Volume expansion during cardiopulmonary resuscitation reduces cerebral no-reflow

Resuscitation of the brain after cardiac arrest requires homogeneous blood recirculation which, however, may be impaired by low reperfusion pressure, intravascular coagulation, increased blood viscosity and endothelial cell swelling. Intravascular volume expansion induced by intravenous infusion of a small volume of hypertonic solution has previously been shown to improve nutritional flow to the brain after severe hemorrhage shock. We therefore investigated whether this therapy also improves cerebral reperfusion after cardiopulmonary resuscitation. Fourteen adult normothermic cats were resuscitated after 15 min of ventricular fibrillation by closed-chest cardiac massage in combination with epinephrine, bicarbonate and DC-defibrillations. Eight animals were submitted to the standard resuscitation protocol. Six cats received additionally 2 ml/kg/10 min 7.5% NaCl/6% hydroxyethyl starch solution for post-ischemic volume expansion. EEG, ECG, CBF, and the aortic, left ventricular, central venous and intracranial pressures were monitored. Reperfusion of the brain was visualized 30 min after cardiac resuscitation by labelling the circulating blood with fluorescein isothiocyanate albumin. Areas of impaired brain reperfusion (no-reflow)-defined by the absence of microvascular filling-were identified by fluorescence microscopy at eight standard coronal levels of the forebrain, and expressed as percent of total sectional area. All animals were successfully resuscitated although volume expansion decreased myocardial and cerebral reperfusion pressure during cardiopulmonary resuscitation. Treatment with hypertonic solution increased serum osmolality transiently and prevented hemoconcentration throughout the experiment. Cerebral no-reflow was significantly reduced from 28 +/- 13% to 15 +/- 6% of total forebrain sectional area. Volume expansion by small volume hypertonic solutions may, therefore, improve recovery of brain function following cardiac arrest.