Physostigmine increases the dose of propofol required to induce anaesthesia.
Author(s): Fassoulaki A, Sarantopoulos C, Derveniotis C.
Affiliation(s): Department of Anaesthesia, St Savas Hospital, Athens, Greece.
Publication date & source: 1997, Can J Anaesth. , 44(11):1148-51
PURPOSE: This prospective, randomized, double-blind study was performed to
determine the effect of administration of physostigmine on the dose of propofol
required to produce loss of consciousness.
METHODS: Forty female unpremedicated patients were assigned in a random blind
design to receive either 2 mg physostigmine or equal volume of normal saline i.v.
five minutes before induction of anaesthesia with propofol. All patients received
general anaesthesia for breast surgery. Propofol was infused at a constant rate
of 200 ml.hr-1 while patients were breathing oxygen 100% via a face mask. In each
patient the dose of propofol required to produce loss of the ability to grasp a
20 ml syringe was recorded as the end-point of loss of consciousness. At this
point the protocol was terminated and, after intubation of the trachea,
anaesthesia was maintained with a nitrous oxide-isoflurane or sevoflurane mixture
in oxygen, increments of an opioid and a muscle relaxant. Doses of anaesthetic
drugs and duration of anaesthesia varied and depended on the type of breast
surgery, determined by frozen section.
RESULTS: The mean +/- SD dose of propofol required to produce loss of
consciousness was 2.4 +/- 0.6 mg.kg-1 and 2.0 +/- 0.4 mg.kg-1 in the
physostigmine and in the normal saline groups respectively (P = 0.014).
CONCLUSION: Physostigmine pretreatment increases the dose of propofol required to
produce loss of consciousness.
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