Pressure-driven hemorrhage: a new experimental design for the study of crystalloid and small-volume hypertonic...

Fifty pentobarbital anesthetized dogs were subjected to pressure driven hemorrhage (PDH) in which (a) an initial bleeding rate (25 ml/min) was set, and (b) reset min-to-min in proportion to prevailing mean arterial pressure (MAP). When blood loss reached 40 ml/kg, experimental time was set to zero and dogs were divided into five groups: (1) CTR (untreated controls); (2) HSD (NaCl 7.5%-Dextran70 6%, 6 ml/kg, at zero time); (3) LR (lactated Ringers, 25 ml/min from 0-60 min); (4) HSD-LR (combines HSD and LR); (5) DBL-HSD-LR (as HSD-LR, plus second HSD injection, 4 ml/kg, at 30 min). PDH was continued throughout the postresuscitation period. CTR dogs bled 55.5 +/- 2.1 ml/kg and survived to 34.7 +/- 5.0 min postzero; HSD dogs bled 78.6 +/- 2.0 ml/kg, and survived to 51.2 +/- 2.9 min with transient recovery of MAP, cardiac output (CO), and O2 availability (O2A); LR dogs bled 94.5 +/- 3.4 ml/kg and survived for over 60 min, with sustained, partial recovery of MAP, CO, and O2A. HSD-LR dogs bled 111.5 +/- 3.7 ml/kg and survived for over 60 min with improved hemodynamic and metabolic response. In DBL-HSD-LR dogs, the second HSD produced higher MAP, CO, and O2A, but hematocrit was lowered to a critical level. Thus, standard LR resuscitation is effective in PDH, in spite of increased blood loss; a single HSD lengthens survival when used alone and improves recovery when added to LR.