Isoflurane is a volatile anesthetic with hypnotic and muscle relaxant effects. As a volatile, halogenated inhalational anesthetic, it is suitable for induction and maintenance of anesthesia for surgical procedures.
What is isoflurane?
Isoflurane belongs to the group of fluranes on the one hand and to the class of inhalation anesthetics on the other. Isoflurane is a volatile anesthetic. As a structural isomer of enflurane, it has been used for anesthetization since 1984. The hypnotic effect and also the muscle relaxant effect are considered good. However, the effect is only weakly analgesic. Isoflurane has the molecular formula C3H2CIF5O. The molar mass is 184.49 g/mol. Isoflarone has a pleasant odor and is in a colorless liquid state at room temperature. The boiling point is 48-49 degrees Celsius. It has a low solubility in water. The compounds dimethyl sulfate and 2,2,2-trifluoroethanol form the synthesis of isoflurane.
Pharmacological effects on the body and organs
The metabolization rate of isoflurane is extremely low. This has the advantage that it can be used in patients who have renal or hepatic impairment. The rate is around 0.2%. A good hypnotic effect and also muscle relaxant effects are known. The intracranial pressure increase is low. Compared with other anesthetic agents, CNS electrical activity is more suppressed. Acetylcholine receptors are suppressed and NMDA receptors are blocked. On the other hand, GABA receptors are activated. This supports the hypothesis that one of the anesthetic mechanisms is based at least in part on attenuation of cholinergic cells. Isoflurane also affects the cardiovascular system. Here it has a vasodilating effect. A marked reduction in peripheral vascular resistance and a drop in blood pressure are the result. Cardiac output remains virtually unchanged. The effect on the myocardium is negatively introp, but the myocardial depression is rather small compared to halothane. Isoflurane decreases myocardial oxygen consumption as well as coronary vascular resistance without appreciably affecting coronary blood flow rate. The pungent odor can irritate the respiratory tract. This can lead to cough irritation, bronchosis secretion but also breath holding. Any respiratory depression that may occur is dose-dependent. It should be noted that pulmonary vascular resistance increases and pulmonary distensibility may temporarily decrease. A decrease in respiratory rate is based on a central depression of respiratory neurons of the medulla oblongata. This, on the other hand, causes a decreased contractility of the diaphragm. An increase in arterial PaCO2 occurs during anesthesia in spontaneous breathing. This causes a decrease in arterial pH. Eventually, this may result in respiratory acidosis. The decreased blood pressure also affects renal functions. This reduces the glomerular filtration rate as well as the renal blood flow. The result is decreased urine production. These processes are reversible. The automatic regulation of the kidney functions in humans up to a mean arterial pressure of 70 mmHg. Diuresis is therefore not affected. A nephrotoxic effect has not been demonstrated for isoflurane.
Medical use and use for treatment and prevention.
As a volatile halogenated inhalational anesthetic, isoflurane is suitable not only for induction but also for maintenance of anesthesia. As an initial concentration for induction of anesthesia, the concentration of isoflurane should be 0.5% for adequate depth of anesthesia in surgical procedures. Surgical depth of anesthesia within 7 to 10 minutes is achieved with a concentration of 1.5 to 3% in inspiratory air. For maintenance of anesthesia in conjunction with oxygen and nitrous oxide, a concentration of 1.0 to 2.5% is administered. If isoflurane is given with oxygen alone, the dose must be increased by 0.5 to 1%. Muscle relaxants should be administered to achieve additional muscle relaxation. Isoflurane may also be used in conjunction with artificially induced labor, general anesthesia, and cesarean section. No food should be ingested for 8 to 12 hours prior to surgery with isoflurane inhalation anesthesia.The age as well as previous illnesses and existing diseases but also the intake of other medications as well as the operation area have to be considered for anesthesia with isoflurane.
Risks and side effects
The anesthetic isoflurane causes vasodilatation. Depending on the dosage, it therefore causes a drop in arterial blood pressure and an increase in heart rate. The blood flow to the heart is reduced, as is the cardiac output. With regard to the kidneys, it should be noted that their blood flow is reduced and the glomerular filtration rate is decreased as well as the urine production. The active ingredient contained in the drug reduces respiratory activity, which is why it is classified as a respiratory depressant. Irritation of the mucous membranes can also occur easily. In Boston, an experimental laboratory series was able to demonstrate that isoflarone, on the one hand, promotes the deposition of amyloids in nerve cells and, on the other hand, increases apoptosis. These are processes that are characteristic of Alzheimer’s disease. Whether the inhaled narcotic is also responsible for the frequent postoperative cognitive dysfunction (COPD) in the elderly has not yet been conclusively determined. Also, whether a direct damaging effect on brain cells is to be feared could not yet be conclusively proven neurologically by in vitro investigations. However, it has been shown that not only the formation of amyloid beta protein but also programmed cell death (apoptosis) are promoted by toxic products.
