Circulation
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Hemodynamic studies were performed before and after pericardiocentesis in 19 patients with pericardial effusion. Right atrial pressure decreases significantly, from 16 +/- 4 mm Hg (mean +/- SD) to 7 +/- 5 mm Hg in 14 patients with cardiac tamponade. This change was accompanied by significant increases in cardiac output (3.87 +/- 1.77 to 7 +/- 2.2 l/min) and inspiratory systemic arterial pulse pressure (45 +/- 29 to 81 +/- 23 mm Hg). ⋯ This results in pulsus paradoxus. However, if pulmonary arterial wedge pressure is markedly elevated before the onset of tamponade, as in patients with chronic renal failure, then pericardial compliance may only determine right ventricular filling pressure. In such cases, pulsus paradoxus may be absent.
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Both heterologous IgG and Fab fragments of appropriate affinity and specificity have been shown capable of reversing advanced cardiac glycoside toxicity. Fab fragments are more rapidly excreted and theoretically have a smaller risk of unwanted immunologic effects, but relative rates of toxicity reversal have not been established. Rates of reversal of advanced digoxin toxicity by digoxin-specific IgG and Fab fragments were therefore compared in a dog model of advanced digoxin intoxication. ⋯ In contrast, six of six dogs given an equivalent dose of specific Fab fragments returned to sinus rhythm in a significantly shorter mean time of 36 minutes (P less than 0.01). Variability of time to arrhythmia reversion was less in Fab-treated dogs. These data demonstrate a decisive advantage of specific Fab fragments over intact IgG for potential clinical use in advanced, life-threatening digoxin intoxication.