Background: Psychological factors are thought to drive inter-patient variations in anaesthetic and analgesic requirements. This cross-sectional study investigated whether preoperative psychological factors can predict anaesthetic requirements and postoperative pain.
Methods: Before total thyroidectomy, 100 consecutive women completed the Spielberger's State-Trait Anxiety Inventory (STAI) and the pain sensitivity questionnaire (PSQ). Target-controlled propofol was administered for induction of anaesthesia, and sevoflurane-oxygen-air was given to maintain equal depths of anaesthesia, as determined by bispectral index (BIS) monitoring.
Results: Patients with higher anxiety scores (state and trait) required greater amounts of propofol to reach light (BIS=85) and moderate (BIS=75) levels of sedation, but only trait anxiety was significantly associated with propofol requirements in reaching a deep level of sedation (BIS=65). The MAC-hour of sevoflurane was significantly correlated only with PSQ scores. The postoperative pain intensity was significantly correlated with both STAI and PSQ.
Conclusions: Preoperative anxiety and pain sensitivity are independent predictors of propofol and sevoflurane requirements in general anaesthesia. Anaesthetic and analgesic doses could be modified based on the patient's preoperative anxiety and pain sensitivity.