Hemodynamic effects of nitrous oxide in isoflurane-anesthetized cats.
OBJECTIVE
To determine the hemodynamic effects of nitrous oxide in isoflurane-anesthetized cats.


METHODS
12 healthy adult domestic shorthair cats.


METHODS
Cats were anesthetized by administration of isoflurane in oxygen. After instruments were inserted, end-tidal isoflurane concentration was set at 1.25 times the individual minimum alveolar concentration, and nitrous oxide was administered in a Latin-square design at 0, 30, 50, and 70%. Each concentration was administered for 25 minutes before measurements were obtained to allow for stabilization. Heart rate; systemic and pulmonary arterial pressures; central venous pressure; pulmonary artery occlusion pressure; cardiac output; body temperature; arterial and mixed-venous pH, PCO2, PO2, and hemoglobin concentrations; PCV; and total protein and lactate concentrations were measured before and during noxious stimulation for each nitrous oxide concentration. Arterial and mixed-venous bicarbonate concentrations and oxygen saturation, cardiac index, stroke index, rate-pressure product, systemic and pulmonary vascular resistance indices, left and right ventricular stroke work indices, arterial and mixed-venous oxygen contents, oxygen delivery, oxygen consumption, oxygen extraction ratio, alveolar-to-arterial oxygen difference, and venous admixture were calculated.


RESULTS
Arterial pressure, central venous pressure, pulmonary arterial pressure, rate-pressure product, systemic and pulmonary vascular resistance indices, arterial PCO2, and PCV increased during administration of 70% nitrous oxide. Arterial and mixed-venous pH, mixed-venous PO2, and alveolar-to-arterial oxygen difference decreased during administration of 70% nitrous oxide. Results before and during noxious stimulation were similar.


CONCLUSIONS
Administration of 70% nitrous oxide to isoflurane-anesthetized cats resulted in improved arterial pressure, which was related to a vasoconstrictive effect.
Pypendop
Bruno H
BH
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Ilkiw
Jan E
JE
Imai
Ayako
A
Bolich
Jennifer A
JA
D000758:Anesthesia; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002415:Cats / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects*; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000494:pharmacology*
D018685:Anesthetics, Inhalation; D007530:Isoflurane; D009609:Nitrous Oxide