INCREASED BETA-ENDORPHIN BUT NOT LEU-ENKEPHALIN IN PLASMA DUE TO PREOPERATIVE STRESS

The levels of beta-endorphin and Leu-enkephalin were measured in the p lasma of 23 children (16 male, 7 female) who were admitted to the Chil dren's Hospital for elective (non-emergency) surgery, adenoidectomy an d/or tonsillectomy. Two blood samples were obtained preoperatively. Th e first sample was taken during admission to the hospital; the second one 24 h later and just 5 min before the operation, without pre-medica tion or narcosis. beta-endorphin and Leu-enkephalin levels were measur ed using a RIA method after solid phase extraction of the samples. Mea n beta-endorphin concentrations during admission to the hospital were 11.77 +/- 9.36 pg/ml. Twenty four hours later, and just 5 min before s urgery, the mean levels of P-endorphin were increased to 27.45 +/- 16. 66 pg/ml. A statistically significant increase (t-value = -5.42) was f ound for beta-endorphin levels 5 min before the operation compared wit h 24 h earlier (2-tail probability p < 0.0001). The Wilcoxon matched-p airs signed-ranks-test also showed p < 0.0001 (Z = -4.197). In contras t, Leu-enkephalin levels remained unchanged. The mean values were 11.4 4 +/- 1.49 pg/ml on the day of admission, and 12.11 +/- 2.08 pg/ml 5 m in before the operation. We did not find statistically significant dif ferences between the paired samples (t-value = -1.53, 2-tail probabili ty p = 0.139). The increase in beta-endorphin could be the result of p reoperative anxiety about the narcosis and surgery.