Posology : מינונים

4.2   Posology and method of administration

Method of administration
Desflurane is administered by inhalation.
Desflurane should only be administered by persons trained in the administration of general anaesthesia using a vaporizer specifically designed and designated for use with desflurane.

Premedication
Premedication should be selected according to the needs of the individual patient taking into account that salivary secretions are stimulated. The use of anticholinergic drugs is a matter of choice for the anaesthetist.

Individualization
The administration of general anaesthesia must be individualized based on the patient's response.

Effects on Concomitant Therapy
Opioids or benzodiazepines decrease the amount of desflurane required to produce anaesthesia.
Desflurane decreases the required doses of neuromuscular blocking agents (see Table 2, section 4.5). If added relaxation is required, supplemental doses of muscle relaxants may be used (See section 4.5).

Dosage

1
The minimum alveolar concentration (MAC) of desflurane decreases with increasing patient age. The dose of desflurane should be adjusted accordingly. The MAC has been determined as listed in Table 1.
Table 1: MAC for desflurane according to patient age and inhalation mixture (Mean ± SD) 

Age        N*      100% Oxygen          N*        60% Nitrous Oxide/40% Oxygen
2 weeks           6        9.2 ± 0.0           -         -
10 weeks          5        9.4 ± 0.4           -         -
9 months          4        10.0 ± 0.7          5         7.5 ± 0.8  2 years           3        9.1 ± 0.6           -         -
3 years           -        -                   5         6.4 ± 0.4
4 years           4        8.6 ± 0.6           -         -
7 years           5        8.1 ± 0.6           -         -
25 years          4        7.3 ± 0.0           4         4.0 ± 0.3
45 years          4        6.0 ± 0.3           6         2.8 ± 0.6
70 years          6        5.17 ± 0.6          6         1.67 ± 0.4 N*= number of crossover pairs (using up-and-down method of quantal response) 
Induction of Anaesthesia in Adults
In adults, a starting concentration of 3% is recommended, increased in 0.5-1.0% increments every 2 to 3 breaths. Inspired concentrations of 4-11% of desflurane usually produce surgical anaesthesia in 2-4 minutes. Higher concentrations up to 15% may be used. Such concentrations of desflurane will proportionately dilute the concentration of oxygen and commencing administration of oxygen should be 30% or above. After induction in adults with an intravenous drug such as thiopental or propofol, desflurane can be started at approximately 0.5-1 MAC, whether the carrier gas is O2 or N2O/O2.

Desflurane should be administered at 0.8 MAC or less, and in conjunction with a barbiturate induction and hyperventilation (hypocapnia) until cerebral decompression in patients with known or suspected increases in CSFP. Appropriate attention must be paid to maintain cerebral perfusion pressure (See section 4.4).

During induction in adults, the overall incidence of oxyhemoglobin desaturation (SpO2 < 90%) was 6%. High concentrations of desflurane may induce upper airway adverse events. (See section 4.8).


Induction of Anaesthesia in Children
Desflurane is not indicated for use as an inhalation induction agent in children and infants because of the frequent occurrence of cough, breath holding, apnoea, laryngospasm and increased secretions (see section 4.4).

Maintenance of Anaesthesia in Adults
Surgical levels of anaesthesia may be sustained with 2-6% concentration of desflurane when nitrous oxide is used concomitantly. Desflurane at 2.5-8.5 % may be required 2
when administered using oxygen or oxygen enriched air. In adults, surgical levels of anaesthesia may be sustained at a reduced concentration of desflurane when nitrous oxide is used concomitantly.

Maintenance of Anaesthesia in Children
Desflurane is indicated for maintenance of anaesthesia in infants and children. Surgical levels of anaesthesia may be maintained in children with end-tidal concentrations of 5.2 to 10% desflurane with or without the concomitant use of nitrous oxide. Although endtidal concentrations of up to 18% desflurane have been administered for short periods of time, if high concentrations are used with nitrous oxide it is important to ensure that the inspired mixture contains a minimum of 25% oxygen.

If added relaxation is required, supplemental doses of muscle relaxants may be used.

Blood Pressure and Heart Rate During Maintenance
Blood pressure and heart rate should be monitored carefully during maintenance as part of the evaluation of depth of anaesthesia (See section 4.4).

Dosage in Renal and Hepatic Impairment
Concentrations of 1-4% desflurane in nitrous oxide/oxygen have been used successfully in patients with chronic renal or hepatic impairment and during renal transplantation surgery. Because of minimal metabolism, a need for dose adjustment in patients with renal and hepatic impairment is not to be expected.