In-Office Anesthesia
Without Use of Needles
Larry E.
Davis, MD
Associate Professor, Family Medicine;
Director, Geriatric Fellowship,
University of Tennessee Graduate School of Medicine,
Knoxville, Tennessee
Disclosures
Larry E. Davis, MD
Imagine an instrument that could allow the delivery of needle-free,
virtually painless anesthesia for almost all primary care office procedures.
Anesthesia for skin biopsy, wart removal, laceration repair, digital blocks,
cervical biopsy (using 1 of several extension tips), venipuncture, joint
injections/aspirations, and even vasectomy can be provided without use of
needles. In addition, only a very small amount of local anesthetic, usually
0.1 to 0.5 mL, is required, and there is very little tissue distortion with
use.
Freedom from the fear
of being stuck by a needle is a relief to the patient, physician, and office
staff.
The needleless device
that can make these things possible is a high-pressure jet injector. Charles
L. Wilson, MD, from the University of Washington School of Medicine,
Seattle,[1] described the jet-injector technology, general application, and
use of the device in his primary care practice setting. He began by
chronicling the development of needleless injectors, starting with those
that initially utilized various gases as propellants, then described the
evolution into the current pen-sized forms.
Jet-injector
technology has been around for many years. Most physicians have heard about
its use in the military or in other "mass immunization" programs. Units used
for these purposes typically inject larger volumes of medication (0.5 mL or
greater) and were not designed for precision injections.
The device used by
Dr. Wilson in his practice is a U.S.-made jet injection system. This
injector works through use of a spring that compresses a small internal
piston, which produces high pressure without the need for a gas propellant.
The anesthetic solution is then emitted from the high-pressure chamber
through a calibrated orifice. Unlike most injector systems, this unit does
not rely on a gas propellant from a tank or cartridge. Instead, it has a
pump, which is primed each time a small lever on the pen-sized device is
cocked. The unit is made entirely of stainless steel and glass and can be
autoclaved or cold sterilized between uses.
The glass syringe of
the jet injector can be loaded with a variety of anesthetic medications. A
single filling can be used for multiple injections on separate patients.
Because no part of the device penetrates the patient, it is only necessary
to change the disposable tip that touches the patient before using again.
However, cold sterilization between patients is recommended.
The evolution of the
jet device has allowed increased reliability and portability, more
economical operation, and better patient acceptance due to the less
intimidating visual appearance of the device. It is also virtually silent
when delivering a dose of local anesthetic.
Fears that such
devices might spread infection by tiny amounts of "splash back" of blood
created with each discharge of the injector have been alleviated through the
use of disposable tips and by cold sterilization between patients, similar
to the sterilization of a colonoscope. As mentioned earlier, there is no
chance that the physician or office staff can suffer a needlestick that is
contaminated by a patient's blood with use of the jet device.
The cost per
injection is estimated to be about $0.13 with the jet injector, compared
with about $0.90 using a syringe, needle, and larger volume of anesthetic
solution. There may be an additional cost associated with traditional needle
anesthesia if some of the anesthetic solution is wasted, as it typically is
in most clinical situations. Overall, the volume of medical waste associated
with the use of this device is also greatly reduced, compared with the more
familiar syringe-and-needle system used in most family physician's offices.
The anesthesia
produced by the jet injector is rapid and more precise than that of the
standard syringe-and-needle system. It also affords patients who fear
needles an alternative when local anesthesia is indicated.
The injector jet is
held perpendicular to the skin surface and firm pressure is applied. Then
the release button is pushed to disperse the anesthetic. The patient
typically hears a popping sound as the anesthetic is delivered. They usually
report a sensation described similar to that of a rubber band being snapped
against the skin. The injection is instantaneous, so the device may be
removed or repositioned immediately for another injection.
The injection stream
penetrates about 4 mm into tissue, and disperses to about 1.0 to 1.5 cm in
diameter. The skin surface may blanche and a pinpoint entry site may be
visible. Penetration may cause a tiny drop of blood to appear. The
injection-site entry point will be roughly equivalent in size to the
puncture made by a 26-30 gauge needle.
Multiple injections
can be used to anesthetize larger areas if needed. As with standard
injection methods, care must be taken not to injure adjacent tissues, such
as nerves, bones, and blood vessels. Any standard anesthetic solutions may
be used in the device.
Dr. Wilson described
his use of a jet injector when performing no-scalpel vasectomy. He has done
over 1000 of these procedures to date. He is able to use only 2 injections
of 0.1 mL 2% lidocaine in 90% of patients, without supplemental infiltration
of local anesthesia. In the usual vas deferens anesthesia technique, up to 6
mL of local anesthetic is infiltrated into the scrotum. Use of the injector
not only greatly reduces the volume of anesthetic used, but also prevents
the small risk of cord hematoma that can occur when a needle is used to
administer the traditional block.
Most primary care
doctors perform procedures daily that need local anesthesia that is safe,
effective, and as pain-free as possible. Ethyl chloride spray, ice cubes,
and EMLA (lidocaine 2.5% and prilocaine 2.5%) cream and anesthetic discs all
have significant limitations in meeting these objectives in office practice.
A review of the
literature revealed a marked scarcity of research comparing local anesthesia
delivered by needle vs a jet-injector system. The few studies conducted over
the past 20 years showed a mixed pattern of patient satisfaction. However,
the majority of recent research has demonstrated less painful injection when
a jet device was compared with traditional needle delivery. Studies
demonstrating superior results included comparison with a 25-gauge needle
for delivery of anesthesia prior to large-bore intravenous (IV) cannula
insertion[2,3] and for delivery of anesthesia prior to pediatric dental
operative procedures.[4] Another study comparing subcutaneous administration
of midazolam showed less discomfort with the jet injector, but the results
were not statistically significant.[5] However, patient reports of
persistent discomfort at site of needle injection were significantly
greater.
Jet injection was
also shown to be less painful immediately and at 12 hours postprocedure for
patients undergoing digital blocks; adequate anesthesia was obtained in 23
of 24 patients.[6]
Although jet
injection technology has been used by dentists for many years to provide
intra-oral anesthesia, and by some podiatrists, the growth rate of use by
primary care physicians has been low up to this point. Most primary care
physicians remain unaware of the potential usefulness of this device in an
office setting. This may be due in part to the lack of effective marketing.
Use of these devices
in training programs may have given dentists and podiatrists the opportunity
to gain experience with the technology under faculty supervision. Providing
similar exposure to the injectors in the medical residency training setting
could provide the opportunity needed for primary care physicians in training
to gain such experience. Seminars at medical meetings could also provide
opportunity for learning about the devices, but unfortunately only a limited
chance to gain experience under the guidance of an experienced instructor.
Initial purchase
price may also be a contributing factor to the relatively low percentage of
primary care physicians using these devices. The injector device costs
between $600-$800 per unit. But with a savings of $0.75 per use, the device
may "pay for itself" within a few years of use in a busy practice. The
increased safety of staff and the higher patient acceptance of needed minor
procedures are also important considerations in determining whether to
purchase an injector device. Word of mouth could also produce increased
referrals when satisfied patients share their experiences with others.
In review, some of
the procedures that can be performed with needleless anesthesia include:
-
Joint and bursa injection/aspiration
-
Skin lesion excision, biopsy, cryosurgery, curettage
-
Excision of ingrown nails (digital blocks)
-
Laceration repair
-
Incision and drainage of abscesses; cyst excision
-
Cervical biopsy
-
Vasectomy
-
Lumbar puncture
-
Blood drawing and IV access
Advantages of jet-injection anesthesia include:
-
No chance of needle-stick injury
-
Decreased fear of procedures
-
Decreased volume of local anesthetic used
-
More precise local anesthesia
-
Less tissue distortion
-
Less expensive local anesthesia
Disadvantages of jet injection anesthesia include:
-
Initial cost of device
-
Most PCP's not familiar with its use
Hopefully, this technology will soon claim a place in the primary care
office setting.
References
-
Wilson, CL. No-needle anesthesia. Program and
abstracts from the American Academy of Family Physicians 2001 Scientific
Assembly; October 3-7, 2001; Atlanta, Georgia. Session 266.
-
Cooper JA, Bromley LM, Baranowski AP, Barker SG.
Evaluation of a needle-free injection system for local anaesthesia prior
to venous cannulation. Anesthesia. 2000;55:247-250.
-
Zsigmond EK, Darby P, Koenig HM, Goll EF. Painless
intravenous catheterization by intradermal jet injection of lidocaine: a
randomized trial. J Clin Anesth. 1999;11:87-94.
-
Munshi AK, Hegde A, Bashir N. Clinical evaluation of
the efficacy of anesthesia and patient preference using the needle-less
jet syringe in a pediatric dental practice. J Clin Pediatr Dent.
2001;25:131-136.
-
Bennett J, Nichols F, Rosenblum M, Condry J.
Subcutaneous administration of medazolam: a comparison of the Bioject jet
injector with the convential syringe and needle. J Oral Maxillofac Surg.
1998;56:1249-1254.
-
Ellis Gl, Owens A. The
efficacy and acceptability of using a jet injector in performing digital
blocks. Am J Emerg Med. 1993;11:648-650.
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