Animal research on hypovolemic shock and resuscitation: an update.

Animal studies have indicated that volume resuscitation is successful with salt-containing crystalloid solutions as well as colloid solutions. Hyperosmolar salt solutions appear to have benefits over isosmolar solutions. Both, however, produce hypoproteinemia, which can lead to edema formation due to changes in the transcapillary oncotic gradient and possibly by changing the interstitial matrix. The lung appears to be much more resistant to edema formation than the soft tissues. Except for the dog, the lung does not appear to be significantly altered from shock with no substantial increase in protein permeability being evident in most studies. Colloid therapy, either proteins or dextran, effectively restores cardiovascular stability after hypovolemia and also prevents the increased transcapillary fluid flux seen in the lung and soft tissues, the former not appearing to be of much clinical significance, while the latter may lead to significant tissue edema. Blood replacement is necessary to restore adequate oxygen delivery to the tissues. The ideal hematocrit appears to be around 30-35.