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08-12-2011 | Surgery | Article

Psychologic factors influence anesthetic requirement


Free abstract

MedWire News: Psychologic factors are an important determinant of how much general anesthetic patients need to achieve sedation, study results indicate.

The Korean study found that preoperative anxiety and pain sensitivity were each independently associated with propofol requirements in women undergoing thyroidectomy.

"Identifying patients preoperatively who are likely to require higher anesthetic and analgesic doses should aid individualized postoperative management," write Jeong-Yeon Hong (Ulsan University) and co-authors in the British Journal of Anaesthesia.

Hong's team conducted a cross-sectional study to investigate the association between preoperative psychologic factors and subsequent anesthesia requirements and postoperative pain.

They recruited 100 consecutive women due to undergo total thyroidectomy and assessed them using Spielberger's State-Trait Anxiety Inventory (STAI) and a pain sensitivity questionnaire (PSQ).

Anesthesia was induced with target-controlled propofol and maintained with sevoflurane-oxygen-air, with bispectral index monitoring (BIS) used to assess depth of sedation.

Hong et al report that patients with higher preoperative levels of state and trait anxiety required greater amounts of propofol to reach light (BIS85) and moderate (BIS75) levels of sedation.

The amount of propofol required to reach achieve deep sedation (BIS65) was associated with higher levels of trait (long term) but not state (short term) anxiety.

Pain at 1 hour after surgery, assessed on a visual analog scale, significantly correlated with both STAI and PSQ scores. Postoperative pain at 24 and 48 hours correlated only with PSQ, however.

Finally, the minimum alveolar concentration (MAC)-hour of sevoflurane (a standard measure of inhaled anesthetic potency) was significantly associated with preoperative PSQ but not with STAI.

The researchers believe this is the first study to examine the independent effects of psychologic variables on anesthesia requirements and postoperative pain.

Noting that state and trait anxiety correlated with each other and predicted anesthesia requirement, Hong et al write: "People with high anxiety have increased subjective feelings of worry and apprehension, and more dramatic neuroendocrine responses to stimuli and increased cardiovascular activity.

"These might be important causes in more anxious patients of increased baseline haemodynamics and greater requirements for anaesthetics during surgery."

They conclude: "We suggest the modification of anaesthetic dose for general anaesthesia based on the individual patient's preoperative anxiety and pain sensitivity in female patients undergoing elective thyroidectomy."

By Joanna Lyford

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