Localized tension pneumothorax in patients with adult respiratory distress syndrome.

Tension pneumothorax as a complication of ventilatory support may cause severe cardiac problems. The diagnosis may be difficult. Risk factors predisposing to the misdiagnosis of this condition include atypical location of the pneumothorax. Three patients with adult respiratory distress syndrome who had atypical, localized tension pneumothorax are described. Each had an ipsilateral functioning chest tube in place at the time. Placement of chest tubes into the localized pneumothoraces resulted in immediate improvement in hemodynamic status in two patients, but the third patient died before the chest tube could be placed. A diagnosis of tension pneumothorax should be considered in any patient on a ventilator whose hemodynamic status deteriorates in the presence of high airway pressures. In patients with adult respiratory distress syndrome the pneumothorax can remain localized because the heavy, noncompliant lungs cannot collapse enough for air to dissect diffusely through the pleural space; pleural adhesions may also contribute to this phenomenon.

The effect of the fiber components cellulose and lignin on experimental colon neoplasia.

Sixty Sprague-Dawley rats were pair-fed one of three nutritionally identical diets. One diet contained "low-fiber" (3.8% crude fiber); the others contained "high fiber" (28.7% crude fiber) composed of either cellulose or lignin. Although both "high fiber" diets had similar stool bulking effects, only the cellulose diet was associated with a reduction in 1,2-dimethylhydrazine (DMH)-induced colon neoplasms. The cellulose diet was also associated with distinct changes in the gut bacterial profile and with a lowered serum cholesterol.

Chest trauma in a Canadian urban setting--implications for trauma research in Canada.

The trauma registry at the Montreal General Hospital was reviewed to provide basic epidemiologic data on chest trauma in Canada and to compare these data with the minimal data available in the literature. Chest trauma in multiply injured patients resulted in higher Injury Severity Scores (ISSs) than the average. This was reflected in higher mortality for patients with chest trauma. The majority of injuries were caused by blunt trauma. Less than 9% of patients admitted to the hospital required thoracotomy for thoracic vascular and cardiac trauma. Outcome (measured by mortality) was better than that predicted from the literature based on admission ISS. The etiology of trauma in this Canadian setting and the resulting injury profiles were substantially different from those obtained from the predominantly American epidemiologic data available in the literature. This suggests the need for gathering more Canadian population-based trauma data for the planning of trauma prevention and care in this country.

Endoscopic guided percutaneous tracheostomy: early results of a consecutive trial.

Percutaneous tracheostomy is increasingly being used for patients needing prolonged ventilatory support. The purpose of this study was to assess the feasibility of widespread application of endoscopic guided percutaneous tracheostomy. Sixty-one consecutive ICU patients requiring prolonged mechanical ventilation underwent bedside endoscopic guided percutaneous tracheostomy. Using a modified Ciaglia technique, a #6-10 tracheostomy tube was introduced between the second and third tracheal rings. Bronchoscopic transillumination facilitated identification of the appropriate tracheostomy site, and verified satisfactory placement of dilators and tracheostomy tube. There was one procedure-related death due to arrhythmia. Procedure-related complications included (n = 7): bleeding (controlled with local pressure), two infections, two cuff tears, and two obstructions of the tracheal tube. The tracheostomy was eventually removed in 13 patients. Bronchoscopic evaluation of three patients at 4 months post-tracheostomy removal was normal and there has been no clinical evidence suggestive of tracheal stenosis in the remaining ten extubated patients. There was a 50% reduction in cost when compared to operative tracheostomy. Percutaneous tracheostomy is a simple, safe, cost-effective bedside procedure for critically ill ventilator-dependent patients. Endoscopic guidance appears to increase the safety of this procedure and may prevent complications of pneumothorax, subcutaneous emphysema, and paratracheal false passage previously reported with blinded percutaneous methods.

Residual hypothermia in patients recovering in the intensive care unit from cardiac surgery.

Because of inadequate rewarming or equilibration of body temperature, patients who undergo cardiac surgery with hypothermia often are still hypothermic after arrival in the intensive care unit. The incidence of residual hypothermia and its hemodynamic effects were assessed in this study. Of 82 adults who underwent cardiac surgery, 41 were normothermic with core temperatures of 35.5 degrees C or higher (mean 36.0 +/- 0.1 degrees C) and 41 were hypothermic with temperatures below 35.5 degrees C (mean 34.9 +/- 0.1 degrees C) on arrival at the intensive care unit (p less than 0.005). Patients with hypothermia had significantly (1.9 +/- 0.1 versus 2.2 +/- 0.1, p less than 0.05) lower cardiac indices. Although not statistically significant, there was a trend toward higher systemic vascular resistance in the patients with hypothermia. The authors conclude that mild residual hypothermia is still common after cardiac surgery and may contribute to the depressed hemodynamic status of these patients.

Assessing multiple trauma: is the cervical spine enough?

This retrospective study of multiple trauma patients sustaining spinal column fractures was done to assess whether evaluation of the cervical spine alone is adequate. Sixty-three such patients were identified and further descriptive analyses performed. The majority of spinal fractures occurred not in the cervical spine, but in the thoracic and lumbosacral spine areas. Since a number of these spinal fractures have associated neurologic complications, only by prompt evaluation of the entire spinal column can further injuries be prevented. Based on our data, we feel that patients with multiple injuries and an altered sensorium should have the entire spine protected and evaluated radiologically before being cleared.

Proliferative characteristics of chronic crypt cells in C57BL/6J and A/J mice as predictors of subsequent tumor formation.

It has been proposed that the number and extent of tumors formed after chronic exposure to dimethylhydrazine (DMH) can be predicted by the indigenous number and distribution of DNA-synthesizing cells in the murine colonic mucosa, and that this sensitivity to DMH is genetically determined. In order to test this hypothesis we studied two genetically distinct inbred strains of mice; the DMH-sensitive A/J (A) mouse, and the relatively DMH-resistant C57BL/6J (B) mouse before and after a single exposure to DMH. The untreated A strain had the longer crypt column [33.2 +/- 0.8 (SD) cells versus 28.8 +/- 0.9 cells], a higher absolute number of labeled cells per crypt column (4.4 +/- 0.6 versus 2.6 +/- 0.9), a greater labeling index (13.4 +/- 1.6% versus 9.1 +/- 2.9%), a wider proliferative compartment, and a greater number and percentage of labeled cells in the middle and upper thirds of the crypt than the untreated B strain. After acute exposure to DMH the A strain lost 14 +/- 3% of their total body weight, while the B strain lost 0.5 +/- 2% total body weight 48 h post-DMH. There was an initial loss of cryptal cells, a drop in the labeling index, and a subsequent increase and overshoot in the number of labeled cells and the labeling index. This pattern of cell loss and recovery over time was parallel in both strains, and thus cannot explain the differences in ultimate tumor formation after chronic exposure to the carcinogen. The data are consistent with the theory that the susceptibility to DMH carcinogenesis can be predicted by the indigenous proliferative characteristics of the murine colonic mucosa. The acute proliferative response to DMH in these strains is similar and parallel; thus ultimate tumor load may depend on long term effects such as the establishment of stable transmissible mutations.

1,2-Dimethylhydrazine-induced nuclear aberrations in A/J and C57BL/6J mouse colonic crypts.

A single exposure to 1,2-dimethylhydrazine [(DMH) CAS: 540-73-8] produces several forms of aberrant nuclei in the crypts of the murine colon. The frequency of nuclear aberrations (NAs) was examined in the distal colonic crypts in DMH-sensitive A/J mice and relatively DMH-resistant C57BL/6J mice before and after a single exposure to DMH. NAs, mitotic figures, and crypt column heights were scored for all animals as a function of time following administration of DMH. In both strains there was a significant increase in the absolute and relative frequency of NAs by 12 hours, with a corresponding drop and subsequent overshoot in the mitotic index by 48 hours after DMH. The temporal changes in crypt column height correlate closely with the temporal changes in frequency of NAs in both strains. The results showed that both inbred strains respond to acute DMH exposure in a similar and parallel fashion over time. It was concluded that the NA index assay is a sensitive method for detecting early DMH exposure. However, this assay does not relate to ultimate outcome after chronic DMH exposure and should not be used as a predictor of eventual neoplastic transformation of colonic mucosa with this carcinogen.

Effect of long-term metronidazole (MTZ) therapy on experimental colon cancer in rats.

Current reports suggest a beneficial effect of long-term metronidazole ( MTZ ) therapy in Crohn's disease. Since Crohn's disease is associated with a higher risk of bowel cancer and long-term MTZ has been shown to have a tumorigenic potential in rodents and a cocarcinogenic effect in experimental colon cancer, more studies are required to explore this area. Eighty-one rats were divided into four groups. Group A served as a control, groups B and C were given MTZ in their food (50 mg/kg/day). In groups C and D, a 3-cm colonic segment was isolated and brought out as a blind loop fistula. All animals received 20 weekly sc doses of 1,2-dimethylhydrazine (DMH) and were killed 25 weeks after the first injection. The mean number of colon tumors per animal (+/- SEM) in MTZ groups B (1.65 +/- 0.29) and C (2.57 +/- 0.38) were higher than A (1.44 +/- 0.3) and D (1.18 +/- 0.21), but the increase was only significant for group C over groups A and D (P less than 0.05) and group B (P = 0.06). The mean number of tumors per animal in the isolated loop of group C (0.95 +/- 0.28) was similar to group D (0.68 +/- 0.16) P = 0.41, but the mean number of tumors in the functioning colon of group C (1.62 +/- 0.25) was higher than group D (0.5 +/- 0.12) P less than 0.001. These findings suggest that long-term MTZ increased the number of colon tumors per rat in the DMH model but a statistical significance (P less than 0.05) was only noted in the MTZ and surgery group.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased incidence of experimental colon cancer associated with long-term metronidazole therapy.

Using the well-established DMH model for colon neoplasia, we demonstrated that a high-fiber diet pair-fed to animals was associated both with certain changes in bacterial profile and with protection against experimental colon neoplasia. The addition of metronidazole on a long-term basis to both high- and low-fiber diets did not alter stool bacteroides counts as expected and was associated with an apparent cocarcinogenic effect. Concern exists among surgeons and gastroenterologists as to whether metronidazole places their patients at risk. The status of long-term metronidazole therapy for patients with Crohn's disease is a pertinent example. In view of our findings, it is important to further elucidate the metabolism of metronidazole in both the rat and human gut.

Effects of diet on chemically induced bowel cancer.

One hundred and twenty-seven rats were fed one of four diets containing graded amounts of fibre or a diet with vitamin A supplements and were given, subcutaneously, dimethyl-hydrazine or saline. Stool weight correlated directly with fibre intake and the frequency of colonic tumours decreased as fibre intake increased. An artificial fibre-free diet was also associated with a reduction in the number of colonic tumours. Major changes were noted in the profile of bacteria from one dietary group to another but no correlation with the frequency of tumours was noted. A diet which provided vitamin A supplements sufficient to retard growth and raise serum and liver concentrations of the vitamin resulted in a modest reduction in the number of tumours.