Anesthesia and the Brain

Oliver Wendell Holmes Sr. in the year 1846 gave the term ‘anesthesia’ to describe a reversible state of lack of awareness. This can be induced as well. Anesthetics are a single or combination of drugs such as hypnotics, paralytics, sedatives and analgesics that block or temporarily take away the feeling of sensation. Types of analgesics include Ether, Chloroform, Insoflurane, Succinylcholine, Curare, Decamethonium and Gallamine. Certain drugs such as Ether and Chloroform are inhaled. Other drugs, such as Novocain, are localized pain blockers that are applied with an injection or chemical drop. This is particularly helpful during surgeries as it helps patients undergo the procedure without much pain or distress.

Types of Anesthesia

Anesthesia is administered in various ways to a patient depending on the requirement. The four major methods are discussed below,

  • General anesthesia: this refers to the administered drug inhibiting the sensory, sympathetic and motor nerve transmission to the brain. This causes a state of unconsciousness and lack of sensation.
  • Local anesthesia: here, sensory inhibition is restricted to a part of the body e.g. urinary bladder.
  • Regional anesthesia: nerve transmissions between a larger region of the body and the spinal cord are blocked.
  • Dissociative anesthesia: agents used as anesthetics here cause a disruption in the passage of impulses from the higher regions of the brain (e.g. cerebral cortex) to the lower region nerves such as those of the limbic system.

How does anesthesia work?

Anesthesia works on the central nervous system. The CNS (central nervous system) contains the brain and associated nerves. Nerves are made up of long cells called neurons. These neurons contain receptors and neuro-transmitters such as acetylcholine. These help transport messages from the brain to other organs and vice-versa. Anesthesia simply blocks these neural passages. It does not let messages to cross from brain to organs. This can be localized to a particular region or be spread all over the body (general anesthesia). Overtime, this process causes a slowing of brain response and neural transmissions. Thus, the patient is rendered unconscious.


Common effects of anesthesia

These effects have been divided into two categories- long term and short term.

  • Short term effects: Anesthesia administration can produce side effects. Most of these effects last for a couple of minutes to a few hours and are hence termed short term effects. Their occurrence depends on type of anesthesia given, duration for which the patient was under anesthesia, medical condition of the patient, age and gender. The symptoms after effects include sore throat, nausea, blurred vision and dizziness.
  • Long term effects: Some effects may last longer and are termed long term side effects. They may last up to two weeks after surgery and include vomiting, black stool, stomach ache, headache and dizziness. Overall weakness in the body may also exist.

Effects of Anesthesia on the brain

Though anesthesia certainly helps in surgeries, as all drugs, it also has side effects. It majorly impacts the brain and causes a number of changes albeit small in a person. Following is a discussion on some of these changes,

  • Anesthesia impacts the brain and can cause blurredness in vision along with partial, temporary or complete loss of eyesight. Anesthesia being a muscle relaxer causes the smooth muscles to relax and blood capillaries to vasodilate or expand in cross sectional area. Inhalant anesthetics are considered better than injectables as they cause less vasodilation during muscle relaxation. Vasodilation causes slowing down of blood flow. This could cause accumulation of erythrocytes (red blood cells) in tissue which could be problematic. Some patients might also experience retention of fluid emboli in certain tissue spaces due to travel of plasma from vasodilated blood vessels.
  • In the early administration days, effects of anesthesia on the human heart were of major concern. Today, professionals also take into consideration cognitive function or brain function. It is the reason why an anesthesiologist stays with the person pre-surgery and through recovery. Studies have shown that anesthesia patients have trouble with concentrating and focusing post procedure. A number of studies also point to the increasing amount of amyloid in animals caused due to anesthetics. These amyloids are responsible for Alzheimer’s disease. Patients must remember to keep their physician aware of all their discomforts. Effects of anesthesia can take from a few hours to several days to wear off.
  •  Delirium is the state caused by analgesics as they lower the amount of neurotransmitters flowing through the body. People who already experience delirium and dementia must discuss their options with their doctors before the procedure. Arterial hypoxema is the condition where pulmonary artery carrying oxygen to the brain is blocked. In the event of lack of oxygen, patients may experience delirium and this may cause memory loss and mood changes.
  • General anesthesia puts a person into a state of controlled unconsciousness. If anesthesia is not administered properly, the person may be ‘awake’ to varying degrees during the procedure. Some people have reported cases of hearing sounds, smelling smells and blurred visions of their surgery. At times, a person may also be in the state of experiencing conscious pain. This has most often been seen during regional anesthesia. This is administered to women undergoing a cesarean section.

Care of patients post anesthesia surgery

Anesthesia is administered in various forms. A patient must discuss these options with the concerned doctor pre-operation. Post-operation, all discussions with the doctor regarding the pain and discomfort must be open and clear. Patients should also be encouraged to maintain a healthy lifestyle. If they experience anything during the surgery, they must report it to the medical team immediately.

Sources: Effects of Anesthesia after Surgery, M.A. Snider, MedilinePlus, Stanford