Essence and advantages of the combined method
Unlike mask anesthesia, which is difficult to control and requires high consumption of drugs, the endotracheal method is free from these drawbacks. For major surgical interventions, combined endotracheal anesthesia is used. Its main feature is multicomponent administration: hypnotics, analgesics, and muscle relaxants are used.
This cumulative effect makes it possible to reduce the dosage and toxicity of each individual substance, as well as to improve gas exchange by reducing the anatomical "dead" space. The physician achieves three goals simultaneously: reliable analgesia, complete loss of consciousness, and total muscle relaxation (at level I of the surgical stage).
Stages of anesthesia
The classical procedure involves three consecutive stages:
- Stage I — Induction. The goal is to rapidly induce deep sleep without the excitation stage. Intravenous barbiturates are used for this purpose, most commonly a 1% sodium thiopental solution (at a dose of 400–500 mg, up to a maximum of 1000 mg). Muscle relaxants are administered concurrently, followed by tracheal intubation.
- Stage II — Maintenance. Performed at the $III_1–III_2$ level of the surgical stage. Inhalation agents (halothane, dinitrogen oxide with oxygen) or neuroleptanalgesia (NLA) are used. Since relaxants cause total myoplegia of the respiratory muscles, mechanical ventilation is a mandatory prerequisite.
- Stage III — Emergence. By the end of the surgery, the administration of medications is stopped. The patient regains consciousness, muscle tone, and spontaneous breathing. Once blood parameters ($pO_2$, $pCO_2$, pH) return to normal, extubation is performed, and the patient is transferred to the ward.
Neuroleptanalgesia (NLA) and monitoring
NLA is considered a safer type of anesthesia. The regimen includes the inhalation of dinitrogen oxide with oxygen (2:1) and intermittent intravenous administration of 1–2 ml of fentanyl and droperidol every 15–20 minutes.
Hemodynamic correction during NLA is strictly regulated:
- When heart rate increases, fentanyl is administered to enhance analgesia.
- When arterial pressure rises, droperidol is used to suppress autonomic responses.
During surgery, the anesthesiologist monitors the course of anesthesia, breathing patterns, pupil state, eye position, and the corneal reflex. Meanwhile, the nurse monitors blood pressure and pulse.
Muscle relaxants in endotracheal anesthesia
Total muscle relaxation is achieved by fractional administration of relaxants. According to their duration of action, they are divided into three groups:
- Short-acting (5–20 minutes): suxamethonium chloride, mivacurium chloride.
- Intermediate-acting (20–35 minutes): atracurium besylate, rocuronium bromide.
- Long-acting (40–60 minutes): pipecuronium bromide.
Management of complications and procedure completion
If anesthesia inadvertently deepens to the $III_3$ stage, there is a risk of overdose and tongue fall-back. Airway patency must be promptly secured: the anesthesiologist places their thumbs on the angles of the mandible and displaces it forward (so that the lower incisors are positioned anterior to the upper ones), holding the jaw with the remaining fingers. Airways are also used.
Concluding the procedure, the physician turns off the anesthetic agent, ventilates the lungs with pure oxygen for several minutes, removes the mask, closes all valves, and drains the remaining liquid anesthetics. The tubing is sent for sterilization.
Briefly: answers to topical questions
What drugs are used for induction in endotracheal anesthesia?
Any narcotic agents are used for induction, most frequently barbiturates, particularly sodium thiopental. Certain sources also mention the use of propofol, sodium hydroxybutyrate, fentanyl, and benzodiazepine derivatives. Hexobarbital causes less respiratory depression than sodium thiopental.
What complications can occur directly during the stage of tracheal intubation?
Complications related to the technique of the procedure may occur directly during tracheal intubation via direct laryngoscopy. These include:
- Damage to teeth by the laryngoscope blade.
- Damage to the vocal cords.
- Misplacement of the endotracheal tube into the esophagus.
- Insertion of the tube too deep (into the right bronchus).
- Accidental extubation (dislodgement of the tube from the trachea).
- Kinking of the endotracheal tube.
Additionally, in the pre-intubation phase following the administration of muscle relaxants, there is a risk of regurgitation and subsequent aspiration of gastric contents.
What modern inhalation anesthetics are used during the maintenance phase of anesthesia?
Halothane, dinitrogen oxide (nitrous oxide) with oxygen, and other liquid volatile anesthetics such as enflurane and isoflurane are used during the maintenance phase of anesthesia. Liquid volatile anesthetics are administered by inhalation through the endotracheal tube and require precise dosing using vaporizers. Their advantage is high controllability of anesthesia, as they are rapidly absorbed and eliminated via the lungs. Sevoflurane is also indicated as an inhalation anesthetic and can be used for general anesthesia.
What methods exist to verify the correct position of the endotracheal tube in the trachea?
Lung auscultation is used to check the position of the endotracheal tube, verifying whether the tube is located above the tracheal bifurcation. During a cesarean section, correct tube placement is also confirmed by capnography prior to cuff inflation.
Class and exam questions
Preoxygenation?
This is breathing pure oxygen (at a flow rate of at least 1 L/min) for 1–2 minutes. It is necessary to create an oxygen reserve in the lungs before spontaneous breathing is stopped.
What are the criteria for correct mandibular advancement?
The main criterion is that the patient's lower incisors must be positioned anterior to the upper incisors. This reliably prevents the posterior displacement of the tongue base.
At what stage is maintenance anesthesia performed?
Induction and maintenance provide depth at the I–II level of the surgical stage ($III_1–III_2$ state). Further deepening to $III_3$ is considered hazardous.
What else to study on this topic
- Dangers and disadvantages of classical mask anesthesia
- Dosing and administration regimen of sodium thiopental
- Criteria for respiratory adequacy prior to extubation
- Pharmacological properties of droperidol and fentanyl as components of NLA
- Algorithm for jaw subluxation in tongue fall-back
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Other topics in the section "CHAPTER 3. ANESTHESIA"
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