Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is induced for medical purposes. It may include analgesia (relief from or prevention of pain), paralysis (muscle relaxation), amnesia (loss of memory), or unconsciousness. A patient under the effects of anesthetic drugs is referred to as being anesthetized.
Anesthesia enables the painless performance of medical procedure that would otherwise cause severe or intolerable pain to an unanesthetized patient, or would otherwise be technically unfeasible. Three broad categories of anesthesia exist:
In preparing for a medical procedure, the clinician chooses one or more drugs to achieve the types and degree of anesthesia characteristics appropriate for the type of procedure and the particular patient. The types of drugs used include general anesthetics, local anesthetics, hypnotics, sedatives, neuromuscular-blocking drugs, narcotics, and analgesics.
The risks of complications during or after anesthesia are often difficult to separate from those of the procedure for which anesthesia is being administered, but in the main they are related to three factors: the health of the patient, the complexity (and stress) of the procedure itself, and the anaesthetic technique. Of these factors, the health of the patient has the greatest impact. Major perioperative risks can include death, heart attack, and pulmonary embolism whereas minor risks can include postoperative nausea and vomiting and hospital readmission. Some conditions, like local anesthetic toxicity, airway trauma or malignant hyperthermia, can be more directly attributed to specific anesthetic drugs and techniques.J
There are four types of anesthesia:
The type of anesthesia used during your surgery typically depends on the type of surgery, your state of health, the length of the surgery and the preferences of your anesthesia provider and surgeon.
There are multiple types of anesthesia. One type is general anesthesia, the strongest anesthesia, and the type most frequently used during surgery. This type of anesthesia makes the patient unresponsive in what is essentially a medically induced coma.
General anesthesia is a combination of medications that are intended to make the patient unaware of what is happening around them, to prevent pain, and to paralyze the body during a procedure. Typically used during surgery, general anesthesia allows a physician to provide treatments that would be extremely painful if the patient were awake and able to feel.
General anesthesia not only makes the person unaware, but it also paralyzes the muscles of the body including the muscles that make it possible to breathe. For this reason, patients who receive general anesthesia require a ventilator to do the work of the diaphragm and other muscles that help make it possible to inhale and exhale.
General anesthesia is typically used for more serious surgeries, lengthy procedures, and procedures that would typically be very painful. This type of anesthesia not only allows a patient to undergo a procedure without pain but also allows the patient to be unconscious for the procedure.
For some surgeries, it would be very traumatic to be awake for the procedure, whether or not you were able to feel pain. Imagine having a body part removed, such as during an appendectomy to remove the appendix, and being wide awake. While you might not feel any pain, it would still be extremely distressing to have be experiencing surgery while awake and alert.
The risks associated with anesthesia vary widely from procedure to procedure, and between different patients. As you can imagine, each patient has their own individual risk level, as no two people are exactly the same. For example, a 90-year-old patient will have a completely different level of risk when having appendix surgery than a 12-year-old patient.
Here are some of the possible risks:
Before you decide that you need general anesthesia for your procedure, it is important to know the different types of anesthesia that are available. The most common types of anesthesia, outside of general anesthesia, are the following:
The process of general anesthesia often starts with sedation, to make it possible to insert a breathing tube. The type of sedation is left to the anesthesia provider to choose and can vary widely depending upon the patient and the type of surgery.
Once the patient is in the operating room, attached to the monitoring devices, and the safety protocols have been completed, anesthesia can begin. It is common practice that before sedating medications are given, a "time out" is done to identify the patient and the procedure they are having. This is done to prevent surgery from happening at the wrong site or on the wrong patient.
Once the time out is completed the patient can be given medication to sedate them and the anesthesia provider starts the process of preparing the patient for the surgery.
The muscles of the body are paralyzed during general anesthesia, including the muscles that help the lungs draw breaths, which means the lungs are unable to function on their own. For this reason, it is essential that a ventilator is used to provide breaths to the lungs. To be clear, the lungs still work during anesthesia, they just lack the ability to draw a breath because the muscles that do that work are temporarily unable to work.
Being placed on a ventilator requires that a tube, called an endotracheal tube, be inserted into the airway. This tube is then attached to larger tubing that goes to the ventilator, allowing the ventilator to deliver oxygen to the patient. The process of inserting the tube is called intubation.
During surgery, the patient is monitored very closely by electronic monitoring devices that track heart rate, the amount of oxygen in the blood, the number of breaths the patient is taking, and even the patient’s EKG. In addition to electronic monitoring, the patient is also monitored by OR staff and the anesthesia provider.
General anesthesia is typically provided by either a physician anesthetist, called an anesthesiologist, or a CRNA, a certified registered nurse anesthetist. Both provide safe and effective anesthesia and have extensive experience in providing general anesthesia.
During the procedure, the goal is for the patient to be completely unaware of what is happening around them, including being without pain.
How an individual wakes from anesthesia depends on the type of surgery they had and how well they are breathing. The goal after general anesthesia is to extubate the patient—remove the breathing tube—as quickly as possible after surgery ends.
Common and uncomplicated procedures typically end with medication being given that reverses anesthesia, waking the patient and ending the paralysis of the muscles. These patients typically have the breathing tube removed promptly at the end of surgery and are breathing on their own within minutes of the surgery ending. These patients typically wake in the PACU—post-anesthesia care unit—and move to a hospital room or return home once they are completely awake.
For some very serious surgeries, such as open heart surgery or brain surgery, the patient is allowed to slowly wake from anesthesia and no reversal agent is given. This means the patient may remain on the ventilator for 6-8 hours after surgery and then having the breathing tube removed once they are awake.
Some patients will remain ventilator dependent for days or even longer after surgery, but this is less common. Patients who have respiratory diseases that make breathing more challenging are more likely to have difficulty with being removed from the ventilator, as do smokers and obese patients.
Once the patient is awake after surgery, they are often able to suck on ice chips or take sips of water. If this goes well, the next step is to drink regular liquids, followed by a regular diet. This process can take hours, or even days if the patient experiences nausea, vomiting, or just doesn’t feel up to taking food or fluids.
In most cases, the patient is able to eat regular foods within a day of having general anesthesia.
The American Association of Nurse Anesthetists (AANA) makes multiple recommendations for patient safety after receiving general anesthesia. This is because it can take a full day or longer to have anesthesia completely wear off, and until it does, the average patient may find themselves feeling sleepy, nauseated or even confused.
For the first day after surgery, expect to spend most of the time resting quietly, napping, or doing relaxing activities. Plan on taking the day after general anesthesia off from work and other challenging activities.
The AANA recommendations include not operating heavy machinery—including driving a car—or signing any legal paperwork for at least 24 hours after surgery. Arrange to have a driver to take you home from the surgery center, and avoid drinking alcohol or taking sedating medications not prescribed by your surgeon for the first day after surgery.
They also recommend that you find help with childcare if you have young children at home, as you will require more rest than usual for at least a day after surgery, possibly longer.
One benefit of a regional anesthetic is the patient can be consciously sedated or be fully conscious. A C-section is an example of a procedure performed with the patient awake, with regional anesthesia (epidural) used to control the pain of the surgery. The patient can feel things above the abdomen, and she is able to carry on a conversation and see her newborn immediately after birth.
Epidurals and other types of regional anesthesia are typically provided by an anesthesiologist or a nurse anesthetist (CRNA). Depending on the need, the anesthesia may be given with a needle or a needle may be used to insert a flexible catheter line through which anesthetics and other medications can be administered as needed. may be used to insert a flexible catheter line through which anesthetics and other medications can be administered throughout the procedure.
Regional anesthesia is provided by injecting specific sites with a numbing medication that works on the nerves of the body, causing numbness below the injection site. If you are having hand surgery, your anesthesia may numb your entire arm and hand, or the numbness may be mostly limited to your hand.
Epidurals or spinal blocks are given on your back. With an epidural, a flexible epidural catheter is placed in position with a needle and taped in place. Medications can then be administered as needed through the catheter to block pain. Spinal blocks are given with a needle to the spinal sac, with the medication entering the cerebrospinal fluid. It uses a finer needle than an epidural.
A peripheral nerve block may be given in the shoulder-arm, back, or leg regions. By choosing the site, different levels of the limb may be numbed. The anesthetic solution doesn't enter the nerve but is injected near it. A nerve stimulator or portable ultrasound device might be used to locate the nerve that is the target. Specific nerve blocks include the brachial plexus block, paravertebral block, femoral nerve block, sciatic nerve block, and popliteal nerve block.
Unlike general anesthesia where the entire body is paralyzed and the patient is unconscious, local anesthesia allows the patient to remain awake and alert during a procedure. It involves only a small area, whereas regional anesthesia is used for a whole arm or leg, for example.
This type of anesthesia is typically used for minor procedures that can be completed in a short time and the patient is expected to return home the same day. It also is used when the muscles don't need to be relaxed.
During the administration of local anesthesia, a numbing medication is either applied to the skin as a cream or spray or injected into the area where the procedure will be performed. If the medication is injected, this is sometimes done with several small injections. A few minutes after the injections have been given the area should be completely numb. If the area still has sensation, additional injections or applications may be given to ensure total numbness.
While the goal is to prevent pain, it is also true that the injection of local anesthetics is itself often quite painful. You should be prepared for this brief bit of pain in order to not have the pain of the rest of the procedure.
Local anesthesia is most commonly associated with minor procedures that may be painful but are not serious. Some examples of when local anesthesia is appropriate:
The drugs used as local anesthetics are related in structure to cocaine, which was historically used for this purpose. But they differ from cocaine in that they can't be abused for the same effects and they don't produce hypertension or vasoconstriction. These drugs act on the pain receptors, the nociceptors, decreasing the rates at which they can fire.
The drugs used as local anesthetics often end in -caine, such as benzocaine, lidocaine, and novocaine. There are also some naturally derived local anesthetics such as menthol that can be used to provide relief or prevent pain..
Which drug you may be given and how much depends on whether you have any allergies, the previous reactions you or your family members have had to anesthesia, other medications you are taking, the length of the procedure, plus your age, height, and weight. The administration of anesthesia requires many years of education to truly understand the needs of the patient and to anticipate the anesthesia each individual needs.
Local anesthetics are usually safe, but an individual can be unusually sensitive to the drug and have problems with a heartbeat, circulation, breathing, or brain function that require emergency care. This must always be available wherever they are used.
Monitored Anesthesia Care (MAC), also known as conscious sedation or twilight sleep, is a type of sedation that is administered through an IV to make a patient sleepy and calm during a procedure. The patient is typically awake, but groggy, and are able to follow instructions as needed.
This type of sedation is used for outpatient procedures, such as a colonoscopy, where the patient is expected to go home after the anesthesia has completely worn off.
The level of sedation provided with this type of anesthesia can range from light, where the patient just feels very relaxed, to heavier sedation where the patient is unaware of what is happening and only rouses to significant stimulation.
The patient may feel silly and a little sleepy, or under heavier doses may be mostly asleep. In general, with lighter sedation, the patient is able to speak, hear things around them, and answer questions and follow commands. They are aware of the procedure, but not in pain and typically don't feel anxiety about what is happening. With heavier sedation, the patient is breathing on their own but unaware of their surroundings and typically isn't "awake."
While the patient may be heavily sedated, this type of anesthesia is different from general anesthesia because the patient is not chemically paralyzed, nor do they require assistance with breathing. The vital signs are closely monitored to make sure they are stable throughout the procedure.
One medication commonly used for this type of sedation is Propofol, also known as Diprivan, which is given through an IV and looks remarkably similar to milk. This medication is given through an IV and wears off quickly (less than ten minutes for most people) so the patient is able to wake shortly after the procedure is completed.
Depending on the medications used and the doses given, the patient may or may not remember the procedure.
Because the level of sedation varies, the process is monitored, with an anesthesia professional present at all times to continuously monitor the patient's vital signs and maintain or adjust the level of sedation as needed. This usually means a blood pressure cuff and a monitor for oxygen levels are used, at the minimum. Typically, electrodes are placed on the chest to monitor the patient's heart rate and EKG throughout the procedure.
This type of sedation is frequently used with minor surgical procedures and dental procedures and can be combined with local or regional anesthesia to decrease pain. Procedures that look inside the body, such as bronchoscopy (the airways and lungs), colonoscopy (the colon), and esophagogastroduodenoscopy or EGD/Upper GI (the throat, esophagus, stomach and the first part of the small intestine), frequently use this type of anesthesia.
Patient having conscious sedation often have fewer side effects than those who have complete general anesthesia. The most common side effect is nausea, but some patients do experience both nausea and vomiting. If you have experienced nausea or vomiting after anesthesia in the past, be sure to tell your anesthesia provider so medication can be given to help prevent it from happening again.