SMALL-VOLUME RESUSCITATION FOR HYPOVOLEMI C SHOCK THERAPY - CONCEPT, EXPERIMENTAL AND CLINICAL-RESULTS

The concept of small-volume resuscitation, the rapid infusion of a sma ll volume (4 ml/kg BW) of hyperosmolar 7.2 - 7.5% saline solution for the initial therapy of severe hypovolemia and shock was advocated more than a decade ago. Numerous publications have established that hypero smolar saline solution can restore arterial blood pressure, cardiac in dex and oxygen delivery as well as organ perfusion to pre-shock values . Most prehospital studies failed to yield conclusive results with res pect to a reduction in overall mortality. A meta-analysis of preclinic al studies from North and South America, however, has indicated an inc rease in survival rate by 5.1% following small-volume resuscitation wh en compared to standard of care. Moreover, small-volume resuscitation appears to be of specific impact in patients suffering from head injur ies with increased ICP and in severest trauma requiring immediate surg ical intervention. Results from clinical trials in Austria, Germany an d France have demonstrated positive effects of hyperosmolar saline sol utions when used for fluid loading or fluid substitution in cardiac by pass and in aortic aneurysm surgery, respectively. A less positive per ioperative fluid balance, a better hemodynamic stability and improved pulmonary function were reported. In septic patients oxygen consumptio n could significantly be augmented. The most important mechanism of ac tion of small-volume resuscitation is the mobilisation of endogenous f luid primarily from oedematous endothelial cells, by which the rectifi cation of shock-narrowed capillaries and the restoration of nutritiona l blood, flow is efficiently promoted. Moreover, after ischemia reperf usion a reduction in sticking and rolling leukocytes have been found f ollowing hyperosmolar saline infusion. Both may be of paramount import ance in the longterm preservation of organ function following hypovole mic shock. An increased myocardial contractility in addition to the fl uid loading effects of hyperosmolar saline solutions has been suggeste d as a mechanism of action. This, however, could not be confirm ed by pre-load independent measures of myocardial contractility. Some concer ns have been raised regarding the use of hyper osmolar saline solution s in patients with a reduced cardiac reserve. A slower speed of infusi on and adequate monitoring is recommended for high risk patients. Rece ntly, hyperosmolar saline solutions in combination with artificial oxy gen carriers have been proposed to increase tissue oxygen delivery thr ough enhanced O-2 content. This interesting perspective, however, requ ires further studies to confirm the potential indications for such sol utions. Many hyperosmolar saline colloid solutions have been investiga ted in the past years, from which a 7,2 - 7,5% sodium chloride in comb ination with either 6 - 10% dextran 60/70 or 6 - 10% hydroxyethyl star ch 200,000 appear to yield the best benefit-risk ratio. This has led t o the registration of the solutions in South America, Austria, the Cze ch Republic,and is soon awaited for North America.