LASER-DOPPLER SKIN BLOOD-FLOW AND SYMPATHETIC NERVOUS RESPONSES TO SURGICAL INCISION DURING HALOTHANE AND ISOFLURANE ANESTHESIA

The aim of the present study was to evaluate whether a sudden decrease in skin blood flow measured using a laser Doppler velocimeter reflect s sympathetic nervous response to surgical skin incision during haloth ane (n = 17) and isoflurane (n = 16) anesthesia in 33 ASA physical sta tus I or II patients scheduled for laparotomy. Plasma norepinephrine c oncentrations in the responding patients who showed a sudden decrease in the skin blood flow after surgical incision increased significantly and continued to increase 1-10 min after skin incision under halothan e and isoflurane anesthesia. Although plasma norepinephrine concentrat ions in the nonresponders did not increase after surgical incision wit h halothane, the concentrations increased significantly at I min, but not at 3 and 10 min, after skin incision with isoflurane. The results indicate that the sudden decrease in laser Doppler flow reflects the s ympathetic response to surgical incision. However, these also suggest that the factors that control the skin blood flow may not be simply sy mpathetic but may reflect other modulators as well. Plasma epinephrine concentration increased during skin incision, but the concentrations did not differ between the patients with and without a sudden decrease in skin blood flow. Increases in systolic blood pressure and rate-pre ssure product on skin incision were also significantly more in patient s with skin blood flow response compared with those without the respon se. The magnitude of changes in plasma norepinephrine concentration an d hemodynamic variables with skin incision was greater with isoflurane than with halothane at the same minimum alveolar anesthetic concentra tion level.