Thermal skin injury: I. Acute hemodynamic effects of fluid resuscitation with lactated Ringer's, plasma, and hypertonic saline (2,400 mosmol/l) in the rat.

ABSTRACT

Heart rate (HR), central venous pressure (CVP), mean arterial pressure (MAP), and cardiac index (CI) were measured in anesthetized rats subjected to a 40% body surface area full-thickness scald burn. Postburn intravenous fluid therapy with lactated Ringer's (5 ml/hr), plasma (2.5 ml/hr), or very hypertonic saline (2,400 mosmol/l) (0.75 ml/hr) was compared to unburned or burned, untreated controls. HR and CVP were not influenced significantly by thermal injury. MAP decreased steadily in the untreated group from 110 mmHg to 80 mmHg at 3 hr postburn. In the fluid-treated groups MAP did not change significantly. During the first 15 min postburn, CI was reduced to 58-71% of control values (P less than 0.01). CI increased during Ringer's and plasma infusion to 74-80% of control values (P less than 0.02 vs. unburned). Despite infusion therapy, hematocrit increased from 48 to 52%, clearly less than in the unresuscitated group (increase from 48 to 58%). Theoretically, the 2,400 mosmol/l saline would expand extracellular volume by five to six times the infused volume. Still, CI was reduced by 55% at 3 hr postburn in the hypertonic saline as well as in the burned, untreated group (P less than 0.001 vs. unburned). The low CI was mainly due to a reduced stroke volume.