The effect of cervical epidural injection of morphine and the combination of morphine and detomidine on recovery from anesthesia in adult horses.

Overview

• This study investigated whether cervical epidural injections of morphine, alone or combined with detomidine, influence the quality and timing of recovery from general anesthesia in adult horses.
• The results showed that neither morphine nor the combination with detomidine negatively impacted recovery compared to a saline control.

Study Objective

• To evaluate the effect of cervical epidural injection of morphine alone and morphine combined with detomidine on the anesthetic recovery in adult horses.
• The aim was to assess if these treatments altered the quality of recovery or the time taken for various recovery milestones.

Study Design and Methods

• Design: Blinded, randomized, crossover Latin square design, ensuring each horse received all treatments in a randomized order with a washout period.
• Subjects: Six healthy adult horses, average age 9 ± 3 years and weight 471 ± 76 kg.
• Treatments administered during a 1-hour general anesthesia, with a 4-day washout between sessions:
  • S: cervical epidural injection of saline (volume 0.011 mL/kg)
  • M: cervical epidural injection of morphine alone (0.1 mg/kg)
  • MD: cervical epidural injection of morphine (0.1 mg/kg) combined with detomidine (0.01 mg/kg)
• Measures of recovery quality included:
  • Accelerometry-based recovery score (objective movement quality metric)
  • Time to first movement after anesthesia
  • Time to sternal recumbency (when the horse sits up on its chest)
  • Time to standing
  • Number of attempts to stand successfully
• Data were analyzed using a generalized linear mixed model, with significance set at p < 0.05.

Results

• Recovery scores (mean ± SD) were similar across treatments:
  • Saline (S): 24.4 ± 10.0
  • Morphine (M): 23.9 ± 6.7
  • Morphine + Detomidine (MD): 19.9 ± 7.7
  • Overall statistical comparison: p = 0.463, indicating no significant difference.
• Times for recovery milestones (mean ± SD) showed some variation but not statistically significant differences:
  • Time to first movement (minutes):
    • S: 33 ± 16
    • M: 22 ± 18
    • MD: 45 ± 10
  • Time to sternal recumbency (minutes):
    • S: 48 ± 26
    • M: 57 ± 29
    • MD: 69 ± 25
  • Time to standing (minutes):
    • S: 55 ± 20
    • M: 61 ± 28
    • MD: 70 ± 23
• Number of attempts to stand were recorded but not explicitly stated, implying no substantial differences.

Conclusions

• Cervical epidural injection of morphine alone or combined with detomidine does not negatively affect the quality or timing of recovery from general anesthesia in healthy adult horses.
• This suggests these drugs can be used for pain management via cervical epidural routes without compromising anesthetic recovery.
• The findings support the safety and lack of adverse impact on recovery associated with these analgesic techniques in equine anesthesia.