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.
19. Describe measures that can be employed to diminish the pain associated with the injection of local anesthetics.
• Antianxiety measures: Explain the procedure in detail to the patient, and make sure they understand what you are about to do. Premedication with oral diazepam or similar drugs may be useful for extremely anxious patients.
• Topical anesthetics: These are especially useful in children. EMLA cream (2.5% lidocaine, 2.5% prilocaine), topical lidocaine creams and gels (2% to 30%), refrigerant spray, and ice blocks may all be useful. L-M-X-4 cream (4% lidocaine) has a more rapid onset than EMLA cream and does not require a prescription.
20. Discuss injection techniques that can be used to diminish pain.
• Distractive measures: These may include pinching or rubbing of the skin at the proposed needle entry site.
• Small-diameter, long needles: Half-inch, 30-gauge needles are a good choice for smaller areas. For larger areas, 1-inch, 30-gauge needles are best. Insert the needle through an accentuated skin pore, if present (e.g., the face).
• Insert the needle quickly with the bevel pointing upward; a slow insertion leads to greater discomfort. Inject a small aliquot of anesthetic, wait a minute, and then advance the needle slowly, before depositing further anesthetic. When anesthetizing large areas, needle reinsertion sites should be in skin that has already been anesthetized.
22. Describe the mechanisms of action and spectra of coverage for these two preparations.
Povidone-iodine releases free iodine, which enters microbial cells through their cell membranes, causing cell death. Up to 5 minutes of contact time is required for microbial uptake of the free iodine and cell death. It should therefore be allowed to completely dry on the skin surface before starting surgery. The activity of povidone-iodine ends after it has dried. Povidone-iodine is microbicidal for gram-positive and gram-negative bacteria, fungi, viruses, protozoa, and yeasts. At lower concentrations, chlorhexidine gluconate is bacteriostatic, by binding to microbial cell walls with subsequent osmotic disequilibrium. At higher concentrations, it induces precipitation of intracytoplasmic organelles and cell death. Chlorhexidine gluconate is microbicidal for gram-positive and gram-negative bacteria, facultative anaerobes, aerobes, and yeast.
23. What are the most important advantages and disadvantages of povidone-iodine and chlorhexidine gluconate?
Povidone-iodine has a relatively slow onset of action, and its activity ends after it has dried. It is inactivated by contact with blood and other organic substances. It is also toxic to the cells within an open wound, with resultant delayed wound healing.
Table 51-1. Recommended Maximum Total Dosages for 1% Lidocaine (10 mg/mL) with and without Epinephrine in Adults and Children
| ADULTS | CHILDREN |
|---|---|
| 4.5 mg/kg (300 mg or 30 mL), without epinephrine | 1.5–2.5 mg/kg, without epinephrine |
| 7.0 mg/kg (500 mg or 50 mL), with epinephrine | 3.0–4.0 mg/kg, with epinephrine |
Chlorhexidine gluconate has a much faster onset of action and maintains its antimicrobial activity for up to 6 hours. It should not be used for preoperative skin preparation on the head and neck, due to possible ototoxicity and corneal erosions and opacifications with inadvertent exposure at these sites. Povidone-iodine is a better choice for the head and neck. However, chlorhexidine gluconate is preferable to povidone-iodine for the trunk and extremities, due to its more rapid onset of action, broader spectrum of antimicrobial coverage, and longer duration of activity.
24. What is meant by absorbable and nonabsorbable suture material?
The classification of suture material into absorbable or nonabsorbable is based on how quickly its tensile strength is lost. Most nonabsorbable sutures retain the majority of their tensile strength by day 60, and in fact, can, be completely absorbed over a prolonged period. Most absorbable sutures lose the majority of their tensile strength by day 60 and may be present for long periods before being absorbed.
25. How does multifilament suture differ from monofilament suture?
• Multifilament suture is usually in a braided configuration, and offers the advantages of improved ease of handling, low memory, and good knot security. Disadvantages include a supposed increase in the rate of associated wound infection, although this remains controversial. There is, however, increased tissue reaction to this type of suture material.
• Monofilament suture is associated with a lower rate of wound infection, and tissue reaction to the suture is generally much less than for braided sutures. Furthermore, this type of suture demonstrates improved ease of passage through tissue, making it ideal for subcuticular, running stitches. Disadvantages include increased memory with resultant poorer handling qualities and diminished knot security. Difficulties with handling are easily overcome with practice, and knot security can be greatly improved by an extra throw during knot tying.
26. Which types of suture material are best suited for subcutaneous stitches?
Generally, absorbable sutures are used for subcutaneous stitches.
• Polyglactin 910 (Vicryl) is a synthetic, absorbable, multifilament suture. It has a high tensile strength, 50% of which is lost by day 14, and is insignificant by day 30. Absorption occurs by enzymatic hydrolysis and is complete at approximately 90 to 120 days. Tissue reactivity is relatively low.
• Polyglyconate (Maxon) is a synthetic, absorbable, monofilament suture. It has a high tensile strength, 50% of which is lost by day 30, but may remain significant for 3 to 6 months. It is especially useful when prolonged wound support is needed. Complete absorption occurs after approximately 180 days. Tissue reactivity is similar to polyglactin 910 (Vicryl). It has a relatively low memory, very good handling characteristics, and good knot security.
27. Which types of suture material are best suited for cutaneous stitches?
Generally, nonabsorbable suture material is used for cutaneous stitches.
• Nylon is a synthetic, nonabsorbable suture, available in monofilament (Ethilon) and braided (Nurolon) forms. Nylon has high tensile strength and elicits very little tissue response as it is chemically inert. Monofilament nylon induces less of a tissue reaction than does braided nylon, but due to its greater memory, it is more difficult to handle and has lower knot security.
• Polypropylene (Prolene, Surgilene) is a synthetic, nonabsorbable, monofilament suture, characterized by very low tissue reactivity and great ease of tissue passage, making it an ideal choice for a running, subcuticular stitch. It has a high degree of memory, resulting in relatively poor handling and knot security.
28. Which sutures are good choices for mucosal surfaces, the vermilion lip, and intertriginous areas?
• Silk is a natural, nonabsorbable, braided suture with unsurpassed ease of handling and softness. It is an excellent choice for intertriginous areas, intraoral use, and the vermilion lip. It induces a significant tissue response and may be associated with an increased rate of wound infection. Suture removal may be relatively painful and more difficult than with other materials, as silk swells to almost double its original diameter by day 14.
29. How is suture sized?
Suture size does not correspond to a specific diameter, but rather to a specific tensile strength. Thus, 4/0 polypropylene and 4/0 silk have different diameters. For any given suture type, the tensile strength (and diameter) of that suture decreases as the designated suture number (e.g., 4/0, 5/0, 6/0) increases.
30. Which suture needles are best suited to skin surgery?
A three-eighths (or half-circle) needle with a reverse cutting point is the preferred and most commonly used needle in cutaneous surgery. The point of the needle is triangular on cross section, with the apex of the triangle on the outside/convex side of the needle and the base of the needle on the inside/concave side. This decreases the tendency for the suture to cut inward toward the wound, thereby minimizing trauma.
31. What are the indications for a punch biopsy?
A punch biopsy may serve as an incisional or excisional skin biopsy, and is used to diagnose both inflammatory and neoplastic diseases. It provides a sample of tissue, which includes epidermis, dermis, and subcutaneous fat. When the pathology is thought to be localized to the epidermis and/or upper dermis, then a superficial shave biopsy may be more appropriate (Fig. 51-1). However, one should always try to completely remove pigmented lesions by conservative excisional or punch biopsy. When it is not possible to completely remove a pigmented lesion by excisional or punch biopsy, then the darkest and/or most elevated portion of the lesion should be biopsied, to achieve the highest diagnostic yield. It may also be prudent in these cases to take multiple “scouting” biopsies from different areas of concern within the lesion, to increase your chances of an accurate diagnosis and, in the case of a melanoma, to obtain an accurate Breslow depth. Punches range in size from 2 to 8 mm, with 3- or 4-mm punches being the most commonly used sizes. Disposable punches are especially useful for patients with hepatitis B or C, or HIV disease.
32. Describe how a punch biopsy should be performed.
After anesthetizing and prepping the surgical site, the circular blade of the punch is placed over the lesion at 90 degrees to the skin surface. The handle of the punch is gently held between thumb and forefinger, and the blade is rotated in a fairly rapidly alternating clockwise, anticlockwise fashion, while maintaining skin tautness across the biopsy site using thumb and index finger. Initially, very little downward pressure should be applied to the punch while the punch’s blade is still at the level of the epidermis, to prevent shearing of the epidermis from the dermis, which makes histologic examination difficult. Continue until the hub of the punch reaches the level of the skin. In certain anatomic sites with important superficial nerves and vessels, be careful not to hub the punch. Now remove the punch.
33. What is the preferred technique for removing the punch biopsy?
Gently grasp the biopsy specimen with a toothed forceps, preferably at the level of the subcutaneous fat. Be careful not to grasp the specimen with too much pressure as this may cause pressure artifacts, which will make histologic examination difficult. While pulling the specimen gently upward, carefully cut the specimen at the level of the deep subcutaneous fat. Hemostasis is usually achieved with suture closure of the defect. Alternatively, the defect may be allowed to heal by secondary intention.
34. What is meant by electrosurgery, electrocautery, and electrocoagulation?
• Electrosurgery is the use of an electric current in order to achieve hemostasis, tissue cutting, or the destruction of benign and malignant skin lesions.
• Electrocautery uses a low-voltage, high-amperage electric current to heat a filament tip, which transfers the heat to tissue, thereby inducing coagulation. No electric current is transferred to the tissue or patient, which makes this a good choice for cardiac pacemaker patients.
• Electrocoagulation uses a low-voltage, high-amperage current to coagulate blood vessels by generating heat in tissue. The patient forms part of the circuit by using a dispersive electrode, which allows for a greater degree of coagulation than either electrofulguration or electrodesiccation (see following text).
35. Describe what is meant by electrofulguration and electrodesiccation.
• Electrofulguration uses a high-voltage, low-amperage electric current to generate a spark that jumps from the electrode tip to the tissue, thereby achieving coagulation. There is no contact between the electrode and the tissue, resulting in little tissue damage.
• Electrodesiccation, like electrofulguration, uses a high-voltage, low-amperage electric current. However, unlike electrofulguration, there is contact between the electrode tip and the patient. Heat is thereby transferred to the tissue, resulting in desiccation. Tissue damage is typically greater than with electrofulguration.
36. What precautions need to be taken in patients with pacemakers who require electrosurgery?
Electrosurgery may cause a pacemaker to fire prematurely or not at all. Electrocautery is a safer alternative to electrosurgery in these patients. Consultation with the patient’s cardiologist is imperative if electrosurgery is contemplated. Demand-type pacemakers are more sensitive to electrosurgery than are fixed-rate pacemakers. However, many newer pacemakers are protected from interference by electric currents. Demand pacemakers can be converted to fixed-rate pacemakers by placing a magnet over the pacemaker, thereby preventing interference from electrical current. The use of bipolar (biterminal) electrosurgery, with the dispersive electrode placed close to the treatment electrode and away from the pacemaker, and using short bursts of electricity will all reduce the chances of pacemaker interference.
37. Is it necessary to discontinue anticoagulant medications before elective surgery of the skin?
No. Most Mohs surgeons are comfortable performing surgery on patients who are on aspirin, clopidogrel, warfarin, or other anticoagulants. In fact, recent literature suggests that all patients should be kept on their anticoagulant therapy, so as to prevent acute cardiovascular events, including strokes. Meticulous intraoperative hemostasis is crucial to preventing hematoma formation. Consultation with the patient’s internist or cardiologist is imperative if discontinuation of anticoagulant therapy is contemplated.
38. What are the so-called relaxed skin tension lines (RSTLs)? Why are they important?
The insertion of the underlying musculature into the skin results in a somewhat predictable pattern of skin creases, called RSTLs. Typically, these lines run perpendicular to the long axis of the underlying musculature (Fig. 51-2). Surgical incisions placed within or parallel to these lines will create the most favorable scar.
39. How does one determine the direction of the RSTLs in planning a surgical wound closure?
By simply pinching the skin in different directions around the proposed surgical excision site, the direction in which the closure will produce the least amount of tension across the wound (i.e., the direction of the RSTLs) is usually easily revealed. It is important to pinch the skin using the thumb and index finger of the same hand.
41. What is the superficial muscular aponeurotic system (SMAS)?
The SMAS may be defined as the combination of the muscles of facial expression and their enveloping fascia. The SMAS has its origin in the superficial cervical fascia, and allows the muscles of facial expression to act in a coordinated fashion. It is an important anatomic landmark in facial surgery.
Figure 51-1. Schematic demonstrating the technique for a shave biopsy of skin.
(From Fewkes JL, Cheney ML, Pollack SV: Illustrated atlas of cutaneous surgery, New York, 1992, Gower Medical Publishing, with permission.)
42. Describe the boundaries of the danger area for transecting the temporal branch of the facial nerve.
Consider the danger area to be a triangle, made up of a line drawn from a point 0.5 cm below the tragus to a point 2 cm above the lateral eyebrow, a line drawn along the zygoma to the lateral orbital rim, and a line drawn from the point above the lateral eyebrow down past the lateral eyebrow to the medial zygoma (Fig. 51-3). The temporal nerve lies just deep to the SMAS-temporoparietal fascia within this triangle.
Key Points: Fundamentals of Cutaneous Surgery
1. Local anesthetics work by decreasing the sodium permeability of the nerve fiber membrane, thereby lowering the action potential and preventing depolarization.
2. Amide anesthetics are metabolized by hepatic microsomal enzymes, and ester anesthetics are metabolized by plasma pseudocholinesterase.
3. The safe total maximum dose of 1% lidocaine for adults is 7 mg/kg, if combined with epinephrine, and 4.5 mg/kg, if given without epinephrine.
