Definition
Anaesthesia induction is the process of preparing the patient for anaesthesia, an artificially induced state of unconsciousness and painlessness. These preparations follow a fixed scheme. The anaesthetic induction is followed by the anaesthetic continuation, during which this state of unconsciousness is maintained until the operation is finished and the patient can wake up from the anaesthesia.
Requirements
An important prerequisite for the smooth running of the anaesthesia induction is the clarification discussion by the anaesthetist, which usually takes place the day before the operation. Here, the patient is informed about the anaesthesia itself as well as about possible side effects of the anaesthesia. Usually blood is also taken from the patient to check various blood values, such as coagulation, before the operation.
A physical examination of the patient is also performed. During the physical examination, for example, the patient’s height, weight, blood pressure and pulse are determined. In addition, the heart and lungs are listened to and the oral cavity is inspected in order to detect potential problems with ventilation in advance.
At the end of the interview, the anesthesiologist can prescribe a sleeping pill to ensure that the patient has a calm and relaxed night. Sleeping pills can also be administered in the morning of the operation to calm the patient down. These sleeping pills are usually so-called benzodiazepines. Commonly used in this group are midazolam and lorazepam.
Procedure of anaesthetic induction
The further course of the anaesthetic induction follows a fixed schedule on the day of the operation in a room next to the operating room. First of all, the function of the equipment used to induce anesthesia is checked. This is usually carried out by a nurse with further training in anesthesia.
Then the nurse asks the patient’s name and date of birth. Hereby it is checked whether the patient is the right one and, for example, whether the files cannot be mixed up. In addition to the personal data, the nurse also asks when the patient last ate something.
The patient’s sobriety is important to prevent stomach contents from entering the lungs during the induction of anesthesia or during surgery. Careful examination of the documents and questioning of the patient are therefore essential for successful induction of anesthesia. Next, a blood pressure cuff is placed on the patient’s upper arm, which measures the patient’s blood pressure, ECG electrodes are attached to the cuff, which represent the patient’s heart action, a heart rate monitor is attached, which monitors the patient’s pulse, and a device that measures the oxygen saturation in the blood is clipped to the finger.
The devices are connected to a monitor. All these values (blood pressure, heart action, pulse and oxygen saturation of the blood) are together called vital signs and can be constantly observed via the monitor during the operation. In addition, a vein (usually on the forearm) is punctured in order to establish permanent access to the patient’s venous system.
Via this access, drugs and fluids can be administered to the patient during the induction of anaesthesia and during the course of the operation. Depending on the duration of the operation, one or more of these venous accesses are placed. Finally, each patient is given a fluid to drink, which serves to neutralize stomach acid.
This is the so-called tri-sodium citrate (TNC). Now the room is darkened, the doors closed and the actual anaesthetic induction begins. The first step of the anaesthetic induction is the so-called pre-oxygenation.
Here, a mask is placed over the patient’s nose and mouth, through which he or she inhales pure oxygen for a few minutes. This is important because the patient’s lungs do not fill with oxygen for a short time at the beginning of the anaesthesia. Now the anaesthetist gives the patient the first medication through the venous access.
This is a strong painkiller, a so-called opioid. The most commonly used agents are fentanyl and sufentanil, which differ only in their onset of action and duration of action. The analgesic can already cause a slight drowsiness or dizziness.In some cases, the drug may also cause a coughing irritation.
Then the actual anaesthetic is injected, which leads to anaesthesia, i.e. unconsciousness. Propofol is often used for this purpose. Now the patient is no longer able to breathe independently and the anaesthetist takes over breathing.
A mask is placed over the mouth and nose, as in pre-oxygenation. This is connected to a pressure bag through which air is pumped into the lungs. If no problems occur during this so-called bag-mask ventilation, a third medication is administered, which serves to eliminate the muscle function.
Drugs that prevent the muscles from tensing during the operation are called muscle relaxants. Frequently used representatives of this group are called Atacurium and Rocuronium. These two drugs, similar to painkillers, also differ in their onset of action and duration of action, and one therefore decides which is the more suitable substance depending on the type and duration of the operation.
By preventing muscle tension, muscle relaxants facilitate both the intubation that takes place in the next step and the operation itself. During the operation, the patient must of course continue to be ventilated. There are two main methods available for this purpose, ventilation using a laryngeal mask or ventilation using a tube.
The laryngeal mask consists of a plastic tube and an inflatable rubber ring which is placed around the entrance to the trachea. The tube is a plastic tube that is inserted into the trachea. This procedure is called intubation.
The Laryngeal Mask is easier to use and is also gentler on the throat, while the Tube offers a safer protection against the transfer of stomach contents into the lungs. Which of these two procedures is used to ventilate the patient depends, among other things, on the type of operation and the duration of the operation. After the patient has been successfully ventilated by means of a laryngeal mask or intubation, the anaesthesia induction is completed and the anaesthesia is continued, which involves maintaining a state of unconsciousness and painlessness (anaesthesia) during the operation.
In emergency situations, the induction of anesthesia can of course deviate from the above-mentioned scheme, for example, the explanatory talk by the anesthesiologist can then be omitted and other medications are sometimes used to induce anesthesia, namely those with a faster onset of action. Just as there is the beginning of an anaesthesia, there is also the end or the transitional period in which the patient slowly wakes up. This process has its own sequence and is described in detail in our next article: Anaesthetic delivery – sequence, duration and risks
