Assessment of the hemodynamic effects of lidocaine administered IV in isoflurane-anesthetized cats

Objective-To determine the hemodynamic effects of liclocaine (administered IV to achieve 6 plasma concentrations) in isoflurane-anesthetized cats. Animals-6 cats. Procedure-Cats were anesthetized with isoflurane in oxygen (end-tidal isoflurane concentration set at 1.25 times the predetermined individual minimum alveolar concentration). Lidocaine was administered IV to each cat to achieve target pseudo-steady-state plasma concentrations of 0, 3, 5, 7, 9, and 11 mu g/mL, and isoflurane concentration was reduced to an equipotent concentration. At each plasma liclocaine concentration, cardiovascular and blood gas variables; PCV; and plasma total protein, lactate, liclocaine, and monoethylglycinexylidide concentrations were measured in cats before and during noxious stimulation. Derived variables were calculated. Results-In isoflurane-anesthetized cats, heart rate, cardiac index, stroke index, right ventricular stroke work index, plasma total protein concentration, mixed-venous Po-2 and hemoglobin oxygen saturation, arterial and mixed-venous bicarbonate concentrations, and oxygen delivery were significantly lower during liclocaine administration, compared with values determined without lidocaine administration. Mean arterial pressure, central venous pressure, pulmonary artery pressure, systemic and pulmonary vascular resistance indices, PCV, arterial and mixed-venous hemoglobin concentrations, plasma lactate concentration, arterial oxygen concentration, and oxygen extraction ratio were significantly higher during administration of liclocaine, compared with values determined without lidocaine administration. Noxious stimulation did not significantly affect most variables. Conclusions and Clinical Relevance In isoflurane-anesthetized cats, although IV administration of lidocaine significantly decreased inhalant requirements, it appeared to be associated with greater cardiovascular depression than an equipotent dose of isoflurane alone. Administration of liclocaine to reduce isoflurane requirements is not recommended in cats.