I'm so pleased to host a new guest blogger, Dr. Kate O'Reilley, anesthesiologist extraordinaire. Today, she's talking about an anesthesiologist's main job-- putting you to sleep-- in a good way!
Welcome, Kate!
Anesthesia is all about passing gas (no pun intended!) The most common anesthesia gases administered
in operating rooms today include Sevoflurane, Desflurane, Isoflurane, and
Halothane. The gases, which are also
referred to as volatile anesthetics, can be given to a patient in one of two
ways. The first method involves the
anesthesiologist simply holding a mask over the patient’s face and having the
patient spontaneously breathe in a mixture of gas and oxygen. The second method employs the use of a
ventilator that is attached to a breathing tube inserted into a patient’s
airway. Similar to the first method, the
ventilator delivers a mixture of volatile anesthetic and oxygen to the
patient’s lungs.
All of the anesthetic gases have similar effects. They cause sedation, muscle relaxation and
amnesia – the three components to an ideal general anesthetic. The gases have slight differences in how they
are metabolized, toxicities, dosages, and degree of cardiovascular depression.
Induction of anesthesia is simply the process of taking a
patient from an awake, conscious state to a state of unconsciousness. With adults, this process is usually achieved
through the intravenous administration of a series of drugs. Once the patient is unconscious and a
breathing tube is placed, the anesthesiologist turns on one of the gases to an
appropriate concentration, and uses the gas to maintain anesthesia during the
operation.
With children, we rarely have the luxury of a preoperative
intravenous line. It’s simply too
difficult and traumatizing to place an IV in the little rascals while they’re
awake. As a result, anesthesia in
children is often induced with gas instead of drugs. Once the child is asleep, an OR nurse places
and IV and surgery commences.
Watching a patient being anesthetized by gas alone is an
interesting process. It’s the only time one is able to see the distinct stages
of anesthesia. The first stage of
anesthesia is a state of voluntary excitation and euphoria. It lasts from when the patient is awake until
they are rendered unconscious. Until the
patient is unconscious, their movements are purposeful and they can follow
commands. Stage 2 of anesthesia is a
stage of involuntary excitation. In this
stage, patients my flail their arms and legs, giving the appearance of being
combative or agitated. However, they are
completely unaware of their actions. When parents accompany their children to the operating room for
induction, this stage is usually unsettling for them to witness. The third stage of anesthesia is the stage of
surgical anesthesia. In this stage, the
patient has reduced muscle tone and will not respond to surgical
stimulation. This is the stage where we
want patients to be during the operation.
Stage 4 of anesthesia is where we aim not to be. It is the stage where there is severe
cardiovascular and respiratory depression. If allowed to persist, this stage could result in death.
So once the patient’s surgery is done, how do we get rid of
the gases? We simply turn the gas
off. Over time, the patient breathes off
the gas and eliminates it from their bloodstream. Often times, as patients wake up, we will see
the stages of anesthesia in reverse. As
patients pass through the second stage, they often need to be restrained in
order to protect them and the operating room staff from injury. Once a patient returns to stage 1, they may
continue to be groggy and somewhat disoriented, but they should be able to
follow simple commands. Only once a
patient has returned to stage 1 is it safe to remove a breathing tube.
I hope that helps explain a little about anesthesia gases
and how they work. If there are any
questions, always feel free to email me at kateoreilley@gmail.com.
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