Annals of Burns and Fire Disasters - vol. XII - n° 3 - September 1999

SUBESCHAR INFILTRATION OF EPINEPHRINE PRIOR TO EARLY EXCISION OF BURN WOUNDS - TECHNICAL REFINEMENTS

Janezic T.

Burns Unit, Ljubljana Clinical Centre, Ljubljana, Slovenia

SUMMARY. The early excision of burn wounds may lead to massive blood loss, which often becomes a major factor limiting the excision area. In order to diminish intra-operative blood loss following early excision of burn wounds, epinephrine solution may be injected under the burn eschar prior to excision. At the Burns Unit in Ljubljana (Slovenia) the technique of subeschar infiltration of epinephrine solution was started in 1988. Up to now the technique has been used in more than 500 patients. During the last ten years of clinical experience with this technique, several important technical details have been found to be important. The most important points of this technique are anaesthesia, the concentration of epinephrine hydrochloride, marking of the area to be inoltrated, the instruments used, the plane of infiltration, the time interval between infiltration and excision, assessment of the burned tissue to be excised, the volume of epinephrine solution injected, and haemostasis.
All these factors are described and discussed in this report.

Introduction

Excision in the first five days post-injury has been widely accepted as the method of choice in the treatment of full-thickness burn wounds. Early excision produces massive blood loss' which often becomes a major factor that limits the area of excision, thus greatly influencing the survival and the morbidity of burned patients. Many methods of reducing intra-operative blood loss have been described: use of the tourniquet for excision on the extremities' application of a topical solution of epinephrine hydrochloride, infusion of I -desamino-8-D-arginine vasopressin, intravenous application of triglycyl-lysine-vasopressin, early burn wound excision (first 24 h post-burn), and subeschar infiltration of vasoconstrictors such as ornithine 8 vasopressin (POR 8) or epinephrine hydrochloride.
The technique of subeschar infiltration with epinephrine solution in areas where a tourniquet could not be applied was first used at the Ljubljana Department of Plastic Surgery and Burns in 1988. Since then the technique of subeschar infiltration with epinephrine solution prior to excision of burn wounds has been used in more than 500 burned patients. Several technical details have been found to be important if the technique's maximum effect is to be achieved.

Method and technique

Anaesthesia
The anaesthetist needs to know the quantity and concentration of epinephrine solution injected. When epinephrine is injected beneath the burn eschar, certain anaesthetic drugs, e.g. halothane, should be avoided. The type of anaesthesia should be carefully chosen. Even when large quantities of epinephrine are injected (i.e. more than 0.03 mg/kg) there have been no reports of major complications due to epinephrine's systemic effects. Some minor cardiovascular effects of injected epinephrine were occasionally observed but these did not require therapeutic measures. Mild metabolic acidosis was experienced by several patients but this had ceased by the end of the surgical procedure.

Concentration of epinephrine hydrochloride
The epinephrine solution used at the Burns Unit in Ljubljana is composed of 500 ml normal saline, with an added I ml 1/1000 aqueous epinephrine hydrochloride (I mg epinephrine hydrochloride/500 ml solution , 1:500 000). On the basis of my experience this concentration of epinephrine represents the optimurn ratio between the weakest concentration of epinephrine and its effect.

Marking of the infiltration area
It often happens that the areas to be infiltrated are extensive, with the result that the surgeon may fail to inject some areas or even inject some twice. In order to inject the epinephrine solution evenly under the whole burn area, the eschar should be marked with transversal lines, using an ordinary surgical marker, dividing the area into small 4-cm-square rectangles. By injecting the epinephrine solution successively into each rectangle, the volume of epinephrine solution per unit area injected is distributed much more evenly (Fig. 1).

Fig. 1 - Marking the eschar prior to infiltration.

Infiltration instruments
Large quantities of epinephrine solution can be injected manually, using syringes and needles. There are also commercially available pumps on the market. In our department we use a device assembled from parts commonly found in any intensive care unit. The needles used are of standard 0.8 mrn thickness and should be at least 8 cm long if extensive areas to be infiltrated.

Depth or plane of infiltration
The infiltration of the epinephrine solution should be performed in the same plane as the planned excision of the burned necrotic tissue. The depth of infiltration is of utmost importance in order to achieve the maximum vasoconstriction effect in the desired plane of excision and thus to minimize surgical blood loss. The depth of the excision and thus the plane of the epinephrine infiltration are judged on clinical grounds. The results of the eschar biopsy taken for the quantitative bacteriological culture help to determine the depth of the burn and subsequently the plane of the epinephrine infiltration (Fig. 2).

Fig. 2 - Biopsy of the burn eschar for determination of burn depth.

Time interval between infiltration and excision
The time interval between infiltration of the epinephrine solution and excision of burned tissue is very important for epinephrine's optimal vasoconstricting effect. In my experience the optimal time interval between injection and excision is 10-15 min. One can also determine the ideal time to start the excision by clinical observation of the healthy skin adjacent to the burned eschar. Blanching of the area (0.5 to I cm wide) of the healthy skin adjacent to the burned eschar is a sign that epinephrine's vasoconstricting effect has taken place (Fig. 3).

Fig. 3 - Blanching of adjacent healthy skin.

Assessment of viable and nonviable tissues during excision
With the epinephrine infiltration technique, it is not possible during excision of the burn eschar to assess viable and nonviable tissues by the classic signs of tissue bleeding, owing to vasoconstriction. The viability of the tissues should be judged by the appearance of the tissues, which is similar to that seen when performing an excision under a tourniquet. Viable dermis is pearly-white in appearance, moist, and devoid of thrombosed vessels. Healthy subcutaneous fat is shiny and yellow colour and also devoid of thrombosed vessels (Fig. 4).
The minor haernatomas occurring in the course of the epinephrine injections should be carefully considered and not be mistaken for necrotic tissues (Fig. 5).

Fig. 4 - Appearance of healthy tissue on injection of epinephrine, Fig. 5 - Haernatorna in the course of a previous epinephrine injection.

Volume of'epinephrine solution per unit of area injected
The median volume of epinephrine solution injected is about 0.7 to I ml per kg of body weight per 1% debridement. This means that a 70-kg patient would receive 50 to 70 ml of epinephrine solution under each 1% of body surface debrided. Some adult patients therefore received up to 1500 ml of epinephrine solution.

Accurate haemostasis
Haemostasis is performed by bipolar electrocoagulation in small vessels and by ligatures in larger ones. The bleeding of the cut vessels, especially of small arteries in the debridement area, is greatly diminished owing to epinephrine's vasoconstrictor effect. This may mislead the surgeon into not coagulating the smallest bleeding points, with the risk of early post-operative bleeding. When using the epinephrine infiltration technique one must therefore be careful to perform very thorough haemostasis.

Discussion

The early excision of burn wounds may produce brisk, massive bleeding from the excised area. The intra-operative blood loss resulting from the excision of burned tissues often limits the area to be excised, with important effects on the morbidity and mortality of critically ill patients with thermal injuries. After the excision of smaller burn wounds, patients often need transfusions following intra-operative blood loss. The reduction of intra-operative blood loss following early excision of burn wounds therefore lessens morbidity and mortality in extensively burned patients. Also, in patients with minor burn wounds, transfusion may often be avoided.
Several techniques to reduce intra-operative blood loss following the early excision of burn wounds have been described. In our unit we use tourniquets for excisions on the extremities. Epinephrine solution is used topically to reduce blood loss from donor sites. To reduce blood loss from other areas, we have made considerable use over the past ten years of the subeschar infiltration of epinephrine solution. When this technique was being introduced in our unit the most important question was how much epinephrine could be injected without causing any of epinephrine's systemic effects, namely cardiovascular manifestations and metabolic acidosis. Gradually more and more epinephrine solution was injected without any noticeable important systemic effects due to epinephrine. The anaesthetist also gradually adapted the type of general anaesthesia. We now often inject more than 1500 ml of the above-described epinephrine solution in adult patients without any sign of systemic effects of epinephrine requiring additional therapeutic measures.
The second question regarding the technique of epinephrine infiltration is the rebound phenomenon. It is my opinion that post-operative bleeding due to the vasodilatation of vessels previously vasoconstricted by epinephrine is mainly caused by inadequate intra-operative haemostasis.
The coagulation of the vasoconstricted vessels is performed on the basis of a different clinical intra-operative assessment from that in the area where epinephrine was not used. It is necessary to take into an account the changed appearance of the burn wound due to vasoconstriction where the tissues look similar to those under tourniquet
Graft take did not differ from that in areas where epinephrine was not injected, and the infection rate in excised burn wounds was not observed to be higher.
Subeschar injections of epinephrine solution may prolong the operative procedure by about 30 min if injected manually. Use of the injecting device substantially shortens injection time.

Conclusion

To conclude, it can be said that, technically speaking, the subeschar infiltration of epinephrine solution is very easy to learn and can be used even by surgical residents with limited surgical experience.

RESUME. L'excision précoce des brûlures peut causer des pertes massives de sang, ce qui peut devenir un facteur important qui limite l'extension de la zone d'excision. Pour réduire les pertes intraopératives de sang après l'excision précoce des brûlures, il est possible d'injecter une solution épinephrine dans l'escarre avant d'effectuer l'excision. A l'Unité des Brûlures à Ljubjlana (Slovénie) on utilise depuis 1988 la technique de l'infiltration sous l'escarre d'une solution épinephrine. La technique a été employée dans plus de 500 patients. Pendant ces dix années d'expérience clinique avec la technique divers aspects techniques se sont révélés importants, dont les plus significatifs sont l'anesthésie, la concentration de chlorure hydrique épinephrin, l'indication de la zone destinée à l'infiltration, les instruments, le plan d'infiltration, l'interval entre l'infiltration et l*excision, l'évaluation du tissu qu'il faut exciser, le volume de la solution épinephrine qu'il faut injecter, et l'hémostase. Tous les aspects de la question sont décrits et commentés par l'Auteur.

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