Fentanyl (Perioperative Analgesia)

Adult dose table quoted verbatim from the SPC (Fentanyl 50 microgram/ml Injection, section 4.2): Spontaneous Respiration - initial 50-200 micrograms, supplemental 50 micrograms; Assisted Ventilation - initial 300-3500 micrograms, supplemental 100-200 micrograms. 'Doses in excess of 200 micrograms are for use in anaesthesia only.' UNITS ARE MICROGRAMS throughout - do not read as mg. Premedication: 1-2 ml fentanyl (i.e. of the 50 microgram/ml injection) may be given intramuscularly 45 minutes before induction of anaesthesia. Expected effect after IV administration in unpremedicated adults: 2 ml provides sufficient analgesia for 10-20 minutes in low pain intensity surgical procedures; 10 ml injected as a bolus gives analgesia lasting about one hour, sufficient for moderately painful procedures; 50 micrograms/kg provides intense analgesia for some four to six hours for intensely stimulating surgery. INFUSION (exact units as stated in the SPC): in ventilated patients a loading dose may be given as a fast infusion of approximately 1 microgram/kg/min for the first 10 minutes, followed by an infusion of approximately 0.1 micrograms/kg/min; alternatively the loading dose may be given as a bolus. Infusion rates should be titrated to individual patient response and lower rates may be adequate. Lower infusion rates, e.g. 0.05-0.08 micrograms/kg/minute, are necessary if spontaneous ventilation is to be maintained. Higher infusion rates (up to 3 micrograms/kg/minute) have been used in cardiac surgery. Unless post-operative ventilation is planned, the infusion should be terminated at about 40 minutes before the end of surgery. To avoid bradycardia it is recommended to give a small intravenous dose of an anticholinergic just before anaesthetic induction. Obese patients: risk of overdosing if the dose is calculated on body weight - calculate dosage according to estimated lean body mass. Elderly (over 65 years) and debilitated patients: reduce the initial dose and take its effect into account when determining supplemental doses. Fentanyl is chemically incompatible with pentobarbital sodium, thiopentone and methohexitone. Discuss a strategy for ending opioid treatment before starting, to minimise the risk of addiction and drug withdrawal syndrome. NOTE: the fetched SPC section 4.4 was truncated at the source-fetch limit; section 4.5 was not fetched.

SPC dose table for children aged 2 to 11 years: initial 1-3 micrograms/kg and supplemental 1-1.25 micrograms/kg, for BOTH spontaneous respiration and assisted ventilation. Children aged 12 to 17 years: follow adult dosage. UNITS ARE MICROGRAMS/kg - a single dosePerKg value is not given because the SPC states a range (1-3 micrograms/kg), so dosePerKg is deliberately left null. Techniques involving analgesia in a spontaneously breathing child should only be used as part of an anaesthetic technique, or as part of a sedation/analgesia technique with experienced personnel in an environment that can manage sudden chest wall rigidity requiring intubation, or apnoea requiring airway support. Verify against a children's formulary before use.