Friday, October 19, 2012
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!
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 email@example.com.