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The thigh is more amenable to successful expansion compared to
the lower leg. For the proximal upper extremity, regional expanded
transposition flaps from the shoulder and back are used more
frequently.
Arneja and Gosain PRS27 also reported that tissue expansion in
the pediatric population has one of the highest rates of complications
when performed in the lower extremities followed by expanders to
the head and neck. They also noted that there may be increased
complications with multistage expansion procedures when compared
with single stage.
The extremities may be a good location amenable to external
expansion. In a recent paper, Chan et al describe the use of an
external expansion device for the closure of wounds in 11 patients.
38
They believe that this is a viable alternative and may carry less risk
than internal expanders in extremities in certain circumstances.
Congenital
Tissue expanders are used frequently in the pediatric population.
They can be used to treat congenital nevi, conjoined twin separation,
craniofacial anomalies, genitourinary reconstruction, as well as other
applications.
However, there may be a higher complication rate. Wang et al
39
describe a single surgeon’s case series of pediatric tissue expansion
and found that premature expander removal occurs in approximately
10% of cases. Risk factors for premature removal include younger
age, use of multiple expanders, and lower extremity placement.
Pre-expansion
Pre-expansion of skin or muscle allows for greater sized flaps or
grafts to be harvested in closure of large defects while allowing for
less donor site morbidity. The trunk is a common donor site for preexpanded flaps for distant sites. When a pedicled or free flap is
determined as the best option, but possibly too small for the defect,
pre-expansion is performed to increase flap dimensions and allow for
primary closure of the donor site. The tissue also thins during the
expansion flap, which may be desirable at the recipient site.
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Expansion increases vascularity of the flap and the area of adjacent
random tissue that can be carried with it.
40,41
The expander is
carefully placed beneath the vascular pedicle.
Pre-expansion is also used when a large full-thickness graft is
needed to cover an entire subunit with skin of good color match. For
example, the clavicular region may be expanded to develop a large
full-thickness skin graft for a subunit of the face while allowing
closure of the donor site. It is important to place a vacuum assisted
wound closure device over these full-thickness expanded grafts for
best take.
External pre-expansion prior to fat grafting is another application of
the principle of pre-expansion.
CONCLUSION AND FUTURE DIRECTIONS
Tissue expanders remain an integral part of the plastic surgery
armamentarium. Further development will continue in the realm of
external expansion, self-filling expanders, and patient-controlled
expansion.
QUESTIONS
1. Which of the following thickens during the expansion
process?
a. Dermis
b. Epidermis
c. Fat
d. Muscle
2. A 4-year-old girl is undergoing tissue expansion of her back
for staged excision of a congenital nevus. Which of the
following changes is most likely to be observed in the
expanded flap?
a. Increased thickness of adipose tissue
b. Increased muscle mass
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c. Increased blood flow
d. Increased dermal thickness
3. A 44-year-old woman is seeking immediate breast
reconstruction after bilateral mastectomies. Consequence of
prepectoral placement of the tissue expander include which of
the following?
a. Increased animation deformity
b. Improved implant coverage
c. Improved expansion of the lower pole
d. Increased time to completion of expansion
ANSWERS AND EXPLANATIONS
1. Answer: a. The dermis thins during the expansion process;
fat and muscle both atrophy as well. However, the epidermis
thickens.
2. Answer: c. During the expansion process, there is atrophy
or thinning of adipose tissue, muscle, and dermal thickness.
However, there is increased blood flow to the expanded flap due
to the increased expression of VEGF. An expanded flap will
behave similarly to a delayed flap physiologically.
3. Answer: c. Prepectoral tissue expander placement has
been associated with improved lower pole expansion,
decreased animation deformity, and decreased time to
completion of expansion due to less pain during the expansion
process. However, in situations where skin flaps may provide
poor implant coverage due to poor vascularity or thin flaps, a
submuscular approach may provide a more reliable outcome.
REFERENCES
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1. Codvilla A. On the means of lengthening in the lower limbs, the
muscles and tissues which are shortened through deformity. Am J
Orthop Surg. 1905;2:353-357.
2. Pui V. The operative lengthening of the femur. JAMA.
1921;77:934-935.
3. Neuman CG. The expansion of an area of skin by progressive
distention of a subcutaneous balloon. Plast Reconstr Surg.
1957;19:124-130.
4. Austad ED, Rose GL. A self inflating tissue expander. Plast
Reconstr Surg. 1982;70(5):588-594.
5. Radovan C. Breast reconstruction after mastectomy using the
temporary expander. Plast Reconstr Surg. 1982;69(2):195-208.
6. Khosh MM, Meyers AD, Horn CE , et al. Tissue Expansion.
Medscape; 2021. Accessed January 8, 2024.
hps://emedicine.medscape.com/article/880686-overview?
form=fpf
7. Argenta L, Marks M. Principles of tissue expansion. Mathes Plastic
Surgery. Saunders Elsevier; 2007.
8. Johnson P, Kernahan D, Bauer B. Dermal and epidermal response
to soft-tissue expansion in the pig. J Plast Surg. 1988;81(3):390-397.
9. Takai T, Mills I, Arai K, Sumpio BE. Molecular basis for tissue
expansion: clinical implications for the surgeon. Plast Reconstr
Surg. 1998;101(1):247-258.
Increased survival and vascularity of random paern skin flaps
elevated in controlled, expanded skin. Plast Reconstr Surg.
1983;72(5):680-687.
Accessed February 2, 2023. hps://www.jnjmedtech.com/en-
US/product/mentor-spectrum-adjustable-implants
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Air versus saline: the effect of tissue expander fill on outcomes of
prepectoral breast reconstruction. Plast Reconstr Surg.
2022;150(1):28-36.
prepectoral breast tissue expander reconstruction intraoperative
fill: air or saline. Plast Reconstr Surg. 2023;151(4):577e-580e.
hps://www.airxpanders.com/about-us
expansion for breast reconstruction. CADTH Issues in Emerging
Health Technologies; 2017. Accessed February 27, 2023.
hps://www.ncbi.nlm.nih.gov/books/NBK481478/
Bankruptcy. MedtechDive; 2019. Accessed February 2, 2023.
hps://www.medtechdive.com/news/breast-reconstruction-devicemanufacturer-files-for-bankruptcy/558971/
The beginning of a new era in tissue expansion: self-filling osmotic
tissue expander—four-year clinical experience. Plast Reconstr Surg.
2004;114(5):1025-1031.
Reconstruction with an osmotic tissue expander in pediatric
patients. Plast Reconstr Surg. 2012;129(5):863e-865e.
of breast-implant associated anaplastic large cell lymphoma:
history from case report to global recognition. Plast Reconstr Surg.
2019;143(3S A Review of Breast Implant-Associated Anaplastic
Large Cell Lymphoma):7S-14S.
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anaplastic large T-cell lymphoma. Plast Reconstr Surg.
2012;129(5):871e-872e.
Risk of Certain Textured Breast Implants; Requests Allergan
Voluntarily Recall Certain Breast Implants and Tissue Expanders
from Market. U.S. Food and Drug; 2019. Accessed February 2,
2023. hps://www.fda.gov/news-events/press-announcements/fda-
takes-action-protect-patients-risk-certain-textured-breast-implantsrequests-allergan
extension of skin before excision of skin defects. Scand J Plast
Reconstr Surg Hand Surg. 1993;27:179-182.
reconstruction with Brava-assisted fat grafting: a 7-year, 488patient, multicenter experience. Plast Reconstr Surg.
2015;135(3):643-658.
retention in irradiated tissue after preconditioning with external
volume expansion. Plast Reconstr Surg. 2020;145(1):103-112.
the breast with external expansion assist. Aesthet Surg J.
2023;43(6):NP401-NP412.
2024. hps://www.noogleberry.com/
Reconstr Surg. 2007;120(2):26e-40e.
5th ed. Lippinco-Raven Publishers; 1997.
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Graham WP III. Soft tissue expansion, concepts, and complications.
Plast Reconstr Surg. 1984;74(4):493-507.
of tissue expansion: utilization in non-breast applications. Plast
Reconstr Surg Glob Open. 2021;9(1):e3378.
of soft tissue expansion. Br J Plast Surg. 1988;41(3):239-250.
and neck burn reconstruction. Clin Plast Surg. 2000;27(1):121-132.
expansion forpediatric forehead reconstruction: a 13-year
experience. Plast Reconstr Surg. 2009;124:1559-1570.
in head and neck reconstruction. Ann Plast Surg. 1983;11(1):31-37.
expander. Clin Plast Surg. 1990;17(2):339-353.
combination of expanded skin flap and medpor framework: 20
years of experience in a single center. Plast Reconstr Surg.
2021;148(4):850-860.
expansion: a 20-year systematic review and meta-analysis. Plast
Reconstr Surg. 2011;128(3):787-797.
complex extremity wounds using external tissue expansion: as case
series. Plast Reconstr Surg. 2020;10:1097.
Pediatric tissue expansion: predictors of premature expander
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removal in a single surgeon’s experience with 472 expanders. Plast
Reconstr Surg. 2020;145(3):755-762.
deep inferior epigastric perforator flap. Clin Plast Surg.
2017;44(1):109-115.
abdominal super-thin skin perforator flap for total hand
resurfacing. Clin Plast Surg. 2017;44:171-177.
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CHAPTER 11 Principles of Local and Regional
Anesthesia and Procedural Sedation
Matthew D. Treiser and Miguel Medina
KEY POINTS
Many procedures in plastic surgery can be performed safely under local
anesthesia, regional anesthesia, or conscious sedation.
An understanding of the potency, toxicity, duration of action, as well as
treatments for toxicities is essential to the safe administration of local
anesthetics.
Regional blockade provides for the completion of surgical procedures,
minimizing the need for anesthesia.
Procedural sedation represents an essential tool for plastic surgeons and can
provide effective anesthesia to perform surgical procedures in offices and
ambulatory care centers.
LOCAL ANESTHESIA
Local anesthesia uses the topical administration or injection of pharmacologic agents into
the subcutaneous tissues or within the immediate vicinity of nerves to provide pain relief
and comfort. The use of these agents in plastic and reconstructive surgery ranges from
completion of surgical procedures to diagnostic maneuvers for nerve pathology and to
providing temporary analgesia. The use of these anesthetics has multiple benefits to both
the patient and practitioner. Local anesthetics used in conjunction with general anesthesia
may result in better postoperative pain control, increasing patient comfort and decreasing
postoperative use of narcotics.1 Additionally, these agents represent the backbone of
regional anesthesia and peripheral nerve blocks that often allow the completion of complex
surgical procedures in the absence of general anesthesia. This eliminates the need for
endotracheal intubation and the associated risks including but not limited to aspiration and
postoperative nausea and vomiting (PONV). Procedures may be performed in an officebased setting, diminishing the need for traditional operating rooms. Contemporary trends in
plastic surgery demonstrate increased use of such anesthetic options as 82% of cosmetic
plastic surgery occurs in the outpatient office setting, which are dependent on local
anesthetics.2 With the expanding use of local anesthesia in plastic and reconstructive
surgery, practitioners must familiarize themselves with the techniques and risks.
The successful use of local anesthetic drugs requires an understanding of the
pharmacokinetics including onset of action, duration of action, toxicities, risk factors, and
allergenicity. This understanding is essential to ensure patient safety and the delivery of
appropriate anesthesia for patient comfort to maximize outcomes.
Mechanism of Action
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Local anesthetics primarily function via the binding of the intracellular portion of sodium
channels inhibiting depolarization.3 The agents passively diffuse into the cell and prohibit
sodium ion transfer, resulting in blocked threshold potentiation and subsequent signal
transduction. In the absence of depolarization, the cell is unable to propagate electrical
signals, resulting in blocked neuronal transmission. However, while sodium channel
inhibition represents the primary mechanism, local anesthetics may also bind and/or inhibit
potassium channels, calcium channels, the activation of membrane-associated protein
kinases, and even mitochondrial metabolism.4 The complex interactions between individual
agents and multiple signal transduction pathways result in differing toxicities that may affect
multiple organ systems.
Pharmacokinetics
The effectiveness of local anesthetics is dependent on the rate of local absorption once
injected, whereas the toxicity is dependent on the rate of systemic absorption. Once
injected, concentrations of local anesthetics are first achieved within the injection site as the
agents work based on diffusion. Therefore, local tissue will be affected before systemic
effects are noted. Over time, the local anesthetics will diffuse until they enter the blood
stream and plasma concentrations of the agents are achieved. The rate of systemic
absorption is dependent on vascular blood supply of the infiltrated area, the volume/mass
of drug deposited, and the lipophilicity versus hydrophilicity of the individual agents. The
more lipophilic the drug, the more potent it is because it is better able to traverse the cell
membrane to reach the intracellular targets.
Local anesthetics are divided into two classes: amino amides and amino esters. Amino
amides include agents such as lidocaine, bupivacaine, prilocaine, levobupivacaine, and
ropivacaine. These agents are highly bound to a1-acid glycoprotein within the plasma. They
contain an amide linkage within the backbone and undergo metabolism enzymatically by
cytochrome P450 within the liver. The amino esters include cocaine, benzocaine, procaine,
tetracaine, and chloroprocaine. These agents have little to no binding of α1-acid
glycoprotein within the plasma and undergo hydrolysis via plasma cholinesterases, rapidly
resulting in water-soluble metabolites that are excreted via the renal system.4 Adipose
tissue and skeletal muscle often serve as reservoirs of these drugs. Patients with reduced
skeletal muscle mass and adiposity may achieve higher concentrations of plasma drug
levels for a given dose.
The metabolically active form of local anesthetics occurs when the molecule is in its
nonionic form.5 Acidic environments with low pH increase ionization, resulting in greater
distributions of ionized molecules that are unable to pass the cell membrane and bind
intracellular targets. Acidic tissues such as those suffering from inflammation or infection
will shift ionic equilibrium toward ionized forms, deactivating the local anesthetic and
reducing effectiveness. Coinjection of basic solutions such as sodium bicarbonate may help
increase pH, shifting dissociation curves toward the nonionized form, helping to overcome
tissue acidity.
Duration of Action
The duration of action of local anesthetics can range from 15 to 240 minutes (Table 11.1).
This duration depends on the rate at which the drug is transported to intravascular space
where it can be cleared either enzymatically or via hydrolysis. Vasodilators such as calcium
channel blockers and alpha antagonists will increase plasma distribution, resulting in
increased metabolism and clearance and decreased durations of action. Vasoconstrictors
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