Contribution of Russian scientists to the development of the method
Historically, the development of non-inhalational anesthesia is closely linked to the outstanding achievements of Russian medicine. Scientists of our country stood at the origins of developing methods that are now the global standard in surgery.
- N.I. Pirogov (1847): the great surgeon was the first in the world to express an innovative idea and successfully implement rectal administration of ether. This became the first step toward moving away from the exclusively inhalational route of administering anesthetic substances.
- N.P. Kravkov (1909): an outstanding pharmacologist who proposed using hedonal for intravenous anesthesia. This was the first non-volatile agent in history used for this purpose.
- S.P. Fedorov: an outstanding surgeon who took Kravkov's development and conducted large-scale clinical trials of hedonal, ultimately introducing intravenous anesthesia into widespread surgical practice.
Advantages over inhalational anesthesia
Intravenous anesthetics have a number of significant advantages that make them the drugs of choice for anesthesia induction and short surgical procedures.
- Shorter latency period. The drugs act very quickly, making it possible to instantly induce anesthesia in a patient.
- Technical simplicity. Administration of non-inhalational anesthetics does not require purchasing and setting up complex, bulky, and expensive anesthesia and respiratory equipment with vaporizers.
- Environmental safety for staff. When using intravenous agents, there is no issue of volatile anesthetics being released into exhaled air. This eliminates the need for complex air purification systems in the operating room and protects the health of the surgical team.
Features of the action of intravenous anesthetics
The main pharmacokinetic feature of these drugs is their high lipophilicity. Due to their ability to readily dissolve in fats, anesthetic molecules seamlessly and rapidly cross the blood-brain barrier directly into brain tissues.
Differences in the clinical picture: Unlike inhalational anesthesia, when using intravenous agents, the excitation stage is almost completely absent. The patient falls asleep calmly and quickly.
Main disadvantage: The price paid for speed and simplicity is low controllability of the depth of anesthesia. While in inhalational anesthesia one can quickly change the gas concentration in the inhaled mixture and thereby terminate its effect, after an intravenous injection, rapidly altering its blood concentration is no longer possible. The physician has to wait until the substance redistributes in tissues or is metabolized.
Classification by duration of action
Modern non-inhalational drugs (primarily for intravenous use) are classified according to the duration of the effect they produce. There are three main groups:
1. Short-acting drugs (duration of effect up to 15 minutes). This group includes agents for ultra-short interventions or anesthesia induction: propanidid, propofol, etomidate, ketamine.
2. Intermediate-acting drugs (duration of effect from 20 to 30 minutes). These include barbituric acid derivatives: thiopental sodium and hexobarbital.
3. Long-acting drugs (duration of effect 60 minutes or more). A typical representative of this group is sodium hydroxybutyrate.
Briefly: answers to topical questions
What is the mechanism of action of ketamine on CNS receptors?
The mechanism of action of ketamine involves blocking NMDA receptors of the central nervous system. The drug is a non-competitive antagonist of these receptors and eliminates the excitatory effect of glutamate on CNS structures. Ketamine (Ketamine) is a phencyclidine derivative. By blocking receptors, it causes functional dissociation in the CNS, leading to dissociative anesthesia with pronounced analgesia, a mild hypnotic effect, and partial loss of consciousness.
What side effects and complications are characteristic of propofol?
Propofol is characterized by cardiovascular side effects and local reactions upon administration.
- Hemodynamic disorders — causes bradycardia, lowers blood pressure, and may exert a negative inotropic effect (decreased myocardial contractility).
- Local reactions — pain at the injection site along the vein, as well as a rare risk of phlebitis and thrombosis.
- Immune reactions — allergic reactions are possible.
At the same time, the drug is well tolerated, lacks postoperative nausea, and is free of hepatotoxicity and nephrotoxicity.
What is dissociative anesthesia and which non-inhalational anesthetic causes it?
Dissociative anesthesia is a state of functional dissociation in the central nervous system caused by the non-inhalational anesthetic ketamine (Ketamine). This type of analgesia is characterized by the following clinical effects:
- Analgesia — pronounced pain relief.
- Effect on consciousness — a mild hypnotic effect, amnesia, and only partial loss of consciousness (the stage of surgical anesthesia does not occur).
- Preservation of vital functions — the patient retains spontaneous breathing, muscle tone, and protective reflexes (laryngeal, pharyngeal, cough).
How do biotransformation and elimination of thiopental sodium occur in the body?
Biotransformation of thiopental sodium (Thiopental sodium) occurs in the liver, but this process is significantly slower than the redistribution of the drug into tissues. Only 12–16% of the substance is degraded in the liver per hour. Due to its high lipophilicity, the drug redistributes from the brain and accumulates in adipose tissue. The decrease in drug concentration in the brain due to its transfer and accumulation in adipose tissue leads to awakening. Subsequent slow release of the substance from fat depots back into the bloodstream causes prolonged drowsiness after emerging from anesthesia.
Which classic stages of anesthesia are absent or weakly pronounced when using intravenous anesthetics?
When using intravenous (non-inhalational) anesthetics, the excitation stage is practically absent. This is one of the differences and advantages of intravenous anesthesia over inhalational anesthesia. Administration of drugs, such as thiopental sodium, ensures rapid induction of anesthetic sleep and pleasant falling asleep for the patient, bypassing the excitation stage. Non-inhalational agents are used for the induction of anesthesia.
To memorize short-acting anesthetics (up to 15 min), use the mnemonic: Propofol, Propanidid, Etomidate, Ketamine.
Class and exam questions
Why do intravenous anesthetics work faster than inhalation ones?
This is due to their high lipophilicity. The drug, administered intravenously, quickly reaches the brain and easily crosses the blood-brain barrier, bypassing the long process of accumulation in the alveoli.
What is the main danger of intravenous anesthesia?
The main disadvantage is low controllability. The administered dose of the drug cannot be rapidly cleared from the bloodstream if anesthesia proves too deep, unlike inhalational gases, the supply of which can simply be turned off.
Who first proposed using non-volatile substances for anesthesia?
The idea of rectal ether administration was proposed by N.I. Pirogov in 1847, and the first non-volatile agent for intravenous anesthesia (hedonal) was proposed by pharmacologist N.P. Kravkov in 1909.
What else to study on this topic
- Mechanisms of action of individual drugs: propofol, ketamine, and etomidate.
- Pharmacokinetic features of thiopental sodium (redistribution into adipose tissue).
- Specific side effects of sodium hydroxybutyrate during prolonged anesthesia.
- The concept of the blood-brain barrier and the physicochemical properties of lipophilic molecules.
- The difference between induction and maintenance of anesthesia using non-inhalational agents.
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