title: Prolonged hypocapnia does not alter the rate of CSF production in dogs during halothane anesthesia or sedation with nitrous oxide.
abstract: This study examined the effect of prolonged hypocapnia on the rate of cerebrospinal fluid (CSF) production (Vf) and on other CSF dynamics in dogs. Determination of CSF values began 2 h after the onset of hypocapnia and continued for an additional 3 h. Two separate methods were used to determine Vf: modified open ventriculocisternal perfusion and closed ventriculocisternal perfusion. Dogs were examined both during hypocapnia plus anesthesia with halothane (0.8%) and nitrous oxide (66%), and during hypocapnia plus sedation with nitrous oxide (66%) and halothane (0.15%) combined with bupivacaine (0.75%) infiltration of wound edges. There were no differences in Vf measured by the two methods. At the first measurable time period, mean Vf values during hypocapnia and halothane anesthesia, 32 +/- 9 and 35 +/- 10 microliters/min (mean +/- SD), were lower than mean Vf values during hypocapnia and nitrous oxide sedation, 48 +/- 11 and 49 +/- 8 microliters/min. Vf did not change significantly during 3 h of hypocapnia. For both halothane anesthesia and nitrous oxide sedation, mean Vf values during hypocapnia were not significantly different from Vf values previously reported during normocapnia, 31 +/- 12 and 33 +/- 12 microliters/min and 44 +/- 13 and 47 +/- 14 microliters/min, respectively. The results indicate that prolonged hypocapnia does not decrease Vf, and, therefore, reduction of Vf is probably not one of the causes for reduction of elevated CSF pressure by prolonged hypocapnia. Regarding the other data on CSF dynamics, CSF pressure at hypocapnia was similar to that at normocapnia, suggesting that hypocapnia did not affect resistance to reabsorption of CSF.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000768:Anesthesia, General; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood*; D002555:Cerebrospinal Fluid / Q000378:metabolism*; D004285:Dogs; D006221:Halothane; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D006993:Hypnotics and Sedatives; D002245:Carbon Dioxide; D009609:Nitrous Oxide; D006221:Halothane