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Submarine channels conveying sediment gravity flows are often topographically confined, but the effect of confinement width on channel morphodynamics is incompletely understood. We use physical experiments and a reduced-complexity model to investigate the effects of confinement width (B) and the inflow-to-sediment discharge ratio (Qin/Qs) on the evolution of submarine braided channels. The results show that a larger confinement width results in increased active braiding intensity (BIA) and that BIA takes longer to stabilize (i.e., a longer critical time; tc). At a fixed confinement width, a higher Qin/Qs slightly decreases the BIA. Digital elevation models of difference (DoD) of the experiments allow measurement of the morphological active width (Wa) of the submarine channels and the bulk morphological change (Vbulk) within an experiment, defined as the sum of total erosion and deposition. We find that Wa and Vbulk are proportional to B. We further confirm that BIA is proportional to both dimensionless sediment–stream power (ω**) and dimensionless stream power (ω*). These trends are consistent for submarine braided channels both with and without confinement width effects. Furthermore, we built a reduced-complexity model (RCM) that can simulate flow bifurcation and confluence of submarine braided channels. The simulated flow distribution provides reliable predictions of flow depth and sediment transport rate in the experiments. Using kernel density estimation (KDE) to forecast the probability and trends of cross-sectional flow distribution and corresponding BIA under extreme events, we find that skewness of the flow distribution decreases as discharge increases. The development of braided submarine channels, shown here to extend to conditions of topographic confinement, suggests that factors not modeled here (e.g., fine sediment) may be necessary to explain the abundance of single-thread submarine channels in nature.

Study Objective: Although the addition of H 2 blockers to H 1 antagonists has been promoted for use in anaphylaxis, there have been no large studies establishing the advantage of this approach in treating acute allergic syndromes. In this study we tested the hypothesis that combined H 1 and H 2 blockage results in improved outcomes in patients treated for acute allergic syndromes compared with treatment with H 1 blockade alone. Methods: In a randomized, double-blind, placebo-controlled trial, 91 adult patients with acute allergic syndromes were treated with either 50 mg of diphenhydramine and saline solution (control group) or with 50 mg of diphenhydramine and 50 mg of ranitidine (active group). These patients were treated with parenteral administration. Patients were recruited from an emergency department at an urban academic medical center. The primary endpoints were resolution of urticaria, angioedema, or erythema at 2 hours after protocol treatment. Areas of cutaneous involvement, heart rates, blood pressures, respiratory findings, and symptom scores were also assessed at baseline, 1 hour, and 2 hours. Results: There were significantly more patients without urticaria at 2 hours among the patients in the active group compared with those in the control group. Both groups had similar proportions of urticaria at baseline. Logistic regression models to predict resolution of urticaria, which accounted for baseline urticarial involvement, showed odds ratios in favor of the active group treatment. Similar findings were observed when the absence of both urticaria and angioedema was considered as the dependent variable. There was not a significant difference between the 2 groups with regard to the absence of erythema or angioedema (irrespective of the presence of urticaria) at 2 hours. Blood pressure and symptoms did not show differences between the 2 groups over time. Lower heart rates were observed 1 hour after treatment in the active treatment group (mean reduction 10 beats/min) compared with those found in the placebo group (mean reduction 6 beats/min). Conclusion: These data show that adding H 2 blockers to H 1 antagonists results in additional improvement of certain cutaneous outcomes for patients presenting with acute allergic syndromes. These findings favor the recommendation for using combined H 1 and H 2 antihistamines in acute allergic syndromes. [Lin RY, Curry A, Pesola GR, Knight RJ, Lee H-S, Bakalchuk L, Tenenbaum C, Westfal RE. Improved outcomes in patients with acute allergic syndromes who are treated with combined H 1 and H 2 antagonists. Ann Emerg Med. November 2000;36:462-468.]

Background: Emergency department visits for acute allergic reactions are common. Although the diagnosis and classification of these allergic reactions is primarily empiric, it is not always clear whether certain signs and symptoms constitute systemic mediator release syndromes, such as anaphylaxis, and thus may warrant more aggressive therapy or follow-up. Objective: We sought to determine associations between various clinical signs and symptoms with both plasma histamine levels and serum tryptase levels in adult patients presenting to an emergency department with acute allergic syndromes. The clinical correlates of raised β-tryptase levels were also investigated. Methods: Ninety-seven adult emergency department patients were prospectively studied by using a questionnaire, physical examination, and serum-plasma sampling. Plasma histamine and serum total and β-tryptase levels were determined. Clinical groupings were compared for mediator levels by using simple and multivariate analysis. Results: Elevated levels of plasma histamine (>10 nmol/L) and serum total tryptase (>15 ng/mL) were observed in 42 and 20 patients, respectively. Detectable β-tryptase (≥1 ng/mL) was observed in 23 patients, including 15 of the patients with elevated total tryptase levels. Suspected food allergy incidences and the duration of reaction were similar in patients with increased histamine levels and in patients with increased tryptase levels. Increased total tryptase levels, histamine levels, or both were observed in some patients who did not have airway, cardiovascular, or abdominal signs. Histamine levels correlated better with clinical signs than tryptase levels. Histamine elevations (>10 nmol/L) were observed more frequently in patients characterized by the following clinical signs in univariate analysis: the presence of urticaria, more extensive erythema, abnormal abdominal findings, and wheezing. Total tryptase increases were observed more frequently only in patients with urticaria. Histamine levels correlated with initial heart rates. In multivariate analysis the extent of urticaria was the best single predictor of plasma histamine levels and of either an elevated histamine or tryptase level. Detectable β-tryptase levels were observed in some patients who had neither elevated total tryptase nor elevated histamine levels. Unlike patients without detectable β-tryptase levels, patients who had detectable β-tryptase levels had a significant correlation between total tryptase and histamine levels ( P Conclusions: Raised histamine and, less commonly, raised tryptase levels are observed in almost 50% of patients presenting to emergency departments with acute allergic reactions. Some cases associated with systemic mediator release do not have classical features of severe anaphylaxis, such as hypotension or tachycardia. The lack of total tryptase elevations in many patients with elevated plasma histamine levels suggests basophil involvement. The clinical utility of β-tryptase determinations in the evaluation of acute allergic reactions needs further study. (J Allergy Clin Immunol 2000;106:65-71.)

Background Elevations of interleukin 6 (IL-6) have been described in drug-induced anaphylaxis. Although IL-6 is well known to stimulate an acute phase response, profiling acute phase protein levels, such as C-reactive protein (CRP), has, to our knowledge, never been performed in patients with acute allergic reactions. Objective To examine the pattern of IL-6 and CRP levels in patients with acute allergic reactions and to relate these to relevant clinical and laboratory parameters. Methods Plasma CRP and serum IL-6 levels were determined in 85 adult emergency department patients. These patients had been previously studied with questionnaires, physical examinations, and histamine/tryptase levels. Clinical and historical features were related to CRP and IL-6 levels. CRP and IL-6 levels were also examined for relationships with histamine and tryptase levels. Results CRP and IL-6 levels were significantly correlated with one another in the study patients (Spearman ρ = 0.36, P = 0.0008). Similar to histamine levels, IL-6 levels were significantly correlated with the extent of erythema manifested by the study patients. The extent of erythema was independently predicted by both IL-6 and histamine levels. Histamine levels were negatively correlated with CRP levels (Spearman ρ = −0.32, P = 0.003). Unlike histamine levels, IL-6 and CRP did not show significant relationships with the extent or presence of urticaria/angioedema or the presence of wheezing. IL-6 levels were correlated with the duration of symptoms before serologic sampling. An inverse correlation was observed between IL-6 levels and mean arterial blood pressure. Multivariate modeling showed significant independent effects from mean arterial pressure, duration of symptoms, erythema extent, and age in predicting IL-6 levels. Tryptase levels were higher in patients whose IL-6 levels were >20 pg/mL. Conclusions CRP and IL-6 levels are not simple surrogate markers for histamine or tryptase release by mast cells or basophils in acute allergic reactions. Increasing IL-6 levels relate to greater erythema extent, lower mean arterial blood pressure, and a longer duration of symptoms. It would be interesting to speculate that CRP and IL-6 increases characterize a late-phase response in immediate hypersensitivity reactions. In this perspective, the inverse relationship between CRP and histamine levels could be explained. As histamine levels are waning, CRP levels are increasing. Timed studies for histamine and CRP/IL-6 levels in allergic reactions are necessary to confirm this hypothesis.