The clinical (ir)relevance of opioid-induced immune suppression.

PURPOSE OF REVIEW: Opioid-induced immune suppression has been demonstrated in cell culture experiments and in animal models. This review examines whether opioids also increase the risk of infections in the perioperative setting or on the ICU.

RECENT FINDINGS: Only a few studies are available. Patients receiving higher doses of systemic opioids had an increased risk of developing a pneumonia perioperatively. However, these results only occurred if laparoscopic vs. open surgery or epidural vs. systemic opioid therapy were compared. These differences are thought to reflect the better quality of analgesia and the improved ability to clear secretions. Alternatively, systemic opioids could induce an immune suppression leading to infectious complications. In intensive care patients, opioid use correlated with infectious complications in patients with burn injuries but did not increase the rate of sepsis in neonates. One retrospective study indicated that opioid withdrawal might be an important risk factor. At present, it remains unclear whether the choice of an opioid, its dose, and mode of withdrawal influence infectious complications.

SUMMARY: In contrast to in-vitro studies and to animal models, conclusive evidence is currently lacking that opioids induce clinically relevant infectious complications in patients. However, these findings should be interpreted with great caution, as almost no adequately designed trials have been performed. Peripherally selective opioid receptor antagonists might be useful if opioid-induced immune suppression should prove to be clinically relevant.