Genetically Variation - May the Need of Opioids During Surgery be Known Beforehand by Giving Noxious Stimulation and Measure the Skin Conductance Response Before Surgery?

Skin Conductance (SC) shows the emotional state as reflected in changes in the sympathetic nervous system. During sleep or other states of low basic sympathetic activity, activation of the sympathetic nervous system results in filling of the palmar and plantar sweat glands, and the SC increases transiently before the sweat is removed and the SC decreases again. When a short lasting outgoing sympathetic nervous burst occurs, fluctuations of SC will follow. An increase in the number of SC fluctuations (NSCF) can therefore be interpreted as increased activity in this part of the sympathetic nervous system. When remifentanil, an opioid analgetic is given, NSCF is reduced.

Genetic variation influences the pharmacokinetics and the pharmacodynamics of analgesics like morphine derivates and remifentanil. 50 female patients will therefore be blood tested to study if they are Val/Val or Met/Met for the COMT gene, or if they are homozygous or heterozygous for the 118G allele and the 118A allele.

This study will show if skin conductance can be used to measure noxious stimulation response before surgery (by giving a tetanic stimuli), and then predict what level of analgesic a patient will need during surgery.