Elsevier

Burns

Volume 30, Issue 8, December 2004, Pages 798-807
Burns

A clinical randomized study on the effects of invasive monitoring on burn shock resuscitation

https://doi.org/10.1016/j.burns.2004.06.016Get rights and content

Abstract

Background:

Ever since Charles Baxter's recommendations the standard regime for burn shock resuscitation remains crystalloid infusion at a rate of 4 ml/kg/% burn in the first 24 h following the thermal injury. A growing number of studies on invasive monitoring in burn shock, however, have raised a debate regarding the adequacy of this regime. The purpose of this prospective, randomised study was to compare goal-directed therapy guided by invasive monitoring with standard care (Baxter formula) in patients with burn shock.

Patients and methods:

Fifty consecutive patients with burns involving more than 20% body surface area were randomly assigned to one of two treatment groups. The control group was resuscitated according to the Baxter formula (4 ml/kg BW/% BSA burn), the thermodilution (TDD) group was treated according to a volumetric preload endpoint (intrathoracic blood volume) obtained by invasive haemodynamic monitoring.

Results:

The baseline characteristics of the two treatment groups were similar. Fluid administration in the initial 24 h after burn was significantly higher in the TDD treatment group than in the control group (P = 0.0001). The results of haemodynamic monitoring showed no significant difference in preload or cardiac output parameters. Signs of significant intravasal hypovolemia as indicated by subnormal values of intrathoracic and total blood volumes were present in both treatment groups. Mortality and morbidity were independent on randomisation.

Conclusion:

Burn shock resuscitation due to the Baxter formula leads to significant hypovolemia during the first 48 h following burn. Haemodynamic monitoring results in more aggressive therapeutic strategies and is associated with a significant increase in fluid administration. Increased crystalloid infusion does not improve preload or cardiac output parameters. This may be due to the fact that a pure crystalloid resuscitation is incapable of restoring cardiac preload during the period of burn shock.

Introduction

Ever since Charles Baxter first reported his data on fluid resuscitation in 1968, the standard regime for care for burn shock treatment remains crystalloid infusion at a rate of 4 ml/kg/% burn in the first 24 h after the thermal injury [1]. Vital signs and urine output continue to be regarded as the mainstay of resuscitation assessment. Invasive monitoring of burn patients is reserved for selected high-risk patients and for those where resuscitation to clinical goals is failing [2].

These treatment standards, however, have been increasingly objected during the last years [3], [4], [5], [6]. A rising number of publications including those from our group report on underresuscitation and hypoperfusion when the Baxter formula is used [3], [7], [8], [9]. Recent surveys of burn centres in the US revealed a significant excess over the anticipated resuscitation volume in most units [10], [11]. This was ascribed to an increased use of invasive haemodynamic monitoring [10], as a goal-directed resuscitation therapy most often seems associated with significantly increased fluid administration [4], [5], [8], [9]. Thus, it seems that current burn resuscitation delivers far more fluid than Baxter recommended and the literature suggests, indicating a discrepancy between clinical practice and published recommendations.

The consequences of excessive resuscitation and fluid overloading in patients with burns, however, may be as deleterious as those of underresuscitation. These include post-resuscitation pulmonary edema [12], conversion of superficial into deep burns [13], the need for fasciotomies in unburned limbs, and the occurrence of the abdominal compartment syndrome.

Proponents of aggressive fluid treatment argue that enhanced resuscitation might protect vital organs from reperfusion injury and prevent organ failure and death [4], [5], [9]. Opponents argue that the best resuscitation therapy is the one that utilizes minimal fluid [14].

Studies to date of the use of invasive monitoring and more aggressive fluid therapy are all associated with serious methodological problems, such as post hoc subgroup analysis and non prospective design [4], [8], [9]. Randomized, controlled studies comparing goal-directed and clinical-directed resuscitation do not exist.

To address these issues, we performed a randomized, controlled clinical trial to compare burn shock therapy guided by invasive haemodynamic monitoring with standard therapy according to the most frequently used empiric resuscitation formula (Baxter). We used transpulmonary thermodilution (TDD) for haemodynamic monitoring, as volumetric monitoring has been shown to reflect volume status of the burn patient more accurately than the pulmonary artery catheter (PAC) [8]. Methodological studies evaluating precision and reproducibility of this technique in burn patients have been previously published [15], [16].

Section snippets

Patients

During a 3 year period (1999–2002) 50 consecutive patients admitted to our intensive care burn unit with severe burns were studied. Inclusion in the study required a burn surface area greater than 20% body surface area and admission to our burn unit within 8 h of the thermal injury, where fluid infusion had been started within 6 h of injury. Patients with serious pre-existing medical illness compromising cardiopulmonary reserve before the burn or patients with known allergy to contrast media or

Statistics

Haemodynamic and demographic data were entered into a custom-made database (Microsoft Access). Statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS, Chicago).

Power analysis was based on previously published information on the effects of invasive monitoring on survival rate following burn shock [17]. Based on the results of this single available study, it was calculated that a sample size of 44 patients (22 patients in each group) would be sufficient to

Results

Demographics: During a 30 month period a total of 50 patients were included in the study. Enrollment began in February 2000 and ended in August 2002. During this period of time, 12 females and 38 males, ranging in age from 15 to 96 years and with a mean age of 41.3 years were included. The mean percentage of burn sustained was 42.1% TBSA, ranging from 20 to 81% TBSA. Mean ABSI score was 8.8 (5–13). Twenty-five (50%) of the patients had sustained an inhalation injury and 18 patients died (36%).

Discussion

As previously shown for other groups of critically ill—most recently in a prospective, randomized study by Sandham et al. [18]—goal-directed treatment using invasive monitoring leads to more aggressive therapy with increased administration of fluids. Evidence is lacking, however, that such change of clinical practice is associated with improved survival.

Also in patients with burn shock, previous authors have reported substantial deviation from standard care, when a goal-directed treatment

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