When most people think about after effects from anaesthesia, they typically only consider one type of anaesthesia--general anaesthesia. General anaesthesia is used to help put patients to "sleep" during medical procedures. Anaesthetised sleep is different from normal sleep because it stops the brain from feeling pain and forming memories, and it occurs in response to IV drugs or inhaled gases. Unfortunately, some patients will suffer from effects after they wake up.
The four types of anaesthesia include local, conscious sedation, regional and general. Local involves a small area and may be topical or injected. There is generally no after effect once the area wakes up, except for possible pain from the procedure that caused the need for anaesthesia. Conscious sedation is done to keep a patient awake but unable to feel pain. In most cases, you won't remember anything that happened or that you may have said. Regional anaesthesia numbs a large part of your body but generally allows you to stay awake. General anaesthesia puts you to sleep.
After effects for conscious sedation, regional anaesthesia and general anaesthesia are similar, although they vary in severity. Most after effects from anaesthesia are minor, including vomiting, nausea, headaches, a "hangover," sore throat (if a breathing tube was inserted) and some bruising at the site of the IV injection. Allergic reactions are also possible, and these may lead to heart and lung infections or problems later. Your personal risk factors, including your overall health, will also play a part in determining how you respond after anaesthesia.
A common concern is that you will wake up in the middle of a surgical procedure. Anaesthesia awareness, however, only happens in about 0.006 per cent of all surgeries, and most of the patients who do wake up have only vague memories of what they experienced. The majority do not feel any pain, even while awake. The condition is genetic, though, so if you have family members who have experienced it, you may also be at risk.
All anesthetics may cause complications. Local anaesthesia can cause systemic toxicity if used in high doses, which may affect body functions such as breathing and heart rate. Regional anaesthesia, if injected too close to a nerve, can cause permanent damage, including weakness, pain and numbness. If the injection site is the spine, a headache can be caused by leaking fluid. This is a rare complication, affecting only 1 to 2 per cent of all patients who receive spinal cord injections, and it is treatable. General anaesthesia can cause aspiration (inhalation of liquid or an object into the lungs), but if the patient avoids eating and drinking before the procedure, this risk is severely lessened.
To help avoid suffering from after effects, be sure to discuss health problems, medications, allergies, social habits (drinking, smoking and drug use) and any past problems you've had with anaesthesia with your doctor. Be sure to follow the instructions you are given for pre-op, including stopping eating and drinking a predetermined amount of hours before the anaesthesia will be administered. If you eat or drink for any reason during that blocked time, inform your doctor, as the procedure may have to be delayed or moved.