SURFACE REFRIGERATION ANFESTHESIA FOR C UT T ING SPLIT-SKIN GRAFTS

By THOMAS GIBSON, F.R.C.S.Ed. From the Plastic Surgery Unit at Ballochmyle Hospital

GENERAL anmsthesia is commonly employed to-day for cuttingsplit-skin grafts, unless only a very small area of skin is required. The large amount of local infiltration which is necessary, and the uneven surface and tension which result, make infiltration anmsthesia of little value for cutting the larger grafts. This is the more unfortunate, in that not only could the remainder of the operation frequently be performed with local anmsthesia or no anmsthesia at all as in the case of healthy granulating surfaces, but many patients urgently requiring skin grafting may be hardly fit for a general anmsthetic, for example, those with extensive deep burns.

Refrigeration ana:sthesia has been fairly widely used in the past few years for amputations in poor-risk patients. A tourniquet is commonly used to stop the flow of warm blood through the part and avoid chilling the patient, but Cayford and Pretty (1945) have shown that anmsthesia can be produced without a tourniquet. The possibility that surface refrigeration without a tourniquet might be a suitable anmsthetic for skin-graft cutting has been investigated, and it is hoped to show that this is a valuable and useful method whenever general anmsthesia is inadvisable or unnecessary for the remainder of the operation.

Two methods have been used to chill the donor site before cutting the graft : (I) the direct application of ice, and (2) the circulation of ice-cooled water through a bag strapped to the appropriate area.

THE DIRECT APPLICATION OF ICE

It would, of course, have been quite feasible to immerse in ice the whole limb from which the graft was to be cut, but this seemed unnecessary, so that chilling of the donor site only has been aimed at. The method adopted was as follows : -

Several pounds of ice were chopped into small fragments and wrapped in a single layer of thin rubber sheeting to make a parcel appreciably larger than the graft to be cut. A rubber ice bag can be used, but is suitable only for smaller grafts. The parcel of ice was then firmly applied to the donor site--usually the thigh--with cr6pe bandages. As the ice melted, it was replaced with fresh ice. So long as adequate pressure was maintained to keep the bag continually in contact with the skin, complete surface anmsthesia was produced after a minimum period of about two hours. To make quite certain, however, the application was continued usually for three hours before the graft was cut.

This method was used in 15 patients who, for one reason or another, were unfit for general anmsthesia. It worked well but had obvious disadvantages. Continual supervision was necessary to see that pressure was maintained, the ice required frequent changing, and ice-cold water tended to leak all round the area in spite of elaborate precautions with rubber sheeting. For this reason an attempt was made to devise a closed method whereby ice-cold water could be circulated through a rubber bag strapped to the donor area.

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SURFACE REFRIGERATION AN/~STHESIA FOR CUTTING SPLIT-SKIN GRAFTS 7

THE CIRCULATION OF ICE-COLD WATER THROUGH A RUBBER B,~.G

The apparatus to be described was designed after much trial and error, and, with the exception of the electric motor, was constructed almost entirely from

A FIG. i B

A, The completed apparatus showing lids for access to pump, and ice and water mixing tank. B, End view of apparatus. The two stop-cocks on the right control the flow to the bag.

That on the left the overflow pipe.

FIG. 2

Apparatus with one side and most of the asbestos packing removed to show general layout. The motor has been fitted

with a fan, since it tended to heat up in the enclosed space.

scrap (Figs. x and 2). Essentially it consists of an electrically driven circulating pump, an ice and water mixing tank, and a rubber bag.

The pump is of the rotary impeller type and was picked up in a scrap yard --original source unknown. It circulates about x½ litres per minute, and this has

BRITISH JOURNAL OF PLASTIC SURGERY

been found adequate for the size of bag used. With larger bags, however, it would probably be necessary to have a more rapid circulation, to ensure adequate flushing of the bag.

The design of the ice and water mixing tank is important. At an early stage in the experiments it was found that a simple tank with ice floating in water was valueless unless equipped with a mechanical stirrer, and this was considered undesirable. Several designs were tried out, but the one shown here proved to be by far the most efficient.

The tank is in the form of a cylinder, 13 in. long by 4 in. in diameter, and consists of two tins soldered together, the bottom having been cut out of the upper. An overflow pipe (Fig. 3) is soldered in, just above the middle of the tank~

- LEAD WEIGHT

INLET

MOTOR PUMP I I MIXING TANK

OUTLET

FIG. 3

Schematic diagram of apparatus.

LOW

and drains into a pail on the floor. This maintains a constant level and prevents water from the melted ice running over the top. The inlet pipe, carrying water returning from the bag, enters at the foot of the tank, while the outlet is about I in. below the overflow. When in use the cylinder is filled with cubed ice and a lead weight of I½- lb. is placed on the top. This ensures that the ice is kept packed tightly to the bottom of the mixing chamber. The water is therefore forced to flow between the small blocks of ice from the bottom upwards. (Water below 4 ° C. expands, and the coldest water is always at the top of an ice and water mixture.) The upper half of the cylinder acts as a reservoir for the ice. The whole cylinder is surrounded by a 2-in. thick layer of asbestos insulating material.

The rubber bag (Fig. 4) is simply a smooth-surfaced rubber hot-water bottle with a metal screw cap. This cap is drilled to take two i-in. tubes, which are connected to the machine by thick-walled pressure tubing. One of the tubes in the cap has a short length of rubber attached which passes inside the bag to the

SURFACE REFRIGERATION ANPESTHESIA FOR CUTTING SPLIT-SKIN GRAFTS 9

opposite end. The ice-cold water from the apparatus is pumped through this tube and is thus forced to circulate through the whole length of the bag before reaching the outlet in the cap.

After use the bag is thoroughly cleansed with Cetavlon, dried with a sterile towel, and stored in formalin vapour in an air-tight box. It is then ready,, sterilised, for the next case.

FI6. 4 Rubber hot-water bottle adapted for use.

METHOD OF USE

The selected donor site is first thoroughly prepared as if for operation. The bag is then connected to the apparatus and, with all stop-cocks closed, the tank is filled with tap water. The stop-cocks leading to the bag are opened, and the bag is allowed to fill by gravity until about half-full. Overfilling must be avoided or the bag will assume a rigid spherical shape and not mould itself to the limb. When correctly filled it is bandaged firmly to the donor site with cr~pe bandages, and then covered by two thick layers of cotton-wool, also bandaged in place. Great care must be taken not to contaminate the bag itself during its application. The overflow stop-cock is now opened and the mixing tank filled with ice. It is important to avoid finely crushed ice, which tends to pack and may obstruct the outlet. Pieces about the size of the ordinary refrigerator cubes are most suitable. When full of ice the weight is placed on top and the lid closed. The pump is then switched on and thereafter the machine works automatically. Whenever the weight sinks to half-way down the tank, fresh ice is added. In practice the apparatus has to be topped up with ice after the first ten minutes and about every half-hour thereafter.

A period of chilling of at least one and a half hours is advisable, although in the preliminary experiments it was found that some patients were completely anmsthetic to pinprick as early as half an hour after the apparatus had been started. However, attempts to cut a graft at this early stage resulted in complaints of pain. In order to make quite certain of anmsthesia, chilling is now begun approximately two hours before the scheduled operation time.

The preliminary chilling is done in the ward. About fifteen minutes before operation, the patient is brought to a theatre anteroom with the apparatus in situ.

IO B R I T I S H JOURNAL OF PLASTIC SURGERY

This is then switched on again and allowed to run until the surgeon is quite ready for the case. When ready, the apparatus is switched off, the tubes to the bag clipped and disconnected, and the patient placed on the operating table. The bandages are now undone and the bag removed. The area is given a rapid cleansing with ice-cooled Cetavlon, towelled, and the graft cut. Provided that everything is prepared beforehand, the time elapsing between switching off the apparatus and cutting the graft should not exceed three to five minutes.

To allay anxiety and discomfort, it is customary to administer morphine (~ gr.) about half an hour before operation.

FIG. 5

The apparatus in use.

RESULTS

Apart altogether from purely experimental runs, grafts have now been cut with this apparatus from 15 patients, with complete success as regards anmsthesia in all but 2 cases. These cases consisted of a graft from the buttock and a graft from the upper arm respectively, and ,in both cases the cause was obviously inadequate contact between the bag and the skin, resulting in a patchy type of anmsthesia. All the other grafts were cut from the inner or outer aspects o f the thigh.

During cooling the patient has little or no discomfort, provided that the chilling begins with tap water at 50 to 55 ° F. which is slowly cooled to freezing- point. To start with there is a local feeling of cold, but this gradually gives place to an absence of all sensation. In 2 patients a slight sensation of warmth was experienced. The patients themselves have commented on the absence of discomfort. In no case has there been a general feeling of cold or any shivering.

SURFACE REFRIGERATION ANAESTHESIA FOR CUTTING SPLIT-SKIN GRAFTS II

On removing the bag at operation, the chilled area is seen to be sharply differentiated from the surrounding skin by the typical erythema which develops. This erythematous area defines exactly the limits of ana:sthesia, but the corollary does not hold, and it must be stressed that erythema after chilling is not evidence o f surface anmsthesia. Erythema develops much more rapidly and at a higher temperature than ana:sthesia does.

The exact duration of the ana:sthesia is difficult to establish since the time limit can be found only by the active, production of pain. It probably varies with the duration of cooling. Th e longest interval so far which has elapsed before • cutting the graft is eight minutes after a chilling period of two and a half hours, and complete anmsthesia was still present at that time.

It was expected that the patients might feel pain during the post-operative period as the donor area became re-warmed, but in no case has any pain or .discomfort been experienced after cutting the graft. No deleterious effects have been noted either in the take of the grafts or in the healing of the donor area after ,chilling.

DISCUSSION

The apparatus has proved of considerable value in plastic work, as a reliable method of producing surface anmsthesia for a short period. It is also relatively fool-proof. Given an electrically driven pump--and there are several varieties on the market--the construction is well within the scope of a dental technician and hospital carpenter. Many improvements will no doubt suggest themselves to the mechanically minded, but it was felt worth while to publish the essential details, since others might wish to construct a similar apparatus.

One major modification which would be of considerable value is the incorporation of a small refrigeration unit to replace the ice. The machine would then be completely automatic and would require only an electrical supply. A well-known firm of refrigerator manufacturers have kindly undertaken to construct an apparatus on these lines, and details will be published as soon as this has been completed and tested.

The rubber bag also requires modification, first so that a much larger area may be chilled, and secondly, so that it will be suitable for other areas such as the arm. The design of such bags is at present under consideration, but the common hot-water bottle is quite suitable for the average size graft cut from the thigh.

The addition of salt to the ice and water mixture has been frequently suggested. 'There is no doubt that this would give much more rapid and efficient chilling and, adequately controlled, would probably be ideal. However, the technical difficulties o f controlling thi~ method so that the skin is not chilled below freezing-point, and the obvious danger of gross tissue damage from freezing, have prevented its use.

I wish to thank Mr J. S. Tough for his help and encouragement in carrying out this work ; Mr IV. Smith, Dental Technician, Ballochmyle, for his assistance in the design and construction of the apparatus ; and Prof. J. P. Todd, Technical College, Glasgow, for much helpful criticism and advice.

REFERENCE

CAYFORD, E. H., and PRETTY~ H. G. (1945). Ann. Surg., i21, 157.