ANESTHESIA FACTS FOR LAYPEOPLE: TYPES OF ANESTHESIA

the anesthesia consultant

Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group
Richard Novak, MD is a Stanford physician board-certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.
email rjnov@yahoo.com
phone 650-465-5997

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There are several types of anesthesia:

GENERAL ANESTHESIA

A general anesthetic renders the patient asleep and insensitive to pain for surgery. Prior to beginning anesthesia, the anesthesiologist places monitors of blood pressure, electrocardiogram, pulse and oxygen saturation of the blood. Before the anesthetic, oxygen is administered by mask to fill the patient’s lungs with 100% oxygen. Most adult patients are given general anesthesia by intravenous injection, usually of the medication propofol. This injection causes the patient to lose consciousness within 10 – 20 seconds. This is called the induction of anesthesia. The maintenance of anesthesia during surgery is done by mixing an anesthesia gas or gases with the oxygen. Typical inhaled anesthesia gases are nitrous oxide, sevoflurane, or isoflurane. Sometimes a continuous infusion of intravenous anesthetic such as propofol is given as well. The choice and dose of drugs is done by the anesthesia attending, based on the patient’s size, age, the type of surgery, and the anesthesiologist’s experience.

Many patients are given prophylactic anti-nausea medication during the anesthetic. If postoperative pain is anticipated, the anesthesiologist can also administer intravenous narcotics such a morphine, meperidine (Demerol), or fentanyl.

Depending on the patient’s medical condition and type of surgery, the anesthesiologist may protect the patient’s airway during the general anesthetic by placing a breathing tube through the mouth, either an endotracheal tube (ET Tube) into the patient’s windpipe, or a laryngeal mask airway (LMA) just above the voice box.

At the conclusion of surgery, the general anesthetic gases and/or intravenous anesthetic infusion(s) are discontinued. The patient usually regains consciousness within 5 – 15 minutes. The patient is then transferred to the recovery room.

SPINAL ANESTHESIA

Spinal anesthesia is done by the injection of local anesthetic solution into the low back into the subarachnoid space. Prior to beginning anesthesia, the anesthesiologist places monitors of blood pressure, electrocardiogram, pulse and oxygen saturation of the blood. The word subarachnoid translates to “below the arachnoid”. The arachnoid is one of the layers of the meninges covering the nerves of the spinal column. In the subarachnoid space lies the cerebral spinal fluid (CSF) which surrounds the spinal cord and brain. In a spinal anesthetic, the subarachnoid space is located with a needle by the anesthesiologist, and the appropriate anesthetic medications are injected.

Local anesthetics, such as lidocaine or bupivicaine (brand name Marcaine), given into the subarachnoid space, bring on sensory and motor numbness. The anesthesiologist chooses the dose and type of drug depending on the patient’s age, size, height, medical condition, and the type of surgery.

Following the onset of numbness from spinal anesthesia, the patient may either stay awake for surgery, or more often intravenous anesthesia is given to achieve a light sleep. Sometimes light general anesthesia is given to supplement spinal anesthesia.

EPIDURAL ANESTHESIA

Epidural anesthesia is done by the injection of local anesthetic solution, with or without a narcotic medication, into the low back into the epidural space. Prior to beginning anesthesia, the anesthesiologist places monitors of blood pressure, electrocardiogram, pulse and oxygen saturation of the blood. The word epidural translates to “outside the dura”. The dura is the outermost lining of the meninges covering the nerves of the spinal column. The epidural space is located with a needle by the anesthesiologist, and the appropriate anesthetic medications are injected.   Often, a tiny catheter is left in the epidural space, taped to the patient’s low back, to allow repeated doses of the medication to be given.  The catheter is removed at the end of surgery, or sometimes days later if continued epidural medications are administered for postoperative pain control.

Local anesthetics, such as lidocaine or bupivicaine (brand name Marcaine), given into the epidural space, bring on sensory and motor numbness. The anesthesiologist chooses the dose and type of drug depending on the patient’s age, size, height, medical condition, and the type of surgery.

Following the onset of numbness from epidural anesthesia, the patient may either stay awake for surgery, or more often intravenous sedation is given to achieve a light sleep. Sometimes light general anesthesia is given to supplement epidural anesthesia.

REGIONAL ANESTHESIA

Regional anesthesia is the injection of local anesthetic (either lidocaine or Marcaine) near a nerve to block that nerve’s function.  Examples of regional anesthesia include arm blocks (axillary block, interscalene block, subclavicular block), and leg blocks (femoral block, sciatic block, popliteal block, ankle block).  An advantage of regional anesthesia blocks is that the patient may remain awake for the surgery.  If desired, the anesthesia provider may administer intravenous sedation or general anesthesia in addition to the regional anesthetic, to allow the patient to sleep during the surgery–the advantage of this combined anesthetic technique is the regional anesthetic blocks all surgical pain and less sleep drugs are required.

INTRAVENOUS ANESTHESIA

Some minor surgical procedures (for example: breast biopsies, eyelid surgery, some hernia surgeries) can be done with the combination of local anesthesia plus intravenous anesthesia sedation. Prior to beginning anesthesia, the anesthesiologist places monitors of blood pressure, electrocardiogram, pulse and oxygen saturation of the blood. The anesthesiologist is present for the entire surgery, and administers intravenous sedatives as required for the patient’s comfort and the surgeon’s needs.  If the sedation is deep enough, the intravenous sedation will be termed general anesthesia. While the patient is sedated, the surgeon usually injects local anesthetics into the surgical site to block both surgical and post operative pain.

Vigilance by an anesthesiologist during intravenous sedation is also known as Monitored Anesthesia Care, or MAC.

PEDIATRIC ANESTHESIA

Because the separation of a young child from his or her parents can be one of the most distressing aspects of the perioperative experience, many children benefit significantly from oral preoperative sedation with midazolam. This relatively pleasant-tasting liquid is given by mouth about twenty minutes prior to the start of the anesthetic. Although the midazolam rarely causes children to fall asleep, it does reduce anxiety dramatically, allowing for a much smoother separation from parents. It also tends to cause a wonderful short term amnesia, so that the children often have no recollection of separating from their parents, or even of going to the operating room.
Although the initial anesthetic is usually administered via an intravenous infusion in adult patients, this approach requires starting an IV while the patient is still awake. This technique would be quite unpopular with younger children.  Most young children prefer to go to sleep breathing a gas, a technique known as an inhalation induction. This technique is used for almost all routine surgeries, but cannot safely be employed in certain rare situations, such as emergencies.

An inhalation induction consists of the child breathing a relatively pleasant smelling anesthetic vapor – usually sevoflurane – via a facemask for approximately 30 to 60 seconds. The child loses consciousness while breathing the gas, and the IV can then be started painlessly. Generally, the child continues to breath the gas throughout the duration of the surgery, either via the facemask or an endotracheal tube, depending on the duration and type of surgery. It is this breathing of the gas which keeps the child anesthetized. At the end of the surgery, the gas is discontinued, and the child begins to awaken.

Prior to awakening, children may be given either analgesics (pain medicines) or anti-emetics (drugs which reduce the likelihood of nausea and vomiting). The type of surgery will determine which of the many possible medications will be used for these purposes. The purpose of these medications is to make the child’s awakening as calm and pleasant as possible. Equally important in this regard is reuniting the child with his or her parents as quickly as possible.
Despite best attempts, it is important for parents to realize that children, especially those less than five years of age, often are somewhat cranky and irritable following anesthesia and surgery. We do our best to minimize this, but we cannot prevent it in all cases. Similarly, some children will experience postoperative nausea and vomiting despite receiving medications which are intended to prevent it.

 

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