Systemic hemodynamics, gastric intramucosal PCO2 changes, and outcome in critically ill burn patients

Objectives: To define the hemodynamic and gastric intramucosal Pco(2) (Pco( 2)) changes during the first 48 hrs after burn trauma and to analyze their relationship with outcome. Design: Prospective, observational study in a cohort of consecutively admit ted critically ill burn patients. Setting: Intensive care burn unit in a university hospital. Patients: Forty-two patients with burns covering >20% of body surface area or inhalation injury. Interventions: None. Measurements and Main Results: Patients were monitored with an oximetric pu lmonary arterial catheter and a gastric tonometer to measure Pco(2). The di fference between arterial and gastric mucosal Pco(2) (P[i-a]co(2)) was cons idered indicative of gastric mucosal hypoxia. Hemodynamic and Pco(2) measur ements were performed during the first 48 hrs after admission. Patients suf fered burns covering 36.1% +/- 14.3% (mean +/- so) and 45.3% +/- 21.9% of b ody surface area (survivors and nonsurvivors, respectively). All patients w ere successfully resuscitated by conventional standards. Nonsurvivors (n = 16) died a median of 17 days after admission. In univariate analysis, the p resence of shock during the resuscitation phase, age, mixed venous pH, P[i- a]co(2), right atrial pressure, pulmonary arterial pressure, pulmonary arte rial occlusion pressure, cardiac index, systemic and pulmonary vascular res istance, left ventricular stroke work index, mixed venous oxygen saturation , and systemic oxygen delivery, consumption, and extraction ratio, measured over the first 12 hrs after admission, were significantly (p < .05) differ ent between survivors and nonsurvivors. These differences disappeared after 12 hrs after admission. Multivariate analysis identified age, percentage b ody surface area burned, and oxygen delivery index (6 hrs after admission) as factors independently associated with a poor outcome. P[i-a]co(2) (12 hr s after admission) was significantly greater in patients with than in those without inhalation injury (17 +/- 13 torr [2.26 +/- 1.73 kPa] vs. 6 +/- 10 torr [0.79 +/- 1.33 kPa]; p = .005). Patients with a P[i-a]co(2) differenc e (6 hrs after admission) greater than or equal to 10 torr (1.33 kPa) had a mortality rate of 56% vs. 25% of those patients with <10 torr (p = .044). Conclusions: Our data indicate that there are hemodynamic and biochemical c hanges that occur early after burn trauma that are associated with prognosi s after an apparently successful resuscitation. Particularly, a hemodynamic profile characterized by systemic acidosis, low systemic blood flow, and s ystemic and pulmonary vasoconstriction early after trauma is associated wit h a poor outcome. Additionally, intestinal mucosal acidosis occurs after bu rn trauma, is influenced by inhalation injury, and is a variable related to outcome.