A novel means to classify response to resuscitation in the severely burned: Derivation of the KMAC value

Resuscitation fluid rates following burn are currently guided by a weight and burn size formulae, then titrated to urine output. Traditionally, 24h resuscitation is reported as volume of resuscitation received without direct consideration for the physiologic response. We propose an input-to-output ratio to describe the course of burn resuscitation and predict eventual outcomes.

We reviewed admissions to a burn center from January 2003 through August 2006. Inclusion criteria were ≥20%TBSA, admission ≤8h after burn, and survived ≥24h. Demographics, input volume and urine output, and clinical outcomes were recorded. A ratio of input volume (cc/kg/%TBSA/h) to urine output (cc/kg/h) was calculated at 24h. The ratio of fluid intake to urine output reflecting an 'expected' response was developed: 4cc/kg/%TBSA/24h (0.166cc/kg/%TBSA/h) divided by 0.5-1.0cc urine/kg/h for an expected range 0.166-0.334. Subjects were classified based upon the ratio: over-responders (<0.166), expected (0.166-0.334), or under-responders (>0.334). Clinical outcomes were compared and concordance of classification to values was calculated at 12h.

102 subjects met inclusion criteria; 29 in the over-responders, 37 in the expected, and 36 in the under-responders. Resuscitation volume was directly proportional to the calculated ratio while urine output was inversely proportional. Group mortality was 21%, 11%, and 44%, respectively, with a significant difference between the expected and under-responders (p<0.002). We found decreased ventilator-free days in the under-responders, and when deaths were excluded, decreased ICU-free days as well (p<0.05). Concordance of paired data gathered at 12h and 24h was 67% for the under-responder group.

We describe a novel ratio to classify acute resuscitation after severe burn including the patient's response. Such a classification is associated with eventual outcomes.