Local anesthesia for hair restoration
Historically speaking, local anesthesia was used as early as
Inca civilization by chewing coco leaves and dribbling the enriched
saliva in the surgical wounds. It was in 1884 that Karl Koller
used coco leaves to extract cocaine which he used as a local anesthesia
during glaucoma surgery. This surgery saw the introduction of
anesthesia in modern medicine. Halstead in the same year used
cocaine as an injection to create blocks in the nerves. Until
1904 when the first chemical anesthesia procaine was synthesized,
cocaine was the only practical anesthesia option. In 1943 Lidocaine,
the first amide anesthesia was synthesized and to date this is
the most popular of all the different types of anesthesia available.
Types of local anesthesia:
Local anesthesia can be broadly classified into caine and non-caine
anesthetics. The caine anesthetics have a lipophilic aromatic
ring, intermediate chain and a hydrophilic ionizable amine group.
Depending on the chemical linkages between the aromatic ring and
the intermediate chain, the caine anesthetics are classified as
ionized or non-ionized. The ionized form blocks the nerve impulses
by attaching itself to the sodium channel receptors on cells while
the non-ionized form diffuse through the cell membrane.
When an anesthetic with an ester group, such as cocaine, procaine
and tetracaine is used, it has been observed that their effect
is of very short duration due to which their analgesic effect
is less and poses a risk of hypersensitivity in patients. This
group of anesthetics is hydrolyzed in the plasma by an enzyme
called pseudocholinesterase. Patient’s who are deficient
in this enzyme show toxic symptoms when these drugs are administered
in normal doses. Because of these disadvantages, the ester group
containing caine anesthetics are not used in hair transplantation
procedures.
The amide containing caine anesthetics are the most popularly
used agents in hair transplants. This group includes lidocaine,
bupivacaine, prilocaine, etidocaine, mepivacaine and ropivocaine
out of which lidocaine and bupivacaine are extensively used. These
are metabolized in the liver and expelled out of the system by
the kidneys. Hence patients with problems in their liver and kidneys
are administered this anesthesia with caution.
Lidocaine, the most commonly used anesthesia, has varying effects
in different locations in the human body. Its effect is better
in parts of the body other than in the face and this effect may
be attributed to the body vasculature. It is used extensively
in ring blocks because of the early onset of anesthetic effect
and when administered as infiltration anesthesia, the effect is
immediate. Best of all, it does not affect the cardiovascular
system.
Bupivacaine is also used by many surgeons since it has a longer
anesthetic effect, that is 4-8 times longer than lidocaine. One
fourth the amount of bupivacaine in weight as compared to lidocaine
is enough to produce the same anesthetic effect. But in ring blocks,
bupivacaine is slow to produce effect and infiltration is very
painful. Although bupivacaine has certain advantages, one of the
main drawbacks of this agent is that it affects the cardiovascular
system. The main effects are arrhythmic heart [irregular heart
beats] and fibrillation [muscular twitching without coordination].
It also has a profound effect on the potassium and calcium channels
in cells. While it blocks sodium channels rapidly, it takes longer
time to unblock them and this can also be one of the factors for
causing arrhythmia.
In the non-caine category of anesthesia, only a few agents such
as 1% diphenhydramine, 0.9% benzyl alcohol, metoclopramide and
tramadol have been studied. Although they are generally considered
to cause less pain during infiltration, diphenhydramine seems
to be more painful and also leads to localized skin mortification.
All the above studied agents have effect lasting for short durations
of up to 15 mins and hence they are not used in hair transplantation
procedures.
Along with local anesthesia, vasoconstrictors [an agent that
causes narrowing of blood vessels] such as epinephrine and ornipressin
are used to prolong the effect of anesthesia. A vasoconstrictor
not only prolongs anesthetic effect but also limits the absorption
of anesthesia thereby lowering toxicity and improving hemostasis.
A 2% lidocaine solution has effect for 1-3 hrs while the same
when mixed with epinephrine in the ratio 1: 200,000 has an effect
lasting 5-8 hrs. The mixing of local anesthesia with epinephrine
results in oxidation of epinephrine due to which the pH of the
solution turns acidic. To prevent this problem, sodium bisulfate
or meta-bisulfate is added to increase the pH. Since epinephrine
in heavy doses can affect the heart rate and blood pressure, it
must be cautiously used in patients who have hypertension and
other cardio related problems.
Just as epinephrine is widely used in US, ornipressin is used
in Europe and Australia. Anesthetists of these regions claim that
the effect of ornipressin is greater than epinephrine and less
toxic to the cardio system. A higher dose of ornipressin however
causes dilation of the vessels. It is also found that during vasoconstriction,
there is decreased blood flow and higher blood pressure. Hence
ornipressin should be administered with caution in patients with
heart related anomalies.
Maximum permissible amount of anesthesia –
For a man who weighs 70 kg, a maximum of 50ml of 1% lidocaine
with epinephrine can be administered. 1% lidocaine has 10mg of
lidocaine per ml of the solution. Similarly 90 ml of 0.25% of
bupivacaine with epinephrine in the ratio of 1:100,000 is the
permissible limit.
In scalp infiltrations, it has been observed that the level
of lidocaine in plasma differs with the rate of absorption in
the subcutaneous infiltration. Except for one study conducted
by Maloney et.al in 1982 involving punch grafts, in which they
found a correlation between the dosage and concentration of lidocaine
in the plasma, further detailed study could reveal its toxicity
and maximum dosage applicable to hair transplants.
The toxic effects of local anesthesia –
As mentioned above, the concentration of anesthesia in plasma
indicates the degree of toxicity. Local anesthesia is toxic to
the neuro and cardio systems. When lidocaine is administered,
a concentration of 4 mg/L has anticonvulsant effect and as little
as 3 mg/L has neurological effects. The initial symptoms of neurological
effect are drowsiness, light headedness, incoherence in speech,
sight and taste. With increase in concentration, these symptoms
also increase and at 7.5 mg/L concentration a patient can experience
seizures. The toxicity increases when the brain is deprived of
oxygen and the carbondioxide level in the blood is high due to
which the acidity of the blood increases. To prevent neurological
damage, benzodiazepines are administered but they mask cardiovascular
toxicity.
Bupivacaine can cause central nervous system toxicity at 1 mg/L
concentration. Bupivacaine is four times more potent than lidocaine
in its anesthetic effect, but its lethal effect in neuro system
is four times and cardio system is nearly nine times its anesthetic
effect.
The toxicity of local anesthesia can be prevented if the anesthetist
follows the patient’s needs methodically by keeping records
of the patient’s health conditions, preparing the anesthesia
according to need and monitoring it continuously during the surgery.
An anesthetist can easily recognize symptoms related to anesthesia
such as dizziness, paling of skin, sweating, nausea, differences
in blood pressure and fainting. These can be immediately attended
to by positioning the patient with his legs slightly elevated
and applying cool compressions and reassuring the patient. In
patients who have no cardiac problems, 0.4 mg atropine is administered
intramuscularly. Rebreathing masks and different medications such
as benzodiazepines, flumazenil, hydralazine, naloxone and intravenous
fluids are used to prevent toxicity during hair transplantation.
Benzodiazepines also cause respiratory depression and is controlled
by use of flumazenil. Since local anesthesia can cause cardio
vascular collapse, it is usually mandatory that the clinic has
all equipment for cardio life support ready.
Some patients may react to vasoconstrictors and such patients
are given beta-blockers and nitroglycerin with continuous monitoring
of pulse, blood pressure and electrocardiogram. When allergic
reactions occur, the patients are treated with epinephrine and
antihistamines.
Local anesthesia in hair transplants –
Ring blocks are used to anesthetize the donor area while nerve
blocks are used for the recipient areas of the crown and front
of the head. Very fine needles are used for infiltrating the solutions
to avoid damage of the vessels and distension of tissues.
In a hair transplant procedure, any pain is from the initial
local anesthesia injections. To reduce this pain, the following
methods are used:-
1. Conscious sedation – administering anesthesia with the
patient being comfortable and in a conscious state with normal
breathing, continuous monitoring of the patients well being with
respect to breathing, pulse, blood pressure, electrocardiogram
and keeping cardio life support handy collectively form the conscious
sedation procedure. When the sedation is in effect, ring and nerve
blocks can be simultaneously administered.
2. Topical local anesthesia – A mixture of 2.5% prilocaine
and 2.5% lidocaine when applied to the skin 90-120 mins before
injecting local anesthesia reduces the pain of the initial injection.
This however does not reduce the actual local anesthesia penetration
pain and hence finds limited usage in hair transplantation.
3. Injecting without needles – is done by using injectors
that create a weal on the skin so that subsequent injections can
be performed using needles. This procedure does not eliminate
infiltration pain.
4. Use of ice packs or chilled metal plates has been recommended
to numb the skin before injecting the local anesthesia. A combination
of ice packs with other methods to lessen pain can be effective.
5. Scratching the skin or vigorously rubbing the area before
injection lessens pain.
6. Tumescence – using very dilute and large amounts of
local anesthesia increases the turgidity of the tissues and also
helps in easier dissection.
7. Temperature and pH control of the local anesthesia – warming
the solution to body temperature and increasing the pH of the
solution using buffers lessens infiltration pain.
8. Iontophoresis of lidocaine – by transferring lidocaine
ions across a membrane to the skin relives pain.
Of all the above mentioned techniques, use of conscious sedation
coupled with ice packs is the most helpful in lessening pain.
Local anesthesia for hair restoration references
- Seager DJ, Simmons C.
Local anesthesia in hair transplantation. Dermatol Surg. 2002
Apr;28(4):320-8. Review.
PMID: 11966789
- Nusbaum BP. Techniques
to reduce pain associated with hair transplantation: optimizing
anesthesia and analgesia. Am J Clin Dermatol. 2004;5(1):9-15.
Review.
PMID: 14979739
- Swinehart JM. Local anesthesia in
hair transplant surgery. Dermatol Surg. 2002 Dec;28(12):1189.
No abstract available.
PMID: 12472507
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