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PEDIATRIC ANESTHESIOLOGY

Somatosensory Evoked Potentials by Median Nerve Stimulation in Children During Thiopental/Sevoflurane Anesthesia and the Additive Effects of Ketoprofen and Fentanyl

Susanna Westerén-Punnonen, MD^*, Heidi Yppärilä-Wolters, PhD^*, Juhani Partanen, MD, PhD^*, Kari Nieminen, MD, Antti Hyvärinen, MD^||, and Hannu Kokki, MD, PhD^¶

From the *Department of Clinical Neurophysiology, Kuopio University Hospital, Finland; VTT Information Technology, Tampere, Finland; Department of Clinical Neurophysiology, Helsinki University Hospital, Jorvi Hospital, Espoo, Finland; Department of Anesthesiology and Intensive Care, Kuopio University Hospital, Finland; ||Department of Otorhinolaryngology, Kuopio University Hospital, Finland; ¶Department of Pharmacology and Toxicology, University of Kuopio.

Address correspondence and reprint requests to Susanna Westerén-Punnonen, Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 1777, FI-70211 Kuopio, Finland. Address e-mail to susanna.westeren-punnonen{at}kuh.fi.

Abstract

BACKGROUND: Somatosensory evoked potentials (SEPs) are used to determine the spinal cord and brain function during surgical procedures. In general, SEPs are sensitive to volatile anesthetics, but little is known about the effects of anesthesia maintenance with sevoflurane on SEPs in children. Analgesics are often provided during anesthesia, and supplementary drugs may also affect the SEPs. In this prospective clinical trial of 27 healthy, 3- to 8-yr-old children, we evaluated the effects of sevoflurane anesthesia after IV induction with benzodiazepine and barbiturate on median nerve SEP. In addition, the effects of two analgesics (ketoprofen and fentanyl) on SEPs were evaluated.

METHODS: Median nerve SEPs were recorded before premedication with midazolam 0.1 mg/kg IV, and at three separate times during anesthesia maintenance with sevoflurane 2% end-tidal concentration in air/oxygen (after 15 min of sevoflurane inhalation), supplemented with/without ketoprofen 1 mg/kg (after 25 min) and fentanyl 1 µg/kg (after 35 min).

RESULTS: Compared with baseline measurements, an increase both in N20 latency (P = 0.015) and in central conduction time (P = 0.001) was noted during anesthesia maintenance with sevoflurane. The administration of analgesics did not have an influence on the N20 latency or central conduction time. In children 5 to 8 yr of age, the mean cortical N20-P25 amplitude was decreased (P = 0.008). In addition, in older children, the N20-P25 amplitude decreased after the co-administration of ketoprofen and fentanyl compared with the values measured before the analgesics (P = 0.03). These decreases were not seen in the younger children.

DISCUSSION: In children, anesthesia maintenance with 2% sevoflurane prolongs median SEP latencies in a manner that is similar to those reported for other volatile anesthetics. However, SEP monitoring can be done with sevoflurane inhalation, but the dosage should be adjusted due to interindividual variabilty. Co-administration of ketoprofen, and fentanyl did not affect the SEP latencies, but post hoc analysis suggested that older children had a decrease in cortical amplitudes.