A narcotic is a medicine that can induce profound loss of consciousness and painlessness in the central nervous system for diagnostic or surgical purposes. The different narcotics have different effects on the receptors and signal molecules in the brain, which explains the different effects of the substances.
A distinction is made between inhalation anesthetics and injection anesthetics. The former are taken up through the respiratory system, i.e. they are administered to the patient in gas form through a mask and then inhaled. Injection anesthetics are injected into a patient's vein.
The currently mainly clinically used inhalation anesthetics are Isoflurane, Sevoflurane, Desflurane and Enflurane. Laughing gas and Halothane lose importance. The individual narcotics of this class of substances each have different properties, which relate, for example, to their solubility in the blood, their potency and their solubility in fat. Fat solubility in particular plays a major role in the effect of inhalation anesthetics, as they have to migrate into the blood via the airways. The more fat-soluble the substances, the easier it is. This means that inhalation anesthetics with high fat solubility achieve a higher potency and above all lead to a faster onset of action. In addition, a smaller amount of anesthetic is required to achieve the desired depth of anesthesia. In contrast to this is the solubility of inhalation anesthetics in blood. Substances with high blood solubility dissolve more poorly in fat and therefore need more time to achieve the desired depth of anesthesia. It also takes longer for the narcotic to wash out and for the patient to wake up again. In order for the induction of anesthesia to take place quickly enough, the dose in the gas mixture that the patient inhales is increased in the case of inhalation anesthetics that are readily soluble in blood.
Inhalation anesthetics are mainly excreted via the lung. The narcotic is exhaled again.
Effects and side effects
Inhalation anesthetics cause the blood vessels in the brain to expand. This can lead to a Increase in intracranial pressure which can reduce blood flow to the brain. Especially with patients who already have increased intracranial pressure or also Brain tumors injection anesthetic is therefore preferable. In addition, inhalation anesthetics can do that Cardiovascular system influence differently. The contraction force of the heart muscle can decrease, it can too Cardiac arrhythmias and to Increase in blood pressure or waste come. For people with Heart disease are the inhalation anesthetics Sevoflurane and Isoflurane recommended because they relieve the heart most of all by widening the vessels. One advantage of inhalation anesthetics is that they can relax the airways. This is especially true for patients with asthma of importance because the muscles of the airways tend to cramp in them. In principle, inhalation anesthetics can cause liver and kidney damage.
Sevoflurane is particularly popular for Induction of anesthesia in children used because it has a pleasantly sweet smell.
Advantages over injection anesthetics
The advantages of inhalation anesthetics are e.g. in the fact that you can get one very quickly and easily anesthesia can initiate. The anesthesia can be deepened or flattened by simply changing the concentration of the substances in the gas mixture. In addition, the breakdown in the organism takes place largely independently of liver and kidney function, which makes them better tolerated. A reduction in breathing activity after the operation is less common with inhalation anesthetics.
The injection anesthetics are given to the patient through a vein. Can be used, for example. Barbiturates, Etomidate, Ketamine and Propofol, Propofol is used almost without exception nowadays, as it offers some advantages over the other substances. Patients wake up faster and recover better under propofol than under the influence of barbiturates. The depth of anesthesia can also be better controlled with Propofol. nausea and Vomit are also less common with propofol. The most common side effect of this narcotic is a possible drop in blood pressure. With injection anesthetics, it should be noted that they must be injected slowly into the vein. This is important because the injection anesthetics bind to proteins in the blood (Plasma protein binding). The most effective part of the narcotic is that which is not bound to proteins. The faster the injection, the less narcotic can bind to proteins. This can quickly lead to an overdose which can be very dangerous for the patient. In addition, injecting too quickly can irritate the veins, which can also inflame the affected vein (phlebitis). This is very uncomfortable for the patient.
The injection narcotics are mainly broken down by the liver and excreted via the liver or kidneys. It can also cause liver and kidney damage.
In contrast to inhalation anesthetics, the duration and strength of the injection anesthetics can no longer be influenced well once they have been administered to the patient. However, they are well suited for induction of anesthesia, as they usually lead to a quick, peaceful fall asleep. The time it takes for Propofol to take effect is only about 30 seconds.
Injection anesthetics can cause some undesirable effects. These include the suppression of breathing (Respiratory depression), Lowering blood pressure, Muscle cramps, allergic reactions, and bad dreams. Seizures may occur less frequently, acute kidney failure or very rarely one Propofol Infusion Syndrome (PRIS) come. This leads to acute kidney failure, cardiac arrhythmias with heart failure, muscle breakdown (Rhabdomyolysis) and strong acidification of the blood (Lactic acidosis).
TIVA (total intravenous anesthesia)
Injection anesthetics are usually combined with opioids (strong pain relievers) and muscle relaxants (muscle relaxants) during an operation, as they alone cause anesthesia, but cannot yet relieve muscle tension and pain sensation. This combination of injection anesthetic, muscle relaxant and opioid is also called TIVA (total intravenous anesthesia) designated. It has the advantage that the anesthetist can control the depth of anesthesia well and the patient suffers less nausea and vomiting after the anesthesia. The TIVA is particularly suitable for patients who do not tolerate inhalation anesthetics well. It is also used in patients with increased intracranial pressure for whom balanced anesthesia should not be used.
In addition to the TIVA, there is also the balanced anesthesiawhere inhalation anesthetics are combined with injection anesthetics. This form of anesthesia is particularly recommended for patients with pre-existing diseases of the cardiovascular system, as the total dose can be reduced by combining the various narcotics. This reduces the side effects and the burden on the organism.
Narcotics are often misused. Often they come to play in sports Doping purposes for use. Narcotics dampen the excitation in the brain, which is why they are used in sports that require a steady hand, e.g. golf, sports shooting or archery. Narcotics are also often used in martial arts, such as boxing, as they reduce the athlete's sense of pain. Strikes are less perceived and the athlete can hold out longer. Also using a combination of narcotics Stimulants was in use for a long time. This made it possible to combine the dampening and pain-relieving effects of narcotics with the drive-increasing and concentration-promoting effects of stimulants.
The use of narcotics for such purposes has been banned since 1967. In doping tests more attention is paid to the use of narcotics, which is why they are used less nowadays. The dangers of improper use of narcotics should not be underestimated. Accidental overdosing in particular can lead to respiratory paralysis with circulatory collapse and, in the worst case, death.