Isoflurane is 1-chloro-2, 2, 2-trifluoroethyl difluoromethyl ether.
Isoflurane Dexa Medica is colourless, nonflammable and contains no additive or stabilizer.
Isoflurane is a general inhalation anaesthetic which provides rapid induction of anaesthesia and rapid recovery. In common with all inhalational anaesthetics, isoflurane induces a dose-dependent depression of central neural activity and cerebral metabolism, while cerebrospinal fluid pressure may increase due to cerebral vasodilatation. Isoflurane causes a dose-dependent depression of breathing and a decreased ventilatory response to carbon dioxide. The decrease of blood pressure which occurs during isoflurane anaesthesia is predominantly due to peripheral arterial and venous dilatation, whereas heart rate and cardiac output are well maintained up to maintained inspiratory concentrations of 2.5%. Isoflurane, which has minimal effects on atrioventricular conduction, causes significantly less sensitisation of the heart to the arrhythmic effects of catecholamines than does halothane. Isoflurane shows very low solubility in blood and body tissues, much lower than for enflurane and halothane. This low solubility results in a rapid development of an alveolar pressure sufficient to cause anaesthesia.
General inhalation anaesthetic for use in patient of all ages.
Isoflurane has a slight pungent ethereal odour which may limit the rate of gas induction but despite this, induction and particularly, recovery are rapid.
Minimum alveolar concentration (MAC) value for isoflurane carry with age. The following text indicates average MAC values for different age groups.
Mid-60's: 1.05%; mid-40's: 1.15%; mid-20's: 1.28%; 1-5 years: 1.6%; 6-12 months: 1.8%; 1-6 months: 1.87%; 0-1 month: 1.6%.
Premedication: Premedication drugs should be selected according to the needs of the patient. The ventilatory depressant effect of isoflurane should be taken into account. Anticholinergic drugs (eg, atropine, glycopyrrolate USP) may be used for their effects in drying oral secretion (antisialogogue) at the discretion of the anaesthesiologist, but they may enhance the weak effects of isoflurane in increasing heart rate.
Induction: As isoflurane has a mild pungency, inhalation should usually be preceded by the use of a short-acting barbiturate, or other IV induction agents to prevent coughing. Salivation and coughing may be troublesome in small children induced with isoflurane. Alternatively, isoflurane with oxygen-nitrous oxide mixture may be administered. It is recommended that the induction with isoflurane be initiated at a concentration of 0.5%. Concentrations of 1.5-3% usually produce surgical anaesthesia in 7-10 min. Blood pressure decreases during induction, but this may be compensated by surgical stimulation.
Maintenance: Adequate anaesthesia for surgery may be sustained with an inspired isoflurane concentration of 1-2.5% in an oxygen 70% nitrous oxide mixture. Additional inspired isoflurane (0.5-1%) will be required with lower nitrous oxide levels or when isoflurane is given with oxygen alone or with air/oxygen mixtures. Blood pressure decreases during maintenance anaesthesia in relation to the depth of anaesthesia ie, blood pressure is inversely related to the isoflurane concentration. Provided there are no other complicating factors, this is probably due to peripheral vasodilatation. Cardiac rhythm remains stable. Excessive falls in blood pressure may be due to the depth of anaesthesia and, in such circumstances, can be corrected by reducing the inspired isoflurane concentration.
Induced hypotension can be achieved by artificially ventilating patients with isoflurane 2.5-4.6%. Pre-treatment with clonidine significantly decreases the isoflurane requirement for maintaining induced hypotension. For caesarian section: 0.5-0.75% isoflurane in a mixture of oxygen/nitrous oxide is suitable to maintain anaesthesia for this procedure.
Elderly: As with other agents, lesser concentrations of isoflurane are normally required to maintain surgical anaesthesia in elderly patients. See previously mentioned MAC values.
Recovery: The concentration of isoflurane can be reduced to 0.5% at the start of closing the operation wound, and then to 0% at the end of surgery. Provided that the anaesthesiologist is satisfied that the effect of any neuromuscular-blocking drug has been reversed and the patient is no longer paralysed. After discontinuation of all anaesthetics, the airways of the patient should be ventilated several times with oxygen 100% until complete recovery. Isoflurane is a general inhalational anaesthetic which provides rapid induction of anaesthesia and also rapid recovery. The decrease of blood pressure which occurs during isoflurane anaesthesia is predominantly due to peripheral arterial and venous dilatation, whereas heart rate and cardiac output are well maintained up to maintained inspiratory concentrations of 2.5%.
Caesarean Section: A suitable level of anaesthesia for caesarean section can be maintained with 0.5-0.75% isoflurane in oxygen nitrous oxide. Increased blood loss has been observed.
Overdose with isoflurane will result in marked depression of breathing and a marked decrease in blood pressure. The latter being predominantly due to peripheral vasodilatation rather than direct myocardial depression. If it appears that an overdose has been administered, stop during inspiration immediately, ensure a clear airway and ventilate the lungs with oxygen.
Known sensitivity to isoflurane or to other halogenated agents. Isoflurane should not be given to patients with known or suspected susceptibility to malignant hyperthermia. Isoflurane must not be used in patients who have developed an icterus and/or fever of unknown origin after administration of isoflurane or another halogenated anaesthetic, or history of unexplained jaundice after previous exposure to halothane.
Isoflurane is a profound respiratory depressant. This effect being accentuated by narcotic premedication or concurrent use of other respiratory depressants. Isoflurane causes an increase in cerebral blood flow at deeper levels of anaesthesia (1.5%) and this may give rise to an increase in cerebral spinal fluid pressure. Where appropriate, this can be prevented or reversed by hyperventilating the patient before or during anaesthesia. As with other halogenated anaesthetic, isoflurane must be used with caution in patients with increased intracranial pressure. As with all halogenated anaesthetics, repeat anaesthesia within a short period of time should be approached with caution since the risk of hepatotoxicity is not fully understood. There is insufficient experience of use in repeated anaesthesia to make a definite recommendation in this regard.
Isoflurane has been reported to interact with dry carbon dioxide adsorbents during closed circuit anaesthesia to form carbon monoxide which may lead to formation of significant levels of carboxyhaemoglobin in exposed patients. Carboxyhaemoglobin is toxic even in low concentrations and is not easily detected by standard anaesthesia monitors eg, pulse oximeters. Direct measurement of carboxyhaemoglobin should be carried out in the event that a patient on closed circuit anaesthesia with an implicated agent develops oxygen desaturation which does not respond to the usual therapeutic measures. All necessary precautions should be taken to ensure that carbon dioxide adsorbents are not allowed to dry out.
Caution should be exercised when administering isoflurane to patients with preexisting liver disease.
Isoflurane is a powerful systemic and coronary arterial dilator. The effect on systemic arterial pressure is easily controlled in the normal healthy patient and has been used specifically as a means of inducing hypotension. However, the phenomenon of "coronary steal" means that isoflurane should be used with caution in patients with coronary artery disease. In particular, patients with subendocardial ischaemia might be anticipated to be more susceptible. Salivation and tracheobronchial secretions may be stimulated in children but pharyngeal and laryngeal reflexes are quickly diminished. The level of anaesthesia may be changed quickly with isoflurane. Heart rhythm remains stable but spontaneous breathing should be monitored closely and supported where necessary.
Effects on the Ability to Drive or Operate Machinery: As with all anaesthetics, it is advisable to allow 24 hrs to elapse before driving or operating machinery.
Adverse reactions encountered with isoflurane similar to those observed with other halogenated anaesthetics are hypotension, respiratory depressions and arrhythmias. Other minor adverse effects encountered while using isoflurane are an increase in the white blood cell count (even in the absence of surgical stress) and also shivering, nausea and vomiting during the postoperative period. These adverse effects are only observed in a similar number of patients to anaesthetics.
Isoflurane is compatible with all commonly used muscle relaxants. The effects of which may be markedly potentiated by isoflurane. The effect is most notable in nondepolarising agents. Thus, lower doses should be used in the presence of isoflurane. The effect of nondepolarising muscle relaxants can be counteracted by administering neostigmine as this has no effect on the relaxant properties of isoflurane. Administration of adrenaline (epinephrine) by any route, and some other β-sympathomimetic drugs during isoflurane anaesthesia may cause supraventricular or ventricular arrhythmias.
Isoflurane can cause marked hypotension in patients receiving concomitant therapy with calcium antagonists, especially those of the dihydropyridine class. Patients receiving chronic therapy with other vasodilators eg, ACT inhibitors (eg, captopril, enalapril, lisinopril) or α1-adrenoreceptor antagonists (eg, prazosin) may show unpredictable hypotension with any type of anaesthesia.
Store at controlled room temperature (15-30°C) with cap tightly closed.
N01AB06 - isoflurane ; Belongs to the class of halogenated hydrocarbons. Used as general anesthetics.
Inhalation soln 250 mL x 1's.