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General Anesthesia

General Anesthesia

Samuel Seelig (Anesthesiologist, Los Angeles, California) gives expert video advice on: What are the risks of general anesthesia?; Is it true that some people remain aware during surgery, despite anesthesia?; What is the safest method of anesthesia? and more...

What are the risks of general anesthesia?

There are risks to general anesthesia. If you read the package inserts of any of the medications that are prescribed in the community, or any of the medications that you take, they would have a long history of side effects. The anesthetic agents are the same as they have side effects as well. When a patient has a general anesthetic, the risks begin from the start of the IV process. The intravenous can be placed incorrectly, it could be outside of the vein, the medication can be injected subcutaneously, and there can be an infiltrated IV with some burning of the skin, and discomfort. When the patient is brought to the operating room, and the anesthesia is induced, side effects can occur from the anesthetic agents. Side effects can be cardiac dysrhythmias, hypotension, a drop in blood pressure, hypertension, or an increase in blood pressure; all of which have adverse sequeli associated with them. This being said, these things rarely occur, and rarely have any adverse consequences.

What are the mortality rates for general anesthesia?

With the advent of the sophisticated monitoring techniques that we have, the pulse oximeter, the cathnographic measures, and titers CO2, the mortality rate for anesthesia has gone down significantly since the 1970's. In the 1970's the mortality rate was one in approximately 10,000, and it did not matter whether there was a general anesthetic or regional anesthetic. Presently the mortality rate is 5 to 6 per million which is can fused to about a 120 deaths per year in the United States because about 20 million anesthetics are done in the United States each year. The evidence that anesthesia has become safer is clear as our malpractice premiums have dropped from $56,000 a year to about $12,000 a year. And these have all been a function of the sophisticated monitoring devices that we use.

What are the causes of mortality under general anesthesia?

The causes of mortalitly under general anesthesia relate mostly to airway management. As we mentioned, securing of the airway is paramount when you first anesthetize a patient. It may be difficut to secure the airway because of anatomic difficulties. The patient can have an abcess, a large abcess in the mouth. He can have a mass in the throat. Some airway problems are unexpected, others are anticipated. But the bulk of the complications are related to the airway management of a patient. After that, cardiac disrhythmias become significant in elderly patients, or in patients who might have electrolyte imbalance, for one reason or another. Another reason for mortatity would be aspiration of stomach contents. The patients are supposed to be NPO, Nothing Per Os, not eat anything after midnight the night before surgery. Some people have delayed emptying of their stomach, diabetics in particular, and they may have a full stomach despite their best efforts. Other emergency cases, patients have full stomachs and they need surgery, status post haste, and you have to protect against aspiration in those patieints as well. There are other genetic abnormalities such as malignant hyperthermia which can cause mortality in the operating room. And then there is, of course, surgeon error. It can be nursing mistakes. And the anesthesia machine itself can fail. You have to be constantly vigilant that that is working properly.

Is it true that some people remain aware during surgery, despite anesthesia?

Awareness under anesthesia is a real phenomenon. It rarely occurs, but when it does occur, it gets a lot of press; so it seems to occur more than you would expect. The actual incidents, with twenty million anaesthetics accomplished in the United States is approximately one to two per thousand, which means twenty-six thousand cases of awareness under anesthesia. That being said, most cases of awareness under anesthesia do not feel pain. They hear things. They think they may have been dreaming, but they are not in pain. Some patients are, and that's been reported, as well. The most common cases of awareness under anesthesia have been with coronary artery bypass graft anesthesia, because they used a balanced technique with a lot of narcotics, and avoided some of the inhalation agents, and the cracking of the sternum, per se, has been what many people remember under anesthesia.

What are the possible side effects of general anesthesia?

General anesthesia can produce many side effects. It can start with infiltration of the intravenous, which is the portal of entry of the medication into the person. They can have an infiltrated IV if the medication is placed under the skin instead of in the circulation, and you can have burning at the IV site. You can have a reaction to any of the medications that are given through that IV, which can present as hives, itching, or nausea. You can also have anaphylactic reaction to any of the medications that have been given, which is a full blown allergic action and which must be treated immediately.

Who is most at risk from using anesthesia?

Common sense rules with this question. The patients most at risk for anaesthesia are the patients who are sickest when they arrive for their surgical procedure. Patients with severe cardiac disease, those that have chest pain or shortness of breath, unstable angina, patients that have had histories of congestive heart failure are at risk under anaesthesia. Patients with respiratory problems, those with severe COPD, heavy smokers, patients with asthma, they're at risk. Patients with multi-system organ disease, kidney failure and liver failure are at risk. The morbidly obese patient is at risk; they tend to have more complications during and after surgery.

What is the safest method of anesthesia?

That's a difficult question. In the 70's when the complication rate for anesthesia was 1 in 10,000, it was reported that the complication rate was similar for general and regional anesthesia, so it didn't matter what type of anesthetic you got as the complication rate was the same. In this era, it is hard to judge which anesthetic is safest. The older, sicker patients tend to have their procedures done under local with sedation or regional anesthesia, if possible. The morbidly obese have general anesthetics almost all of the time because of the technical difficulties of performing regional anesthesia. I don't know if the statistics are valid because the sicker patients tend to have one type of anesthesia and will by definition have more complications and a higher mortality rate. That being said, the safest anaesthetic is the one that the anaesthesiologist is most comfortable in delivering to that particular patient with his medical history taken into account.

What factors determine what type of anesthesia is used?

Some operative procedures by definition must be done under general anesthesia. For example, open craniotomies, coronary artery bypass graphs with an open chest, or an emergency caesarean section, can only be done under general anesthesia for the safety of the patient. Regional anesthesia is difficult to perform on morbidly obese patients, so they would probably have a general anesthetic for most of their procedures. The choice of anesthesia is dictated by the patient's medical history and the medication that the patient takes. For example, if the patient is on anticoagulants or has a bleeding disorder, you would not do a regional anesthetic because you do not want to put a needle in the spinal canal and chance bleeding in that area. The choice of anesthetic is a coordination between the surgeon, the anaesthesiologist and the patient, all within the common sense ground rules of why it's appropriate for the procedure.

What do I need to tell my anesthesiologist before surgery?

When you meet your anaesthesiologist in the pre-operative area, it's important that you give a complete history and answer the questions that he poses to you. For example, he may first ask you "What prior surgeries have you had?" and specifically if you've had any problems with the anaesthetics that were given to you. Any patient that's had a problem in the past, we would investigate that thoroughly to make sure that we don't reproduce that problem. It may be an allergy or an adverse reaction to a particular medication. We need to know the list of medications that the patient is on, because many medications will react with some of the aesthetic agents that we use and it could dictate which medications we do or do not use. It's important for us to know the medical history; chest pains, shortness of breath, cardiac status of the patient. We like to know their exercise tolerance. I frequently ask a patient, "Do you have stairs in your home? Are you able to navigate those stairs?" That gives a pretty good indication of the conditioning of the patients, even if they're elderly. Certain diseases make anaesthesia difficult. In addition to morbid obesity, asthma, coronary artery disease, those sorts of problems we need to know about in advance.

How does anesthesia affect other organs?

In the past, many of the aesthetic agents adversely affected various organs in the body. Historically, halothane had an effect on the liver of some patients and the patients developed halothane hepatitis. Methoxyflourane, which is a gas that is no longer used, had renal toxicity - it affected the kidneys. The anaesthetic agents today are what I would call cleaner, not completely clean but cleaner than those in the past. And the side effects on the organ systems are minuscule and insignificant in the long term.

What is a 'spinal headache'?

A spinal headache is seen after a spinal tap or a spinal anaesthetic is performed. A small nick in the Dura, which is the membrane outside of the spinal canal, is made when the spinal needle punctures it. If cerebral spinal fluid leaks out in any significant quantity, a spinal headache can ensue. It can be a mild headache and present as nausea, dizziness, ringing in the ears, some hearing deficit and some visual changes, or it can be the mother of all headaches. A bad spinal headache is very specific in its presentation. When the patient sits up, stands up, coughs, or bears down it feels as if their head is blowing off their shoulders. When they lie down the headache goes away immediately. This is diagnostic of a spinal headache.

Is it true that having surgery earlier in the day is safer?

This is only true for certain patients, in particular, diabetics. Diabetics are always done early in the day because their blood sugar will wax and wane, and hypoglycaemia or hyperglycaemia are dangerous for the diabetic patient. The other class of patient you like to do earlier in the day are the paediatric patients because they are not eating or drinking, and you don't want them to get dehydrated because it creates a fever in the small child. That being said, if you're having your surgery very late in the day, there is a chance that the anaesthesiologist will be tired and less vigilant, or the surgeon will be tired and less facile. As you probably know, Congress has passed a law limiting the hours of interns and residents in recent years, because of just such incidents of fatigue causing mistakes, so the hours of interns and residents are now limited. Congress has had some laws that they attempted to pass for anaesthesiologists, the same laws that pilots abide by whereby their hours would be limited. Remember, vigilance is the Gold Standard for anaesthesia.

Is it true that using fewer drugs while undergoing general anesthesia is safer?

That's not true. General anesthesia is accomplished with an armamentarium of medications that we have at our disposal. One anaesthetic agent does not fit all. We are constantly changing the medications we use in both dosage and also the family of medications that we use, based on the vital signs of the patient and what's going on during the procedure. We may have to give more narcotics, we may have to give more or less muscle relaxants, and we may have to turn up the inhalation agents, or even turn them off. But the best anaesthetic is a balanced anaesthetic, using a potpourri of medications. We may have to use anti-hypertensive agents or agents to increase the blood pressure, for example, vasopressers. So, less is not more when it comes to anesthesia.