Pathogenesis of hyperadrenergic orthostatic hypotension. Evidence of disordered venous innervation exclusively in the lower limbs.
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The pathogenesis of hyperadrenergic orthostatic hypotension was studied in eight patients. Correction of the abnormal orthostatic changes by an inflated pressure suit (MAST) confirmed previous evidence of excessive gravitational pooling of blood in the leg veins. Intravenous L-norepinephrine infusion raised diastolic blood pressure in the same relationship to the infusion-induced increments in plasma norepinephrine concentrations as in normal subjects, indicating normal arteriolar responses. Contractile responses of the veins to infused L-norepinephrine were measured with a linear variable differential transformer (LVDT). The venous responses of hand veins in the patients fell within the 95% confidence limits of the responses of normal hand veins, as did the responses of foot veins in the seven normal subjects. However, foot veins of the patients with hyperadrenergic orthostatic hypotension, and both hand and foot veins of patients with "diffuse" autonomic failure, were supersensitive to norepinephrine, as reflected by a steeper slope of the regression of log (norepinephrine infusion rate) on percentage reduction in venous distensibility, and a significantly lower ED50 (i.e., norepinephrine infusion rate that induced 50% reduction in venous distensibility). The findings suggest anatomical or functional postganglionic denervation of lower limb veins causing excessive gravitational blood pooling with consequent orthostatic hypotension in these patients. (+info)
Definitive control of mortality from severe pelvic fracture.
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Within a group of 271 patients with pelvic fracture, 69 patients met criteria for severe hemorrhage. Sixty consecutive patients were treated by a combined multispecialty musculoskeletal trauma service using a protocol designed to control bleeding, rapidly diagnose and control associated injuries, as well as to prepare the patient for open reduction of the pelvic fracture, if appropriate. The pneumatic antishock garment, external fixation, and angiography were selectively used to control bleeding. Abdominal injuries were diagnosed using clinical examination and diagnostic peritoneal lavage. When lavage aspirate was grossly bloody, patients had no negative explorations. Microscopically positive lavages were associated with a 50% false-negative rate. Using the protocol, the mortality rate was 5%. Overall mortality rate was 10%. The combination of a trauma team approach and a specifically designed protocol reduces the number of deaths from pelvic fracture. (+info)
Combined analysis of the non-pneumatic anti-shock garment on mortality from hypovolemic shock secondary to obstetric hemorrhage.
(30/47)
The sequential external counter pulsator: a circulatory assist device.
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THE THREE GOALS OF CARDIAC ASSISTANCE ARE: (1) To maintain systemic blood flow; (2) To reduce cardiac work and tension development; and (3) To increase oxygen availability to the heart. Toward these ends, various devices and techniques have been developed, including several different types of vascular shunts in combination with or without extracorporeal oxygenation of blood, implantable auxiliary ventricle and augmentation of diastolic pressure by direct counter pulsation of blood through femoral cannulae or intra-aortic balloon.The sequenced counter pulsator is an external cardiac assist device being developed for the therapy of low output syndromes. Investigation in the laboratory has shown that it is capable of increasing cardiac output and diastolic systemic pressure with concomitant reduction in left ventricular end-diastolic pressure. Therefore, it appears to be clinically useful in patients with low cardiac output syndromes. (+info)
Effect of optimization of hemodynamics on fibrinolytic activity and antithrombotic efficacy of external pneumatic calf compression.
(32/47)
External pneumatic calf compression is effective but imperfect for antithrombotic prophylaxis in surgical patients. In preliminary studies, sequential filling of multisegmented leggings with graded pressure decreasing from ankle to knee increased venous flow velocity and wall shear stress, decreased residual venous volume, and enhanced postoperative fibrinolysis more than uniform compression. To determine if improved hemodynamics also increased antithrombotic activity, we performed a prospective randomized trial in neurosurgical patients comparing sequential application of graded pressure with uniform pressure applied to either a segmented bladder or to a single bladder. Deep vein thrombosis was diagnosed by leg scanning and impedance plethysmography and confirmed by phlebography. Venous thrombosis developed in 3 of 45 patients with graded-sequential filling, 6 of 50 with uniform compression-multiple compartments, and 3 of 41 with uniform pressure single bladder (differences not significant). These results suggest either that uniform compression offers all that can be expected of external pneumatic calf compression in prevention of venous thrombosis, or that even if a study with greater statistical power showed graded-sequential filling to be superior, the benefit/cost ratio of the more complex latter system is not likely to be large. (+info)