Objective—To evaluate the effects of ketamine, magnesium sulfate, and their combination on the minimum alveolar concentration (MAC) of isoflurane (ISO-MAC) in goats.
Animals—8 adult goats.
Procedures—Anesthesia was induced with isoflurane delivered via face mask. Goats were intubated and ventilated to maintain normocapnia. After an appropriate equilibration period, baseline MAC (MACB) was determined and the following 4 treatments were administered IV: saline (0.9% NaCl) solution (loading dose [LD], 30 mL/20 min; constant rate infusion [CRI], 60 mL/h), magnesium sulfate (LD, 50 mg/kg; CRI, 10 mg/kg/h), ketamine (LD, 1 mg/kg; CRI, 25 μg/kg/min), and magnesium sulfate (LD, 50 mg/kg; CRI, 10 mg/kg/h) combined with ketamine (LD, 1 mg/kg; CRI, 25 μg/kg/min); then MAC was redetermined.
Results—Ketamine significantly decreased ISOMAC by 28.7 ± 3.7%, and ketamine combined with magnesium sulfate significantly decreased ISOMAC by 21.1 ± 4.1%. Saline solution or magnesium sulfate alone did not significantly change ISOMAC.
Conclusions and Clinical Relevance—Ketamine and ketamine combined with magnesium sulfate, at doses used in the study, decreased the end-tidal isoflurane concentration needed to maintain anesthesia, verifying the clinical impression that ketamine decreases the end-tidal isoflurane concentration needed to maintain surgical anesthesia. Magnesium, at doses used in the study, did not decrease ISOMAC or augment ketamine's effects on ISOMAC.