Intravenous anesthesia (IVA), together with total intravenous anesthesia (TIVA), forms a subspecialty of general anesthesia. General anesthesia is the conventional anesthesia or general anesthesia (Greek nàrkosi: to put to sleep). The name of this form of anesthesia refers to the exclusively intravenous administration of the anesthetic. In contrast to balanced anesthesia and inhalation anesthesia, an inhalation anesthetic is not used. IVA differs from TIVA in the use of nitrous oxide (laughing gas), which is omitted in TIVA.
Indications (areas of application)
In principle, IVA or TIVA can be performed for short, medium, and long procedures. Because the drugs used today are very effective after a short time, IVA/ TIVA is particularly well suited for very short procedures. In addition, the patient’s recovery time is short, so this form of anesthesia can be used for outpatient surgery without any problems. Another indication for IVA/ TIVA is when an inhalation anesthetic is contraindicated (i.e., must not be used) due to a disposition to malignant hyperthermia (MH; synonyms: malignant hyperpyrexia, anesthetic hyperthermia syndrome). Malignant hyperthermia is a life-threatening metabolic derailment caused by a genetic dysregulation within skeletal muscle. In addition to numerous symptoms, a severe increase in body temperature occurs. Volatile inhalation anesthetics (anesthetics administered through an anesthesia machine vaporizer) and so-called depolarizing peripheral muscle relaxants (drugs that cause muscle relaxation) can trigger this reaction. TIVA is preferable to IVA when the use of nitrous oxide has potential disadvantages. These include problems caused by increases in pressure or volume in air-containing body cavities, such as an increase in pressure in the middle ear when the tuba eustachii (tympanic meatus) is occluded. Another advantage of TIVA is when intensive ventilation with 100% oxygen is required. This situation occurs, for example, during bronchoscopy (lung endoscopy) or in patients with severe respiratory insufficiency (inability to breathe adequately or to take in oxygen).
Contraindications
- No possibility of ventilation – Because of the respiratory depressant effect of opioids, there must always be a possibility of ventilation.
- Opioid allergy
Before surgery
Before any surgery, the anesthesiologist (anesthesiologist) must conduct an educational interview with the patient to clarify questions, obtain a medical history, and inform the patient of risks and complications.The patient is often given premedication. This is administered about 45 minutes before the procedure and serves primarily to anxiolysis (anxiety resolution).Immediately before the induction of anesthesia, the anesthesiologist makes sure of the identity of the patient so that there is no confusion. It is obligatory to ask about the last food intake and to check the oral and dental status (also for forensic traceability in case of damage during intubation). Before any planned anesthesia, the patient must be fasting, otherwise the risk of aspiration (carryover of food residues into the airway) is increased. For emergency procedures performed on non-fasted individuals, a special form of anesthesia induction, Rapid Sequence Induction, is used to address the increased risk of aspiration.Medical monitoring is now begun, this includes: Electrocardiogram (ECG), pulse oximetry (measurement of pulse and oxygen content of the blood), venous access (for the anesthetic drugs and other medications), blood pressure measurement (if necessary, invasive arterial blood pressure measurement in high-risk patients).
The procedure
TIVA is characterized by a dosing regimen that closely follows the pharmacokinetics of the administered substances. The goal is to maintain the substance plasma levels of the drugs in a state of equilibrium or “steady state.” In addition, the drug levels must be flexibly adaptable to the surgical phases; short-acting substances that are administered either manually or with the aid of a computer are suitable for this purpose.First, a bolus (injection, which serves to administer a defined amount of a drug within a certain, relatively short period of time) is given, which initially saturates the substance concentration, then the maintenance dose is applied, e.g. via an infusion pump. In total intravenous anesthesia or intravenous anesthesia, the combination of the following different substances is used:
- Hypnotics (sleeping pills) or i. v. anesthetics for hypnosis and amnesia (memory loss); a well-known hypnotic is, for example, propofol
- Opioids for analgesia (abolition of pain), attenuation of autonomic reflexes; e.g., remifentanil
- Muscle relaxants (slackening of the muscles).
- IVA: nitrous oxide
- Oxygen
TIVA or IVA can be performed as mask anesthesia, intubation anesthesia, or with the aid of a laryngeal mask (laryngeal mask) (see General Anesthesia).
After the procedure
After general anesthesia, extensive monitoring of the patient is indicated, usually performed in a recovery room by experienced skilled nursing staff. In addition to surgical follow-up, the focus is on monitoring the patient’s cardiovascular system.
Potential complications
- Anaphylactic (systemic allergic) reaction – e.g., to medications.
- Aspiration of stomach contents
- Bradycardia – slowing of heart activity or heartbeat.
- Drop in blood pressure
- Intubation damage – e.g., damage primarily to the anterior teeth when the tube is inserted or further injury to the mouth and throat.
- Hypothermia (hypothermia)
- Air embolism – obstruction of a vessel by air bubbles entering the vascular system during surgery.
- Respiratory disorders
- Nausea (nausea)/vomiting
