ACUTE PAIN
The sharp, stinging, well-localized pain transmitted by the A delta fibers is followed by the deeper, poorly localized, more continuous ache due to C fiber activation. Consider the mosquito bite, the stinging pain identifies the site of the bite and often the offending insect. This is followed by a phase of relatively little pain while the released chemical mediators sensitize the pain receptors (nociceptors). Once enough C fiber nociceptors are stimulated, the itching, aching pain commences. How one reacts to the pain of the bite depends on various environmental and social factors. If left alone, the pain of the bite, if the site does not become infected, will settle down.
There are ways several ways to treat acute pain.
PHARMACOLOGICAL:
Nonsteroidal anti-inflammatories (NSAIDS): These decrease the formation of prostacyclins, prostaglandins and some peroxides by inhibiting cyclo-oxygenase activity. Prostaglandins have an effect both peripherally and centrally, to sensitize nociceptive endings or neurones. The newer COX 2 NSAIDs, although inhibiting inflammation, may have less effect on pain than the older less selective ones.
Opioids: These act on receptors centrally to inhibit afferent pain impulses. It has been shown that peripheral mu opioid receptors are exposed on C fiber terminals in areas of inflammation.
Acetaminophen: This is thought to act centrally perhaps by inhibiting the release of substance P and glutamate, two neurotransmitters involved in pain perception in the central nervous system. Although the daily dose of acetaminophen is recommended to be less than 4 grams, many people take more without apparent liver damage. Patients with liver problems should use this drug with caution.
Local anesthetic creams or injections: Local anesthetics block sodium channels thus inhibiting nerve conduction. Local application on the skin seldom blocks the nerves themselves but can "numb" cutaneous areas of discomfort.
NON-PHARMACOLOGICAL:
Ice: By decreasing edema formation, ice limits tissue damage and may speed up the recovery process. It also slows nerve conduction and diminishes pain.
Rubbing: Local counter-irritation may decrease pain. Care must be taken not to damage the skin by too vigorous rubbing or scratching.
TENS: Transcutaneous electrical nerve stimulation has been shown to help decrease acute postoperative pain. It may work by releasing endorphins and other pain inhibitory neurotransmitters.
Distraction: By focusing the mind away from pain, the emotional, unpleasant, attributes of acute pain can be decreased. In animal experiments neurophysiological changes have been show to occur when the animal has a focuses on a painful stimulus before it has been delivered.
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