A study of regional nerve blocks and local anesthetic creams (Prilox®) for donor sites in burn patients

1. Background 

Burns is a devastating epidemic in India. Not only is it a huge financial drain on the patients family, it is a harrowing emotional and physical trauma to the patient and the treating surgeon. It necessarily commits the patient to a long follow-up, repeated procedures of grafting to cover the resultant areas of grafting, and subsequent visits for surgical treatment of contractures with subsequent long periods of rehabilitation. The burn patient requires multiple visits to the operation theatres and undergoing anesthesia with its attendant risks and post anesthesia recovery. It is possible now with the availability of local anesthetic creams like prilox, which is a mixture of prilocaine and lignocaine, available in other names, such as EMLA, to conduct these procedures in the minor OT without any discomfort to the patient. These creams allow local absorption of the anesthetic agent with blocking of nerve endings in the superficial layers of skin. However, these agents require time for action with periods ranging from 2 to 5h, and the areas which can be covered are also limited in view of possible toxicity.

Another technique of nerve blocks is available which allows a simple way to achieve large areas of anesthesia with single injection [1], [2]. These blocks are the femoral nerve block, the lateral cutaneous nerve of thigh (LCT) block and 3-in-1 block.

2. Anatomy of nerve blocks 

The nerve supply of the lower limb is derived from the lumbar and sacral plexuses, a network of nerves composed of the anterior primary rami of all the lumbar and the first three sacral nerve roots (and sometimes with a contribution from the 12th thoracic nerve root) [2].

3. Materials and methods 

Hundred patients were part of the study. These patients had post burn raw areas ranging from 1 to 15 percent of TBSA.

3.2. Exclusion criteria 

(1)History of drug allergy.

(2)Patients on other prior medications.

(3)Patients insisting for general anesthesia.

Hundred consecutive patients were distributed into the two groups after prior consent and explanation of both the procedures. In Group 1, Prilox® was applied to the area from where graft was required. Cream was applied for 2h at a concentration of 12.5gm per 100cm2 area. The observations are tabulated in Table 1. In Group 2, the patients were planned for nerve blocks. There was a bias towards age distribution in this group with minimum age being 18 years. The local anesthetic used was lignocaine and adrenaline(1:200,000) at 5mg/kg of body weight. After an average period of 15–20min grafts were harvested. The results are tabulated in Table 2.

Table 1.

	S no.	Age of patient	Amount of Prilox® used in grams	Graft size (measured preoperative) cm	Pain analogue score (/10)	Duration of pain relief post operative (min)	Post operative complication
	1	26	20	15×10	2	45	Nil
	2	13	10	10×8	4	60	Nil
	3	6	10	10×10	3	30	Nil
	4	65	25	25×10	0	60	Nil
	5	47	25	25×10	2	80	Nil
	6	31	15	10×10	1	40	Nil
	7	28	25	20×10	2	45	Nil
	8	7	10	5×5	4	50	Nil
	9	52	25	5×5	6	60	Nil
	10	10	10	3×5	3	30	Nil
	11	45	20	12×8	0	45	Nil
	12	32	25	20×10	1	70	Nil
	13	33	25	20×10	0	50	Nil
	14	26	20	15×10	0	40	Nil
	15	29	20	15×10	0	60	Nil
	16	40	25	25×10	3	35	Nil
	17	56	25	20×10	2	45	Nil
	18	70	25	10×5	7	60	Nil
	19	38	25	20×10	2	65	Nil
	20	21	20	15×10	4	90	Nil
	21	18	20	15×10	1	45	Nil
	22	19	25	25×10	0	50	Nil
	23	45	20	15×10	1	50	Nil
	24	42	25	20×10	1	60	Nil
	25	49	25	20×10	1	45	Nil
	26	31	25	20×10	1	55	Nil
	27	64	20	15×10	1	35	Nil
	28	28	25	20×10	2	60	Nil
	29	30	25	20×10	2	45	Nil
	30	12	15	10×10	2	60	Nil
	31	34	25	25×10	3	65	Nil
	32	26	20	20×10	1	20	Nil
	33	28	15	10×10	0	45	Nil
	34	47	25	20×10	2	60	Nil
	35	41	20	15×10	1	50	Nil
	36	40	25	20×10	0	40	Nil
	37	30	25	20×10	2	30	Nil
	38	37	20	15×10	1	80	Nil
	39	24	25	20×10	3	55	Nil
	40	71	25	25×10	2	75	Nil
	41	43	25	20×10	2	40	Nil
	42	56	20	15×10	1	65	Nil
	43	39	25	20×10	1	40	Nil
	44	51	25	20×10	0	50	Nil
	45	22	25	20×10	0	60	Nil
	46	27	20	15×10	3	45	Nil
	47	52	25	20×10	2	50	Nil
	48	9	15	10×10	1	45	Nil
	49	35	15	10×5	1	50	Nil
	50	40	20	15×10	5	60	Nil

Table 2.

	S no.	Age	Block (s) used	Graft size (measured preoperative)	Pain analogue score (/10)	Duration of pain relief post operative (min)	Post operative complication
	1	20	F	15×10	0	160	Nil
	2	39	F, LCT	20×10, 10×10, 10×5	2	200	Nil
	3	47	F	25×10	1	180	Nil
	4	65	F	25×10	0	200	Nil
	5	73	F	25×10	0	100	Nil
	6	25	F	15×10	0	230	Nil
	7	45	F	10×5	0	110	Nil
	8	65	F	5×5	4	190	Nil
	9	23	F/LCT	20×10, 10×10	2	110	Nil
	10	26	LCT	20×10	3	90	Nil
	11	40	LCT	10×10	1	125	Nil
	12	21	F, LCT	25×10, 20×10	1	130	Nil
	13	32	S	15×10	1	100	Nil
	14	37	F	10×10	1	60	Nil
	15	34	LCT	10×10	5	160	Nil
	16	29	PF	12×8	0	100	Nil
	17	18	F, LCT	15×10, 15×10	2	90	Nil
	18	32	F	10×10	2	150	Nil
	19	26	F	15×10	2	160	Nil
	20	49	F	15×10	2	135	Nil
	21	63	F, LCT	10×5, 10×5	3	160	Nil
	22	50	F, LCT, +pri (15 grams)	20×10, 15×5, 5×5	1	125	Nil
	23	60	F	5×5	1	110	Nil
	24	24	F	10×10	1	90	Nil
	25	51	F/LCT	10×10, 10×10	1	95	Nil
	26	18	PF	10×5	1	100	Nil
	27	20	F	10×10	0	185	Nil
	28	21	F	20×10	0	145	Nil
	29	43	F	15×10	0	160	Nil
	30	34	F	25×10	0	125	Nil
	31	35	F	25×10	0	100	Nil
	32	38	F	25×10	2	90	Nil
	33	30	F, +pri (15 grams)	8×5, 10,10	4	120	Nil
	34	20	F/LCT	25×10, 15×10	3	120	Nil
	35	21	F	25×10	2	130	Nil
	36	54	F, LCT	25×10, 20×10	3	120	Nil
	37	65	F	15×10	3	110	Nil
	38	24	F	8×10	2	100	Nil
	39	48	F	5×8	1	95	Nil
	40	49	F, LCT	10×10, 5×5	0	150	Nil
	41	36	F, LCT	15×10, 10×10	1	140	Nil
	42	38	F	20×10	1	135	Nil
	43	35	F	15×10	1	150	Nil
	44	41	F	10×10	2	100	Nil
	45	21	F, LCT	10×10, 15×10	2	120	Nil
	46	23	F, LCT	25×10, 20×10	2	145	Nil
	47	27	F	25×10	0	185	Nil
	48	29	F, +pri	15×10, 10×10	2	100	Nil
	49	32	F	25×10	0	60	Nil
	50	33	F/LCT	25×10	1	100	Nil

F, femoral block; LCT, Lateral cutaneous nerve of thigh; PF, popliteal fossa block; S, sciatic block; +pri, block +Prilox®.

4. Results 

In Group 1, the average post operative analgesia is 51.8min with a range of 30–90min. The graft size taken was a factor of the amount of the cream applied. There was no post operative problem or complication.

In Group 2, there is a noticeable bias towards grouping of patients where larger grafts are required. Most patients in this group were those where more than one sheet or larger sheets were harvested. In two patients, Prilox® was also used, as virgin skin was short, and patches of skin were available on posterior thigh. In the patients where the popliteal fossa block was used, the skin was harvested from the lateral leg. The average duration of anesthesia was 128.9min with a range from 60 to 230min. The procedure was largely painless, with no patient requesting for abandoning the procedure.

5. Discussion 

The use of Prilox® allows a convenient alternative to local infiltration for skin grafting. It can be easily applied in the ward, by the doctor or nurse on duty. It is essential to form a thick layer of the cream on the desired area. An important precaution is to mark the area with indelible marker before application of cream, as the ink tends to fade out at the time of cleaning. After approximately 2h it is noticed that the desired area appears blanched. A needle prick test is done before proceeding with the procedure. The femoral block anesthetizes the anteromedial thigh and anterior thigh completely, and the LCT, the lateral aspect. The posterior thigh is blocked by the sciatic block. The popliteal fossa block allows graft harvesting from the lateral leg. This latter block is of use, when the thigh is not available for grafting, and a long but not very broad sheet is required. Of course, Prilox® itself may suffice in such a situation. The advantages of the block are that it is faster in onset of action, and much larger areas can be harvested. It however requires a trained medical professional. Sensitivity testing is also mandatory.

An obvious advantage is the duration of pain relief. The average duration with nerve blocks is over 2h, while with Prilox® it is less than an hour. This long period allows the patient to be safely shifted to the ward and allows the patient to settle in his surrounding before worrying about pain, which is then tackled with injectables. The use of bupivacaine in nerve blocks allows a much longer period of anesthesia, with periods ranging from 5 to 15h [2], [3]. I have not used bupivacaine frequently, but do plan to do so.

Lets focus on Group 2 patients. Femoral block combined with LCT was used in 14 patients. This allowed us to harvest the graft from the anteromedial and anterolateral thigh. LCT block was used alone in three patients, where the anteromedial area was unavailable. Sciatic block is a difficult block to administer, without a nerve stimulator. It was used in only one patient where anterior surface was unavailable. It is possible to use Prilox® if smaller area is required. In two patients, we combined Prilox® with nerve blocks. This allowed us to take a small sheet from the posterior thigh. This is an example of the complimentary use of the two techniques.

The use of eutectic mixture of prilocaine and lignocaine has been used in intravenous line insertion [8], [10], [11]. There are reports of the use in infantile circumcision [9], [10], [12]. However, this agent has not been compared to nerve blocks in skin grafting in recent literature. The emphasis here is the judicious use of either technique in burn patients.

To summarise Prilox® is indicated in:

Nerve blocks are indicated in:

Nerve blocks are not used in pediatric patients as chances of vascular injury are high.

6. Conclusion 

Prilox® and nerve blocks are safe and effective techniques for skin grafting normal burn patients. They can be combined judiciously in selected patients. In pediatric patients, Prilox® is specially indicated, and nerve blocks are specially indicated where larger amount of graft is required, the procedure can be used in other cases also.