It's about time: small mammal communities and Lyme disease emergence.

Theory predicts that biodiversity changes due to climate warming can mediate the rate of disease emergence. The mechanisms linking biodiversity-disease relationships have been described both theoretically and empirically but remain poorly understood. We investigated the relations between host diversity and abundance and Lyme disease risk in southern Quebec, a region where Lyme disease is rapidly emerging. We found that both the abundance of small mammal hosts and the relative abundance of the tick's natural host, the white-footed mouse (Peromyscus leucopus), influenced measures of disease risk in tick vectors (Borrelia burgdorferi infection abundance and prevalence in tick vectors). Our results suggest that the increase in Lyme disease risk is modulated by regional processes involving the abundance and composition of small mammal assemblages. However, the nature and strength of these relationships was dependent both on time and geographic area. The strong effect of P. leucopus abundance on disease risk we report here is of significant concern, as this competent host is predicted to increase in abundance and occurrence in the region, with the northern shift in the range of North American species under climate warming.

Reducing Implant Infection in Orthopaedics (RIIiO): Results of a pilot study comparing the influence of forced air and resistive fabric warming technologies on postoperative infections following orthopaedic implant surgery.

BACKGROUND: Active warming during surgery prevents perioperative hypothermia but the effectiveness and postoperative infection rates may differ between warming technologies. AIM: To establish the recruitment and data management strategies needed for a full trial comparing postoperative infection rates associated with forced air warming (FAW) versus resistive fabric warming (RFW) in patients aged >65 years undergoing hemiarthroplasty following fractured neck of femur. METHODS: Participants were randomized 1:1 in permuted blocks to FAW or RFW. Hypothermia was defined as a temperature of <36°C at the end of surgery. Primary outcomes were the number of participants recruited and the number with definitive deep surgical site infections. FINDINGS: A total of 515 participants were randomized at six sites over a period of 18 months. Follow-up was completed for 70.1%. Thirty-seven participants were hypothermic (7.5% in the FAW group; 9.7% in the RFW group). The mean temperatures before anaesthesia and at the end of surgery were similar. For the primary clinical outcome, there were four deep surgical site infections in the FAW group and three in the RFW group. All participants who developed a postoperative infection had antibiotic prophylaxis, a cemented prosthesis, and were operated under laminar airflow; none was hypothermic. There were no serious adverse events related to warming. CONCLUSION: Surgical site infections were identified in both groups. Progression from the pilot to the full trial is possible but will need to take account of the high attrition rate.

Vital imaging and ultrastructural analysis of individual axon terminals labeled by iontophoretic application of lipophilic dye.

We describe a method for in vivo confocal fluorescence imaging of synaptic terminals and subsequent electron microscopic reconstructions of the same terminals. By iontophoretically applying lipophilic dye to nerve terminals at a single neuromuscular junction with a sharp microelectrode in living neonatal mice, we were able to quickly label other synaptic terminals of the same motor unit. This vital labeling technique allows the same synapses to be imaged in living animals for several days. By using two dyes applied to separate junctions we could visualize competing axons converging at the same site. We also show that similar approaches can be used to study synaptic inputs to neurons. Following photoconversion, the dye labeled axons and synapses were easily identified and distinguished from unlabeled synapses of other axons ultrastructurally. This new labeling technique thus provides a useful means to study reorganization of synaptic structure at high temporal and spatial resolution.

Rapid and reversible effects of activity on acetylcholine receptor density at the neuromuscular junction in vivo.

Quantitative fluorescence imaging was used to study the regulation of acetylcholine receptor (AChR) number and density at neuromuscular junctions in living adult mice. At fully functional synapses, AChRs have a half-life of about 14 days. However, 2 hours after neurotransmission was blocked, the half-life of the AChRs was now less than a day; the rate was 25 times faster than before. Most of the lost receptors were not quickly replaced. Direct muscle stimulation or restoration of synaptic transmission inhibited this process. AChRs that were removed from nonfunctional synapses resided for hours in the perijunctional membrane before being locally internalized. Dispersed AChRs could also reaggregate at the junction once neurotransmission was restored. The rapid and reversible alterations in AChR density at the neuromuscular junction in vivo parallel changes thought to occur in the central nervous system at synapses undergoing potentiation and depression.

Traumatic aortic injury: diagnosis with contrast-enhanced thoracic CT--five-year experience at a major trauma center.

PURPOSE: To review the literature and the authors' experience with admission contrast material-enhanced computed tomography (CT) in patients admitted after blunt trauma. MATERIALS AND METHODS: From January 1990 to December 1994, thoracic CT was performed to evaluate traumatic aortic injury in 677 patients with positive or equivocal findings at chest radiography. CT scans positive for mediastinal hemorrhage or aortic injury were retrospectively reviewed and interpreted by consensus, with angiographic and surgical confirmation. RESULTS: CT findings were negative for TAI in 570 (84%) of the 677 patients. Mediastinal hemorrhage was reported in 100 patients and was the only abnormality in 79 of them. Findings at angiography were negative for traumatic aortic injury in 77 (97%). CT signs of traumatic aortic injury in 21 patients included contour abnormality or pseudoaneurysm (n = 19), intimal flap(s) (n = 8), and pseudocoarctation (n = 3). Findings at angiography were positive for traumatic aortic injury in 19 (90%). For aortic injury and mediastinal hemorrhage, respectively, specificity for traumatic aortic injury was 99% and 87% and sensitivity was 90% and 100%; at meta-analysis of data from the authors and the literature, sensitivity was 97.0% and 99.3% and specificity was 99.8% and 87.1%. Reliance on findings at admission CT rather than radiography to indicate suspicion for traumatic aortic injury before angiography resulted in savings of more than $365,000. CONCLUSION: The CT finding of mediastinal hemorrhage alone is sensitive for traumatic aortic injury, but the finding of aortic injury is more specific.

A quantitative fluorescence-imaging technique for studying acetylcholine receptor turnover at neuromuscular junctions in living animals.

We have developed a technique to measure changes in the amount of fluorescently labeled acetylcholine receptors in living muscles over long time periods. The measurements of fluorescence are made relative to a novel, photolytically stable fluorescence standard (Spectralon) which allows changes in fluorescence to be followed over days, even months. The method compensates for spatial and temporal variations in image brightness due to the light source, microscope, and camera. We use this approach to study the turnover of fluorescently labeled acetylcholine receptors at a single neuromuscular junction in a living mouse by re-imaging the same junction in situ over a period of 3 weeks. In addition we show that the SIT video camera, which is generally considered inadequate for quantitative imaging (in comparison to CCD cameras), is actually a very good quantitative device, especially in situations requiring both fast acquisition and high resolution.

Paraplegia after thoracotomy: report of five cases and review of the literature.

Paraplegia complicating thoracotomy is rare but catastrophic. This report comprises 40 cases: 5 of our cases and 35 reported cases. Our cases comprised a stab wound of the left chest (1), decortication (1), lobectomy for bronchogenic carcinoma (2), and segmental resection for tuberculosis (1). The reported cases included 25 cases following thoracotomy for thoracic pathology (bronchogenic carcinoma, 12; pulmonary tuberculosis, 7; thoracic trauma, 2; bronchiectasis, 1; peptic esophagitis, 1; neurogenic tumors, 2; and benign lung lesion, 1 and 10 cases following operation for malignant hypertension. The surgical procedures performed on the 25 patients with thoracic pathology were lobectomy (8), bilobectomy (1), pneumonectomy (7), decortication (1), thoracoplasty (1), excision of neurogenic tumors (2), drainage of tuberculous cavity (1), and Nissen procedure (1). The intraoperative factors contributing to the neurologic deficit were bleeding at the costovertebral angle (9), migration of oxidized cellulose into spinal canal (9), thrombosis of anterior spinal artery (4), epidural hematoma (2), epidural narcotic (2), metastatic carcinoma (1), and hypotension (1). This serious complication can be prevented by meticulous operation and careful hemostasis. The immediate use of tomographic scanning or magnetic resonance imaging followed by surgical decompression might avert this serious complication.

Tracheal rupture and atlanto-occipital dislocation: case report.

Blunt trauma associated with tracheal rupture (TR) or atlanto-occipital dislocation (AOD) occurs rarely. Survival after sustaining either injury is even more uncommon. We describe a case of a patient who remarkably survived both injuries concurrently.

Practice satisfaction and dissatisfaction in general internal medicine departments of large multispecialty clinics.

General internal medicine (GIM) physician practice satisfaction and dissatisfaction in large multispecialty clinics were assessed utilizing a survey designed to elicit physician perceptions of practice. 420 GIM physicians in 22 multispecialty clinics were contacted, and 168 participated in the survey. The most significant positive components of practice satisfaction were patient interactions and favorable physician colleague interactions. The prominent negative components were paperwork hassles and perceived "second-class" physician status. Coping strategies were varied and included increased political involvement, career change, and withdrawal via depression.

Blunt traumatic rupture of the heart and pericardium: a ten-year experience (1979-1989).

Blunt traumatic rupture of the heart and pericardium, rarely diagnosed preoperatively, carries a high mortality rate. From 1979 to 1989, more than 20,000 patients were admitted to a Level I trauma center. A retrospective review identified 59 patients requiring emergency surgery for this condition. Injuries resulted from vehicular accidents (68%), motorcycle crashes (10%), pedestrians being struck by vehicles (7%), falls (5%), crushing (7%), and being struck by a horse (2%) or crane (2%). Seventeen patients (29%) had isolated rupture of the pericardium; 37 (63%) had ruptures of one or more cardiac chambers. All patients had signs of life at the scene or during transportation, but only 29 (49%) had vital signs on admission: 15 with chamber injury, 12 with pericardial rupture, and two with combined injuries. Diagnosis was established by emergency thoracotomy in the 30 patients who arrived in cardiac arrest. In the remaining 29 patients, diagnosis was made by urgent thoracotomy (41%), by subxiphoid pericardial window (34%), during laparotomy (21%), or by chest radiography (3%). The overall mortality rate was 76% (45 patients), but only 52% for those with vital signs on admission. Rapid transportation and expeditious surgical treatment can save many patients with these injuries.

Blunt traumatic cardiac rupture. A 5-year experience.

Blunt traumatic cardiac rupture is associated with a high rate of mortality. A review of the computerized trauma registry (1983 to 1988) identified 32 patients with this injury (ages 19 to 65 years; mean age, 39.5 years; 21 men and 11 women). Twenty-one patients (65.6%) were injured in vehicular crashes, 3 (9.4%) in pedestrian accidents, 3 (9.4%) in motorcycle accidents; 3 (9.4%) sustained crush injury; 1 (3.1%) was injured by a fall; and 1 (3.1%) was kicked in the chest by a horse. Anatomic injuries included right atrial rupture (13[40.6%]), left atrial rupture (8 [25%]), right ventricular rupture (10[31.3%]), left ventricular rupture (4[12.5%]), and rupture of two cardiac chambers (3 [9.4%]). Diagnosis was made by thoracotomy in all 20 patients presenting in cardiac arrest. In the remaining 12 patients, the diagnosis was established in seven by emergency left anterolateral thoracotomy and in five by subxyphoid pericardial window. Seven of these 12 patients (58.3%) had clinical cardiac tamponade and significant upper torso cyanosis. The mean Injury Severity Score (ISS), Trauma Score (TS), and Glasgow Coma Scale (GCS) score were 33.8, 13.2, and 14.3, respectively, among survivors and 51.5, 8.3, and 7.0 for nonsurvivors. The overall mortality rate was 81.3% (26 of 32 patients), the only survivors being those presenting with vital signs (6 of 12 patients [50%]). All patients with rupture of two cardiac chambers or with ventricular rupture died. The mortality rate from myocardial rupture is very high. Rapid prehospital transportation, a high index of suspicion, and prompt surgical intervention contribute to survival in these patients.

Rupture of thoracic aorta caused by blunt trauma. A fifteen-year experience.

During the 15 years from 1971 through 1985, 114 patients with rupture of the thoracic aorta caused by blunt trauma were admitted to the Shock Trauma Center of the Maryland Institute for Emergency Medical Services Systems. Mean age was 31.3 years (range, 15 to 80). Ninety were male and 24 were female, a 3.75:1 ratio. Of the 114, 89 (78.1%) survived initial resuscitation in the admitting area. Twenty five of the 89 initial survivors (28.1%) died during or after surgical repair. Paraplegia occurred in 11 of the 78 operating room survivors (14.1%). Further analysis was done of the 83 patients admitted in the 10-year period from 1976 through 1985. Mean Injury Severity Score, excluding aortic injury, was 18.2. Twenty-five of the 83 (30.1%) died during resuscitation in the admitting area or operating room. Seven others died during surgical repair and 12 died postoperatively, leaving 39 survivors (39/83 [47%] of total admissions and 39/58 [67.2%] of survivors of resuscitation). Paraplegia/paresis developed postoperatively in six of 34 (17.6%) cases involving shunt and four of 17 (23.5%) without shunt. Other major complications occurred in 21 of the operating room survivors. Statistically significant risk of death or major complication was associated with female sex, higher Injury Severity Score, lower admission blood pressure, larger hemothorax on admission, less qualified surgeon, major operation before aortic repair, use of shunt, and transfer directly from scene of injury. There was no advantage in this series to using or not using a shunt in preventing paraplegia. Mortality rates are realistic for a highly developed trauma system. Better techniques are needed to manage exsanguination and prevent paraplegia.

An expert system for the nutritional management of the critically ill.

While there have been considerable advances in the last several years in the nutritional management of the critically ill, these improvements are not always recognized in intensive care environments. In this paper we describe the development and testing of an expert system, NUTRITIONAL ADVISOR, which would be be an aid in providing nutritional assessment and support of critically ill patients. We discuss various approaches to treating time-varying data in the knowledge base in order to provide a recommended level of nutritional support which varies smoothly from day to day.

Blunt traumatic pericardial rupture. A ten-year experience 1979 to 1989.

Blunt traumatic pericardial rupture is rarely diagnosed preoperatively and is associated with high mortality. During a ten-year period from 1979 to 1989 over 20,000 patients were admitted to a major trauma center and 22 were found to have blunt traumatic pericardial rupture. Sixteen of the 22 (72.7%) were injured in vehicle accidents, 3 (13.6%) in motorcycle crashes, and 2 (9.1%) in falls; 1 (4.5%) was crushed. Eighteen (81.8%) were diagnosed intraoperatively during resuscitation or surgery for associated injuries, and four (18.1%) were diagnosed preoperatively with pericardial window. Eighteen were males and four were females. The median age was 40.14 years (range, 17 to 68). The tears were found at the following sites: left pleuropericardial (14/22 [64%]), diaphragmatic (4/22 [18%]), right pleuropericardial (2/22 [9%]), and superior mediastinal (2/22 [9%]). Associated cardiac injuries were found in only 5 of the 22 (22.7%); all of those patients died. The overall mortality rate was 63.6% (14/22). A high index of suspicion should alert the trauma surgeon to make the diagnosis intraoperatively during emergency surgical resuscitation in the hemodynamically unstable patient and by pericardial window in the stable patient.

Multichannel 18-test panels: are 60% of panels abnormal by chance?

Current teaching concerning the frequency of abnormal results secondary to chance alone in a multichannel panel is theoretically based on the binomial distribution. However, this distribution can be used only when the probability of an abnormal result (pi) is the same for each test in the panel. In modern-day multichannel testing, pi varies from test to test and most often is less than the usually reported 0.05. On the other hand, a test such as cholesterol may have a pi level as high as 0.55. Theoretically the only distribution that can take this variability into consideration is the Lexis distribution, a form of the binomial distribution that allows for varying pi s. Since no formula is available to calculate this distribution, we wrote a computer program to generate it. We arranged 18-test panels from 203 normal patients in a frequency distribution. This was then compared with the theoretical Lexis and binomial distributions. This analysis showed that although there was a 50% chance of having one abnormality per panel and a 16% chance of having two abnormalities per panel, there was less than 4% chance of having three or more abnormalities per 18-test panel. In addition, most of the abnormalities noted were minor and were thought to be clinically unimportant.

Nanometre-level analysis demonstrates that lipid flow does not drive membrane glycoprotein movements.

Nanometre-level analyses of the movements of membrane glycoproteins tagged with gold particles demonstrate that diffusing particles are not under the influence of a lipid flow, although a subset of particles which appear attached to the cytoskeleton are moving rearward.