Distractions Cut Pain

It is established that distracting mental activities can minimize perception of pain, but how this happens has not been well understood.  A study published in Current Biology online has found that it is related to a spinal process involving opioid neurotransmission.

A study of 20 men with an average age of 27 found that distraction not only takes the focus away from the pain, but can dampen the body’s initial physiological response to pain through endogenous opioids.
Painful levels of heat were administered to the subject while undergoing functional MRIs.  Those doing complex memory tasks were pre-occupied to the extent that they experienced 19% less pain than those doing simpler mental tasks.

“This phenomenon is not just a psychological phenomenon, but an active neuronal mechanism reducing the amount of pain signals ascending from the spinal cord to higher-order brain regions,” said lead author Christian Sprenger, of the University Medical Center Hamburg-Eppendorf in Hamburg, Germany.

Sprenger and his colleagues repeated the experiment with another group of 15 men, average age 25.  This time they administered naloxone to block opioid effect or saline solution.  Perception of pain was 40.5% greater for those with the difficult cognitive task when given the opioid antagonist naloxone. This provided the evidence that endogenous opioids play a role in the distraction phenomenon.

“Our findings strengthen the role of cognitive-behavioral therapeutic approaches in the treatment of pain diseases, as it could be extrapolated that these approaches might also have the potential to alter the underlying neurobiological mechanisms as early as in the spinal cord,” Sprenger and colleagues concluded.  

For more information see the May 17, 2012 online issue of Current Biology.

This article was originally published in Pathways Physician & Health Professional Bulletin - Issue 25.  To download this issue in PDF format, or past issues, visit our newsletter archives online at www.pathwayshealth.org/publications.

How Morphine Can Help in Heart Failure at the End of Life

Morphine is most often used as a pain reliever.  But for heart patients, it is often used for shortness of breath.  There are several ways that morphine interrupts the cycle of breathlessness.

• Morphine lowers the breathing rate in the brain’s respiratory center. This means the heart doesn’t have to work so hard to supply blood to the chest muscles for breathing.  It reduces excessive breathing drive.
• Morphine widens blood vessels in the arms and legs.  Pooling blood in the extremities reduces the amount of blood that returns to the heart.  This means the heart doesn’t have to pump as often—it can rest more.  When the heart doesn’t have to pump so hard, it also needs less oxygen—so the resident doesn’t have to breathe as hard.
• It eases anxiety, and when a resident is less anxious, he or she will breathe more calmly.  If you breathe more slowly, you are less anxious.
• When we are in pain, we tend to breathe faster and harder.  So relieving pain also reduces respiratory rate.

Used correctly, morphine is safe.  Addiction is very, very rare.  The chance of becoming addicted is so small that it is considered unethical to withhold morphine because of a fear of addiction.

But if we don’t know how opioids like morphine, fentanyl, Vicodin or Dilaudid work, we may mistake initial responses.  If an opiod is new to a person, he or she may be sleepy for the first 2 or 3 days—especially if they have not been sleeping well (maybe because of shortness of breath or pain).  When symptoms are relieved, the resident may want to “catch up” on sleep.  After a few days, the sleepiness wears off.

At the end of life, morphine is the most important medicine for providing comfort to heart patients.  It reduces the breathless feeling that can be so frightening to people at the end of life.

Men, Women, and Pain

Rigorous research has concluded that men have a higher threshold for pain.  In a large-scale prospective study of 700 patients conducted by physicians from Tufts-New England Medical Center and San Ignacio Hospital, Bogata, Colombia, researchers examined post-surgical morphine use.  After adjusting for type of surgery and age, women had higher levels of pain intensity throughout the study than men, requiring an average of 30% more morphine on a per-weight basis than men to attain a similar decrease in pain intensity. 

Research results have been mixed, some finding that men required more morphine after surgery than women.  A very large Chinese study found women used significantly less morphine when using patient-controlled analgesia post-operatively, indicating that cultural, ethnic or genetic factors may account for differing research results.  But in animal models, male rats exhibited greater analgesia than female rats to equal doses of opioids.

The researchers wrote that, “Sex differences in pain perception have been attributed to a different socialization process for men and women that influences bodily experience and the willingness to communicate distress. Hormone variations could also in part explain sex differences in pain experience and response to morphine.”