General Anesthesia - How It Done, Risks and Benefits

General anesthesia is an anesthetic technique that promotes the abolition of pain (hence the name anesthesia), muscular paralysis, abolition of reflexes, amnesia and, mainly, unconsciousness.

This form of anesthesia causes the patient to become unable to feel and / or react to any stimulus from the environment, being the technique most indicated in complex, long and large surgeries.

General anesthesia is very feared by the general population, much because there are several myths about it and little information available to the lay public.

General anesthesia
General anesthesia

How is general anesthesia done?

General anesthesia has four phases: pre-medication, induction, maintenance and recovery.

The premedication phase is done so that the patient arrives at the calm and relaxed surgical act. A short-acting anxiolytic (tranquilizer), such as midazolam, is usually given, leaving the patient with a mild degree of sedation. In this way, it enters the operating room under less stress.

The induction phase is usually made with intravenous drugs, with Propofol being the most commonly used.

After induction, the patient quickly enters deeper sedation, that is, loses consciousness, getting into a state popularly called induced coma. The patient, despite being unconscious, may still feel pain, and it is necessary to further deepen the anesthesia for the surgery to be performed. For this, the anesthetist also usually administers an opioid analgesic (from the morphine family) such as Fentanyl.

At this moment the patient already presents an important degree of sedation, being no longer able to protect his airways from secretions of the oral cavity, such as saliva. In addition, in most surgeries with general anesthesia, it is important to relax the muscles, causing the respiratory muscles to be inhibited. The patient then needs to be intubated* and coupled to mechanical ventilation in order to receive adequate oxygenation and not aspirate their secretions.

* In some fast surgeries, or that do not approach the chest or abdomen, intubation may not be necessary, the patient being left with only an oxygen mask.

At the start of the maintenance phase, the drugs used in induction, which have a short duration, begin to lose their effect, causing the patient to need more anesthetics to continue the procedure. At this stage, anesthesia can be done with anesthetics either inhalation or intravenously.

In most cases, the inhalation route is preferred. Anesthetics are administered through the orotracheal tube in the form of gas (vapors) along with oxygen, being absorbed by the alveoli of the lung, passing rapidly into the bloodstream.

Some examples of inhalational anesthetics are halogenated nitrous oxide and anesthetics (halothane, sevoflurane and desflurane), drugs that are given continuously throughout the surgical procedure.

The depth of the anesthesia depends on the surgery. The level of anesthesia to cut the skin is different from the level to approach the intestines, for example.

As the surgical procedure progresses, the anesthetist always tries to leave the patient with as few anesthetics as possible. Very deep anesthesia can cause hypotension and deceleration of the heartbeat, which can greatly reduce the blood perfusion to the body tissues.

When the surgery enters its final phase, the anesthetist begins to reduce the administration of the drugs, already planning a cessation of the anesthesia along with the end of the surgical procedure. If there is excessive muscle relaxation, drugs that work as antidotes are given.

At this stage of recovery, again opioid analgesics are administered so that the patient does not wake up from anesthesia with pain in the place where he was cut.

As the inhalational anesthetics are being eliminated from the bloodstream, the patient begins to regain consciousness, being able to breathe again on his own. When the patient is already in full control of the airway reflexes, the orotracheal tube can be removed.

At this time, although the patient already has a reasonable degree of consciousness, he will hardly remember what happened at this stage of recovery due to the amnesic effects of drugs.

Risks of general anesthesia

There is a myth that general anesthesia is a dangerous procedure. Exclusive complications of general anesthesia are rare, especially in healthy patients.

In most cases, the complications are derived from serious illnesses that the patient already had, such as advanced heart, kidney, liver or lung disease, or complications of surgery, such as bleeding or injury/failure of vital organs.

Just as an example, a 1997 Canadian study, with only general anesthesia dental surgeries, that is, low-risk surgeries performed on healthy patients, detected a mortality rate of only 1.4 per 1 million procedures. This type of study shows us that the anesthesia itself is very safe.

In general, the mortality rate of general anesthesia is only 1 in 100,000 to 200,000 procedures, which means a death risk of miserable 0.0005% to 0.001%.

It is important to note that many surgeries under general anesthesia are performed in patients with severe diseases or in complex high-risk surgeries. However, in the vast majority of cases, when the outcome is tragic, it is rarely the fault of general anesthesia.

It should also be noted that general anesthesia is a complex procedure, and should be done only by qualified professionals and in environments with ample structure for such.

Factors that increase the risk of general anesthesia

Before any surgery, an anesthesiologist will consult you to assess your surgical risk. In addition to the prior recognition of serious diseases that may complicate the surgical procedure, it is important for the anesthesiologist to know some of the patient's personal information that may increase the risk of anesthesia, such as:
  • Previous history of anaphylactic reaction
  • Food allergies or drugs
  • Frequent use of alcoholic beverages
  • Use of drugs, mainly cocaine
  • Use of medications
  • History of smoking
  • Sleep apnea
  • Obesity
  • Conclusion on general anesthesia

General anesthesia is an extremely safe procedure when performed by a trained team, and is usually the most appropriate anesthetic method for medium/large surgeries.

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