Changes in human sensory axonal excitability induced by an ischaemic insult.

OBJECTIVE: To identify the sensitivity and the patterns of change in sensory excitability that accompany an ischaemic insult. METHODS: Sensory excitability studies were undertaken in 10 subjects (mean age 36), and monitored throughout ischaemia and following its release. Ischaemia was induced using a sphygmomanometer inflated to 200mm/Hg above the elbow. RESULTS: During ischaemia there was reduction in threshold (P<0.001), associated with a significant increase in refractoriness (106+/-6.62%; P<0.001), reduction in superexcitability (30.4+/-0.42%; P<0.001), and 'fanning in' of threshold electrotonus, all indicative of axonal depolarization. Paraesthesiae were minimal during ischaemia, but became severe on release, at which stage numbness was prominent. Late subexcitability in sensory axons was completely abolished by a relatively shorter period of ischaemia than previously observed in motor axons. CONCLUSIONS: The present study has successfully developed a template for changes in sensory axonal excitability parameters that accompany ischaemia, and established their relative sensitivity to an ischaemic change. Further, it is proposed that the inhibition of the Na+/K+ pump, in the setting of increased persistent Na+ currents and abolition of late subexcitability may underlie the development of paraesthesiae during ischaemia. SIGNIFICANCE: Changes in axonal excitability induced by ischaemia may serve as a tool to identify and interpret changes in axonal membrane potential recorded in neuropathic patients.     

Postamputation neuromas and other symptomatic stump abnormalities: detection with CT

One of the potentially troublesome sequelae of limb amputations is the development of stump neuromas at the severed ends of major nerves. The ability to define them and to distinguish them from other causes of stump pain is of considerable clinical significance. Computed tomography was performed on ten lower limb amputees with stump pain. Five patients had neuromas that were manifest as focal or generalized alteration in the caliber, size, or contour of the nerve trunk in the affected stump. The remaining five patients each had an abnormality detected; these abnormalities included heterotopic bone formation, popliteal artery aneurysm, lipoma, scar tissue, and abscess in the contralateral limb.     

Coercive sexual behavior among Mexican-American college students

This study investigates the self-reported occurrences of coercive sexual behavior among Mexican-American college students and compares the results with Anglo-American college students. College class standing, income, total number in the household, the presence of male siblings, and age were used as independent variables. Two hundred and forty-two female college students (53% Mexican-American, 47% Anglo-American), from introductory psychology classes completed a survey concerning violence occurring in dating situations. Being the victim of date rape was reported by 11.4% of the Mexican-American students, while Anglo-Americans reported 16.4% incidence, this was not a statistically significant difference. Unwanted sexual advances, other than intercourse, were reported by 36.6% of all female respondents, and 48.8% had experienced at least one kind of physical violence or threat in dating situations. Similarities with other researchers' findings and implications are reported.     

Risk and management of upper gastrointestinal bleeding associated with prolonged dual-antiplatelet therapy after percutaneous coronary intervention

Prolonged dual-antiplatelet therapy with aspirin and clopidogrel is mandatory after drug-eluting stent implantation because of the potential increased risk of late stent thrombosis. The concern regarding prolonged antiplatelet therapy is the increased risk of bleeding. Gastrointestinal bleeding is the most common site of bleeding and presents a serious threat to patients due to the competing risks of gastrointestinal hemorrhage and stent thrombosis. Currently, there are no guidelines and little evidence on how best to manage these patients who are at high risk of morbidity and mortality from both the bleeding itself and the consequences of achieving optimum hemostasis by interruption of antiplatelet therapy. Managing gastrointestinal bleeding in a patient who has undergone recent percutaneous coronary intervention requires balancing the risk of stent thrombosis against further catastrophic bleeding. Close combined management between gastroenterologist and cardiologist is advocated to optimize patient outcomes.     

The Effects of Temperature and Time on Thermal Bond Strength in Tendons

Flexor tendon injuries are a common problem requiring sutured repair followed by early postoperative mobilisation. Results are better if active rather than passive flexion is allowed, however active movement increases the incidence of dehiscence. This has prompted examination of thermal bonding as a strategy for strengthening tendon repairs. Three experiments are described, using method and experimental design similar to those previously described. The strength of thermal bonds created between sections of bovine Achilles tendon at a range of temperatures and times was measured. Bonds were created by heating compressed sections in a water bath. Bond strength was measured on a tensiometer as load (N) and stress (N/mm² and N m kg⁻¹) then calculated using measured cross-sectional area, weight and length. Results were in broad agreement with those previously described, showing peak bond strength in samples heated to 62°C for 8 min (median 17.11 N/cm², SD 2.13). The effects of cooling to 0°C for 10 min immediately after bonding was to increase median bond strength when compared with non-cooled samples bonded under similar conditions (non-cooled, 9.11 N/cm², SD 3.11; cooled, 11.96 N/cm², SD 2.93). Statistical analysis using a quadratic regression model showed a close correlation between experimental data and curves modelled to best fit the data. Peak values for thermal bonds created using the methods described approached and in some cases exceeded that reported for the epitendinous element of modified Kessler tendon repairs in human digital flexor tendons. If such bonds could be created in vivo, thermal bonding may have a role in augmenting the strength of tendon repairs. The methods described are impractical for a non-laboratory environment. A laser would seem the most attractive alternative source of heat energy. Paper received 27 March 2000; accepted 20 November 2000.     

Demographic characteristics and prevalence of serologic markers among donors who use the confidential unit exclusion process: the Retrovirus Epidemiology Donor Study

BACKGROUND: Most blood centers utilize a confidential unit exclusion (CUE) process, intended to reduce the risk of transfusion-associated infectious diseases by allowing high-risk donors confidentially to exclude their blood from use for transfusion. The effectiveness of this method remains controversial. STUDY DESIGN AND METHODS: Confirmatory or supplemental test results for antibodies to human immunodeficiency virus, human T-lymphotropic virus type I, and hepatitis C virus, as well as hepatitis B surface antigen and syphilis and screening test results for antibodies to hepatitis B core (antigen) and alanine aminotransferase levels were obtained for approximately 1.8 million units donated during 1991 and 1992 at five blood centers within the United States. The prevalences of these infectious disease markers in units that the donors confidentially excluded (CUE+) and units that the donors did not exclude (CUE-) were calculated and examined within demographic subgroups. RESULTS: Units that were CUE+ were 8 to 41 times more likely to be seropositive for antibodies to human immunodeficiency virus and hepatitis C virus, hepatitis B surface antigen, and syphilis and three to four times more likely to react for antibody to hepatitis B core (antigen) or to have elevated alanine aminotransferase levels than units that were CUE- (p < 0.001). The positive predictive value of CUE (the percentage of CUE+ units that were confirmed seropositive for any marker) was 3.5 percent, and the sensitivity of CUE (the percentage of confirmed-seropositive units that were CUE+) was 2.3 percent. CONCLUSION: The current CUE process has low sensitivity and apparently low positive predictive value, and in many cases, it appeared that donors misunderstood it. Yet, CUE was not a “random process,” as CUE+ units were more likely to be seropositive for any infectious disease marker than CUE- units. This suggests that efforts to improve the CUE system may be warranted. As risk factors for transfusion-transmitted infection become more difficult to identify by history-based screening, however, such efforts may have limited effect.