Influence of spinal deafferentation on pain threshold and offset analgesia (OA) in surgical male and female patients: the SPINAL study

Deafferentation or the traumatic or anesthetic disruption of afferent input
from the peripheral to the central nervous system results in cortical,
subcortical or brainstem reorganization and alters neuronal connectivity. In
general, deafferentation causes adaptive plasticity, such as cortical expansion
of brain areas adjacent to deafferentated areas, due to a rebalancing of
excitatory and inhibitory neuronal modulators involved in plasticity.
Deafferentation may be associated with behavioral changes. While some studies
show improved acuity of motor or sensory function related to cortical
plasticity, it is well known that deafferentation may additionally have
negative behavioral effects related to maladaptive plasticity, as may occur in
traumatic deafferentation, including phantom limb pain or pain after spinal
cord injury. Spinal and epidural anesthesia are forms of short-term
deafferentation. There is evidence that both types of neuraxial blockade are
associated with sensory distortions or pain. In patients that require a
subarachnoid or epidural block for surgery, illusionary limb position, pain in
the deafferented limbs, or paradoxical heat perception upon application of a
cold stimulus on the transition from normal to deafferentated skin are often
observed. Additionally, in healthy volunteers, we showed that spinal
deafferentation is associated with hyperalgesic responses above the level of
deafferentation coupled to
a reduction in offset analgesia. Offset analgesia (OA) is a manifestation of
endogenous pain modulation. OA is characterized by profound analgesia after a
slight decrease in noxious stimulation and is considered an expression of
temporal filtering of nociception related to post-stimulus inhibition. See
Figure 1. In Figure 2, we give the results of our prior study in volunteers.

To measure offset analgesia in surgical patients before and after they received

Open intervention study (intervention is application of a noxiousstimulus)

Application of a noxious stimulus to the arm

Risc and burden are nill to very light.