Effects of small-volume bolus treatment with intravenous normal saline and 7.5 per cent saline in combination with 6 per cent dextran-40 on metabolic acidosis and survival in burned mice

Abstract

Standard murine burn models include the administration of intraperitoneal (i.p.) saline solutions which are intended to resuscitate the animals during subsequent burn shock. Prehospital administration of small volumes of concentrated salt solutions has been recommended for the early treatment of haemorrhagic shock, and have also been utilized for burn shock. We studied the effects of bolus intravenous (i.v.) hypertonic saline (HS) or hypertonic saline/dextran-40 (HS + DEX) on animal survival and acid—base balance following 25 per cent total body surface area, full-thickness burn injury in mice. I.v. injections were administered via a tail vein immediately prior to burn injury. Some mice received 1 ml i.p. normal saline (NS) immediately after burn injury. Acid—base balance of vena caval blood was measured during the period of maximal metabolic acidosis following burn injury (12 h postburn). Preburn i.v. administration of 5 ml/kg of HS or HS + DEX, followed by 1 ml i.p. NS, only slightly decreased the degree of metabolic acidosis compared to animals receiving i.p. fluid alone, the standard resuscitation regimen for burned mice. Preburn i.v. administration of 0.2 ml volumes of HS or HS + DEX, without i.p. fluid administration, resulted in extremely high mortality. Immediate preburn i.v. administration of HS or HS + DEX did not eliminate metabolic acidosis in this murine burn model, and markedly increased the mortality when subsequent i.p. fluids were not administered. The degree of metabolic acidosis in the murine experimental burn model has not previously been clearly described. Furthermore, adequate fluid resuscitation of these animals may be difficult to achieve without indwelling vascular catheters which could deliver continuous i.v. fluids following burn injury.