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What is Anaesthesia ?



   Surgery without adequate pain control may seem cruel to the modern reader, yet this was the common practice throughout most of history. While anesthesia is considered a relatively new field, surgery predates recorded human history. Human skull trephinations occurred as early as 10,000 BC, with archaeological evidence of post-procedure bone infection and healing, proving these primitive surgeries were performed on living humans. Juice from coca leaves may have been dribbled onto the scalp wound but the recipient of these procedures was almost certainly awake while a hole was bored into his or her skull with a sharp flake of volcanic glass. This was a unique situation in anesthesia; there are no other instances in which both the operator and his patient share the effects of the same drug.



   In contemporary practice, we are prone to forget the realities of pre-anesthesia surgery. Fanny Burney, a well-known literary artist from the early nineteenth century, described a mastectomy she endured after receiving a “wine cordial” as her sole anesthetic. As seven male assistants held her down, the surgery commenced: “When the dreadful steel was plunged into the breast-cutting through veins-arteries-flesh-nerves-I needed no injunction not to restrain my cries. I began a scream that lasted unintermittently during the whole time of the incision—& I almost marvel that it rings not in my Ears still! So excruciating was the agony. Oh Heaven!—I then felt the knife racking against the breast bone-scraping it! This performed while I yet remained in utterly speechless torture.”1 Burney's description reminds us that it is difficult to overstate the impact of anesthesia on the human condition.


   An epitaph on a monument to William T. G. Morton, one of the founders of anesthesia, summarizes the contribution of anesthesia: “BEFORE WHOM in all time Surgery was Agony.”2 Although most human civilizations evolved some method for diminishing patient discomfort, anesthesia, in its modern and effective meaning, is a comparatively recent discovery with traceable origins in the mid-nineteenth century. How we have changed perspectives from one in which surgical pain was terrible and expected to one where patients may fairly presume they will be safe, pain free, and unaware during extensive operations is a fascinating story.


   Anaesthesia is a word derived from the Greek, meaning 'without sensation'. ‘An’-means absence and asthesia or esthesia means Anaesthesia may be applied to the whole body, when it is known as general anaesthesia, or to part of the body, when it is known as regional or local anaesthesia. All of these techniques involve giving specific drugs that interfere with the transmission of nervous impulses so as to reduce sensation.



   ‘Anaesthetic’ is the term applied to some or all of the drugs used to produce anaesthesia and is also used to describe the whole process. For example, one might say, ‘Peter had a general anaesthetic.’



   Anesthesia is used in a wide range of procedures, from highly invasive surgeries, such as open heart surgery, to more minor procedures, such as having a tooth extracted.



Anesthesiologists: Physicians Who Provide Anesthesia


   Anesthesia is given by a wide range of medical practitioners for many different reasons. The training and experience level of anesthesia providers varies greatly, ranging from a four-year residency in anesthesia to training classes added to a dental school program.


   An anesthesiologist is a physician who, after completing four years of medical school, completed a four-year residency in anesthesia to earn the credential MDA. In addition to residency, board-certified anesthesiologists have passed a grueling 3-part written test and a 2-part oral examination on the practice of anesthesiology. Anesthesiologists may elect to supervise the work of other types of anesthesia providers, including nurse anesthetists (CRNA) and anesthesiologist assistances (AA).Anesthesiologists primarily function in the operating room and post-anesthesia care unit, but some elect to practice in the area of chronic pain management.


Nurses may provide anesthesia



   A CRNA is a registered nurse who typically has a bachelor’s degree in nursing or a related field, and who obtains a master's degree in the administration of anesthesia. Most CRNAs have practiced in a critical care setting as a nurse for at least one year.

   In some states, nurse anesthetists work under the supervision of an anesthesiologist. In others, CRNAs practice independently. CRNAs are not permitted to supervise other anesthesia providers, such as anesthesia assistants.

   Currently, there are approximately 37,000 CRNAs that provide the majority of hands-on anesthesia care and practice in all 50 states.


Anesthesiologist Assistants: Professionals Who Provide Anesthesia


   An anesthesiologist’s assistant (AA) is a trained professional who has obtained a bachelor’s degree in a health or science field, then completed a master’s level program in the administration of anesthesia.

   Anesthesiologist assistants must be supervised by an anesthesiologist, and they may not practice independently.

There are currently less than 1,000 licensed AAs in the United States.

Dentists and Oral Surgeons: Providers of Anesthesia For Dental Procedures

   Dentists and oral surgeons can obtain education on the administration of anesthesia in addition to their general dental education. For very invasive dental procedures, such as the removal of wisdom teeth, sedation is recommended due to the painful nature of the surgery and the force that is required to remove teeth.

   While dental practitioners have less training in the administration of anesthesia than full-time providers, studies have shown that office-based dental anesthesia is as safe as traditional surgical anesthesia (1 death in 350,000 due to anesthesia administration).


The Types of Anesthesia


There are four types of anesthesia:

  • General Anesthesia
  • Regional Anesthesia
  • Local Anesthesia
  • Monitored Anesthesia Care (MAC)


General Anesthesia


   General anesthesia is a type of sedation that uses several medications to render the patient unconscious and unable to move. The medications are given both through an IV and mixed with oxygen and inhaled.

This combination of medications insures that the patient is unaware of any pain caused by surgery and also prevents the patient from moving during surgery, potentially causing a surgical error.


   The patient is unable to move after the medications are given so a breathing tube is placed into the patient's airway and connected to the ventilator to help the patient breathe.


   General anesthesia has somehow acquired very bad publicity in many modern Western countries. In my personal experience this may even be expressed in the rather extreme attitude; "It's OK to die as a result of the operation, but it's not OK to die as a result of the general anesthesia needed to make the operation possible!" A colleague of mine, Professor Anneke Meursing, also once expressed this attitude in a pithy little sentence; "The surgeon gets flowers, and the anesthesiologist gets sued."



Regional Anesthesia


   Regional Anesthesia is a method of pain prevention for surgeries and procedures. Instead of making the patient sleep through surgery, the area of the body that would feel pain is numbed, allowing the patient to have the procedure while awake.


   One benefit of a regional anesthetic is the patient can be 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.



Local Anesthesia


   Local anesthesia is a type of pain prevention used during minor procedures to numb a small site where pain is likely to occur without changing the patient's awareness.

   A numbing medication is either applied to or injected into the area, sometimes with several small injections, and after a few minutes the area should be completely numb. If the area still has sensation, additional injections or applications may be given to insure total numbness.


   Local anesthesia is most commonly associated with dental procedures, where the gum is numbed with an injection of medication, or minor medical procedures like stitches.


Monitored Anesthesia Care (MAC)


   Monitored Anesthesia Care (MAC) 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.

The level of sedation provided with this type of anesthesia can range from light, where the patient just feels very relaxed, to heavy, where the patient is unaware of what is happening and only rouses to significant stimulation.


   Because the level of sedation varies, the process is monitored, with a anesthesia professional present to continuously monitor the patient's vital signs and maintain or adjust the level of sedation as needed.This type of sedation is frequently used with minor surgical procedures and dental procedures and can be combined with local or regional anesthesia.


   Depending on the medications used as the doses given, the patient may or may not remember the procedure.



Questions to Ask Before Having Anesthesia


   Before you have anesthesia, it is important that any questions you may have are answered clearly. This helps prevent any surprises before your surgery, one of the last times when you want to receive new information.


   Your opportunity to ask questions usually happens during the pre-anesthesia interview, a time where the anesthesia provider asks you questions about your medical history, medications and any other pertinent information. This interview is not just for the provider to ask questions: Use this time ask any questions that you have during this phase of planning.


Questions To Ask Your Anesthesia Provider

  1. Who will be providing my anesthesia?
  2. If there is an emergency situation during my procedure, will I need to be transported to another facility for care?
  3. Will I be awake immediately after surgery or will I wake slowly?
  4. What type of monitoring will be done during my surgery?
  5. What type of anesthesia will be used and will I be awake?
  6. For childbirth: What are my anesthesia options for delivery?
  7. Will the anesthesia provider be with me during the entire procedure?
  8. What medications should I take before surgery and which ones should I not take?
  9. What is my personal risk of anesthesia complications?
  10. When should I quit eating and drinking before surgery?


10 Things To Tell Your Anesthesiologist

   It is important that your anesthesiologist has a complete understanding of your current health when you have surgery and anesthesia. Before you have a scheduled proceedure, you will have an interview with your anesthesiologist to discuss your health and any concerns you may have. These are some important points that you should cover during that interview.


  1. When you last ate and drank
  2. The medication you are taking, the dosage and the last time you took the medication. This includes prescription and over-the-counter medications, natural and herbal medications and supplements.
  3. If you are pregnant or think you may be pregnant
  4. If you have had a previous problem with anesthesia
  5. If your family has a history of malignant hyperthermia
  6. If you have ever had an episode of anesthesia awareness
  7. Any medical problems you have, including diabetes, heart disease, lung disease or any other major illness
  8. If you have a fever
  9. If you have a cold
  10. If you have an infection

Understanding the Risks of Anesthesia

All Types of Anesthesia Have Risks:

   In addition to the general risks of surgery, anesthesia given during surgery to help sedate you and control pain poses its own risks. While anesthesia is considered safe for both adults and children, no anesthesia is risk-free, just as no surgery is risk-free.

   The level of risk varies with your procedure, the age and health and the type of anesthesia. Your surgeon or anesthesia provider should give you an accurate assessment of your personal risk.

Why Can't I Eat or Drink Before Surgery:

   Aspiration happens when vomit is produced during surgery and is then inhaled into the lungs. Normally, you cough when a foreign object enters your airway, but the medications given during anesthesia can prevent coughing. Aspiration can cause lung infections, a blockage in the airway or a severe cough.

   Patients are asked to refrain from eating or drinking in the 12 hours prior to surgery to prevent aspiration.

Heart Problems and Anesthesia:

   Over 25% of the patients who undergo surgery each year have heart disease, including coronary artery disease, high blood pressure or congestive heart failure. Heart problems, commonly referred to as cardiac disease, does not prevent surgery in most cases, but can increase the risk of surgery.

   The type and severity of your heart disease is the primary indicator of the likelihood that surgery will trigger heart problems in the days after surgery. For example, if you have been diagnosed with atrial fibrillation and take medication for it, you would be much more likely to have problems with atrial fibrillation after surgery than a patient who has no history of heart disease.

   Problems that are the most likely to occur during and after surgery include high or low blood pressure, altered heart rhythms and in much rarer cases, heart attack.


Malignant Hyperthermia (MH):

   Malignant hyperthermia is a rare inherited disorder in which a patient has a severe, life-threatening reaction when anesthesia gases are inhaled or a muscle relaxant called succinylcholine is given. When a patient who has the malignant hyperthermia gene has a reaction, his temperature rises rapidly, his muscles become rigid and the body begins to break down muscle fibers. The condition is serious and can result in the death of healthy patients if doctors cannot halt or control the symptoms with medication.

Testing is available for malignant hyperthermia and is recommended prior to surgery if close relatives have been diagnosed with the disorder. A muscle biopsy, a procedure where a small piece of muscle is removed by inserting a needle into a muscle, must be taken and analyzed to determine if a patient is a carrier

Severe Headache:

Approximately 1% to 2% of patients who have had a spinal epidural, a type of regional anesthesia, suffer a severe headache after the medication is given. An epidural is given by injecting a numbing medication into the cerebral spinal fluid that surrounds the spine. If the spinal fluid leaks from the injection site, the decrease in spinal fluid causes a severe headache.

The headache is treated with pain medication or a “blood patch.” For a blood patch, a small amount of the patient's own blood is injected a closely as possible to the original epidural site where it can clot and stop the loss of cerebral spinal fluid.

Nausea and Vomiting:

Nausea and vomiting are the most common side effects of anesthesia, but both are far better controlled after surgery than they were in the past. IV medications can now be given at the first hint of nausea to control the symptoms and prevent vomiting, which can cause significant stress on surgical incisions.

Some anesthesia providers actually provide anti-nausea medications at the end of surgery to help prevent nausea during the early part of recovery from anesthesia.

Risk of Nerve Damage During Surgery:

Nerve damage can results from general anesthesia, local anesthesia and regional anesthesia. While the cause of damage varies, it can range in severity from mildly annoying to disabling. In most cases, the damage is temporary and the discomfort or numbness decreases in the weeks following surgery. But a small percentage of patient have lasting nerve problems. During local or regional anesthesia, damage can occur when medications are injected into a nerve and either the syringe or the medication used for the injection injures the nerve tissue. Damage can also occur during a spinal epidural, one type of regional anesthesia, if the spinal cord is injured by the injection of anesthetics.


Nerve damage can also result during general anesthesia, if the patient is placed in a position that when medication if the patient is lying in a position for extended periods of time that block blood flow to the nerves. An example of this type of damage is the “pins and needles” sensation when a leg is “asleep.” A person that is awake can stand up or move to relieve the problem, but a patient who is under anesthesia does not know there is a problem and cannot move.

Sore Throat:

Many patients complain of a sore throat for a few days after having surgery with general anesthesia. The soreness is caused by the insertion of the endotracheal tube through the mouth into the airway. The tube is necessary for the the patient to breathe during surgery. The pain is usually minor and is treated like a typical sore throat.

In rare cases, the vocal cords can be damaged when the breathing tube is inserted, or when the tube must remain in place for an extended period of time.

Anesthesia Awareness:

Anesthesia awareness happens when the medications provided to render the patient unconscious during general anesthesia are not effective but the agents used to paralyze the patient are. This means that the patient is unable to move or speak, but is wide awake, hearing and feeling the entire procedure.

   Awareness during a surgical procedure is a rare, but it remains a concern for many patients who are anticipating having surgery with general anesthesia.

   If you are concerned about anesthesia awareness or have experienced it in the past, be sure to inform your anesthesia provider. Doctors can address your concerns and your specific situation to make sure your anesthesia is adequate for your surgery.

The Inability to Urinate After Surgery:

   The medications that are used to paralyze the muscles of the body during general anesthesia work on many areas of the body. In some patients, the muscles of the bladder become paralyzed, and the patient is unable to urinate. The ability to urinate typically returns within 24 hours, but during that time the bladder can become uncomfortably full, making a urinary catheter necessary.


Anesthetic equipment

   In modern anesthesia, a wide variety of medical equipment is desirable depending on the necessity for portable field use, surgical operations or intensive care support. Anesthesia practitioners must possess a comprehensive and intricate knowledge of the production and use of various medical gases, anaesthetic agents and vapours, medical breathing circuits and the variety of anaesthetic machines (including vaporizers, ventilators and pressure gauges) and their corresponding safety features, hazards and limitations of each piece of equipment, for the safe, clinical competence and practical application for day to day practice.


Anesthetic monitoring


   Patients being treated under general anesthetics must be monitored continuously to ensure the patient's safety. In the UK the Association of Anaesthetists (AAGBI) have set minimum monitoring guidelines for General and Regional Anaesthesia. For minor surgery, this generally includes monitoring of heart rate (via ECG or pulse oximetry), oxygen saturation (via pulse oximetry), non-invasive blood pressure, inspired and expired gases (for oxygen, carbon dioxide, nitrous oxide, and volatile agents). For moderate to major surgery, monitoring may also include temperature, urine output, invasive blood measurements (arterial blood pressure, central venous pressure), pulmonary artery pressure and pulmonary artery occlusion pressure, cerebral activity (via EEG analysis), neuromuscular function (via peripheral nerve stimulation monitoring), and cardiac output. In addition, the operating room's environment must be monitored for temperature and humidity and for buildup of exhaled inhalational anesthetics which might impair the health of operating room personnel.




Anesthesia and surgery - a blind spot

   There is a curious blind spot in the perception of many people. Many people seem to just look at anesthesia alone, seemingly forgetting that anesthesia is necessary to make the operation possible. People never undergo anesthesia without undergoing an operation. So when we talk about the risk of anesthesia, we are not talking about the risk of anesthesia alone, but the risk of anesthesia plus the risk of undergoing an operation. The discussion above clearly shows that the risk of dying due to an operation is generally very much higher than the risk of dying due to anesthesia. Moreover, the risk of dying due to undergoing an operation under anesthesia differs for different types of operation, and is also influenced by the health of the person undergoing the operation. In general, the larger the operation, the greater the risk of dying, and the unhealthier the person undergoing the operation, the greater the risk of dying. The health of a person undergoing an operation is usually expressed in terms of the ASA-score (American Society of Anesthesiologists score) (Keats 1978).

  • ASA-1: A completely healthy patient.
  • ASA-2: A patient with mild systemic disease.
  • ASA-3: A patient with severe systemic disease that is not incapacitating.
  • ASA-4: A patient with incapacitating disease that is a constant threat to life.
  • ASA-5: A moribund patient who is not expected to live 24 hours with or without surgery.
  • E: Emergency case suffix. (always a higher risk category)

   This is a simple scoring system, which is why there is some variation in how different anesthesiologists score the same patient (Owens 1978). In general, the higher the score, the greater the chance of dying as a result of anesthesia and surgery. This is clearly shown in the table below. The reader should realize that these figures are statistics for large numbers of patients who underwent all manner of operations ranging from trivial to major. Accordingly, they should not in any way be misconstrued as applying to any specific individual, or to any specific combination of anesthesia and surgery. What these figures do show, is that unhealthy individuals are more likely to die as a result of anesthesia and surgery than healthy individuals.


Mortality (%)
All ages

Mortality (%)
Ages ≥ 70 yrs
















Scope of Anesthesia as profession


   The practice of anesthesia is no longer limited to the operating room nor even confined to rendering patients insensible to pain Anesthesiologists are now routinely asked to monitor, sedate, and provide general or regional anesthesia outside the operating room—for lithotripsy, magnetic resonance imaging, computed tomography, fluoroscopy, endoscopy, electroconvulsive therapy, and cardiac catheterization. Anesthesiologists have traditionally been pioneers in cardiopulmonary resuscitation and continue to be integral members of resuscitation teams. An increasing number of practitioners have sub-specialized in cardiac anesthesia, critical care, neuroanesthesia obstetric anesthesia, pediatric anesthesia, and pain medicine .Certification requirements for special competence in critical care and pain medicine already exist in the United States. Anesthesiologists are actively involved in the administration and medical direction of many operating rooms, intensive care units, and respiratory therapy departments. They have also assumed administrative and leadership positions on the medical staffs of many hospitals and ambulatory care facilities.



Is anesthesia safe?


How Safe is "Safe"?

   Safety, of course, is relative. We all participate in activities that are not 100% safe. For example, we know that we face risks when we travel by air. Society's concerns about safety in aviation can be judged by a recent cover story in Newsweek (April 24, 1995). The magazine introduced the story with a stirring: "How safe is this flight? Hundreds of Americans died in plane crashes in 1994, sounding a wake-up call for an industry lulled into complacency."

  • How terribly unsafe is it to fly? Newsweek says that in the past decade with U.S. carriers the "death risk" (the probability that someone who randomly flew on one of the flights would be killed en route) ranged from zero deaths in 10 years of airline operation to 1 in 1 million flights.

Relative Risk of Anesthesia Compared to Air Travel

   Clearly, we cannot point to a record of no anesthesia related death in the last decade. Even a death rate of 1 in 1 million anesthetics would be far better than we can boast. The death risk is sometimes calculated as the deaths attributable to accidents in 100 million hours of exposure. Assuming a death risk of 1 in 10 million for commercial aviation and assuming an average of 2 hours per domestic flight, the death risk would be about 5 per 100 million hours of exposure. If we assume a preventable anesthetic mortality of 1 in 100,000 and assuming the average anesthetic to last about 2 hours, the anesthesia death risk would be 500 per 100 million hours of exposure. Feel free to play with the data. If you think the average anesthetic lasts longer or shorter, or if you believe anesthetic mortality to be higher or lower than these data used here just plug them into the formula. You won't be able to get away from the fact that anesthesia is far less safe than flying as a passenger with one of the big commercial airline companies.

   Of course, flying and undergoing anesthesia have nothing in common except that both are not entirely safe, that in both examples the victim does not contribute to a disaster, and that in both examples the passenger or patient has every right to expect that he or she will not be harmed by the trip - be it a flight or anesthetic. One might, therefore, reasonably ask, "What anesthetic death risk is acceptable?" And if the death risk in anesthesia is deemed to be unacceptable, what is society willing to invest in improving safety in anesthesia? Or, in other words, how much (in money and resources) should we commit to saving a life?

Article By: Dr. Md. Rajib Pervez

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