Why does a patient have no memory from the time before surgery until waking up in the recovery room after receiving spinal and epidural (Regional) anesthesia for a surgical procedure?

Why Memory Loss Occurs with Spinal/Epidural Anesthesia

The patient experienced complete memory loss because they likely received sedative medications (such as midazolam, fentanyl, or diphenhydramine) in addition to the spinal/epidural anesthesia, which caused anterograde amnesia—the inability to form new memories during the perioperative period. 1, 2

Understanding the Mechanism

Spinal/Epidural Anesthesia Alone Does Not Cause Unconsciousness

• Regional anesthesia (spinal and epidural) blocks pain sensation but does not inherently cause loss of consciousness or memory impairment. 3
• Patients receiving only neuraxial anesthesia without sedation typically remain awake and can observe their procedure, with surgeons able to explain findings in real-time. 3

Sedation is the Culprit for Memory Loss

• The amnesia experienced by this patient was almost certainly due to intravenous sedative medications administered alongside the regional anesthesia. 2
• Common sedative combinations include fentanyl, midazolam, and diphenhydramine, which are routinely given to provide comfort and anxiolysis during procedures under neuraxial anesthesia. 2
• These medications cause profound anterograde amnesia—the inability to form new memories from the time of administration through the early recovery period. 1

The Perioperative Memory Timeline

Severe Memory Impairment in Recovery Room

• Memory for neutral stimuli in the recovery room is severely impaired, with recall declining from 12% in the holding area to 0% in the recovery room, and recognition dropping from 43% to 7%. 1
• This represents a complete or near-complete inability to form new memories during the immediate postoperative period. 1

Memory Gradually Returns

• Memory function typically returns as sedative medications are metabolized and eliminated from the body. 3
• The duration of amnesia depends on the specific drugs used, their doses, and individual patient factors including age and metabolism. 1

Clinical Context and Considerations

This is Expected and Often Desirable

• Most patients prefer not to remember the perioperative experience, and sedation is routinely provided for this purpose during regional anesthesia. 3
• The combination of regional anesthesia with sedation allows patients to avoid the anxiety of being awake during surgery while maintaining the benefits of neuraxial techniques. 3

Potential for Spinal Anesthesia to Affect Memory

• Some evidence suggests spinal anesthesia itself may have modest effects on certain memory domains, though this is less pronounced than the effects of sedative medications. 4
• One study found significant differences in logical memory and overall memory scores 24 hours after spinal anesthesia with bupivacaine (Marcaine). 4

Rare Complications

• While uncommon, flashbacks and nightmares after neuraxial anesthesia with sedation have been reported, though their incidence is unknown. 2
• These complications can lead to depression, physical complaints, and prolonged convalescence in rare cases. 2

Key Clinical Pitfall

Do not assume memory loss indicates a complication or problem. The complete amnesia from before surgery until waking in recovery is the expected and intended effect of the sedative medications given with regional anesthesia. 1, 2 This should be explained to patients preoperatively so they understand this is normal and not a cause for concern.