A protocol for resuscitation of severe burn patients guided by transpulmonary thermodilution and lactate levels: a 3-year prospective cohort study

Abstract

Introduction: The use of urinary output and vital signs to guide initial burn resuscitation may lead to suboptimal resuscitation. Invasive hemodynamic monitoring may result in over-resuscitation. This study aimed to evaluate the results of a goal-directed burn resuscitation protocol that used standard measures of mean arterial pressure (MAP) and urine output, plus transpulmonary thermodilution (TPTD) and lactate levels to adjust fluid therapy to achieve a minimum level of preload to allow for sufficient vital organ perfusion.

Methods: We conducted a three-year prospective cohort study of 132 consecutive critically burned patients. These patients underwent resuscitation guided by MAP (>65 mmHg), urinary output (0.5 to 1 ml/kg), TPTD and lactate levels. Fluid therapy was adjusted to achieve a cardiac index (CI) >2.5 L/minute/m² and an intrathoracic blood volume index (ITBVI) >600 ml/m2, and to optimize lactate levels. Statistical analysis was performed using mixed models. We also used Pearson or Spearman methods and the Mann-Whitney U-test.

Results: A total of 98 men and 34 women (mean age, 48 ± 18 years) was studied. The mean total body surface area (TBSA) burned was 35% ± 22%. During the early resuscitation phase, lactate levels were elevated (2.58 ± 2.05 mmol/L) and TPTD showed initial hypovolemia by the CI (2.68 ± 1.06 L/minute/m²) and the ITBVI (709 ± 254 mL/m²). At 24 to 32 hours, the CI and lactic levels were normalized, although the ITBVI remained below the normal range (744 ± 276 ml/m²). The mean fluid rate required to achieve protocol targets in the first 8 hours was 4.05 ml/kg/TBSA burned, which slightly increased in the next 16 hours. Patients with a urine output greater than or less than 0.5 ml/kg/hour did not show differences in heart rate, mean arterial pressure, CI, ITBVI or lactate levels.

Conclusions: Initial hypovolemia may be detected by TPTD monitoring during the early resuscitation phase. This hypovolemia might not be reflected by blood pressure and hourly urine output. An adequate CI and tissue perfusion can be achieved with below-normal levels of preload. Early resuscitation guided by lactate levels and below-normal preload volume targets appears safe and avoids unnecessary fluid input.

Figure 1

Resuscitation decision tree. A diagram of a decision tree for the adjustment of fluid and catecholamine therapy according to a permissive hypovolemia protocol with lower preload targets and lactate measurements to ensure tissue perfusion is shown.

Figure 2

ITBV, the CI and lactate. The table shows low initial values of the ITBVI and its progressive elevation, similar to the CI. Lactic acid mirrors the CI (lower panel). With below-normal preload, at 32 hours, the CI and lactate levels were normal. CI, cardiac index; ITBV, intrathoracic blood volume; ITBVI, intrathoracic blood volume index.

Figure 3

ITBV and EVLW. The ITBV index slowly rises while the EVLWI increases, especially during the first 40 hours. EVLWI, extravascular lung water index; ITBV, intrathoracic blood volume.

Figure 4

Troponin I levels. A small peak of troponin I levels was observed at eight hours with a subsequent decline.