Hypovolemia in shock due to acute myocardial infarction

Twelve patients with the clinical features of shock following acute myocardial infarction were treated with low molecular weight dextran (LMWD) as a plasma volume expander. Two of the patients had elevated central venous pressures (CVP), and neither responded favorably to plasma volume expansion. The remaining 10 patients had CVPs under 7 mm Hg prior to dextran infusion; five survived. Each survivor responded favorably to dextran infusion manifested by an increase in arterial pressure and cardiac index. The average increase in CVP in these patients was 1.0 mm Hg per 100 ml of dextran infused. The other five patients died either without recovering from shock or in chronic cardiac failure. These patients failed to show a significant increase in arterial pressure or cardiac index after dextran infusion; CVP increased by an average of 1.9 mm Hg per 100 ml infused. Hypovolemia must be considered in all patients in whom clinical evidence of shock develops as a complication of acute myocardial infarction, and if the CVP is normal or low, plasma volume expansion should be undertaken with caution. Increase in arterial pressure and evidence of improved cardiac index with little rise in CVP indicate a good response to the infusion and excellent prognosis for survival.

Heart rate after cardiac transplantation

Two patients who have undergone heart transplantation 7 and 15 months previously were studied to determine basal heart rate, the effects of exercise, and acute changes in venous return and blood pressure as well as of vagal stimulation. In one case the effects of body temperature, isoprenaline (isoproterenol), beta blockade, and atropinization on heart rate were studied. Mean resting heart rates of 110 and 90, respectively, were observed in the two cases without any significant change with time since the surgical implantation. Sinus arrhythmia was not observed and heart rate was found to increase with exercise following isoprenaline infusion and following increase in body temperature. A decrease was observed after beta blockade, but no significant direct or baroreceptor reflex effects could be produced by changes in venous return, systemic blood pressure, vagal stimulation, and atropinization. Both patients are thus effectively denervated, and there is no evidence of reinnervation to date.

The significance of central venous pressure and cardiac output measurements in shock

The central venous pressure changes which occur in shock syndromes vary with the aetiology and other factors.

Two methods of measuring CVP have given different results, and their advantages and disadvantages are discussed, together with an appraisal of the diagnostic and therapeutic value of such measurements.

The CVP changes produced by transfusion are related to changes in cardiac output and the value of the latter as a guide to treatment is discussed. The relationship of these measurements to clinical signs is emphasized.

Renal function during the early post-burn period: a comparison of colloid versus non-colloid containing balanced salt solution

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