Experimental constraints on left-right symmetric models from muon decay

The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters ρ, δ, and P(μ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578  GeV/c(2), both 90% C.L.

Measurement of the Michel parameter rho in muon decay

The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.

The accuracy of computed tomography in the diagnosis of blunt small-bowel perforation

BACKGROUND

Computed tomography (CT) is commonly used to evaluate patients with possible blunt intra-abdominal injury. One of its reported weaknesses is failure to demonstrate intestinal trauma. However, CT accuracy in identifying blunt small-bowel perforation has not been adequately assessed.

PATIENTS AND METHODS

We tracked 883 consecutive stable trauma victims who had abdominal CT because of equivocal physical findings. Initial "wet reading" results were compared with laparotomy findings and patient outcome.

RESULTS

Small-bowel perforation occurred in 26 patients (3%). Twenty-four had CT abnormalities suggesting the injury. Twelve had CT findings considered diagnostic: contrast extravasation (n = 5) and/or extraluminal air (n = 11). One additional patient was thought to have free air on CT, but had no intestinal injury at laparotomy. Another 12 patients had CT scans that were non-diagnostic but suggestive: free fluid without solid organ injury (n = 10), or small-bowel thickening (n = 4) or dilatation (n = 3). Two patients with small-bowel injuries had normal CT scans. Of 857 patients without small-bowel disruption, 802 had normal abdominal CT scans, and 55 had 67 CT findings suggesting intestinal injury. Thus, CT diagnosed small-bowel perforation with a sensitivity of 92%, a specificity of 94%, and negative and positive predictive accuracies of 100% and 30%, respectively. The test had an overall accuracy (validity) of 94%.

CONCLUSIONS

Blunt small-bowel injury is uncommon. When it is present, abdominal CT is usually abnormal. CT findings in intestinal perforation can be subtle and nonspecific. Any unexplained abnormality on CT after blunt abdominal trauma may signal the presence of intestinal perforation and warrants close clinical observation or further diagnostic tests.

Mortality in retroperitoneal hematoma

Eighty-one patients sustained retroperitoneal hematoma (RH) from blunt (70%) and penetrating (30%) trauma. Retroperitoneal hematomas were classified into 10 centro-medial Zone I, 25 lateral Zone II, and 46 pelvic Zone III hematomas. The mean injury Severity Score (ISS) for the entire series was 26.4 +/- 14. The mean ISS of nonsurvivors was 37.6 +/- 12. Overall mortality was 20%; if head injury deaths are excluded (six), mortality was 13%. Retroperitoneal hematoma associated with pelvic fracture had a mortality of 19%. Incidence of respiratory failure for entire series, excluding head trauma, was 29%. Respiratory failure occurred in 37% of patients with Zone III injuries. A requirement for ventilatory support greater than 48 hours was associated with a mortality of 35%. PaO2/FIO2 at 48 hours in intubated patients was significantly decreased in nonsurvivors compared to survivors, whereas the mean ISS of this subset of patients did not differentiate between survivors and nonsurvivors.

Management of foreign body ingestion

Management of ingested foreign bodies (FB) is a common clinical problem. A 10-year experience of 101 foreign body ingestions is reported. The experience suggests that endoscopic removal of foreign bodies is curative for objects located in the cricopharynx or upper esophagus. Foreign bodies which pass into the stomach can be observed for development of symptoms, as 80% of FB which reach the stomach spontaneously pass. Only 12% of patients required operation, which was done without mortality.

Effect of abdominal operations on survival after septic challenge in normal rats

We evaluated the effect of 60% small-bowel enterectomy that removed 75% of Peyer's patches, and the effects of lesser abdominal operations, on the survival of rats following inducement of peritonitis. We divided 286 female Fischer rats weighing 140 to 200 g into four experimental and two control groups. Following enterectomy, rats recovered for ten to 14 days before peritonitis was induced by intraperitoneal injection of 0.7 mL/100 g of body weight of a solution of 4% hemoglobin and Escherichia coli (10(9)/mL). At 48 hours after enterectomy, the survival rate was better than that in rats not operated on or anesthetized. Survival rates for rats having lesser intra-abdominal operations were significantly greater after peritonitis than the rates for controls, but were similar to rates for rats having enterectomies. Our results suggest that intra-abdominal operation of minimal or large magnitude is associated with improved survival from hemoglobin-E coli adjuvant peritonitis.