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Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group ( CRBG). A heat and mass transport model ( SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability ( k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600-900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic ( kx/ kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To assess the safety and efficacy of the hemoglobin-based nitric oxide scavenger, pyridoxalated hemoglobin polyoxyethylene (PHP), in patients with distributive shock. DESIGN: Phase II multicenter, randomized (1:1), placebo-controlled study. SETTING: Fifteen intensive care units in North America. PATIENTS: Sixty-two patients with distributive shock, > or = 2 systemic inflammatory response syndrome criteria, and persistent catecholamine dependence despite adequate fluid resuscitation (pulmonary capillary wedge pressure > or = 12). INTERVENTIONS: Patients were randomized to PHP at 0.25 mL/kg/hr (20 mg/kg/hr), or an equal volume of placebo, infused for up to 100 hrs, in addition to conventional vasopressor therapy. Because treatment could not be blinded, vasopressors and ventilatory support were weaned by protocol. MEASUREMENTS AND MAIN RESULTS: Sixty-two patients were randomized to PHP (n = 33) or placebo (n = 29). Age, sex, etiology of shock (sepsis in 94%), and Acute Physiology and Chronic Health Evaluation II scores (33.1 +/- 8.3 vs. 30 +/- 7) were similar in PHP and placebo patients, respectively. Baseline plasma nitrite and nitrate levels were markedly elevated in both groups. PHP infusion increased systemic blood pressure within minutes. Overall 28-day mortality was similar (58% PHP vs. 59% placebo), but PHP survivors were weaned off vasopressors faster (13.7 +/- 8.2 vs. 26.3 +/- 21.4 hrs; p = .07) and spent less time on mechanical ventilation (10.4 +/- 10.2 vs. 17.4 +/- 9.9 days; p = .21). The risk ratio (PHP/placebo) for mortality was .79 (95% confidence interval, .39-1.59) when adjusted for age, sex, Acute Physiology and Chronic Health Evaluation II score, and etiology of sepsis. No excess medical interventions were noted with PHP use. PHP survivors left the intensive care unit earlier (13.6 +/- 8.6 vs. 17.9 +/- 8.2 days; p = .21) and more were discharged by day 28 (57.1 vs. 41.7%). CONCLUSIONS: PHP is a hemodynamically active nitric oxide scavenger. The role of PHP in distributive shock remains to be determined. [ABSTRACT FROM AUTHOR]