TYPES OF ANESTHESIA
There are 25 million surgeries performed each year in the United States,
in Hospitals, Out-patient Surgery Centers, Ambulatory Surgery Centers
and private doctors offices. Majority of them will need anesthesia to
provide patient comfort and insensibility to pain. There are 4 million
babies delivered each year, often requiring some form of anesthesia.
Most of these anesthetics will be provided by a physician Anesthesiologist
who may also be working together with a nurse anesthetist/CRNA.
What types of anesthesia are there, and what types of anesthesia are
given for the typical kinds of surgeries performed today?
GENERAL ANESTHESIA
REGIONAL ANESTHESIA
MAC ANESTHESIA (SEDATION/TWILIGHT SLEEP)
LOCAL ANESTHESIA
GENERAL ANESTHESIA--this is when a patient is asleep
deeply to the point of unconsciousness. It is deeper than when you are
asleep at night. General Anesthesia is administered by an intravenous
induction or a gas induction. Induction means the patient is placed
into the sleeping state of unconsciousness. IV induction is done by
giving medications into the IV that quickly puts the patient to sleep
(10-12 seconds). A gas induction is performed with a mask, where the
patient, usually a child, breaths gases from a mask until they fall
asleep. This take longer than the IV induction, on the order of a few
minutes. Mask inductions are done for children because they don’t
have an IV in place. Most infants and young children do not tolerate
being prodded or poked with needles while they are awake--so the IV
is started after they go to sleep.
Now that the patient is asleep, they need to stay asleep for the entire
time of the surgery. This is accomplished with anesthesia gases (commonly,
sevoflurane, isoflurane) or with a continuous intravenous infusion of
induction agents (usually propofol, diprivan).
How do patients wake up from this general anesthesia? In the case of
anesthesia gases, they are turned off at the end of the surgery and
the patient awakens slowly as they breathe off the gases. In the case
of IV infusions, the medicine infusion is stopped and the patient awakens
slowly as their body redistributes the medications away from the brain,
and metabolizes these medicines in the liver and excretes them through
the kidney.
During general anesthesia there is intense monitoring of the patients
vital signs: every heartbeat, every breath, is followed, along with
the exact concentration of oxygen in the patients bloodstream. These
and many other vital signs and parameters are checked frequently to
ensure they stay fully asleep during the surgery, tolerate it well,
then a safe return of the patient to consciousness when the surgeon
is finished with the procedure.
Examples of types of surgeries that are performed under general anesthesia
include: gynecologic surgery BTL's laparoscopy, laparoscopic cholecystectomy
(gallbladder surgery), inguinal and ventral hernia repairs, abdominal
surgery like colon resections, appendectomy, small and large bowel surgery,
head and neck surgery such as tonsillectomy and adenoidectomy(T/A or
TA), bilateral myringotomy tube placements (BMT's, children’s
ear tubes), thyroidectomy, gastric bypass, peptic ulcer and duodenal
ulcer surgery, gastroesophageal surgery, orthopedic surgery, plastic
surgery like breast implants/augmentation, facial and facelifts, abdominoplasty,
and of course heart/lung/cardiac/thoracic surgery, and neurosurgery.
REGIONAL ANESTHESIA--there are several types of regional
anesthesia: spinal anesthesia, epidural anesthesia, and regional block
anesthesia.
Spinal Anesthesia involves an injection of anesthesia into the low
back on into the spinal fluid (opposite of a "spinal tap",
where a needle goes into the spinal fluid to withdraw a sample--to check
for meningitis). When anesthesia is injected into the spinal fluid (CSF-cerebrospinal
fluid), it numbs the spinal nerves that are present in the spinal fluid
and blocks pain in the lower part of the body. It can work anywhere
from the chest on down. 'saddle blocks' work to numb only from the waist
down. A patient can be awake during surgery when under spinal anesthesia,
because they have no sensation or feeling in the parts of the body being
operated on. Of course, only certain types of surgery can be done under
Regional Anesthesia. An example of types of surgery that can be done
under regional/spinal/epidural anesthesia include: cesarean section
(CSX, or C-Section), orthopedic procedure such as knee arthroscopy and
hip or knee joint surgery, lower abdominal surgeries, urologic procedures
like TURP or prostatectomy, and gynecologic cerclage (suture around
an incompetent cervix), BTL (bilateral tubal ligation), LBTL (laparoscopic
bilateral tubal ligations). That said, spinal and epidural anesthesia
is NOT used for outpatient surgeries very often. Out patient surgery
is usually done under IV sedation or General Anesthesia.
EPIDURAL ANESTHESIA--the word "epidural"
is a general term to refer to a way to deliver anesthetic medications
--there are several different types of epidurals, depending on their
use and the mix of medications infused into them.
The definition or meaning of the word "epidural" has to do
with "an area on top of the dural space" which is the covering
of the spinal canal. So an epidural is placement of medications into
the epidural space, directly by injection or more usually through a
tiny catheter, so the medicines can be as a continuous infusion. There
are epidurals that are used for labor and delivery, epidurals that are
used for surgery, such as cesarean section or other abdominal surgery,
and epidurals that are given as back pain treatments (these usually
have steroids added).
Epidurals that are used for surgery make the body numb from the chest
down. The patient is awake during the surgery but can be sedated to
they do not become too anxious. Epidurals can be continued after the
surgery to keep the site of surgery pain-free during the postoperative
recovery period.
MAC--Monitored Anesthesia Care--is sometimes called
"IV Sedation" or "twilight sleep" or "twilite
sedation" or "conscious sedation" (sp.concious/consious).
No matter how it is referred to, it is still a very important method
of anesthetic delivery. The name implies a 'light sleep', and there
are many variations and levels of anesthesia dependent on the anesthesiologist.
It is the anesthesiologist who determines how much medication to give.
During this procedure, the anesthesiologist may give intravenous medications
to place the patient in a light sleep. The surgeon administers injections
of local anesthetics at this time so as not to cause discomfort to the
patient. The patient breathes on their own, and does not need a ventilator
or anesthetic gas. By having an anesthesiologist give sedation, even
minor procedures can be easily performed without pain. These procedures
are done in hospitals or surgery centers.
Examples of types of surgery that can be done with MAC or IV Sedation/conscious
sedation include: breast biopsy, Gynecologic procedures like LEEP/LOOP,
D/C, D and C, D/E, D and E (dilatation and evacuation for spontaneous
incomplete abortion or miscarriage), and colonoscopy or EGD (esophagogastroduodenoscopy).
There are risks to all surgery and anesthesia. Anesthesia Risks are
dependent on the type of anesthesia that is given.
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Readers may send questions to this
email address. This column is for informational purposes
only and is not a substitute for professional or medical advice.
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