Role of colloids in burn resuscitation...........

Doc, what is the role of albumin in early burn resuscitation? Do we have to give it in all cases?

Jessie p,

Colorado, USA

When a patient suffers a burn injury there is a temporary loss of the integrity of the capillaries as we have discussed before. This loss leads to the leakage of plasma proteins like albumin into the interstitial space.  This loss continues for the first eight hours following which the capillaries start to regain their integrity. Therefore if one were to replace the colloids in the first eight hours they would obviously leak out. It seems reasonable that one may start to replace giving colloids in the 2nd eight hours of the burn.

Different types of colloids may be used for resuscitation in burns: fresh frozen plasma, albumin and Dextran. Fresh frozen plasma is often given at a rate of 0.5ml-1ml/kg %TBSA and has a theoretical advantage - it replaces other plasma proteins besides albumin.

Dextran, another colloid used in burn resuscitation increases capillary blood flow, reduces RBC aggregation and helps to reduce tissue edema though this effect is limited to the time that Dextran is being administered as the body will metabolize it eventually. Dextran is composed of polymerized high molecular weight glucose chains and has double the osmotic pressure of albumin.

Hypertonic saline (180-300 mEq/L) has been used in some centers as it helps to shift extracellular fluids ( third space fluid loss) back into the vascular space by osmosis resulting in a reduction of fluid requirements. However there are some disadvantages: hypernatremia and intracellular fluid depletion can occur and therefore serum sodium levels should be closely monitored and maintained below 160mEq/L.

Albumin which is a regular component of our plasma is a protein that maximally raises the intravascular oncotic pressure. When it is given intravenously fifty percent of it remains intravascular, when compared to other colloid solutions where only twenty to thirty percent remains intravascular. Albumin is often infused as the rate of 0.3-1ml/kg /% burn over 24 hours.

In many centers colloids are added in the 2^nd eight hours though Parkland formula advocates only crystalloids in the first 24 hours.  Colloids help to reduce the fluid load in the first 24 hours and they also help to increase the urine output which often tends to go down during resuscitation. Colloid resuscitation is of great benefit in geriatric patients, major burns (>40%), patients associated with inhalation injury and those with cardiac disorders as it is difficult to resuscitate them with limited fluids and they are constantly in the danger of being overloaded. Fluid infusion should be tapered off after the first 24-32 hrs, when one finds that the patient has been adequately resuscitated. Fluid administration should then be planned on the basis of requirements of albumin (keep>2) and free water requirements (electrolyte free) to counter   irreversible water loss. Free water requirement is estimated as (25% + % burn) x BSA (m²) = ml/hr free water. The maintenance of all the clinical parameters like the urine output at normal levels is critical to the continuation of the resuscitation process to its logical conclusion. Prudent use of fresh frozen plasma and albumin can be very helpful and safe when compared to other colloids in burn resuscitation.

(An original initiative in burn care and education from asktheburnsurgeon++)

Monitoring the burn patient during burn resuscitation….

 Doc, we recently had a patient with 80 percent burns. Though we calculated the fluid loss and replaced it adequately the patient died. Could you tell us why this may have happened?

Sohail k,

Karachi, Pakistan.

Patient with major burns have two major issues that need to be dealt with:

a) Calculating the fluid requirement and replacing it

b) Monitoring the burn patient to know if the fluids replacements are adequate

We have already seen the calculation of fluids requirements in a previous post. We shall have a look at how to monitor burn patients. With fluid replacements there can be two issues- inadequate fluid replacement or fluid overload. If the calculated fluids are less then the patient will end up in shock and deteriorate. If the fluids are over calculated then fluid overload, increased pulmonary complications and increased compartmental pressure will result and finally end in circulatory failure and collapse.

All burn patients must therefore be monitored with great care.  A number of clinical parameters that are commonly used in ICU monitored patients are also applicable here:

Pulse

Temperature

Respiration

Blood pressure

Oxygen saturation

Central venous pressure

 Hourly urine output

These are the most common clinical parameters used. As the body looses fluids from burns and the intravascular pressure falls from the fluids shifts the blood pressure tends to fall. However the human body has a lot of inbuilt mechanisms to control this fall and deceptively maintains the blood pressure by releasing catecholamines or chemicals which will cause contraction of the blood vessels and thereby maintain the blood pressure. The pulse also rises from the pain reaction (tachycardia). The body has a limit till which it can support the blood pressure, once the fluid loss crosses this limit the homeostatic mechanisms will fail and  burn shock will result. The increasing compartmental edema that results in burns can result in an erroneous blood pressure reading. Similarly the vasospasm that occurs in the extremities can lead to incorrect oxygen saturation reading by pulse oxymetry.

Urine output is one of the most important parameters while monitoring the burn patient and this should be 0.5ml (kg/hr) in adults and in children    about 1ml (kg/hr). In most cases if an adequate urine output is maintained one can assured of an adequate fluid resuscitation. Major burn patients will need placement of a urinary catheter to monitor the hourly urine output. The volume status can also be gained from the central venous pressure or CVP. Insertion of a cvp line helps in monitoring this pressure and helps prevent fluid overload in normal patients. However in patients with previous poor cardiac function or in geriatric patients one may need the use of a swan ganz catheter. Similarly diabetic patients and those using long term diuretics and also patients with resuscitation difficulties may benefit from the use of the swan ganz catheter. Pulmonary vasoconstriction may lead to faulty CVP or swan ganz measurements. Maintenance of the acid base balance in the body as seen from the various blood gas measurements and analysis suggest adequate resuscitation. Some patients with cardiac co morbidities may need invasive cardiac monitoring. In these patients one must be careful while increasing the fluid administered and should only be done gradually to maintain adequate urine output (0.5ml/kg/hr adult and 1ml/kg/hr in children).

The requirement of fluid may be higher than calculated in some patient groups. Those patients who have suffered inhalation injury need 30-40%more fluids than suggested by Parkland formula. Patients with electrical burns need more fluids as they have greater underlying tissue damage. Patients undergoing diuretic therapy have prior free water deficits and need more fluids for resuscitation. Patients who have undergone escharotomies and have large open wounds may have higher free water losses that need to be adequately replaced. Patients in whom resuscitation is delayed probably have higher inflammatory response, greater fluid needs and attempts should be made to replace the fluid deficit calculated by Parkland in the immediate resuscitation period without causing hemodynamic failure.

(An original initiative in burn care and education from asktheburnsurgeon++)