General Anaesthesia
General anaesthesia is a combination of medications that put you in a sleep-like state before a surgery or other medical procedure. Under general anaesthesia, you don’t feel pain because you’re completely unconscious. General anaesthesia usually uses a combination of intravenous drugs and inhaled gases (anaesthetics).
General anaesthesia is more than just being asleep, though it will likely feel that way to you. But the anaesthetized brain doesn’t respond to pain signals or reflexes.
An anaesthesiologist is a specially trained doctor who specializes in anaesthesia. While you’re under anaesthesia, the anaesthesiologist monitors your body’s vital functions and manages your breathing.
In many hospitals, an anaesthesiologist and a certified registered nurse anaesthetist (CRNA) work together during your procedure.
Why it’s done
Your anaesthesiologist or nurse anaesthetist, along with your doctor, will recommend the best anaesthesia option for you based on the type of surgery you are having, your overall health and your individual preferences. For certain procedures, your team may recommend general anaesthesia. These include procedures that may:
- Take a long time
- Result in significant blood loss
- Expose you to a cold environment
- Affect your breathing (particularly chest or upper abdominal surgery)
Other forms of anaesthesia, such as light sedation combined with local anaesthesia (for a small area) or regional anaesthesia (for a larger part of your body), may not be appropriate for more involved procedures.
Risks
General anaesthesia is overall very safe for most people, even those with significant health conditions, are able to undergo general anaesthesia itself without serious problems.
In fact, your risk of complications is more closely related to the type of procedure you’re undergoing and your general physical health, rather than to the type of anaesthesia.
Older adults, or those with serious medical problems, particularly those undergoing more extensive procedures, may be at increased risk of postoperative confusion, pneumonia, or even stroke and heart attack. Specific conditions that can increase your risk of complications during surgery include:
- Smoking
- Seizures
- Obstructive sleep apnea
- Obesity
- High blood pressure
- Diabetes
- Stroke
- Other medical conditions involving your heart, lungs or kidneys
- Medications, such as aspirin, that can increase bleeding
- History of heavy alcohol use
- Drug allergies
- History of adverse reactions to anaesthesia
These risks are more generally related to the surgery itself rather than the anaesthesia.
Anaesthesia awareness
Estimates vary, but about 1 or 2 people in every 1,000 may be partially awake during general anaesthesia and experience what is called unintended intraoperative awareness. It is even rarer to experience pain, but this can occur as well.
Because of the muscle relaxants given before surgery, people are unable to move or speak to let doctors know that they are awake or experiencing pain. For some patients, this may cause long-term psychological problems, similar to post-traumatic stress disorder.
This phenomenon is so rare that it’s difficult to make clear connections. Some factors that may be involved include:
- Emergency surgery
- Cesarean delivery
- Depression
- Use of certain medications
- Heart or lung problems
- Daily alcohol use
- Lower anaesthesia doses than are necessary used during procedure
- Errors by the anaesthesiologist, such as not monitoring the patient or not measuring the amount of anaesthesia in the patient’s system throughout the procedure.
How you prepare
General anaesthesia relaxes the muscles in your digestive tract and airway that keep food and acid from passing from your stomach into your lungs. Always follow your doctor’s instructions about avoiding food and drink before surgery.
Fasting is usually necessary starting about six hours before your surgery. You may be able to drink clear fluids until a few hours prior.
Your doctor may tell you to take some of your regular medications with a small sip of water during your fasting time. Discuss your medications with your doctor.
You may need to avoid some medications, such as aspirin and some other over-the-counter blood thinners, for at least a week before your procedure. These medications may cause complications during surgery.
Some vitamins and herbal remedies, such as ginseng, garlic, Ginkgo biloba, St. John’s wort, kava and others, may cause complications during surgery. Discuss the types of dietary supplements you take with your doctor before your surgery.
If you have diabetes, talk with your doctor about any changes to your medications during the fasting period. Usually you won’t take oral diabetes medication the morning of your surgery. If you take insulin, your doctor may recommend a reduced dose.
If you have sleep apnea, discuss your condition with your doctor. The anaesthesiologist or anaesthetist will need to carefully monitor your breathing during and after your surgery.
What you can expect
Before the procedure
Before you undergo general anaesthesia, your anaesthesiologist will talk with you and may ask questions about:
- Your health history
- Your prescription medications, over-the-counter medications and herbal supplements
- Allergies
- Your past experiences with anaesthesia
This will help your anaesthesiologist choose the medications that will be the safest for you.
During the procedure
Your anaesthesiologist usually delivers the anaesthesia medications through an intravenous line in your arm. Sometimes you may be given a gas that you breathe from a mask. Children may prefer to go to sleep with a mask.
Once you’re asleep, the anaesthesiologist may insert a tube into your mouth and down your windpipe. The tube ensures that you get enough oxygen and protects your lungs from blood or other fluids, such as stomach fluids. You’ll be given muscle relaxants before doctors insert the tube to relax the muscles in your windpipe.
Your doctor may use other options, such as a laryngeal airway mask, to help manage your breathing during surgery.
Someone from the anaesthesia care team monitors you continuously while you sleep. He or she will adjust your medications, breathing, temperature, fluids and blood pressure as needed. Any issues that occur during the surgery are corrected with additional medications, fluids and, sometimes, blood transfusions.
After the procedure
When the surgery is complete, the anaesthesiologist reverses the medications to wake you up. You’ll slowly wake either in the operating room or the recovery room. You’ll probably feel groggy and a little confused when you first wake. You may experience common side effects such as:
- Nausea
- Vomiting
- Dry mouth
- Sore throat
- Muscle aches
- Itching
- Shivering
- Sleepiness
- Mild hoarseness
You may also experience other side effects after you awaken from anaesthesia, such as pain. Your anaesthesia care team will ask you about your pain and other side effects. Side effects depend on your individual condition and the type of surgery. Your doctor may give you medications after your procedure to reduce pain and nausea
Regional Anesthesia
Regional anaesthesia is the use of local anaesthetics to block sensations of pain from a large area of the body, such as an arm or leg or the abdomen. Regional anesthesia allows a procedure to be done on a region of the body without your being unconscious.
Major types of regional anaesthesia include:
Peripheral nerve blocks. A local anaesthetic is injected near a specific nerve or bundle of nerves to block sensations of pain from the area of the body supplied by the nerve. Nerve blocks are most commonly used for surgery on the arms and hands, the legs and feet, the groin, or the face.
Epidural and spinal anaesthesia. A local anaesthetic is injected near the spinal cord and major nerves that enter the spinal cord to block sensations of pain from an entire region of the body, such as the lower abdomen, the hips, or the legs.
For regional anaesthesia, the anaesthetic is injected close to a nerve, a bundle of nerves, or the spinal cord. Skill and experience are needed for the anaesthesiologist to inject the anaesthetic at the proper location, because the site of injection of the anaesthetic has a significant impact on its effect. Careful technique is needed to reduce the risk of rare complications, such as infection or nerve damage.
The site of the injection also strongly affects how quickly the anaesthetic is absorbed into the rest of the body. People who receive regional anaesthesia are carefully watched, because the anaesthetics used may affect the central nervous system, cardiovascular system, and respiratory system (airway and lungs). This is particularly important with spinal and epidural anaesthesia, because they may affect blood pressure, breathing, heartbeat, and other vital functions.
Regional anaesthesia may be given with other medicines that make you relaxed or sleepy (sedatives) or relieve pain (analgesics). These other medicines are given through a vein (intravenously, IV).
Regional anaesthesia is most often used when the procedure:
- Is confined to a specific region of the body.
- Involves a large area of the body where injection of large amounts of an anaesthetic might
cause side effects that affect the entire body. - Does not require general anaesthesia.
Local Anaesthesia
Local anaesthesia is used to numb the feelings in a specific part of the body. This prevents pain during surgical procedures. An anaesthetic drug is applied to the part of the body that is to undergo surgery.
It may be used with sedation, which calms the patient and reduces stress levels. Together, they enable the surgeon to carry out the procedure without pain or distress. Local anaesthesia only lasts a short time, so it is mainly used for minor outpatient procedures, where the patient can leave on the same day.
Local anaesthesia is used when:
- surgery is minor and does not require general or regional anaesthesia
- the procedure can be done quickly and the patient does not need to stay overnight
- the operation does not need the muscles to be relaxed or for the patient to be unconscious
E.g. include dental surgery, the removal of a verruca, a mole, or a cataract, and biopsies.
Types
The type and dose of anaesthesia will depend on many factors and is decided on by your Anaesthetist. These include the patients’ age, weight, any allergies, the part of the body to be operated on, and any current medical condition.
Various drugs are used to block the pain. They can be applied as an injection or through applying a spray or an ointment.
The drug works by acting on certain nerve pathways to prevent the nerves in the area of application from sending signals to the brain.
It normally takes a few minutes for the drug to take effect, and it wears off after a few hours. A stronger and higher dose will last for longer.
Lidocaine is now the most widely used local anaesthetic, but different drugs are used for different purposes.
For longer procedures, bupivacaine is more suitable, but it can be more painful when first administered. An anaesthetist may, therefore, use lidocaine first, then inject with bupivacaine later, if numbness is needed for a longer period.
Risks and complications
Local anaesthesia is generally considered very safe. For minor surgery, it is safer than general anaesthesia. There may be some tingling and pain when the drug is administered, and when it is wearing off, and there may be some bruising, but these are usually minor.
A person who has had a local anaesthetic should be careful not to injure themselves while they cannot feel pain, for example, by biting their cheek after dental treatment.
Monitored Anaesthesia
Monitored anaesthesia care (MAC) is a type of anaesthesia service in which an anaesthesia clinician continually monitors and supports the patient’s vital functions; diagnoses and treats clinical problems that occur; administers sedative, anxiolytic, or analgesic medications if needed; and converts to general anaesthesia if required. Approximately one-third of ambulatory anaesthesia services for diagnostic or therapeutic procedures are provided as MAC. often in out-of-operating-room locations for example in the MRI in a Dentist office, in Gastro Intestinal Unit for Colonoscopies or in the Cardiology Agiography suites.
