الفهرس 
Pathophysiology of burn shock and burn edemaOnly 14 pages are availabe for public view
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Abstract
Treatment of burn shock according to empirical resuscitation formulas is still considered the gold standard, and the burn community does not advocate the use of invasive cardiorepiratory monitoring in general. As a consequence, data dealing with early postburn hemodynamics are sparse, and only few studies have paid attention to the topic of end-point burn shock resuscitation.
Our study included 30 severely burned patients with total burn surface area between 20% and 60 %, they were received within the first 6 hours after burn. Patients were randomly divided into two groups; The study group (15 patients) were connected to the PiCCO system and resuscitation was directed to achieve volumetric hemodynamic goals. These goals in order of priority included an intrathoracic blood volume index above 800 ml/m2 and a cardiac index above >3.5l/min/m2. The control group (15 patients) were assigned to receive fluid resuscitation according to the Parkland formula, adequacy of resuscitation was assessed by CVP, MAP, HR and UOP. This is the standard regimen used in our burn unit. The aim of our work was to estimate and monitor fluid resuscitation in acutely burned patients using the PiCCO system, and to compare this system with our standard regimen.
The study group received significantly more fluid than the control group. However, both treatment groups showed similar, substantial intravascular fluid deficits throughout the study period, and a significant rise in plasma volume could not be demonstrated until 24 h following burn. There was no statistical difference between the study and the control group as regards the CVP or the serum albumin. This indicates that the additional crystalloid fluid that was infused in the study group, was lost from the intravascular space, and had no noticeable effect on the plasma volume. The reason is probably the burn induced capillary leak, which causes a continuous fluid extravasation as the rate of crystalloid fluid infusion is increased.
The mean hourly urine output was five to six-folds higher than the 30-50 ml traditionally defined as sufficient, and significantly higher in the study group, this still left the patients substantially overhydrated. Interesting, the higher filtration rate in the study group seem to protect the patients from early acute renal failure.
The fact that the HR, the MAP and the incidence of early ARF were significantly lower in the study group as compared to the control group may denote better stabilization of the patients and less SVR which suggest better resuscitation efforts in the study group observed in our study.
However attention should be withdrawn to the increase in the incidence of sepsis seen in the study group, which was related to the substantial increase in the subcutaneous edema seen in this group, this sepsis resulted, in some cases, to MOF and death.
It has been proven that typical ”vital signs” such as urine output, heart rate, and mean arterial pressure do not correlate with cardiac index and oxygen transport parameters. This indicates that these vital signs provide insufficient information to serve as end points for major burn resuscitation.
The TBVI could be an ideal value to guide resuscitation since the augmentation of TBVI during fluid resuscitation correlated well with increased cardiac output and stroke volume and thus led to improved organ perfusion.
ITBV-guided resuscitation was associated with restoration of preload and peripheral delivery of oxygen within 48 hours in the majority of patients. Augmentation of ITBV was significantly correlated with changes in cardiac index and oxygen transport rate. No such correlation could be demonstrated for the conventional preload parameters such as central venous pressure and UOP measurements.
In conclusion, fluid resuscitation of burn patients remains a double weapon. After all, we are left with the basic problem of burn shock resuscitation, caused by the capillary leak, which condemns every attempt to restore intravascular volumes without causing over infusion and edema. Even though most studies on burn resuscitation have been focusing on the infusion volume, a much more important subject for future studies seems to be the manipulation of the capillary permeability.
We believe that resuscitation by using information from invasive monitoring should become the standard in the treatment of large burns, as only invasive monitoring may reflect the true hemodynamic status of these patients. An adjustment of the calculated fluid requirements requires adequate end points, which reliably reflect the adequacy of tissue perfusion. Studies not only in burned, but also in trauma and surgical patients, have demonstrated that vital signs and urine output may not fulfill criteria.