Whealton, 1998  Title: Advances in office anesthesia.
Author: Whealton EG
Journal: J Am Board Fam Pract 11(3):200-206,
1998
PMID:
Affiliated institution: Department
of Family Medicine, Naval Medical Center, Portsmouth, Virginia.
(reprints: Edward G. Whealton, MD, 160 Sir Oliver Road, Norfolk,
VA 23505.)
Cited in: http://www.medscape.com/ABFP/JABFP/1998/v11.n03/fp1103.05.whea/fp1103.05.whea-03.html
Background: Recent developments in anesthesia applicable to family
practice settings are reviewed. Methods: MEDLINE was searched
using the key words "EMLA"; "iontophoresis";
"lidocaine," "tetracaine, adrenaline, cocaine";
and "lidocaine, epinephrine, tetracaine." Results and
Conclusions: Clinical experience has shown that there is a definite
and evolving role for the newer methods of office anesthesia.
Patient care can be improved by reducing the discomfort of patient
procedures.
Eutectic Mixture of Local Anesthetics - EMLA
EMLA is an abbreviation of eutectic mixture of local anesthetics.
It is a compound formed by combining 25 mg/mL of lidocaine, 25
mg/mL of prilocaine, a thickener, an emulgent, and distilled water
with pH adjusted to 9.4. It is applied in a thick layer, covered
with a patch (Tegaderm), and usually left on for 30 to 60 minutes.
The effectiveness of anesthesia will increase during the 30 to
60 minutes after removal.[38] The application can result in pallor
and then erythema of the affected skin. It has not been studied
in human lacerations.
Systemic toxicity from EMLA is extremely rare. Monitored absorption
levels of prilocaine and lidocaine from EMLA have been in the
low 100 ng/mL range; lidocaine toxicity occurs at 3 to 5 µg/mL.[39]
The major concern regarding toxicity is formation of methemoglobin.
This side effect has been reported only once. A 12-week old boy
on a sulfonamide developed a brownish color caused by a methemoglobin
level of 28 percent after a prolonged application of EMLA. He
was treated with methylene blue without adverse sequelae. Methemoglobin
levels above 30 percent can produce systemic compromise. It is
believed that this unusual clinical occurrence was secondary to
an age-related immaturity of the enzyme that converts methemoglobin
to hemoglobin and the concomitant treatment with sulfamethoxazole,
which also placed the patient at risk for methemoglobinemia.[40]
Subsequent studies have shown EMLA to increase concentration of
methemoglobin in infants 6 months old and younger, although not
to a clinically important level.[41] At present it is best not
to use EMLA on infants younger than 6 months who are also taking
nitrates, sulfonamides, primaquine, or other medications that
cause methemoglobinemia. The only other reported major side effect
has been contact dermatitis, which is rare. When tested, the dermatitis
appeared to be secondary to prilocaine.[42] Irritation from the
Tegaderm patch has also been noted.[38]
The effectiveness of EMLA is based on its ability to penetrate
intact skin and block pain. Its anesthetic effect has been shown
to reach a depth of 5 mm after a 120-minute application. In several
patients who had EMLA for anesthesia, needle sticks penetrated
to the fascia without pain.[43] This depth allows for painless
curettage of molluscum.[44-46] Treatment of condylomata acuminata
was successful in men after a 30-minute application, but it was
only 40 percent effective in women.[47] Subsequent response for
vulvar condylomata improved after the application time on the
genital mucosa was changed to 5 to 10 minutes. There was a progressive
decrease in effectiveness after a 10-minute application time on
the vulvar mucosa.[48-49] These studies involved multiple modalities
-- laser, cautery, and, less frequently, excision.[47-49]
Experience reported in the literature for other uses of EMLA
is very broad but not deep. EMLA has been shown to be useful in
a variety of primary care procedures, including superficial biopsies.
Anesthesia was not adequate for deeper biopsies.[44] Neonatal
circumcision was much less painful and improved oxygen saturations
resulted when using EMLA compared with placebo.[50] Pain during
vasectomy procedures diminished considerably only when EMLA was
used in addition to local anesthetic infiltration.[51] There is
one report of painful external otitis treated with EMLA application
for 1 hour. The symptoms improved, and further cleaning of ear
by suction was made easier.[52] One case of vertigo caused by
EMLA in the external auditory canal has been reported.[53] Refractory
postherpetic neuralgia was relieved after a 24-hour application.
Long-term use brought continued relief, but there were no suggestions
for frequency and duration of dosing.[54] Vaccination pain was
reduced, but not eliminated, after applying EMLA for 60 minutes.[55]
EMLA reduced response to pain from heel lancing in preterm infants,
but not in term infants.[56,57] EMLA has been beneficial in venipuncture,
lumbar puncture, and arterial catheterization, as well as many
plastic surgery applications.[58,59]
When EMLA is applied to atopic or psoriatic skin, its anesthetic
effect is quicker, and there are higher, but less than toxic,
levels of the lidocaine and prilocaine in the circulation. Anesthesia
effect is noted after 15 minutes and resolves quickly.[60] One
would want to consider the quicker time from application to procedure
if dealing with a patch of atopic or psoriatic skin. As noted
above, mucosal surfaces are anesthetized in 5 to 10 minutes.[49]
EMLA offers a potential anesthetic agent that can be used on intact
skin and mucosa for a variety of procedures. The drawback is that
1 hour of application might be necessary to achieve benefit, with
an additional hour of waiting. This can be dealt with by planning.
It certainly offers potential to improved patient tolerance of
certain common procedures. EMLA is still being investigated in
many settings, and its evolving role is yet to be completely defined.
Pediatric and other hospital nursing units are probably using
it already. If not, it would be valuable to check to ensure that
these units are aware of the benefits of using EMLA. It would
be easy to implement using EMLA in a private office.
Iontophoresis
Iontophoresis is a relatively new technique for anesthesia of
intact skin. A small current is applied to lidocaine-soaked sponges.
The concentration of lidocaine appears not to be important; 4
percent lidocaine was as effective as 50 percent. Duration, however,
is important; a 10-minute duration was significantly more effective
than 5 minutes in reducing pain scores.[61] The effectiveness
of iontophoresis has been compared with EMLA. One study found
that iontophoresis was more effective than EMLA after 30 to 60
minutes of application.[62] Iontophoresis permitted painless needle
insertion to an average depth of 6.0 mm compared with 4.4 mm for
EMLA[63]; however, the duration of EMLA application was not clear.
Depth of anesthesia to 1 to 2 cm has been described.[64] When
iontophoresis with 4 percent lidocaine and 1:50,000 epinephrine
was used for minor surgical procedures, the type of lesion made
no difference in efficacy of iontophoresis, although the size
of the lesion and type of procedure did. Iontophoresis was 80
to 100 percent effective in injections, incisions, abrasions,
laser surgery, and cautery. It was much less effective in excisions.
Lesions greater than 1.0 cm were noted by physicians to have less
pain relief, although patients noted little change. Iontophoresis
was less effective on hands and feet.[65] Complications have included
prolonged erythema that resolved in 24 hours, tingling, burning,
and pulling sensations that were especially apparent at the start
of the current or if the amperage was turned up too rapidly. A
metallic taste was noted when iontophoresis was used on the face.[65]
Cutaneous burns have also been reported.[66]
38.Evers H, von Dardel O, Juhlin L, Ohlsen L, Vinnars E. Dermal
effects of compositions based on the eutectic mixture of lignocaine
and prilocaine (EMLA). Studies in volunteers. Br J Anaesth 1985;57:997-1005.
39.Engberg G, Danielson K, Henneberg S, Nilsson A. Plasma concentrations
of prilocaine and lidocaine and methaemoglobin formation in infants
after epicutaneous application of 5% lidocaine-prilocaine cream
(EMLA). Acta Anaesthesiol Scand 1987;31:624-8.
40.Jakobson B, Nilsson A. Methemoglobinemia associated with a
prilocaine-lidocaine cream and trimethoprim-sulphamethoxazole.
A case report. Acta Anaesthesiol Scand 1985;29:453-5.
41.Nilsson A, Engberg G, Henneberg S, Danielson K, DeVerdier
CH. Inverse relationship between age-dependent erythrocyte activity
of methaemoglobin reductase and prilocaine-induced methaemoglobinaemia
during infancy. Br J Anaesth 1990;64:72-6.
42.Thakur BK, Murali MR. EMLA cream-induced allergic dermatitis:
a role for prilocaine as an immunogen. J Allergy Clin Immunol
1995;95:776-8.
43.Bjerring P, Arent-Nielsen L. Depth and duration of skin analgesia
to needle insertion after topical application of EMLA cream. Br
J Anaesth 1990;64:173-7.
44.Juhlin L, Evers H, Broberg F. A lidocaine-prilocaine cream
for superficial skin surgery and painful lesions. Acta Derm Venereol
1980;60:544-6.
45.de Waard van der Spek FB, Oranje AP, Lillieborg S, Hop WC,
Stolz E. Treatment of molluscum contagiosum using a lidocaine/prilocaine
cream (EMLA) for analgesia. J Am Acad Dermatol 1990;23(4 Pt 1):685-8.
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of molluscum contagiosum in children: analgesia by topical application
of a lidocaine/prilocaine cream (EMLA). Acta Derm Venereol 1988;68:149-53.
47.Hall„n A, Ljunghall K, Wallin J. Topical anaesthesia with
local anaesthetic (lidocaine and prilocaine, EMLA) cream for cautery
of genital warts. Genitourin Med 1987;63:316-9.
48.Ljunghall K, Lillieborg S. Local anaesthesia with a lidocaine/prilocaine
cream (EMLA) for cautery of condylomata acuminata on the vulval
mucosa. The effect of timing of application of the cream. Acta
Derm Venereol 1989;69:362-5.
49.Rylander E, Sjoberg I, Lillieborg S, Stockman O. Local anaesthesia
of the genital mucosa with a lidocaine/prilocaine cream (EMLA)
for laser treatment of condylomata acuminata: a placebo-controlled
study. Obstet Gynecol 1990;75:302-6.
50.Benini F, Johnston CC, Faucher D, Aranda JV. Topical anesthesia
during circumcision in newborn infants. JAMA 1993;270:850-3.
51.Honnens de Lichtenberg M, Krogh J, Rye B, Miskowiak J. Topical
anesthesia with eutetic mixture of local anesthetics cream in
vasectomy: 2 randomized trials. J Urol 1992;147:98-9.
52.Premachandra DJ. Use of EMLA cream as an analgesic in the
management of painful otitis externa. J Laryngol Otol 1990;104:887-8.
53.Raine NM, Whittet HB. EMLA cream and induced vertigo. Br J
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54.Stow PJ, Glynn CJ, Minor B. EMLA cream in the treatment of
post-herpetic neuralgia. Efficacy and pharmacokinetic profile.
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55.Taddio A, Nulman I, Goldbach M, Ipp M, Koren G. Use of lidocaine-prilocaine
cream for vaccination pain in infants. J Pediatr 1994;124:643-8.
56.Fitzgerald M, Millard C, McIntosh N. Cutaneous hypersensitivity
following peripheral tissue damage in newborn infants and its
reversal with topical anesthesia. Pain 1989;39:31-6.
57.Larsson BA, Jylli L, Lagercrantz H, Olsson GL. Does a local
anaesthetic cream (EMLA) alleviate pain from heel-lancing in neonates.
Acta Anaesthesiol Scand 1995;39:1028-31.
58.Halperin DL, Koren G, Attias D, Pellegrini E, Greenberg M,
Wyss M. Topical skin anesthesia for venous, subcutaneous drug
reservoir and lumbar punctures in children. Pediatrics 1989;84:281-4.
59.Buckley MM, Benfield P. Eutectic lidocaine/prilocaine cream.
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60.Juhlin L, Hagglund G, Evers H. Absorption of lidocaine and
prilocaine after application of a eutectic mixture of local anesthetics
(EMLA) on normal and diseased skin. Acta Derm Venereol 1989;69:18-22.
61.Oshima T, Kashiki K, Toyooka H, Masuda A, Amaha K. Cutaneous
iontophoretic application of condensed lidocaine. Can J Anesth
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