA can be safely performed for both symptomatic and asymptomatic CS in appropriately selected patients irrespective of age.

Role of radiation after operative palliation in cancer of the proximal bile ducts.

Cancer of the proximal bile ducts continues to pose a formidable problem to even the most experienced biliary surgeon. From 1977 through 1985, 51 patients with histologically confirmed proximal bile duct cancers underwent surgical treatment. The lesion was confined to the hilar region in 30 patients; there was extensive hepatic infiltration or distant metastatic disease in 21 patients. One patient underwent resection. Biopsy only was performed in six patients. In the remaining 44 patients, transtumoral dilation and intubation were performed. These 44 patients were further analyzed with regard to how survival was affected by the presence of metastatic disease and by the adjunctive use of radiation therapy. Mean survival in those patients with metastatic disease (n = 16) was 6.1 months, and survival was not improved by the use of postoperative radiation. In the absence of metastatic or advanced local disease, however, the addition of external beam radiation did significantly extend the mean survival from 4.5 to 12.2 months and the median survival from 2.2 to 12.2 months. The operative mortality for the series was 14% and postoperative complications occurred in 18 patients. These findings suggest that the addition of external beam radiation improves survival in patients undergoing palliative treatment of hilar tumors. Further confirmation of the value of radiation awaits prospective investigation.

Extralobar pulmonary sequestration.

A neonate presenting with a density of the right mid-thorax was found, at thoracotomy, to have an extralobar pulmonary sequestration. The sequestration was resected, and the infant made an uneventful recovery. The morphogenesis, diagnosis, and management of this uncommon lesion are discussed.