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Perioperative Information

Anesthesia

Your choices in Anesthesia

There are a few choices that you may have for anesthesia although not all surgeons and their practices will offer every one. 

The three main categories of anesthesia are:

  • local anesthesia
  • regional anesthesia 
  • general anesthesia 

Local anesthesia: is what you have when you receive a shot to numb the immediate treatment area. You most commonly receive local at the dentist's office but also receive it during a Rhinoplasty or other type of surgery in addition to Sedation. 

The injection is most commonly of Lidocaine (or Xylocaine, Marcaine), Epinephrine (as a vasoconstrictor to impede bleeding in the treatment area and absorption of the Lidocaine by the patient). Injections of anesthetic are thought to block nerve impulses by decreasing the permeability (think of microscopic openings for the impulses to leak through) of nerve membranes to sodium ions.

Regional anesthesia : was named such because a region of the body is anesthetised without rendering the patient unconscious. For instance: spinal anesthesia for childbirth. Do not get this confused with an epidural as they are very similar in effects but a different locale is injected with the anesthetic. In an epidural the injection is in the area outside the spinal fluid called the epidural space, the catheter is placed inside this area so that anesthetic injections may be given or can be tube-fed if needed for longer periods of time (from hours to weeks). With spinal anesthesia, the local anesthetic is injected into the spinal fluid that causes a loss of sensation to the areas below the navel. Also, in spinal anesthesia, such narcotics as morphine and fentanyl can be infused in addition to or partially substituting the anesthesia. 

You may have also heard them referred to as nerve blocks. A nerve block is considered regional as an anesthetic is injected into a nerve cluster and it affects sensation in all areas which this cluster controls. There are nerve clusters all over your body; for instance, under the jaw, in the chin, and under the eye.  They sometimes feel like little holes in the bone where your nerves are clustered, then branch out to the different areas of the face or anywhere on the body. 

General Anesthesia: General can be given by an inhaled gas or / and intravenously.  

  • An injection is indicated for outpatients as an adjunct to general anesthesia to facilitate both rapid sequence and routine tracheal intubations, and to provide skeletal muscle relaxation during surgery or mechanical ventilation.
  • An odourless, rapid-acting opioid (or synthetic opiate, narcotic analgesia), which depresses central nervous system and respiratory function. It is the most powerful opioid known, with potency approximately 80 times that of morphine.
  • A serotonin receptor antagonist used mainly as an antiemetic to treat nausea and vomiting following surgery. Its effects are thought to be on both peripheral and central nerves.
  • A short-acting intravenous sedative agent used for the induction and maintenance of general anesthesia. Yet in some studies, when patients receive this sedative compared to inhalation agents for anesthesia, postoperative pain is decreased.

Gas Or Liquid? Inhaled, Injected Or Swallowed?

Anesthesia in a gaseous state
is inhaled into the lungs; the blood that travels to the lungs for oxygenation is then saturated by the oxygen and anesthetic gas absorbed by your aveoli (the little spongy things in your lungs that grab oxygen out of the air) which is then carried to the central nervous system (CSN).  The effects of the anesthesia and the rate at which they affect the patient are dependent upon these factors:

  • gas concentration
  • rate of gas flow from the anesthesia machine
  • rate/depth of breathing (that's why they say breathe deeply)
  • amount of blood the patient's heart pumps each minute
  • solubility of the gas in the patient's blood (some gases are more soluble than others)

One of the inhalants used is:

  • Sevofluorane

Once the anesthesiologist turns off the anesthetic gas and only delivers pure oxygen; or alternatively removes the mask entirely (as in gaseous state Twilight, Laughing Gas), the blood stream returns the gases to the lungs where it is then eliminated by exhalation.  However, the more soluble the gas is in blood, the longer it will take to purge from the body.

Some procedures require a urinary catheter to catch any accidental urinating.  They usually insert the catheter after you are already under anesthesia. 

Anesthesia in a liquid, injectable state is administered by injection directly into the bloodstream, usually through an intravenous catheter (IV). Some of these anesthetics include:

Barbiturates such as:

  • Propofol: The rapid, pleasant offset makes it suitable for monitored sedation, maintenance of anaesthesia.
  • Ketamine: has a wide range of effects in humans, including analgesia, anesthesia, elevated blood pressure, and bronchodilation. It is primarily used for the induction and maintenance of general anesthesia, usually in combination with some sedative drug.

Just like gases, the effects and duration depend on a few factors such as the amount injected, the weight of the patient, the fat-solubility of the drug and the fat percentage of the patient's body as well as the patient's body and how it reacts to drugs. 

Used in small doses most of these can be used for Light Sleep Sedation.

Just like gases, the effects and duration depend on a few factors such as the amount injected, the weight of the patient, the fat-solubility of the drug and the fat percentage of the patient's body as well as the patient's body and how it reacts to drugs.  Pentothal (sodium thiopental) is fat soluble and its effects are felt soon after injection. 

Used in small doses most of these can be used for Light Sleep Sedation.

What Does It Feel Like?
Regardless if you have IV or gas you will more than likely have an IV inserted for a ringer lactate drip to keep you hydrated and have a vascular doorway should the need arise. Having an IV inserted feels sort of like blood being drawn, but for a shorter period of time. It's the initial placement of the IV catheter that may sting a bit. After the needle is inserted into the vein it is pulled out and a little plastic tube is left in your vein. This is called a catheter, which is taped to your skin so it is not knocked out and is ready to be used as a sort of entryway for anything the anesthesiologist deem suitable for your body. This is usually done before you get into the actual O.R. (by a nurse). Some people get it in the crook of the elbow, some the hand. You are then brought to the O.R. if you aren't on the table yet.


IV Liquid Sedative The effects of the anesthesia are felt soon after injection, a few seconds in fact. It feels like heat going into you veins then creeping up your arm; then it jumps from your shoulder to a metallic-like taste under your tongue and then you are blissfully anesthetised.  

Gaseous-state anesthesiaAll this entails is breathing through a mask.  However this depends upon what type. The newer intubation (LMA) is a lot like the older intubation for General but there is a shorter tube and a little balloon the size of your two thumbs holds your tongue out of the way so it does not obstruct your breathing.  With the older intubation you have the pleasure of having a tube down your throat but you don't usually remember it going in.  You may wake up with a raw throat. You may wake up with a sore, dry throat regardless because cylinder air is dry.

Also be advised that if you have bronchospasm, asthma or other disorders such as this, intubation is contraindicated.

Regardless of the type, you basically are told to count up to 10. After the gas hits the alveoli in your lungs, your blood is saturated by the anesthesia gases where they are carried to your central nervous system (CNS) where you are in all actuality, knocked out.

Your Anesthesiologist
The anesthesiologist basically must know for your weight and body fat percentage what will work best for you and in what amounts plus they monitor your heart rate, breathing rate, your blood pressure, etc.
If you are going under light sleep (IV) an anesthesiologist may not be present in the O.R.  Some use nurses, in others the surgeon may be in charge of it. The amount of anesthetic is determined per your individual body weight with anesthetic to body-ounce formulations and fed via a drip system mixed with your IV. Personal tolerances are also taken into account. However, any reactions by the body while under anesthesia should be monitored closely by a highly qualified individual.

Why Shouldn't I Eat Before Surgery?

You are often told "don't eat past midnight the night before your surgery". Gastric emptying may be influenced by many factors, including anxiety, pain, abnormal autonomic function (e.g., diabetes), and mechanical obstruction. The danger isn't vomiting under general anesthesia, it's vomiting under *induction* of general anesthesia. When the patient is under, there is an endotracheal tube with a balloon on it in the trachea, which prevents aspiration of any vomit into the airway. It's getting to that situation that is worrisome since there is a transition period as the patient is going under (being "induced") where there is no tube protecting the airway, but they are deep enough that their reflexes are gone and they cannot protect their own airway. It’s that 15 second period of time that worries anesthetists, since vomiting/aspiration is the most common dangerous anesthetic complication these days.

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