Anxiety before surgery may increase morphine demand: study

Patients who worry a great deal about upcoming surgery may push the painkiller button more frequently when the surgery is over, a new study from York Professor Joel Katz has found.

Katz, a psychology professor in York’s Faculty of Health and Canada Research Chair in Health Psychology, surveyed 117 women one week before major gynecological surgery and measured their demand for self-administered morphine following the surgery. The results are reported in the February 2008 issue of the Canadian Journal of Anesthesia, in the article “Locked out and still knocking: predictors of excessive demands for postoperative intravenous patient-controlled analgesia”.

Left: Joel Katz

Patient-controlled analgesia (PCA), which delivers morphine through a pump that is linked to a button the patient pushes, is considered the gold standard for managing acute postoperative pain. However, little research has been done to understand the psychological and emotional factors related to its use and the motivation behind patients’ requests for morphine during lockout intervals when, for safety reasons, the pump does not deliver the drug if the button is pressed.

It is not possible at this point to say that there is a direct causal relationship between pre-operative worrisome thoughts and trying to self-administer more pain medication after surgery, says Katz, but there is clearly a relationship. The patients in the study were asked to rate the level of stress-related feelings they were experiencing in relation to the upcoming surgery, including feeling worried or nervous, low in energy, or even experiencing a racing heart or spells of terror.

“People who find that thoughts of the surgery intrude into their consciousness quite a lot in the days before the surgery, or who spend a lot of time trying to avoid thinking about the surgery, may be more likely to engage in avoidance behaviours after the surgery,” says Katz. “That includes pushing the button for more painkiller even if they are not in pain.”

Right: Patient-controlled analgesia involves delivering morphine through an infusion pump that is controlled by a button tthe patient pushes

This is important because morphine is used to control pain, but it has some negative side effects, such as grogginess and depressed respiration, and some of these side effects can prolong hospitalization, says Katz. In addition, if a patient is demanding more morphine because she is anxious, then when she is in pain, she may not be eligible for a dose. 

Katz’s study of unmet demands for morphine is novel: in contrast to most research on acute pain, which is medically based, his study examines how preoperative psychological and emotional states relate to pain and medication use after surgery. 

“As much as possible, we want to help patients not worry or not have intrusive thoughts before surgery,” says Katz. “Our study shows that excessive demands for patient-administered morphine after surgery – when a patient is locked out by the pump but still pressing the button – are related to these negative feelings and thoughts prior to surgery.”