General anesthesia

The general Anesthésie is a medical act whose main aim is the temporary suspension and reversible of the conscience and of the painful sensitivity, obtained using drugs (anesthetic drugs) managed by intravenous way and/or inhalatoire. This key objective, allowing the realization without memorizing and Pain of the surgical interventions and some invasive examinations, joins the need for a continuous monitoring and often for an artificial control (physical and/or pharmacological) of the vital functions: Breathing (respiratory frequency and volumes, oxymetry), Hémodynamique (frequency and rate of heartbeat, blood pressure), Thermoregulation, Muscular tone.

Because of specificities of the technical approach, physiopathological and pharmacological of the anaesthetized patient and safety requirement which surrounds this act with all the stages, the practice of the general anesthesia is legally possible in France only under the direct control of a Médecin anesthetist-réanimateur (decree of December 5th, 1994).

Methods

Except for the emergency cases, the general Anesthésie is always carried out with jeun (six hours minimum for the adults, four hours for the children), because the body relaxation is accompanied by a loss of the reflexes of protection of the air routes and by a risk of inhalation of the gastric contents, whose consequences can be extremely serious (pneumopathy of inhalation).

It is held in three parts:

a consultation of Anesthesia;
the Anesthesia in itself;
the alarm clock under monitoring.

The consultation of Anesthésie has several goals:

to examine the patient and to evaluate his state
to prescribe the complementary examinations if necessary
to decide anesthetic technique according to the preceding elements to even contra-indicate the so necessary Anesthesia
to inform the patient of the procedure and the risks of the Anesthesia

the premedication consists with the catch of one tranquillizing (Hypnovel ®, Atarax ®) by oral way which starts to release the patient (who is often distressed to undergo an surgical operation).

the general Anesthésie rests on the association of a narcosis (sleep) and an analgesia (fight against the pain), according to the type of surgery an associated curarization can be necessary.

The general Anesthésie is accompanied by a loss of conscience and in general by a loss of the Réflexe S of protection of the air routes; this is why it is often accompanied by the Intubation trachéale. Nevertheless short Anesthesia S general and for not very aggressive surgical gestures can be carried out without intubation, with a facial mask, by preserving the ventilation (breathing) spontaneous of the patient, or by assisting it with the balloon via the mask.

Because of depression of the respiratory function, the General anesthesia can also require a ventilation assisted, normally after intubation. During the intubation, the patient is in total apnea. The first phase consists in making breathe pure Dioxygène with the patient so that its Poumon S contains 100 % of dioxygene; this operation, intended to drive out the Diazotizes (component majority Air), is called denitrogenation or preoxygenation . This saturation of the Poumon S makes it possible to ensure a food of dioxygene blood during the short moment between the consecutive ventilatory stop the anesthesia and the beginning of artificial ventilation (time of intubation). For a few years, one has used also the Masque laryngé to replace the intubation: its placement is simpler and less traumatisant but it does not offer sure protection of the air routes against the inhalation of gastric liquid. The sealing is sometimes difficult to obtain.

At the end of the intervention , the patient is always led in a room of post-interventionelle monitoring (recovery room) to be supervised there in a continuous way before regaining its room or leaving the Hôpital.

Safety

A cushion heating or a heating cover with pulsated air makes it possible to decrease the body loss of heat. The monitors of breathing, of ECG, tissue oxygenation (saturation taken with the finger) and of the blood pressure are very useful apparatuses for the monitoring of the patient. The monitoring continues by a doctor anesthetist, one (E) inhalothérapeute or one (E) male nurse (E) anethesist and the compilation of the data in a report/ratio of anesthesia offer very important advantages to the level of safety.

Anesthesia by inhaled agents

It is the famous black mask (or other even transparent colors) which makes you sleep. Although it is possible to obtain unconsciousness, these agents do not have a clean analgesic effect and they create a blocking neuromusculaire (paralysis) very moderate. These agents are rather seldom used only, except for the pediatric anesthesia; in this case, they allow the induction of the anesthesia without " piqûre".

The protoxide of Azote makes it possible to obtain an euphoria (laughing gas) and a certain analgesia. (painful care, childbirth when a péridurale is not realizable)

Anesthesia by intravenous way

There are several kinds of morphinomimetic (analgesics) according to their power; they are morphine derivatives. First of all, the Sufentanil (Sufenta ®) which is 1000 times more powerful than morphine. It is used the most in the heavy surgical acts because it lasts one high action (50 to 70 minutes). Its peak of maximum action is reached in approximately 6 minutes. Fentanyl (Fentanyl ®) which is 100 times more powerful than morphine, is an older derivative. Its principal disadvantage is its accumulation during the prolonged use (long surgery, sedation in reanimation…) There is also Alfentanil (Rapifen ®) which, is to him only 10 times more powerful than morphine. It lasts one action from 7 to 15 minutes and a time of 20 seconds action per intravenous way. Rémifentanil (Ultiva ®) is an analgesic of very short duration, very powerful. Its originality comes from its " effect; on/off". It does not accumulate even in the event of prolonged use. It is used in anesthesia, the studies for its broad use in reanimation are in hand. He is accused in occurred of phenomena of operational hyperalgesy post.

The leader of hypnotic intravenous and the first used (about 1940) are the Thiopental (Pentothal ®). The hypnotic modern one more used is the Propofol (Diprivan ®). It lasts a time of action from 30 to 50 seconds and action from 5 to 10 minutes. It accumulates little, and has an anti effect emetic very useful. The pain during the intravenous injection can sometimes be important (fast injection on a vein of small gauge).

The Curare S act on the level of the driving plate by being opposed to conduction nerve impulse between the nerve and the muscle. The use of curare causes a respiratory stop by paralysis of the diaphragm and the intercostaux muscles, which implies an respiratory assistance throughout their effect.

There are two principal types

depolarizing curares or leptocurares: used in urgency because their action is fast and quickly reversible. They allow a fast intubation under good conditions, which makes it possible to protect the Breathing apparatus from the inhalation of the contents of the Estomac. The only representative of this class is the succinylcholine (Celocurine ®)

Its use is limited by a certain number of undesirable effects, among which: secondary muscular pains, hyperkaliemy, disorders of the cardiac rhythm, malignant hyperthermia, anaphylaxie with risk of shock.

nondepolarizing curares or pachycurares: during AG, for the relaxation of the muscles (for example in digestive surgery and in the coelioscopies.)

is used

Which are the risks of the general Anesthésie?

The anesthetic risk decreased considerably in France these twenty last years. The creation of the “recovery rooms” contributed much to that. Even if the Anesthésie is directly responsible only for one death out of 10.000 on average, the 600 to 800 patients who die each year in an illegitimate way must lead us to make progress: techniques of anesthesia, the organization and the equipment of the places of activity, the rational organization of the operational programs (made jointly by the surgeon S, the panseuses anesthetists and the ) and to make progress safety in the exercise of this trade particularly anxiogene for those which practice it.

nauseas and the vomiting with the alarm clock became less frequent with the novel methods and the new drugs. The accidents related to the passage of the contents of the Estomac in the Poumon S are very rare if the instructions of fast are respected.
the introduction of a tube into the Trachea (intubation) or into the Throat (laryngé mask) to ensure breathing during the Anesthésie can cause evils of Gorge or enrouement momentary.
Of the dental traumatisms is also possible. This is why it is important that you announce any apparatus or any particular dental brittleness.
a painful redness on the level of the vein into which the products were injected can be observed. It disappears in a few days.
the position prolonged on the operating table can involve compressions, in particular of certain nerves, which can cause a numbness or, exceptionally, the Paralysie of an arm or a leg. In the majority of the cases, the things return in the order in a few days or some weeks.
Of the passing disorders of the memory or a fall of faculties of concentration can occur in the hours following the anesthesia.
Of the unforeseeable complications involving a vital risk like an allergy engraves, an cardiac arrest, an asphyxiation, are extremely rare. To give an order of magnitude, a serious complication occurs only on hundreds of thousands of anesthesia.

In 50 years, mortality passed from 1/1000 to 1/100.000 according to certain studies.

Combined anesthesia

This technique combines the use of several agents, having each useful particular property at the time of a Anesthésie. There exist 3 principal categories of products used for a General anesthesia :

Opiated (ex: Sufentanil) They make it possible to decrease or eliminate the painful feeling.
Hypnotic (ex: Propofol) They induce the sleep and the amnesia of the events. They are managed by intravenous way or in the form of gas which one breathes (ex: isoflurane, sevoflurane…)
Curare (ex: succinylcholine) They allow the total muscular relaxation often necessary to the course of an operation (in particular in abdominal surgery)

The patient receiving these Médicament S is plunged in an artificial coma, and it will be thereafter intubé and ventilated artificially with a mixture of Oxygène, volatile Anesthetic agent and Protoxyde of nitrogen or Air.

Of curare the Bolus or opiate seronts managed with the needs thereafter.

References

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