Alteration of current perception threshold in severely injured patients

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Background

Measurements and assessment of current perception threshold with Neurometer in patients with chronic pain is well established. However, pathogenesis of acute pain in severely injured patients is not fully understood.

Purposes

To measure current perception threshold in severely injured patients with and without intravenous fentanyl and to determine if pain threshold is increased with sufficient analgesia.

Patients and methods

Twenty severely injured patients with normal mental status were studied. Patients were given bolus injection of fentanyl (1 g/kg) upon arrival at the emergency room. After resuscitation and surgery, patients were transferred to ICU and given continuous intravenous fentanyl started at 50 g/h and increased up to 150 g/h on patient's demand. Pain threshold (PT) was measured with a Neurometer. VAS (visual analogue scale) and VRS (verbal rating scale) were also measured before and after bolus injection of fentanyl and during ICU care (every hospital day until seventh).

Findings

Before bolus injection of fentanyl, PT of the patients was significantly lower than that of control (106 mA vs 221 mA; P<0.01). After continuous intravenous fentanyl in ICU, VAS decreased significantly. However, no change was observed in PT of the patients during continuous analgesia with fentanyl.

Conclusions

Severely injured patients were more sensitive to nociceptive stimuli than normal healthy controls. Fentanyl is an effective analgesia in trauma patients and decreased VAS significantly in the patients. But pain threshold itself did not show any change even with sufficient analgesia.

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