Cardiovascular function and fluid compartments in newborn canine hemorrhagic shock.

Hemorrhage in the adult disrupts cellular function, resulting in a redistribution of fluids and electrolytes. There is little data about the effects of hemorrhage on body fluids in the neonate. The purpose of this study was to determine the effects of hemorrhage on cardiovascular function, coronary blood flow, red blood cell mass (RBCM), plasma volume (PV), and extracellular fluid (ECF) volume in newborn dogs. Group 1 consisted of 88 dogs, 1-20 days old, and group 2 was 81 dogs, 3-6 wk old. There is a significantly higher ECF volume in younger (256 +/- 10 ml/kg) compared with older puppies (121 +/- 5 ml/kg). A 40% hemorrhage caused ECF to fall less in the younger (-27%) than in the older puppies (-51%), whereas PV and RBCM decreased to a similar extent in both groups. After returning shed blood, PV and RBCM returned to prehemorrhage values, but there was a 12% deficit in functional ECF volume in both groups. A similar degree of bradycardia, myocardial depression, and acidosis occurred in both groups during shock and after returning shed blood. Cardiac output and coronary blood flow, measured only in group 2, fell significantly in shock (-60 and -50%, respectively; P less than 0.05) and remained below control values after returning shed blood. Our data indicate that inadequate perfusion of the myocardium and persistent acidosis impairs cardiac function in newborn shock.