Comparison of Dexmedetomidine-Ketamine-Midazolam and Isoflurane for Anesthesia of Black-tailed Prairie Dogs (Cynomys ludovicianus)

Abstract

Few studies evaluate anesthesia in black-tailed prairie dogs (Cynomys ludovicianus). Isoflurane inhalant anesthesia is used in this species most commonly, but injectable protocols are poorly described. Here we compared the physiologic effects, including anesthetic depth, vital signs, and hematologic changes, of anesthetic protocols using isoflurane or a combination of dexmedetomidine, ketamine, and midazolam in black-tailed prairie dogs. In a randomized, complete crossover study design, intact male black-tailed prairie dogs (n = 9; age, 6 mo) were anesthetized by using a combination of dexmedetomidine (0.25 mg/kg IM), ketamine (40 mg/kg IM), and midazolam (1.5 mg/kg IM). For reversal, atipamezole (0.15 mg/kg) and flumazenil (0.05 mg/kg) were administered 45 min after induction. For comparison, isoflurane was administered at 5% in 100% oxygen at 5 L/min in an anesthetic induction chamber, followed by maintenance isoflurane 2% in 2 L/min oxygen through a tight-fitting facemask for 45 min. Induction and recovery time, respiratory rate, heart rate, body temperature, SpO₂, indirect blood pressure, and reflexes were monitored every 5 min during the anesthetic period. Blood samples for venous blood gases, PCV, and refractometric total protein were obtained from the cranial vena cava at 5 min and 45 min. Both protocols appeared to achieve safe and effective anesthesia. Except for blood pressure, all vital signs differed between the 2 treatments. Isoflurane anesthesia resulted in a slightly longer induction and lower respiratory rate and body temperature but increased likelihood of absent reflexes. DKM anesthesia resulted in a faster induction and less hypothermia but also prolonged recovery and lower heart rate and SpO₂ readings. These findings suggest that isoflurane provides a more stable and consistent anesthetic plane, whereas dexmedetomidine-ketamine-midazolam anesthesia may be an effective alternative for short procedures that require fast induction and limited analgesia.

Figure 1.

Heart rate (mean ± 1 SD) of black-tailed prairie dogs (n = 9) anesthetized with isoflurane (ISO) or dexmedetomidine–ketamine–midazolam (DKM) over 45 min in a randomized, crossover design. Heart rate was significantly (P < 0.05) lower in the DKM treatment group and decreased over time with isoflurane and DKM.

Figure 2.

Respiratory rate (mean ± 1 SD) of black-tailed prairie dogs (n = 9) anesthetized with isoflurane or dexmedetomidine–ketamine–midazolam over 45 min in a randomized, crossover design. Respiratory rate was significantly lower in the isoflurane treatment group but remained stable over time in both groups.

Figure 3.

SpO₂ (mean ± 1 SD) of black-tailed prairie dogs (n = 9) anesthetized with isoflurane or dexmedetomidine–ketamine–midazolam over 45 min in a randomized, crossover design. SpO₂ was significantly lower in the DKM treatment group and increased over time; SpO₂ remained high in the isoflurane treatment group.

Figure 4.

Temperature (mean ± 1 SD) of black-tailed prairie dogs (n = 9) over 45 min while anesthetized with isoflurane or dexmedetomidine–ketamine–midazolam in a randomized, crossover design. Rectal temperature was significantly lower in the isoflurane treatment, and temperature decreased over time in both treatments.

Figure 5.

Mean arterial blood pressure (mean ± 1 SD) of black-tailed prairie dogs (n = 9) anesthetized in a randomized, crossover design with isoflurane or dexmedetomidine-ketamine-midazolam over 45 min. There was no effect of treatment or time observed on indirect MAP.