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Anesth Analg 2008; 106:916-923
© 2008 International Anesthesia Research Society
doi: 10.1213/ane.0b013e3181618669
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NEUROSURGICAL ANESTHESIOLOGY

Xenon/Hypothermia Neuroprotection Regimes in Spontaneously Breathing Neonatal Rats After Hypoxic-Ischemic Insult: The Respiratory and Sedative Effects

John Dingley, MD*{dagger}, Catherine Hobbs, PhD*, James Ferguson, BSc*, Janet Stone, PhD{ddagger}, and Marianne Thoresen, MD, PhD*

From the *Clinical Science at South Bristol, Child Health, University of Bristol, St. Michael's Hospital, Bristol, UK; {dagger}University of Wales Swansea, Singleton Park, Swansea, UK; and {ddagger}Department of Biochemistry, Children's Hospital, Bristol, UK.

Address correspondence and reprint requests to J. Dingley, Department of Anaesthetics, Morriston Hospital, Swansea SA6 6NL, UK. Address e-mail to j.dingley{at}swansea.ac.uk.

Abstract

BACKGROUND: Hypothermia (HT) reduces neuronal injury after perinatal asphyxia. The anesthetic gas xenon (XE) may enhance this effect. We investigated the sedative and respiratory effects of variable XE concentrations at 37°C normothermia (NT) or 32°C HT after a hypoxic-ischemic (HI) insult to determine the concentration at which XE was a respiratory depressant in spontaneously breathing 7-day-old rat pups.

METHODS: (I) In three control groups, the effects of fasting at NT and HT were investigated. (II) Six groups were subjected to a HI insult (left carotid ligation then 90 min breathing 8% oxygen); three then breathed Air, 50%Xe or 70%Xe for 5 h at NT (NTAir, NT50%Xe, NT70%Xe), while three breathed identical mixtures during HT (HTAir, HT50%Xe, or HT70%Xe), in addition to a control group. Blood gases, glucose, and lactate were measured. Sedation (spontaneous movement/respiratory rate) was recorded.

RESULTS: Blood chemistry data were successfully obtained from 70 pups. (I) Pups maintained normal blood gas, glucose, and lactate values after 9 h fasting at NT or HT. (II) After HI insult, in comparison with control and NTAir groups, 70%Xe at both NT and HT produced higher PCO2 and lower pH values while the HTAir and HT50%Xe groups only had lower pH values. The HT70%Xe combination produced the highest PCO2 and lowest pH values (56.8 mm Hg, 7.35, respectively) and the greatest sedative effect.

CONCLUSION: After HI insult, 70%Xe at both NT and HT induced sedation, respiratory depression, CO2 retention, and a decrease in pH relative to air and control groups. The effects were largely avoided with 50%Xe.






Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press
Copyright © 2008 by the International Anesthesia Research Society.