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.

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.

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.

Postpartum lymphocytic thyroiditis. Prevalence, clinical course, and long-term follow-up.

A group of 238 women were surveyed for thyroid disease at six and 12 weeks post partum. Twenty-seven (11.3%) of 238 entered into the study were found to have thyroid disease. Fifteen (56%) of 27 had positive microsomal hemagglutinin antibody titers. A spectrum of thyroid disease was found: persistent hypothyroidism (two patients), transient thyrotoxicosis followed by persistent hypothyroidism (one) or transient hypothyroidism (three), euthyroid goiter (five), transient thyrotoxicosis (seven), transient hypothyroidism (three), high-normal thyroxine levels (five), and low-normal thyroxine levels (one). All nine patients who underwent biopsy had active lymphocytic thyroiditis. Three-year follow-up of 25 of the 27 affected individuals revealed that 12 (48%) still had thyroid disease. This study demonstrates that there is a high incidence of postpartum thyroid disease, usually of a transient nature, and that only about one fourth of the cases are detected or clinically obvious.

Traumatic rupture of the aorta. A five-year experience.

In the five-year period ending in October, 1975, 31 consecutive patients with traumatic rupture of the thoracic aorta underwent surgery at the University of Maryland Hospital or the Maryland Institute for Emergency Medicine. All cases were confirmed by preoperative aortogram. Rupture was confined to one or more sites in the descending thoracic aorta at or distal to the origin of the left subclavian artery. The age was a mean of 26 years. Operation was done within an average of 18 hours after injury. Significant nonthoracic injuries were present in every case. Six patients with positive findings on peritoneal lavage underwent exploratory laparotomy prior to thoracotomy because of shock. Surgical repair was done by use of left heart bypass in 2 cases (one death), a passive aorta-aorta shunt in 23 cases (5 deaths), and without shunt or bypass in 6 cases (no deaths). An end-to-end tubular Dacron graft was used to reconstruct the aorta in all but one patient. Over-all survival rate was 25 of 31 patients (81 per cent). Paraplegia developed in one patient and renal failure in 3 patients (2 deaths) in the aorta-aorta shunt group. Hypertension was present in 18 (72 per cent) of the survivors. Palsy of the left recurrent laryngeal nerve persisted in 8 (32 per cent) of the survivors. Two of the deaths were related to technical problems of the shunting procedure and 2 to intrapleural exsanguination before proximal aortic control could be achieved. Complications and blood loss were reduced in the group with no shunt. The series lends support to the rigorous aortographic search for ruptured thoracic aortas in trauma patients with widened mediastinum. Once experience has been gained with shunting techniques, tears of the descending thoracic aorta may be safely repaired without shunt if done expeditiously.

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.

New method of respiratory gas analysis: light spectrometer.

A multigas concentration analyzer particularly suited for respiratory gas analysis has been developed using a new principle based on the measurement of the intensity of light emitted by excited atoms or ions in a direct current glow discharge. This glow discharge spectral emission gas analyzer (GDSEA), or light spectrometer, simultaneously measures O2, N2, CO2, He, and N2O gas concentrations with a 0-90% response time of 100 ms and a sample rate of less than 20 ml/min in a short gas sample line configuration. Mole accuracy and resolution of the GDSEA using a short sample line were determined in the laboratory to be +/- 0.15 to +/- 0.7% and 0.02-0.05%, respectively. In the clinical setting a comparative evaluation was made with a mass spectrometer in a long sample line, computerized, multibed, respiratory monitoring system. Results indicate a close agreement between the two instruments with differences in mixed inspiratory or expiratory O2 and CO2 concentrations of less than 2% and of derived variables, such as O2 consumption, CO2 production, and respiratory exchange ratio, of less than 5%.

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.

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.

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.

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.

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.