Tierärztliche Hochschule Hannover Vergleichende Studie zur

Publikation 2
Discussion
All three anaesthetic regimes investigated in this study were suitable for umbilical
surgery in calves. However, according to VAS assessment, most nociceptive
responses to all stages of surgical intervention occurred during ketamine based
injection anaesthesia. Ketamine, as dissociative anaesthetic agent, is known to
induce good somatic, yet poor visceral analgesia (Carroll & Hartsfield 1996). The
overt responses to exploration of the abdominal cavity in the calves might be a
reflection of this, even though it was used in combination with xylazine. Monitoring of
anaesthetic depth in ketamine based injection anaesthesia is difficult because
protective reflexes are maintained and often the occurrence of purposeful
movements is the only parameter indicating inadequate depth of anaesthesia. In the
current study, ketamine re-doses were often necessary ahead of schedule and it was
difficult to accomplish a constant level of anaesthesia. Respiratory depression after
IV redosing of ketamine, as seen in all calves in this study, have also been described
by other authors (Lin 1996; Carroll & Hartsfield 1996) and may, in the extreme cases
of respiratory arrest, lead to severe problems in the field situation, especially if the
surgeon has no qualified assistance.
Regional anaesthesia like epidural anaesthesia represents a type of local
anaesthesia without any influence on consciousness. Even though epidurally
administered xylazine exerts some systemic effects owing to the absorption of the
drug through the longitudinal epidural veins and possibly the lymphatics (Lee et al.
2001), sedative or hypnotic effects are only mild. Therefore, it is difficult to distinguish
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