Rostral spread of epidural morphine

Area of Science:

• Pharmacology
• Neuroscience
• Anesthesiology

Background:

• Morphine is a potent analgesic used for pain management.
• Understanding the distribution and effects of epidural morphine is crucial for optimizing pain relief and minimizing side effects.

Purpose of the Study:

• To compare the effects of intravenous versus lumbar epidural morphine administration.
• To investigate the sensory changes, analgesia, and side effects following epidural morphine.
• To determine the cephalad spread of epidural morphine in the cerebrospinal fluid.

Main Methods:

• Ten healthy males received 10 mg morphine sulfate intravenously or via lumbar epidural injection in a randomized sequence.
• Observations included segmental hypalgesia, cold pressor response, side effect onset/duration, and serum morphine concentrations over 22 hours.

Main Results:

• Lumbar epidural morphine induced significant cutaneous hypalgesia in the thoracolumbar region, extending cephalad to the midthoracic and trigeminal areas in some subjects.
• Epidural morphine reduced cold pressor response in both foot and hand, indicating systemic analgesia.
• Common side effects of epidural morphine included pruritus, nausea, and vomiting, which were not correlated with serum morphine levels.

Conclusions:

• Lumbar epidural morphine causes widespread sensory changes and analgesia, likely due to cephalad spread within the cerebrospinal fluid.
• The observed effects suggest epidural morphine reaches the brainstem and fourth ventricle.
• Intravenous morphine produced minimal non-respiratory effects compared to epidural administration.