Current perception thresholds and postoperative pain in schizophrenic patients.

Background and Objectives: Schizophrenic patients may have less sensitivity to pain; however, pain insensitivity in schizophrenia has not been adequately evaluated. We investigated current perception threshold (CPT) and postoperative pain intensity in patients with long-standing and treated schizophrenia and control patients.
Methods: We measured CPTs for 2,000 Hz, 250 Hz, and 5 Hz and postoperative pain intensity using a visual analogue scale (VAS) in 50 chronic schizophrenic patients who were on chronic phenothiazine derivatives (> 10 years) and for 25 control patients.
Results: CPTs for 2,000 Hz, 250 Hz, and 5 Hz in schizophrenic patients were 334.2 +/- 112.2, 303.9 +/- 117.1, and 165.0 +/- 72.3, respectively. CPTs for 2,000 Hz, 250 Hz, and 5 Hz in schizophrenic patients were significantly higher than those of control patients. VAS pain scores of schizophrenic patients were 4.0 +/- 1.7 at 2 hours post-operatively and 3.8 +/- 1.5 at 5 hours postoperatively, which were significantly (P < .05) lower than those (5.0 +/- 1.6 and 5.1 +/- 1.9) of the control group.
Conclusions: Chronic schizophrenic patients have increased current perception threshold and lower VAS pain scores in postoperative pain compared with control patients.