RESUMO
In chronopharmacology the biological rhythm variations caused by drug administration is assessed. Evaluation of the time of drug administration and the qualitative and quantitative effects of reactions to drugs is called Chronopharmacodynamics. In this study, we assessed the Chronopharmacodynamics of intrathecal co-administration of sufentanyl and bupivacaine in surgical operations of lower extremities. In 2006, patients aged 20-50 with ASA physical status of I and II, who underwent surgical operation of lower extremities were entered into this prospective study. The patients received a slow intrathecal injection of 10 micro g sufentanyl and 15mg bupivacaine into subarachnoid of third and fourth lumbar spaces in 30 seconds. After the operation, the time of first pain sensation and the visual analogue scale [VAS] score, as the measure of severity of pain, were recorded. 115 patients were studied in this project. The pain-free interval was considered as the time between injection and patient's demand for pain relief. This interval was 746 [ +/- 322] minutes. The average score of pain severity on VAS at the time of demand for pain relief was 24.7 [ +/- 9.3]. The average pain-free duration in patients injected about noon or at midnight was significantly longer than the pain-free interval of other patients. The results show that intrathecal co-administration of sufentanyl and bupivacaine at noon or midnight [conforming to the circadian rhythm] causes better pain-relief with longer duration in comparison with other times of the day or night