Circulation
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A new noninvasive method for determining arterial blood pressure is presented. Using a fast servo system, the pressure in the arm cuff is controlled so that the flow is maintained at a low value. ⋯ Mean arterial blood pressure was determined from the noninvasive recordings using the same mathematically valid procedure as was used for the invasive recordings. The deviation between the invasive and the noninvasive determinations of this measurement was -0.6 +/- 2.2 mm Hg (mean +/- SD) in 23 subjects.
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The effect of pulsatile flow during cardiopulmonary bypass on the hormonal stress response was studied in 26 patients. Thirteen had routine and 13 had pulsatile bypass with an average pulse pressure of 30 mm Hg. Plasma vasopressin levels were significantly elevated during bypass in both groups, but were lower with pulsation (66 +/- 11 vs 36.3 pg/ml, p less than 0.05). ⋯ There were no significant changes in renin activity in either group, but the increase after cardiopulmonary bypass was greater in the nonpulsatile group (2.0 +/- 0.7 vs 1.36 +/- 0.4 ng/ml/hr, NS). These data suggest that pulsatile flow significantly attenuates the vasopressin and catecholamine stress response to cardiopulmonary bypass. This may explain the increased flow requirements and better tissue perfusion and organ function and the decreased incidence of postoperative hypertension after bypass using pulsatile flow.