Chapter 51 Fundamentals of cutaneous surgery
1. What does the term “dermatologic surgery” embrace?
Dermatologic surgery is a somewhat generic term, used to describe a variety of procedures, most commonly performed by dermatologists with specialized training in these procedures. This includes the surgical removal of tumors, both benign and malignant, with repair of the subsequent defects by simple side-to-side closure, flaps, or grafts; Mohs micrographic surgery (see Chapter 53); cryosurgery (see Chapter 52); laser treatment of vascular and pigmented skin lesions and tattoos (see Chapter 54); laser skin resurfacing for photodamaged skin; and techniques such as dermabrasion, chemical peeling, sclerotherapy, hair transplantation, liposuction, and soft tissue augmentation. Many of these procedures were pioneered by dermatologists. Several excellent textbooks have been devoted to dermatologic surgery.
Lask GP, Moy RL: Principles and techniques of cutaneous surgery, New York, 1996, McGraw-Hill.
Lawrence C: An introduction to dermatological surgery, London, 1996, Blackwell Science.
Wheeland RG: Cutaneous surgery, Philadelphia, 1994, WB Saunders.
2. Local anesthetics can be broadly classified into one of two groups. Name these two groups and give a few examples of each.
The ester group of local anesthetics, which is seldom used in skin surgery, includes procaine (Novocaine), chloroprocaine (Nesacaine), tetracaine (Pontocaine), and cocaine hydrochloride. The amide group of local anesthetics, commonly used in skin surgery, includes lidocaine (Xylocaine), mepivacaine (Polocaine), bupivacaine (Sensorcaine, Marcaine), and prilocaine (Citanest).
4. What are the onset of action and the duration of action of the most commonly used local anesthetics in skin surgery?
The amides, especially lidocaine and bupivacaine, are the most commonly used local anesthetics in skin surgery. Lidocaine has an onset of action of approximately 5 minutes. Its potency and duration of action is significantly greater than that of procaine. When combined with epinephrine, it provides anesthesia for 60 to 400 minutes (average: 180 minutes), compared to 30 to 120 minutes (average: 90 minutes) without epinephrine. Bupivacaine, which is more potent than lidocaine, has an onset of action of approximately 8 minutes, and an average duration of action of 120 to 140 minutes without epinephrine, and 240 to 480 minutes with epinephrine. This makes it an ideal agent for regional nerve blocks and Mohs micrographic surgery.
5. How are the amide and ester anesthetics metabolized?
The amides are metabolized by hepatic microsomal enzymes. These drugs should therefore be used with great caution in patients with underlying liver disease. The esters are metabolized by plasma pseudocholinesterase, to form para-aminobenzoic acid (PABA) and diethylamino ethanol, both of which are excreted by the kidneys.
8. What are the symptoms and signs of lidocaine toxicity and how is it treated?
The effects on the central nervous system can be divided into early (serum lidocaine levels of 1 to 5 gm/mL), mid (5 to 12 gm/mL), and late (20 to 25 mg/kg) effects.
• Early effects: Talkativeness, metallic taste, diplopia, tinnitus, lightheadedness, nausea, circumoral pallor, and vomiting. Observation is the only treatment necessary. Recognition of early lidocaine toxicity is of paramount importance.
9. Do true allergic reactions to local anesthetics exist?
Yes, but they are very uncommon. Usually, these reactions are seen with the ester anesthetics. These patients are either allergic to the paraben preservatives found in these preparations or to the ester metabolite, PABA. Parabens are known to cross react with PABA. Lidocaine is an excellent substitute in cases of true ester anesthetic allergy, as no cross-reactivity exists between the amide and ester groups of anesthetics. True allergic reactions to lidocaine are extremely rare. Most of the so-called allergic reactions to lidocaine are, in fact, due to vasovagal syncope or, less commonly, epinephrine side effects. However, patients may be allergic to the parabens and sodium metabisulfite preservatives. Preservative-free lidocaine is available.
11. What is the clinical presentation of patients with a vasovagal response to local anesthesia? How is this presentation best treated?
Psychological factors, including needle phobia and altered pain perception, may induce a vasovagal response, the clinical features of which include pallor, diaphoresis, hyperventilation, nausea, vomiting, hypotension, and syncope. Usually, placing the patient in the Trendelenburg position (i.e., supine, with the head lower than the legs) and the application of moist towels to the patient’s face is sufficient to reverse the condition. Aromatic spirits of ammonia may also be of benefit. For prolonged hypotension, an intravenous line must be established and vasopressors given, as needed. ACLS protocols should be followed.
12. How does one manage the patient who refuses, or is truly allergic to, both the ester and the amide anesthetics?
Normal saline (0.9%) may be an effective alternative to the ester and amide anesthetics for performing shave excisions and punch biopsies. “Anesthesia” is thought to result from the compression of nerve endings by the hydrostatic pressure of the injected saline. There may also be an added anesthetic effect from benzyl alcohol, a preservative in normal saline. Non-bacteriostatic saline should be used for patients sensitive to methylparaben. Diphenhydramine (10 to 25 mg/mL) is effective, but painful and sedating. It has a short duration of action and may induce tissue necrosis. Epinephrine, 1:200,000, can be added to prolong the anesthetic effect.
13. What concentrations of epinephrine are the most effective for skin surgery? What is the safe maximum total dose?
Epinephrine, 1:100,000 (1 mg/100 mL), is the most commonly used concentration in skin surgery, although a concentration of 1:200,000 is just as effective. Always try to use the lowest concentration possible. Dilutions of up to 1:500,000 are still effective. Concentrations of 1:50,000 or higher may induce tissue necrosis due to prolonged ischemia. The safe, maximum dose of epinephrine given at any one time is 0.2 mg for an adult. Onset of action may be as long as 15 minutes.
17. When should epinephrine be used with great caution?
In patients with hypertension, ischemic heart disease, peripheral vascular occlusive disease, hyperthyroidism, or pheochromocytoma, epinephrine should either be avoided or diluted, and the patient must be carefully monitored. Epinephrine should either be avoided or diluted in patients taking beta-blocking drugs, especially propranolol, as they are at risk for developing paradoxical hypertension, reflex bradycardia, and cardiac arrest. Epinephrine is contraindicated in patients taking phenothiazines, tricyclic antidepressants, and monoamine oxidase (MAO) inhibitors. Epinephrine should also be avoided in pregnancy, especially during the first and third trimesters, and in patients with a history of psychiatric disease. Many authors also suggest avoiding epinephrine for the digits, especially if the patient is a heavy smoker or has peripheral arteriosclerosis, vasospastic disease, collagen vascular disease, or other peripheral vascular disease.
Buy Membership for Dermatology Category to continue reading. Learn more here
