Basics of Anaesthesia

INTRODUCTION
Many patients, and even some physicians, automatically assume that surgery requires general anaesthesia, and that the patient should be asleep during surgery. This is not true. Many procedures can be performed on awake patients, using local or regional anaesthesia. This not only avoids the risks and unpleasantness sometimes associated with general anaesthesia, but may also provide specific benefits such as reduced blood loss and better postoperative analgesia.
Patients are often concerned about having surgery under a local or regional anaesthetic. These concerns are not usually justified by the facts. The more patients understand the reasons for, and the benefits of, local or regional anaesthesia, the more likely they are to choose this type of anaesthetic. Unfortunately, in these days of cost-cutting and same day surgery, patients may never get the opportunity to discuss their anaesthetic options with an anaesthetist in detail prior to surgery. In the rush to get through a busy operating list the anaesthetist may, unfortunately, decide that it is quicker and simpler just to put the patient to sleep, rather than enter into the discussion and education necessary to allow the patient to make an informed choice about the most appropriate type of anaesthesia.
Patients are becoming more involved as consumers of health care. They are actively seeking out information about treatment choices, and some are turning to the Internet as a source of medical information. This site is dedicated to patients who want to learn more about local and regional anaesthesia. However, they must understand that this article provides background information only. The final decision about the best type of anaesthetic depends on the specific operation, patient, surgeon, and anaesthetist involved.
If you are faced with the possibility of needing surgery in the future, chances are you will need some type of anaesthesia to go along with it. There are many different types of anaesthesia. Which one you will need depends on a variety of factors such as the type of surgery you are having and your state of health. Some surgical procedures require only an injection of local anaesthesia into the incision area. Other procedures cannot be performed unless you are completely anesthetized -- unconscious and unaware of pain.

The Basics
Anaesthesia is divided into four basic categories:
· general anaesthesia
· regional anaesthesia
· local anaesthesia
· sedation
Each type of anaesthesia has an effect on a part of the nervous system, which results in a depression or numbing of nerve pathways. General anaesthesia affects the brain cells, which causes you to lose consciousness. Regional anaesthesia has an effect on a large bundle of nerves to a particular area of the body, which results in losing sensation to that area without affecting your level of consciousness. Local anaesthesia causes you to lose sensation in a very specific area.
Some of the drugs that produce general anaesthesia in large doses can be used to produce sedation, or "twilight sleep" in lower doses. Sedation can be given in many ways. A common example of an anesthetic gas that is used for sedation is nitrous oxide or laughing gas.
If you are scheduled to have surgery, you may be told not to eat anything for eight hours. It is very important that you follow whatever instructions you are given for not eating or drinking anything prior to surgery. Why? Because when you are given anaesthesia, you lose the ability to protect your lungs from inhaling something you're not supposed to inhale. When you are awake, you can usually swallow saliva and food without choking because part of the swallowing mechanism involves a reflex that results in covering the opening into the lungs. When you are anesthetized, you lose that reflex. So, if you have any solids or liquids in your stomach, they could come up into your mouth and be inhaled into your lungs. The result could be very serious lung damage.
Sleep is a state of reduced consciousness, depressed metabolism, and little activity of the skeletal muscles. Strong stimuli such as loud noise, bright light or shaking can arouse the sleeper. Consciousness is being clearly aware of yourself and your environment.
Unconsciousness is when you are completely or partially unaware of yourself and your environment, or you don't respond to sensory stimuli.
Conscious sedation is caused when an anesthesiologist administers depressant drugs and/or analgesics in addition to anaesthesia during surgery. Consciousness is depressed and you may fall asleep, but are not unconscious.

General Anaesthesia
General anesthetics produce an unconscious state. In this state a person is:
· unaware of what is happening
· pain-free
· immobile
· free from any memory of the period of time during which he or she is anesthetized
It is not completely clear exactly how general anesthetics work at a cellular level, but it is speculated that general anesthetics affect the spinal cord (resulting in immobility), the brain-stem reticular activating system (resulting in unconsciousness) and the cerebral cortex (seen as changes in electrical activity on an electroencephalogram).

General anaesthesia can be administered as an inhaled gas or as an injected liquid. There are several drugs and gases that can be combined or used alone to produce general anaesthesia. The potency of a given anesthetic is measured as minimum alveolar concentration (MAC). This term describes the potency of anesthetic gases. (Aveolar is the area in the lung where gases enter and exit the bloodstream via the capillary system). Technically, MAC is the alveolar partial pressure of a gas at which 50 percent of humans will not move to a painful stimulus (e.g. skin incision). Injected liquid anesthetics have a "MAC equivalent" which is the blood concentration of the liquid anesthetic that provides the same effect. Using MAC as a guideline, the amount of anesthetic given to a patient depends on that particular patient's needs.
When anesthetics reach the bloodstream, the drugs that affect the brain pass through other blood vessels and organs so they are often affected too. Therefore, patients must be carefully monitored. The anesthesiologist continuously monitors the patient's heart rate, heart rhythm, blood pressure, respiratory rate, and oxygen saturation. Some patients may have even more extensive monitoring depending on their health and which type of procedure or surgery they are having.

Most adults are first anesthetized with liquid intravenous anesthetics followed by anesthetic gases after they are asleep. Children, however, may not like having an injection or intravenous catheter placed in them while they are awake. Therefore, they often breathe themselves to sleep with anesthetic gases given through a mask.
What is local or regional anaesthesia?
Anaesthesia means the absence of sensation. Regional anaesthesia means blocking the nerve supply to part of the body, such as an arm, so the patient cannot feel pain in that area. Local anaesthesia, strictly speaking, means putting local anaesthetic ("freezing") around the affected area to make it pain free. However, many people use the phrase loosely to include regional anaesthesia.
Local Anaesthesia
Local anaesthesia involves numbing a small area by injecting a local anesthetic under the skin just where an incision is to be made. When used alone, this type of anaesthesia has the least number of risks. Local anesthetics are thought to block nerve impulses by decreasing the permeability of nerve membranes to sodium ions. There are many different local anesthetics that differ in absorption, toxicity, and duration of action.
One of the most commonly used local anesthetics is lidocaine (Xylocaine). Lidocaine can be administered as an injection or placed topically on mucous membranes. Another topical anesthetic is cocaine. Cocaine is primarily used to anesthetize the nasal passages for surgical procedures. A topical anesthetic that is gaining popularity for anesthetizing the skin prior to painful procedures, such as injections, is known as eutectic mixture of local anesthetics (EMLA) cream which contains lidocaine and prilocaine. This white cream is placed on the skin and then covered with an occlusive dressing for approximately one hour to obtain a good numbing effect. In addition, EMLA can be used to numb the skin prior to giving injections or pulling superficial splinters.

Regional Anaesthesia
Regional anaesthesia is so named because a "region" of the body is anesthetized without making the person unconscious. One example of this is spinal anaesthesia, which is often used on women during childbirth. A local anesthetic is injected into the spinal fluid and causes a loss of sensation of the lower body. Spinal anaesthesia can be used for surgery on the legs or lower abdomen (below the bellybutton).
Epidural anaesthesia is similar to spinal anaesthesia in that a patient loses sensation in the legs and lower abdomen, but instead of injecting the local anesthetic into the spinal fluid, the anesthetic is injected into a space outside the spinal canal called the epidural space. A small tube or catheter can be placed into this space and a local anesthetic can be infused (fed) through the tube for hours, days, or even weeks. This type of anaesthesia can be used for surgery with larger doses of anesthetic, or for chronic pain relief with lower doses of anesthetic. Regional anaesthesia techniques can be used to block very specific areas such as one foot, one leg, one arm, or one side of the neck. In these cases, a smaller group of nerves is blocked by injection of the local anesthetic into a specific area. For spinals and epidurals, narcotic painkillers such as morphine and fentanyl can be used in addition to a local anesthetic.

Sedation
Some of the drugs that produce general anaesthesia in large doses can be used to produce sedation or "twilight sleep" in lower doses. Sedation can be given in many ways. A common example of an anesthetic gas that is used for sedation is nitrous oxide or laughing gas. Liquid sedating drugs are usually given by injection but some can also be given by mouth. Ketamine and Versed are examples of sedating drugs that can be given by injection or by mouth. The oral route is particularly useful for sedating children who do not like injections.
Children who refuse to drink medications may also receive sedation through the rectum via a small, lubricated tube or via the nasal route by spraying it into the nose. Regional and local anaesthesia can be combined with sedation to make patients more comfortable during a procedure in which general anaesthesia is not necessary, or when general anaesthesia may be too large a risk for the patient.

How is it used?
Local or regional anaesthesia can often be used to prevent pain during surgery. Sometimes it is used by itself, with no other medications, so that the patient remains wide awake during surgery. It can also be combined with sedative drugs to make the patient relaxed or sleepy during surgery.
Sometimes local or regional anaesthesia is used in addition to a general anaesthetic (i.e., in patients who are asleep during surgery). This is done to reduce the stress associated with surgery, to allow a lighter level of anaesthetic during surgery, and to provide pain relief after surgery.
Inhaled Anesthetics
Many adults may remember having ether for their anesthetic when they were young. Ether is an inflammable anesthetic that is no longer used in the United States. Today, the commonly used inhaled anesthetics are nitrous oxide (also known as laughing gas), sevoflurane, desflurane, isoflurane and halothane.
Why do we have so many different kinds of gases? Because each gas has its own special properties. For example, sevoflurane and halothane are easy to inhale while desflurane is very irritating to inhale and has a shorter duration of action. If you need to breathe yourself to sleep, halothane or sevoflurane would be easiest to inhale. If a very short-acting anesthetic is needed, the anesthesiologist can switch to desflurane after you fall asleep. Nitrous oxide is easy to inhale, but when used alone is not potent enough to be a complete general anesthetic. However, it can be used alone for sedation, or combined with one of the other inhaled anesthetics or injected liquid anesthetics for general anaesthesia.
These gases have different effects on other organs as well. For example, halothane may cause the heart rate to slow down and the blood pressure to decrease while desflurane may cause the heart rate to speed up and the blood pressure to increase. How do these inhaled anesthetics reach the brain? When an anesthetic gas is inhaled into the lungs, the blood that travels through the lungs carries the anesthetic gas to central nervous system cells. The rate at which the bloodstream takes up the anesthetic is dependent on many factors including the concentration of the inspired gas, the rate of flow of the gas from the anaesthesia machine, the solubility of the gas in blood, the rate and depth of breathing, and the amount of blood the heart pumps each minute in the person breathing the gas.
An important property of anesthetics is reversibility. When the surgery is over, the anesthesiologist wants to shut off the anesthetic and have the patient wake up from the anesthetic-induced sleep. Once the anesthetic gas is turned off, the blood stream brings the gas back to the lungs where it is eliminated. The more soluble the gas is in blood, the longer it takes to eliminate. Nitrous oxide and desflurane are the shortest-acting anesthetic gases because they are the least soluble in blood.

Injected Anesthetics
A liquid anesthetic drug is delivered to the brain by injecting it directly into the bloodstream, usually through an intravenous catheter. Examples of injected drugs are barbiturates, propofol, ketamine, and etomidate, as well as larger doses of narcotics (such as morphine) and benzodiazepines (Valium-like drugs). These drugs quickly reach the brain and their effect is dependent on several factors including the volume in which the drug is distributed in the body, the fat-solubility of the drug, and how quickly the body eliminates the drug.
A commonly used injected barbiturate anesthetic is sodium thiopental, also known as Pentothal. This drug is fat-soluble and acts very quickly. If you receive sodium thiopental and then you are asked to count backward from 100 after the drug is injected, you probably won't remember counting past 95. Some injected anesthetics are used in low doses for sedation. A small dose of a narcotic or a benzodiazepine like Valium or Versed can significantly decrease anxiety. These drugs are used in these doses either as a premedication prior to general anaesthesia or as "twilight sleep" or sedation when used in conjunction with local or regional anaesthesia.

DISCLAIMER: This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Health Mirror, the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.
In case of any queries please feel free to contact Dr Anil K Dhull

Alzheimer's Disease

Introduction
Alzheimer's disease (AD) is a degenerative disease of the brain from which there is no recovery. The disease slowly attacks nerve cells in all parts of the cortex of the brain and some surrounding structures, thereby impairing a person's abilities to govern emotions, recognize errors and patterns, coordinate movement, and remember. Ultimately, a person with AD loses all memory and mental functioning.

The major areas of the brain have one or more specific functions.
Alzheimer's disease is a disorder in which there is a steady deterioration of brain function, resulting in progressive loss of memory, recognition, personality, and mental powers. Although Alzheimer's disease may begin as early as age 40, it is most prevalent in the elderly. It accounts for about half of all serious mental impairment in persons over age 65.Changes in the BrainIn Alzheimer's disease, as in any senile mental disorder, there is atrophy (shrinkage or wasting) of the cerebral cortex (the outer layer of the brain, which is mostly concerned with intellectual and social functioning). There are also more specific abnormalities, such as the presence of tangles of fibers within the nerve cells and of senile plaques, which are probably deposits of amyloid (a semisolid protein complex seen in many degenerative diseases). These abnormalities are scattered through-out the cortex of a person with Alzheimer's disease; they distinguish the disease from other forms of senility. Because brain biopsy specimens (tissue samples taken from the brain for laboratory examination) are not obtained without very specific reasons and without intention of specific treatment, these abnormalities are usually discovered only after death.CausesTheories abound as to the possible causes of Alzheimer's disease. So-called slow viruses (viruses acquired early in life that take many years to do their damage) have been considered, as have environmental factors and damage from previous diseases. Recently, a diminished amount of the enzyme choline acetyltransferase (which is necessary to manufacture the neurotransmitter acetylcholine) has been found in some patients, and theories about replacement of the enzyme or the neurotransmitter are being formulated.Deficiencies of other neurotransmitters are constantly being discovered. Heredity seems to play some part, since a family history of the disease makes some individuals more likely than others to develop the condition. It is generally agreed that hardening of the arteries is not a cause. Alzheimer's disease does not appear to be contagious, nor is it caused by emotional upsets.SymptomsSymptoms vary considerably from one person to another and may occur days or months apart. They begin with small memory lapses, almost always first involving loss of recall for recent events. Such lapses can happen to anyone, but in Alzheimer's disease they grow more serious with time. A person may forget a close relative's name, get lost coming home from the office, forget to turn off the oven, misplace articles, recheck to see if a task was done, or repeatedly ask questions that have already been answered. Eventually, the gaps in memory and the failure to recognize friends and family members will interfere with normal life. As the disease progresses, the victim of Alzheimer's disease becomes confused, frustrated, and irritable. Although at first the person seems physically unaffected by the disease, as the condition advances, the patient becomes restless, always moving about, and must be watched so that he or she does not wander away or into danger. Endless repetition of unnecessary actions, such as the opening and closing of drawers, is another characteristic symptom of the disease. Some victims of Alzheimer's disease may even become extremely agitated with little or no provocation.The course of the disease may range from 1 year to as many as 20 years. The disease may eventually result in deterioration of the rest of the nervous system and other parts of the body and in loss of control over bladder and bowels. It may cut life expectancy by contributing to death from another cause, such as pneumonia or heart or kidney failure.
Can a study on reversing memory loss lead to new treatments for Alzheimer's?

Alzheimer's is a particularly tragic disease, devastating both those who suffer from it and their family members. Alzheimer's patients experience a loss of neurons (brain cells). This leads to a progressive loss of memory as well as loss of the ability to reason, communicate, learn and perform other tasks. Typically, Alzheimer's patients die four to six years after being diagnosed, though some live up to 20 years.
Five million people in the United States have Alzheimer's. Of those five million, 200,000 to 500,000 are under the age of 65, afflicted with dementias, including s early-onset Alzheimer's [Source: Alzheimer's Association]. There is no cure for Alzheimer's, but there are several different groups performing research to develop new treatments and possibly a cure. One new study, conducted on mice by researchers at MIT's Howard Hughes Medical Institute (with its findings published in the journal "Nature") offers exciting treatment possibilities.
Researchers have already discovered that a protein called p25 is linked to neurodegeneration found in Alzheimer's and similar diseases. The mice used in the MIT study are engineered so that the p25 gene can be turned on whenever the scientists desire. When the p25 gene is on, the mice develop a condition similar to Alzheimer's, characterized by a loss of neurons and brain atrophy.
Before activating the gene, the researchers, led by neuroscientist Dr. Li-Huei Tsai, taught the mice to associate a chamber with an electric shock -- called a "fear-conditioning test" -- and to navigate a maze. After the mice learned these tasks, the gene was turned on and the illness induced. It only took six weeks for the illness to erase the memories of the mice. They could no longer remember how to avoid being shocked or how to maneuver the maze with success.
Prior to this study, scientists already knew that a stimulating environment can promote learning in mice. However, they didn't know the effect of this type of environment on mice experiencing long-term memory loss (six weeks is "long-term" for a mouse). To test the effects of environmental cues on the mice, half the population was moved to a new habitat complete with engaging elements, including toys, exercise wheels and additional mice. The other group of mice was kept in an environment without any stimulation. After four weeks, the mice in the stimulating environment could remember the shock test and maze better than the mice in the non-stimulating environment. They could also learn new tasks better.
For Dr. Tsai and her team, the results were encouraging and pointed to a new possibility for the treatment of Alzheimer's disease. While the stimulation in mice didn't regenerate neurons, the treatment did promote the growth of new connections between existing ones. In other words, the neural networks of the stimulated mice re-established connections to previously "lost" memories. Dr. Tsai described the treatment as "actually rewiring the brain" [Source: Atlanta Journal Constitution].
A second part of the study conducted by Dr. Tsai's team involved treating mice experiencing neurodegeneration with a drug called an HDAC inhibitor. These drugs are usually used to treat cancer and have not been used on Alzheimer's patients. The mice treated with the HDAC inhibitors did better on memory-dependent tasks than the control group. According to Dr. Tsai, more research must be done to understand the effect before this therapy is tried on people. Her team is going to conduct further research to explore how these drugs work.
Both treatments by the MIT team are intriguing, especially because they achieved similar results. The big breakthrough is that memories lost to Alzheimer's disease don't appear to be actually "lost". They still exist in the patient's brain and simply need to be accessed by "regrowing" the neural pathways leading to them. The ability of sick mice to learn new tasks also offers hope to people with advanced Alzheimer's. Even if memories can't be fully recovered, it may be possible to boost their learning capacity and their ability to form new memories. If the study's results are reproduced in human patients, it will go a long way towards turning Alzheimer's into a treatable, manageable illness. Much like some types of cancer, Alzheimer's could one day be, if not curable, a disease that people can live with for a long time and in relative peace and comfort.

Sources

"Scientists 'reverse' memory loss." BBC News. Apr. 29, 2007. http://news.bbc.co.uk/2/hi/health/6606315.stm

"Enhanced Environment Restores Memory in Mice with Neurodegeneration." HHMI News. Apr. 29, 2007. http://www.hhmi.org/news/tsai20070429.html

"Scientists Restore Lost Memory in Alzheimer's-Like Mice." AJC.com. Apr. 29, 2007. http://www.ajc.com/health/content/shared-auto/healthnews/ alzh/604018.html

Peck, Peggy. "Teaching Old Mice New Tricks Opens Doors to Lost Memories." Apr. 30, 2007. Psychiatric Times. http://www.psychiatrictimes.com/psychiatryNews/showArticle.jhtml? articleID=199202782&cid=BreakingN

"What is Alzheimer's?" Alzheimer's Association. http://www.alz.org/alzheimers_disease_what_is_alzheimers.asp

DISCLAIMER: This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Health Mirror, the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

In Case of any queries feel free to contact Dr Anil K Dhull