BRADYCARDIA DURING SEVERE BUT REVERSIBLE HYPOVOLEMIC SHOCK IN MAN

  • 1 January 1984
    • journal article
    • research article
    • Vol. 14  (4) , 267-274
Abstract
Severe bleeding and hypovolemic shock causing hypotension are most often associated with tachycardia. In response to passive head-up tilt, 5 healthy men exhibited an increase in heart rate (HR) from 62 to 79 beats .times. min-1 and a gradual increase in the plasma concentration of aldosterone and protein. The increase in HR was followed by a decrease of 29 beats .times. min-1 (range 11-46) at the time when blood pressure decreased 38 mmHg (6-73). When tilted back to 0.degree., blood pressure immediately reversed while HR remained unchanged. Hypotension was associated with large but variable increases in plasma vasopressin (86 .+-. 28 pg .times. ml-1) accompanied by peripheral vasoconstriction. In 2 cases where patients with internal bleeding presented with a moderate HR of 96 beats .times. min-1, the ensuing fall in blood pressure was associated with a decrease in HR to 68 and 76 beats .times. min-1, respectively. Administration of albumin solution and blood normalized cardiovascular function. Two other patients showing initial HR of 130 and 100 beats .times. min-1, respectively, also developed relative bradycardia in conjunction with a decrease in blood pressure. Administration of ephedrine and atropine increased HR temporarily from 56 to 90 and from 36 to 110 beats .times. min-1, respectively. The latter 2 patients died in extreme bradycardia and autopsies revealed severe internal bleeding. Although hypovolemic shock is most often associated with an increase in HR, the increase is modest and a paradoxical bradycardia apparently develops in severe but potentially reversible hypotensive hypovolemic shock.