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PEDIATRIC ANESTHESIA

Does Halothane Really Preserve Cardiac Baroreflex Better Than Sevoflurane? A Noninvasive Study of Spontaneous Baroreflex in Children Anesthetized with Sevoflurane Versus Halothane

Isabelle Constant, MD PhD^*, Dominique Laude, BSc, Elizabeth Hentzgen, MD^*, and Isabelle Murat, MD PhD^*

*Service d’Anesthésie Réanimation Pédiatrique, Hôpital Armand Trousseau, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France; and Institut National de la Santé et de la Recherche Médicale E0107, Paris, France

Address correspondence and reprint requests to Isabelle Constant, MD, PhD, Service d’Anesthésie, Hôpital d’enfants Armand Trousseau, AP-HP, 26 ave. du Dr. Arnold Netter, 75571 Paris, Cedex 12, France. Address e-mail to isabelle.constant{at}trs.ap-hop-paris.fr

Heart rate profiles during the induction of anesthesia differ markedly between the administration of sevoflurane and halothane. Previous investigations have shown that halothane preserves cardiac parasympathetic activity more than sevoflurane. Because vagal drive to the sinus node is the main effector of arterial baroreflex control of heart rate, halothane may preserve cardiac baroreflex better than sevoflurane. To investigate cardiac baroreflex in anesthetized children, we used two noninvasive methods providing different approaches to the arterial blood pressure (BP) and R-R interval (RRI) relationship: the sequence methods investigating beat-to-beat changes in BP and RRI (time domain) and the cross-spectral analysis investigating relationships between oscillations of BP and RRI (frequency domain). Children were randomly assigned to mask induction with sevoflurane in 100% oxygen, sevoflurane in 50% nitrous oxide/50% oxygen, or halothane in 50% nitrous oxide/50% oxygen. After tracheal intubation, the inspired fraction of volatile anesthetic was reduced to 1 minimum alveolar anesthetic concentration (MAC). The spontaneous baroreflex (SBR) sensitivity was calculated with the sequence method at baseline, during induction, and after intubation. The cardiac baroreflex was also estimated with cross-spectral analysis at baseline and at 1 MAC (stationary conditions). In the three groups, the induction of anesthesia was associated with a marked decrease of SBR sensitivity, which occurred earlier with sevoflurane than with halothane. Five minutes after intubation (1 MAC), the sequence method showed a similar decrease of the SBR sensitivity in the three groups. Similarly, the cross-spectral analysis between systolic blood pressure and RRI showed a decrease of the gain calculated in the low-frequency band, but the gain in the respiratory band was higher with halothane compared with sevoflurane. In children, the induction of anesthesia with halothane and sevoflurane is associated with a marked decrease of cardiac baroreflex activity. The persistence of respiratory RRI fluctuations under halothane might reflect reflex respiratory arrhythmia rather than efficient parasympathetic baroreflex activity.

IMPLICATIONS: Using noninvasive methods of cardiac baroreflex investigation, we have demonstrated that despite the relative preservation of vagal activity during halothane anesthesia, halothane and sevoflurane have a similar depressor effect on cardiac baroreflex activity during the induction of anesthesia in children.