• Bruno H Pypendop, Jan E Ilkiw, Ayako Imai, and Jennifer A Bolich.
• Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
• Am. J. Vet. Res. 2003 Mar 1;64(3):273-8.

ObjectiveTo determine the hemodynamic effects of nitrous oxide in isoflurane-anesthetized cats.Animals12 healthy adult domestic shorthair cats.ProcedureCats 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.ResultsArterial 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 And Clinical RelevanceAdministration of 70% nitrous oxide to isoflurane-anesthetized cats resulted in improved arterial pressure, which was related to a vasoconstrictive effect.

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