Anaesthesia is a state of reversible unconsciousness (hypnosis), pain relief (analgesia) with or without muscle relaxation. Muscle relaxation is not required by every surgery.
Hypnosis is induced by drugs and maintained by anaesthetic gases. Pain relief is obtained by a combination of a variety of drugs. The most widely used group is opiates. One can also achieve pain relief by blocking the nerve supply to the part of the body that is going to be operated.
This is done by blocking one or a group of nerves at the site or placing a drug within the vertebral column. However, this technique is possible only when operations are performed in the peripheral parts of the body like the limbs or the lower abdomen.
As this technique can achieve both pain relief and muscle relaxation, the surgery itself could be performed only with it and hence it is termed regional anaesthesia. As hypnosis is not induced by this technique, the patient will be awake during the operation but will not feel any pain.
When drugs are used to achieve muscle relaxation it paralyses one type of muscle in the body called the skeletal muscles. This type of muscle is seen mostly outside the body such as the limbs and the body wall. Body organs have different types of muscles and will continue to function. However, the muscles of breathing (respiration) will get paralyzed and therefore the patient will have to be given artificial breaths with the help of a machine (ventilation) during the procedure. The action of the drug can be reversed when necessary.
What should the patient divulge to the anaesthetist before an anaesthetic?
As anaesthesia affects the function of many organs in particular the heart and the lungs, a patient should reveal details of all past medical problems to the anaesthetist. One should also disclose the details of previous surgeries undergone. It is important to inform the doctor of any known drug or food allergies as such patients may have an allergy to some of the anaesthetic drugs as well. The patient should bring along previous diagnosis cards if available and prescriptions of any current medication.
What should the patient do before anaesthesia?
Generally an anaesthetist will visit the patient before the proposed surgery to get the necessary information and to examine the patient. This is called the pre-anaesthetic visit. During this visit the anaesthetist will give all the necessary information to the patient and may prescribe medication and may omit some of the medication the patient is already taking.
If the anaesthetist feels that the patient's medical status is not suitable for anaesthesia the surgery will be postponed. Patients should fast for six hours before anaesthesia. This is to give time for the stomach to empty. If food remains in the stomach it can come up the food pipe and go down the wind pipe into the lungs and result in an infection (pneumonia).
How safe is anaesthesia?
It has to be realized that no medical procedure is without an associated risk. However, the chances of an anaesthetic complication in an otherwise normal patient is extremely small. One has a higher chance of meeting with an accident on the way to hospital than a complication by an anaesthetic.
(The writer is a Consultant Anaesthetist) |
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