Are there risks associated with anesthesia? Quite simply, yes. Having anesthesia is not unlike most things in life: there is always a chance that things will not go as expected. Patients often ask "What is the risk of having anesthesia?" Unfortunately, there is no quick and easy answer to that question. To understand why, consider the following:

I suppose that the underlying reason that risk exists in anesthesia, or, for that matter, in medicine or even life in general, is that we are dealing with man-made technologies administered by human beings. We are thus wedded to the fact of our human imperfections. Having said that, let us consider how an anesthesiologist views risk during surgery. The number of potential complications that have been known to occur during anesthesia is vast; it is impractical to aspire to discuss each of them fully. In fact, it would not be too far off the mark to say that just about anything you can imagine could happen during anesthesia and surgery. But realistically, what are the chances?

When the question of risk arises, we must further refine our question to: risk of what? That is to say, to answer questions about risk, we must first know which complication you are asking about. For instance, what is the risk of death (i.e., "not waking up") resulting from anesthesia? When a patient dies in the operating room, there are usually many contributing factors, anesthesia possibly being one. It becomes difficult, however, to ferret out only those cases when patients died solely as a result of having anesthesia. In fact, this seems to be a rare enough event that it takes a long time to collect data on enough operations to draw statistically valid conclusions. And then, once the results of the study are in, we find that our agents and techniques have evolved over time and the relevance of the study to modern practice is questioned. Nevertheless, using the best data we have at this point, it appears that death as a direct result of anesthesia occurs about 2 or 3 times out of each million anesthetics.

Other complications, of course, each have their own statistical probability. And all of them are influenced by individual factors such as the physical status of the patient and the nature of the proposed operation. Fortunately, major complications, i.e., complications that result in death or permanent disability are uncommon. In fact, I often present patients with a good analogy to put it all in perspective. In truth, you could be asked to sign a consent form outlining all the potential complications that could occur during anesthesia before climbing into an automobile for a ride to the grocery store, and every item on the list would be just as relevant. Surely, someone could run a red light and collide with you; the brakes might fail and result in an accident; a telephone pole might topple over onto your car...   Any of these events could result in injury resulting in death or permanent disability. The difference between this and having anesthesia? All of those thing are much more likely to happen to you during your automobile ride than they are during surgery. In fact, one authority has stated that, statistically speaking, a person is more likely to incur death or injury at home, performing normal daily activities, than during anesthesia.

Many people think of the anesthesiologist as the person who comes in and "knocks you out" for surgery. That is, they see our primary role as that of providing unconsciousness or amnesia during surgery. Certainly that is one of our functions. However, from the anesthesiologist's viewpoint, our number one role is in managing each anesthetic with an eye towards minimizing the risk of problems. And, our training prepares us to recognize and deal with complications as they evolve so as to minimize their impact upon the patient. The bad news? We haven't yet succeeded in making anesthesia entirely risk-free. The good news? Modern anesthesia techniques combined with the skill and judgment of anesthesiologists has made anesthesia safer than many of our normal daily activities.

In our practice at CAA, every patient is evaluated by an anesthesiologist before surgery. Usually this occurs before the patient comes to the operating room, but sometimes, such as with emergency surgery, the patient may not meet an anesthesiologist until he or she actually arrives in the operating room holding area. During this evaluation the anesthesiologist reviews the patient's medical information and makes note of those factors that may become important during surgery. After this evaluation, the anesthesiologist is in a position to discuss the risk profile of that particular patient.

Many patients ask about the possibility of waking up in the middle of an operation. At this time in our practice it remains an unlikely event, however, there have been instances when it has occurred. In anesthesiology, we refer to this as "recall." Why do we call it that? And why does it happen? To answer these questions, we must understand the distinction between unconsciousness (lack of awareness) and amnesia (lack of memory). To illustrate this distinction, I make use of an analogy from everyday life that most adults have had some exposure to. Have you ever been around someone who had consumed too much alcohol? The next day, when you say, "Gee, that was really funny when you were dancing on the table wearing the lampshade on your head!", you are not surprised when that person expresses no memory of doing so. Was he unconscious? No. He may have had slurred speech and poor motor coordination, but he was aware of his surroundings, carrying on conversations, etc. Was he amnesic? Yes.

When most people think of anesthesia, they equate amnesia with unconsciousness. Patients often report "They put something in my IV and the next thing I knew I was in the recovery room!" What this really means is that they have no memory of events that occurred during that time. Were they unconscious during that time? That's sometimes hard to tell. In fact, knowledge of awareness under anesthesia virtually depends upon recall. It is very hard to separate the two issues in both research and clinical practice. Interestingly, some studies involving hypnotic regression suggest that many if not all patients may have awareness during anesthesia, at least for sound. Very few, however, have recall.

Modern anesthesia techniques and agents are very reliable in producing amnesia during surgery. Certainly there are differences among individuals with respect to their tolerance to medications of all kinds, just as different people have differences in their tolerance, for instance, to alcohol. Your anesthesiologist may inquire about your habits with respect to alcohol consumption in an effort to gain some appreciation of your individual tolerance profile. Also, certain medications you may be taking can affect your tolerance to anesthetic agents or interact with them in other ways. It will be important for you to be frank with your anesthesiologist about your habits with alcohol as well as to know the names of all the medications you are taking.

During surgery your vital signs (pulse, blood pressure, heart rate, etc.) are closely monitored. If a patient begins to awaken from the anesthetic or "get light", there are usually signs of this in the form of increases in blood pressure, increases in heart rate, movement, changes in respiratory pattern, etc. These changes generally occur well before the patient is awake enough to have recall; if more anesthetic is needed, appropriate actions are taken. However, there have actually been cases where patients have experienced recall of events during anesthesia even with greater than average amounts of anesthetic in their system and/or in the absence of telltale changes in their vital signs.

Today we have reliable agents and techniques to provide efective anesthesia to our patients. The vast majority of patients have no recall whatsoever of events that transpire during their operation. Close monitoring of our patients during surgery allows us to tailor each patient's anesthetic to fit the needs of both patient and surgeon as best we can. Although it is not yet possible to guarantee 100% that no patient will have recall during anesthesia, it remains a fairly rare occurrence.

For purposes of discussion, the nervous system is divided into two parts. The Central Nervous System consists of the brain and spinal cord. The Peripheral Nervous System comprises basically everything else, i.e., all of the nerves that travel to the various parts of the body after exiting from the spinal cord. Nervous tissues are extremely sensitive and vulnerable structures. Occasionally in the period of time surrounding surgery or childbirth patients exhibit signs of nerve damage. Sometimes the cause of their symptoms seems obvious, but in many instances it is obscure. Although nerve damage as a direct result of anesthesia is not often seen, we will on this page look at a few of the different types of problems that have been known to occur in association with anesthesia, surgery, and childbirth. Here we will examine:

• Stroke and Brain Damage (Central Nervous System)
• Peripheral Nerve Damage (numbness or weakness in arms, legs, etc.)
• Nerve Damage in Associationwith Vaginal Delivery

Many types of surgery carry a risk of stroke and brain damage, irrespective of the anesthesia received. Such operations as open heart surgery, surgery on the major blood vessels, certain operations on the brain itself or its blood vessels, etc. are associated with a risk of brain damage.

Brain damage contributed by anesthesia can come about from many causes. Historically, one of the major factors was inadequate oxygen delivery to the patient, which can arise from many different causes. At CAA, all of our patients are monitored with a device known as a pulse oximeter. This is a monitor that shines a small ray of light, usually through the nail bed of the finger or toe, and a special sensor analyzes the wavelength of the light to see what has been absorbs by the tissues in transit. This is then translated into a measurement of the amount of oxygen that is actually in the patient's bloodstream. Using this monitor, slight changes in oxygen levels, which would not have been detected by earlier cruder observations, provide a prompt to search for causes and take corrective action well before a critical situation has arisen. Pulse oximetry has thus provided anesthesiologists with a very powerful monitor to help prevent brain damage from inadequate oxygen delivery. Although other factors can interfere with oxygen delivery to the patient (such as lung disease, smoking, obesity, heart failure, or anatomical abnormalities of the breathing passages), in most normal circumstances brain damage from anesthesia has become a fairly rare event.

For many years, it has been observed that patients have noted abnormalities of the peripheral nerves after anesthesia and surgery, usually showing up as numbness and/or loss of muscular control in the arms, legs, hands, or feet. In the past, it was speculated that these symptoms might be related to stretching or pressure on the involved nerves, causing a temporary or in some cases, even a permanent form of nerve injury. Accordingly, steps were taken in the hopes of reducing the risk of this complication by paying careful attention to the positioning of the patient during anesthesia, and placing cushions at pressure points where nerves were near the surface. Of course, different operations require different positions of the patient, and there are many different variations in our approaches to positioning. Combined with the fact that there are wide variations in patients' physical build as well as many diseases that affect the bones and joints, and you can see that there are situations that may arise where positioning can become a challenge. It is not always obvious how best to position any individual patient. Using our knowledge of the anatomy of the nervous system and our best judgment, most patients can be properly positioned on the operating room table. At CAA, your anesthesiologist will work with your surgeon to position you in the safest way that is compatible with the needs of your surgeon.

However, even when positioning has to the best of our knowledge been perfect, there have been cases in which post-operative nerve problems have arisen. Mysteriously, some have not surfaced until after the patient has been discharged from the recovery room, raising the question of when exactly did the problem occur? Was it related to a variation of anatomy in the patient that could not have been determined in advance? Indeed, a recent editorial in a respected anesthesia journal pointed out that these observations cast doubt on the theory that nerve injuries of this variety are caused by positioning at all. A ready explanation for each case is thus frequently not to be had. The good news is that, in most individuals that sustain this sort of complication, the nerve tissues slowly regenerate over a period of weeks to months, and nervous function returns. This complication appears to occur about once per 20,000 anesthetics.

Vaginal delivery can result in trauma to peripheral nerves, usually nerves that go to the legs and feet. The reason for this appears to be due to anatomical considerations. The nerves that go to the legs and feet arise in the lower (lumbar and sacral) part of the spine and travel within the pelvic cavity on their way to the legs. The interior surface of the pelvis forms a ridge called the pelvic brim, and sometimes, especially with large fetuses or small pelvises the baby's head compresses and "bruises" the nerves at this location. Another vulnerable site is where the Femoral Nerve, which goes to the front of the leg and the quadriceps muscle, courses just beneath the inguinal ligament (the thick cord-like structure that goes from the from the front of the hip area down to the pubic bone; this is where the crease forms when you raise your knee towards your chest). Sometimes during vaginal delivery it becomes necessary to raise the legs up high to provide help with pushing the baby out. It is thought that in some patients this maneuver may stretch or compress the Femoral Nerve resulting in numbness across the front of the thigh and/or weakness of one or both quadriceps muscles. Either of these conditions may follow vaginal delivery, albeit infrequently. As anesthesiologists, we are sometimes asked to evaluate these patients because they had an labor epidural and their symptoms did not appear until the epidural had worn off, leaving the residual neurologic deficit. Some patients initially fear that they have encountered a complication from their epidural, but a classic pattern of nerve damage with no sign of nerve trauma during the epidural insertion leaves little doubt as to the true cause.

Many patients fear nausea and vomiting after anesthesia and surgery. Fortunately, today nausea after anesthesia is much less common than it once was. Nevertheless, it is still a problem. One of the problems with predicting its occurrence and taking steps to prevent it is that it appears that many different factors influence its incidence. It appears to be the final common pathway for a variety of different disturbances. Think of all the non-anesthetic situations where nausea shows up, and you will appreciate how many different things can result in nausea.

One thing is for certain: it is not so simple as to be the result of using any one drug. Many studies have attempted to elucidate the factors involved in producing post-op nausea, and several factors seem to influence the probability of having it. Factors such as the type of surgery (irrespective of the type of anesthesia), sex, age, and obesity all alter the chances of getting sick after anesthesia. Some studies have suggested that some anesthetic agents are more likely than others to produce this effect, but other equally good studies have failed to support their findings. Patients who have a history of getting post-op nausea are at higher risk for getting it again. And having said all this, I have happened upon the chance to observe two different patients who had two operations on the same part of the body and received practically the same anesthetic both times; one time they felt fine, and the other they felt poorly. Clearly there are other things going on that we have yet to discover.

In fact, at this point in time, all we can say is that we do not yet have a full understanding of why some people get sick after surgery and others don't. Some patients have said "Once I got sick, but the next time I told the anesthesiologist about it and he changed it so I didn't get sick. Please find out what they gave me the second time and do it just like that." By now you should understand that its hard to tell if you did better because of the change, or if it was coincidental. Furthermore, anesthesia must often be tailored to suit the planned operation as well as possible changes in the physical condition of the patient at the time of surgery. Often it is not feasible to administer exactly the same anesthetic on different occasions, and even if it were, it would still be possible to encounter post-op nausea afterwards.

If you are concerned about the chances of having post-op nausea, your anesthesiologist will be glad to discuss this issue with you. As you have read, there are not many black-and-white answers to be had, and it is not possible to predict for any single patient whether or not they will be sick after surgery. Luckily, most patients do not have major problems with it these days, and for those that do, we have some very effective medications to treat it when it does happen. Still there are a tiny number of patients who seem to get it no matter what, and only time will resolve it in those cases.

The brain and spinal cord are bathed by a fluid known as cerebrospinal fluid, or CSF. This fluid is contained by a membranous structure, the principal member of which is the Dura Mater, usually referred to as simply the dura. Several procedures in medicine involve puncture of the dura: diagnostic lumbar puncture ("spinal tap"), myelogram, spinal anesthesia, and others. Additionally, a small percentage of epidural anesthetics result in an unintentional dural puncture.

Once dural puncture has occurred, the stage is set for the production of a syndrome known as a post-dural puncture headache, or PDH. Not everyone who has a dural puncture, however, develops the headache. Many factors influence the development of headache, including sex, pregnancy, age, and the size and type of needle used. The production of the headache seems to be caused by the leakage of spinal fluid through the puncture site, with a lowering of the CSF pressure. Typical characteristics of PDH include its postural nature, it being worse in the upright position than when lying down, and its temporal relationship to the dural puncture. A small percentage of patients with PDH will also experience disturbances of their vision or hearing.

Therapy for PDH includes several different approaches. Even if no therapy is given, the headache generally resolves within a week to ten days, although there have been rare cases where symptoms have persisted for longer periods of time. For mild headaches, bedrest, hydration, and mild pain medications often suffice. For more severe cases, an epidural blood patch is often performed. This procedure involves placement of a needle into the epidural space in the proximity of the dural puncture site, drawing a sample of the patient's own blood from their arm, and injecting the blood into the epidural space. The blood, by occupying space within the spinal canal, probably repressurizes the CSF, as most patients feel much better almost immediately. In addition, it is speculated that the blood clot may also serve to put a "finger in the dike" and stem the CSF leakage. While most patients are good candidates for epidural blood patch, some are not. Patients with fever who may have bacteria in the bloodstream are are at risk to develop infection within the spine and are not generally considered to be good candidates. In addition, there other medical conditions that may interfere. Should you need a blood patch, your anesthesiologist will evaluate you and decide if it is indicated and feasible.

Some patients experience breathing problems after surgery. This can result from pulmonary aspiration, atelectasis and pneumonia, residual muscle weakness, or may result from pre-existing lung disease such as asthma or emphysema.

Pulmonary aspiration refers to the entry of foreign materials into the lungs. Normally the lungs are protected from this by reflexes; when a foreign body is detected near the larynx ("voice box"), these reflexes close the vocal cords and epiglottis (a trapdoor-like structure that covers the larynx) and thereby protect the lungs. Under the influence of anesthetics, however, these reflexes are impaired and aspiration becomes possible. The most dangerous type of aspiration is aspiration of stomach contents. The high acid contents of stomach juices is extremely damaging to lung tissue, and aspiration of as little as one ounce (25 cc.) can seriously impair the ability of the lungs to transfer oxygen to the blood, producing a pneumonia severe enough to require admission to the intensive care unit. For this reason it is common practice to have patients fast prior to having anesthesia to help reduce the amount of material in the stomach and lower the risk of aspiration. Many different factors influence the risk of aspiration including co-existing disease states, positioning during surgery, and the type of surgical procedure that is planned.

During anesthesia small areas of the lung may collapse; this is called atelectasis. These can be re-expanded by deep breathing and coughing after surgery. Sometimes coughing can be difficult because of pain during coughing. If the lungs are not kept expanded and cleared by deep breathing and coughing, the atelectasis can progress to pneumonia. Your surgeon may prescribe respiratory therapy and breathing exercises for you if you develop this problem. Some studies suggest that epidural post-operative pain management may lower the risk of these problems by making deep breathing and coughing easier to do.

Muscle relaxing drugs are often used during anesthesia. Many operations are made much easier to perform when the muscles are relaxed, providing easier surgical access to underlying tissues. Occasionally the effects of the muscle relaxants extend beyond the end of the operation, and sometimes the patient may require assistance with breathing until the effect of the medications has worn off.

Some families have a deficiency of an enzyme known as pseudocholinesterase. Deficiency of this enzyme does not interfere with normal daily activities and produces no symptoms. However, this enzyme is responsible for metabolizing a commonly used anesthesia drug called succinylcholine. When this enzyme is absent, the effects of succinylcholine are unexpectedly prolonged. Although families with this enzyme deficiency are not frequently encountered, your anesthesiologist may ask about a family history of this problem.

Patients with pre-existing lung disease such as asthma or emphysema are at higher risk for developing pulmonary problems in the period of time surrounding anesthesia and surgery. Asthmatics sometimes experience an asthma attack after surgery, sometimes precipitated by endotracheal intubation. Patients with severe pulmonary problems may need the attention of a lung specialist.

Also, smokers face a higher risk. The effects of smoking can be lessened by quitting prior to surgery, but to fully realize this benefit smoking must be discontinued for about ten days. All patients that require recovery room observation will receive close monitoring of their breathing; sometimes extra oxygen is needed for a while after surgery.

During most general anesthetics, and potentially in any regional or local anesthetic, an endotracheal tube may be inserted through the vocal cords into the trachea, or windpipe. This procedure, an essential one for protecting and maintaining the airway during anesthesia, is called intubation. It is performed using an instrument called a laryngoscope; laryngoscopy (the use of the laryngoscope to intubate) poses a risk to teeth. The jaw and facial structures of some normal healthy individuals may make intubation difficult. In individuals with unhealthy teeth or gums or frontal caps or bridges there is an increased risk of tooth damage. We understand that no one expects tooth damage when having surgery on some other organ system, but this type of damage is a risk during surgery and anesthesia even with experienced personnel.

• Headache: The most frequent complication of spinal anesthesia is known as a spinal headache. Today's spinal needles are specially designed to help prevent this complication, and only a small percentage of patients develop it.
• Back Pain: Most persons experience back pain at some point in their life, and it can have many causes and precipitating factors. Just laying in bed for a few days after surgery can cause back pain, regardless of the type of anesthesia chosen. Some patients assume that when they develop chronic low back pain later in life that it is because they were given a spinal anesthetic when they were younger. However, when well-designed medical studies have examined the issue, spinal anesthesia has not emerged as an important cause of chronic low back pain.
• Nerve damage: There have been rare cases of nervous system damage leading to deficits in sensation or strength following anesthesia of all types, including spinal anesthesia; fortunately, many of these resolve spontaneously. The causes may differ among cases.
• Failed Anesthesia: Occasionally the spinal anesthetic may fail to provide adequate anesthesia for the surgical procedure. Sometimes this occurs because the surgery continues for longer than anticipated, outlasting the anesthetic. In other cases, the spread of anesthesia may be nonuniform, resulting in a "patchy block." Sometimes a surgeon can supplement by injecting a local anesthetic; in other cases a general anesthetic becomes necessary.
• Total Spinal Anesthesia: Various techniques exist for controlling the spread of spinal anesthesia. Occasionally the spread of the anesthetic extends to a higher level than expected. If the spinal level gets too high, then there may be enough muscle weakness to result in inadequate breathing. This is usually managed with endotracheal intubation and assisted breathing until the effect has worn off.

Possible complications differ in their likelihood with the different approaches, but include:

• Collapse of the lung on the same side. The tip of the lung is very near to the brachial plexus, and there have been cases where the needle punctured the membrane lining the lung, resulting in collapse. If the lung collapses far enough, re-expansion by means of a surgically placed chest tube may be required. This is not a frequent complication of brachial plexus block.
• Inadequate or "patchy" block. When anesthetic solutions are injected near the brachial plexus, they normally spread uniformly to anesthetize the entire plexus. On occasion, however, the spread is not uniform and incomplete numbness is achieved. If the surgeon cannot compensate for this by adding a small amount of local anesthesia, a general anesthetic is usually required to complete the operation.
• Phrenic nerve block. More often seen with interscalene and to a lesser degree with supraclavicular block, this happens when enough anesthetic solution spreads upwards from the plexus to anesthetize the phrenic nerve, which controls the half diaphragm on the side of the block. Blockade of this nerve causes weakness of this important breathing muscle until the anesthetic wears off. However, in normal persons with adequate lung reserves, it is usually well tolerated. Patients with advanced lung disease might tolerate it poorly enough to require assistance with the breathing, and possibly endotracheal intubation with breathing assistance, until the effects have dissipated.
• Axillary hematoma. Some approaches to axillary block involve finding the plexus by first locating, with the needle, an artery that lies immediately next to the plexus. Small amounts of blood that escape from the needle hole in the artery can form a blood clot, or hematoma, beneath the skin. This can show up as a discoloration similar to a bruise in the armpit and can cause a little soreness for a few days. This is usually no more than a temporary nuisance, and resolves spontaneously.

While local anesthetics are widely and successfully used to provide pain relief, they are not without potential problems. In addition to the numbing effect they have on nerves, they also have actions on the brain and heart. If too much local anesthetic enters the circulation, it can cause a convulsion or a disturbance of heart rhythm. For this reason there are limits concerning how much local anesthetic medication is safe to administer. In addition, epinephrine (adrenaline) is often added to the local anesthetic solution because it constricts blood vessels, thus reducing blood flow to the area, thus the slowing absorption and lowering the blood levels of the local anesthetic drug. Many patients think themselves to be allergic to local anesthetics because of the way the epinephrine makes them feel (anxious, apprehensive, heart racing). However, such symptoms are not signs of a true drug allergy but rather just the actions of small amounts of epinephrine that have gotten into their systems; local anesthetic drugs can safely be used in these patients.

If the area of the body that is being anesthetized is small enough, a local anesthetic technique can be used. However, if a larger area is being targeted, then regional or general anesthesia should be chosen.