Peripheral Nerve Catheters for Acute Pain Control
The physiologic response to surgical injury to tissues includes endocrine, metabolic, inflammatory and psychogenic consequences as part of the complex phenomenon known as pain. The International Association for the Study of Pain (IASP) defines the pain phenomena more specifically as: an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
Surgical Pain Mechanisms
The neurophysiologic events that connect a surgical insult to the perception of pain are known as nociception. Neurophysiologists have divided the process of nociception into subcomponents:
Transduction is the translation of noxious stimuli into specific electrical activity at sensory nerve endings. The translation is accomplished by the terminal ends of sensory nerves and are known as nociceptors (ie. pain receptors). Some of these nociceptors are very specific, but the majority of nociceptors (95%) are multifunctional. All are the terminal endings of small fibers (A-delta and C fibers). The A-delta mechanoreceptors respond as nociceptors to intense mechanical stimulation and are silent otherwise. There is a small subset of nociceptors that are specifically activated by extremes of temperature. The polymodal nociceptors (PMN) are C fibers, which are nociceptive in response to intense mechanical, thermal, or chemical stimulus. They can produce non-nociceptive sensory information to sub-threshold stimulation.
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