Potential adverse effects of volume loading on perfusion of vital organs during closed-chest resuscitation

To determine whether expansion of blood volume improves vital organ perfusion pressures and blood flow during closed-chest cardiopulmonary resuscitation in dogs, we recorded intracranial and high-fidelity ascending aortic and right atrial pressures and measured total and regional blood flow with radioactive microspheres during cardiopulmonary resuscitation before and after rapid infusion of 1 liter of saline or dextran in 12 animals. Volume loading increased total forward blood flow from 327.1 +/- 50.9 to 692.7 +/- 105.9 ml/min (p less than .01). However, blood flow to the cerebral hemispheres, cerebellum, brainstem, and ventricular myocardium all decreased significantly. For example, blood flow to the left cerebral hemisphere fell from 16.5 +/- 2.4 to 5.5 +/- 1.7 ml/min/100 g (p less than .001), while left ventricular myocardial blood flow fell from 12.0 +/- 3.1 to 4.1 +/- 0.8 ml/min/100 g (p less than .05). These changes in critical regional flow were accompanied by disproportionate increases in right atrial and intracranial pressures (relative to aortic pressure), which reduced the average pressure differences generated across the coronary and cerebral circulations from 11.0 +/- 2.5 to 3.7 +/- 1.3 mm Hg (p less than .01) and from 16.1 +/- 2.3 to 10.5 +/- 1.5 mm Hg (p less than .01), respectively. The overall rise in forward flow was associated with a marked increase in extracranial, brachiocephalic blood flow. These findings suggest that large increments in blood volume can reduce vital organ perfusion during cardiopulmonary resuscitation despite an increase in total forward blood flow.