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What is Anesthesia?
Anesthesia is the partial or complete loss of sensation, with or without loss of consciousness. Anesthesia can be the result of an illness. However, this article is about anesthesia administered by injection or inhalation for the purpose of performing tests or surgery. Anesthesia is used when the pain from the surgery or procedure would be so bad that the patient would not be able to tolerate it. Also, the body’s response to the pain would also prohibit many types of surgery from being done. Surgical anesthesia is a depth of anesthesia that relaxes the muscles along with loss of sensation and consciousness to a level where surgery can be performed.
The main types of anesthesia include:
• General – where you are “asleep”
• Regional (spinal and epidural) – where an entire area is numb, and you may also be sedated
• Local – where a specific area is numb
Anesthesia is performed by an anesthesiologist or by a nurse anesthetist under the supervision of an anesthesiologist. After consulting with the surgeon and patient, the anesthesiologist will decide on which type of anesthesia to use. The type of anesthesia used depends on:
• what kind of surgery the patient is having
• how long the surgery will last
• location of the surgery (where in the body)
• how intricate the surgery will be
• the age and overall health of the patient
• the anesthesiologist’s personal expertise, judgment and preference.
The goals of anesthesia are:
• loss of consciousness
• to block the patient’s memory of the procedure
• to maintain the body’s physiologic stability
• to prevent or reduce pain
• to relax the skeletal muscles
• to stop the body’s normal reflexes
Balanced anesthesia uses a combination of anesthetic agents that enhances the desired effects and limits the undesired side effects. Balanced anesthesia is usually started by giving anesthetic agent through their I.V. followed by breathing in a second anesthetic agent that quickly induces anesthesia. Anesthesia is then maintained during surgery through a breathing tube (endotracheal tube) or mask.
Sedation and Anesthesia
Sedation is the state of being calmed. Types of sedation include
• conscious sedation
• moderate sedation
• deep sedation
There are 4 levels of sedation and anesthesia when a patient receives moderate or deep sedation or general or regional anesthesia. Some of the drugs used to induce anesthesia can be given in a lesser amount to produce sedation.
Level 1 (minimal sedation) – the patient is able to maintain normal breathing and heart function is normal.
Level 2 (moderate sedation) – consciousness is reduced, but the patient responds to verbal commands. He can breathe on his own and heart function is maintained without help.
Level 3 (deep sedation) – the patient can respond to repeated painful stimuli, he can’t be aroused easily. The patient may need help breathing but the heart function still remains normal.
Level 4 (general anesthesia) – The patient loses consciousness and can’t be aroused even with painful stimuli. He needs assistance with breathing. The muscle function is depressed and heart function may be impaired.
General anesthesia consists of 4 stages; each stage causes changes in breathing, muscle tone, and reflexes. Stage 4 is an overdose and can end in death. During surgery, the patient proceeds through the first 3 stages:
Stage I – Analgesia
Stage II – Excitement
Stage III – Surgical anesthesia (which has 4 planes)
Stage IV – Medullary depression
Inhalation agents are gases or vapors that work mainly by depressing the central nervous system. They cause unconsciousness, relax the muscles and make the patient unresponsive to pain. These agents can impair breathing and blood flow, depress the heart muscle and impair kidney function and liver function.
• Inhalation agents – these are vapors or gases used to induce or maintain anesthesia that the patient usually breathes through a tube or mask. They work by depressing the central nervous system. They also impair breathing, heart function and may affect renal and liver function.
Other side effects include over reaction to the medicine, confusion, sedation, nausea, vomiting, abnormal heart rhythm, and a drop in body temperature.
• I.V. Agents – these are commonly combined with inhalation agents for numbing, muscle relaxation and inducing general anesthesia. For short surgeries or when short acting anesthesia is needed, I.V. agents may be used without inhalants. I.V. agents include:
– Barbiturates and Non-barbiturates – Side effects of barbiturates and non-barbiturates include depressed breathing, cough, hiccups, muscle twitching, and spasm of the laryngeal cords.
– Benzodiazepines – Side effects of benzodiazepines (Valium, Versed) – drowsiness, confusion, dizziness, weakness, headache, tremors, eyes crossing, clumsiness, and trouble thinking or speaking.
– Opiods (narcotics) – The side effects of opioids are depression of the central nervous system, difficulty breathing, breathing slower than normal or shallow breathing, abnormal heart rate or rhythms, constipation.
– Dissociative agents – Side effects of dissociative agents are delirium, hallucinations, disorientation, excitement, high blood pressure, rapid heart beat, and increase in intracranial pressure.
What to Expect with General Anesthesia
Before General Anesthesia
Before you have general anesthesia, an anesthesiologist will talk with you about:
• Your health history including whether you have had surgery before
• Any prescription medicines, over-the-counter medicines and herbal supplements that you take
• Any allergies to food or medicine that you have
• Your past experience with anesthesia, such as side effects or reactions
This information will help the anesthesiologist choose the anesthetics that will work best and cause the least unwanted side effects for you.
During General Anesthesia
In most cases, anesthesia is started with an anesthetic delivered through an I.V. in your arm. Sometimes it can be started with a gas that you breathe from a mask. Once you are asleep, a tube (endotracheal tube) may be inserted in your mouth and down your windpipe to make sure you get enough oxygen and protect your lungs from blood or body fluids. Sometimes a breathing tube isn’t needed, which reduces your chance of having a sore throat after surgery.
A member of the anesthesia care team monitors you continuously during your procedure, adjusting your medications, breathing, temperature, fluids and blood pressure as needed. Any abnormalities that occur during the surgery are corrected by administering additional medications, fluids and, sometimes, blood transfusions.
After General Anesthesia
When the surgery is complete, the anesthesia drugs are discontinued, and you gradually wake up, usually in the operating recovery room. You’ll probably feel groggy and a little confused when you first wake up but you shouldn’t feel much pain from the surgery. Other common side effects include:
• Dry mouth
• Sore throat
Risks of General Anesthesia
Most healthy people have general anesthesia and don’t have any problems. However there is a small risk of complications and, rarely, even death. Your chances of having a specific complication is related to your age and overall physical health, the type of anesthesia and surgery that you have.
The following factors can increase your risk of complications:
• Alcohol use may make you susceptible to liver damage
• Allergies to food or medicine
• Family or personal history of bad reactions to anesthesia
• Health conditions with your heart, lungs or kidneys
• Sleep apnea (you stop breathing while you’re asleep)
• Smoking increases your chances of having lung and breathing problems
• Medicines that keep your blood from clotting, such as aspirin and NSAIDS
• Very overweight
The following complications are rare and happen more often in adults over 65 or people with health conditions:
• Heart attack
• Lung infections
• Temporary mental confusion
Regional anesthesia blocks the sensation in either a nerve or a region of the body. Regional anesthesia is sometimes called local anesthesia or nerve block. Types of regional anesthesia include spinal anesthesia, saddle block, nerve block. There are several kinds of regional anesthesia; the two most common are spinal anesthesia and epidural anesthesia.
In regional anesthesia, your anesthesiologist makes an injection near a cluster of nerves to numb the area of your body that requires surgery. You may remain awake, or you may be given a sedative, either way you do not see or feel the actual surgery taking place.
In local anesthesia, the anesthetic medicine is usually injected into the tissue to numb a the specific area of your body, such as an episiotomy.