Shrinking pupils as a warning of respiratory depression after spinal morphine

Side effects of intrathecal and epidural opioids

The purpose of this article is to review the literature on the side effects of intrathecal and epidural opioids. English-language articles were identified through a MEDLINE search and through review of the bibliographies of identified articles. With the increasing utilization of intrathecal and epidural opioids in humans during the 1980s, a wide variety of clinically relevant side effects have been reported. The four classic side effects are pruritus, nausea and vomiting, urinary retention, and respiratory depression. Numerous other side effects have also been described. Most side effects are dose-dependent and may be more common if the opioid is administered intrathecally. Side effects are less common in patients chronically exposed to either intrathecal, epidural, or systemic opioids. Some side effects are mediated via interaction with specific opioid receptors while others are not. It is concluded that the introduction of intrathecal and epidural opioids marks one of the most important breakthroughs in pain management in the last two decades. However, a wide variety of clinically relevant non-nociceptive side effects may occur. All physicians utilizing intrathecal and epidural opioids must be aware of these side effects, for while most are minor, others are potentially lethal.

[Peridural analgesia with high doses of fentanyl: failure of the method for early postoperative kinesitherapy in knee surgery]

Following orthopedic surgery of the lower limb, ten patients were given fentanyl 5 micrograms . kg-1 in a single epidural injection. Almost complete analgesia (P less than 0.001) was rapidly obtained. The total period of analgesia was rather short (182.3 +/- 32.1 min). The maximal analgesia period was 87 +/- 8.34 minutes. Despite this high dose of fentanyl (245 to 450 micrograms), in five patients the passive mobilization of the knee following surgery was extremely painful and, for that matter, impossible in three of them. Such high doses of fentanyl entail the risk of respiratory depression as respiratory rate is decreased (P less than 0.01) and the Pco2 is increased (P less than 0.01). Fentanyl should not be used at such high dosage and should probably not be preferred to morphine, considering that the duration of analgesia is short, that the analgesic score is identical to that obtained with lower doses or with longer lasting narcotics, that it does not prevent passive mobilization pains and that it entails a definite risk of respiratory depression.