Determination of the minimum alveolar concentration of sevoflurane in Holstein steers

Author(s)

Santos, Paulo S. P. ; Gonzaga, Max S. ; Araujo, Marcelo A. ; Deschk, Mauricio ; de Siqueira, Carlos E. ; Floriano, Beatriz P. ; Cancelli, Carlos H. B.

• Document type: Journal article
• Source: VETERINARY ANAESTHESIA AND ANALGESIA; v. 50, n. 5, p. 6-pg., 2023-08-25.

Abstract

Objective To determine the minimum alveolar concentration (MAC) of sevoflurane in Holstein steers using electric stimulation.Study design Prospective experimental study.Animals A total of 15 Holstein steers aged 7.3 & PLUSMN; 1.2 months and weighing 121 & PLUSMN; 25 kg.Methods Animals were anesthetized with sevoflurane at 8% in oxygen at 5 L minute -1 via facemask and were intubated with an orotracheal tube of a compatible size. After 15 minutes of stabilization of the initial expired concentration of sevoflurane (FE'Sevo) at 2.6%, electrical stimulation on the thoracic limb was initiated with a sequence of 2 x 10 ms followed by 2 x 3 second electrical currents of 50 V and 50 Hz, 5 seconds apart. Following each stimulus with a negative response, the FE'Sevo was decreased by 0.2% and a 15 minute interval was awaited before the next stimulus. The procedure was repeated until the first FE'Sevo value with a positive motor response was obtained. The FE'Sevo was then increased by 0.1%, followed by a new stimulus, until a negative response was obtained. The value of MAC was calculated as the arithmetic mean between the lowest FE'Sevo associated with a negative motor response and the highest FE'Sevo associated with a positive response.Results The mean MAC for the 15 steers was 2.0 & PLUSMN; 0.3%, which corresponds to 2.1 & PLUSMN; 0.3% at sea level.Conclusions Based on the proposed methodology, the MAC of sevoflurane for healthy Holstein steers is 2.1 & PLUSMN; 0.3% at sea level. Clinical relevance This FE'Sevo value can be used to guide depth of anesthesia in steers weighing approximately 120 kg in clinical practice. (AU)

• FAPESP's process: 16/00405-9 - Minimum alveolar concentration (MAC) of sevoflurane in calves by nasolabial electrical stimulation
• Grantee: Max Santana Gonzaga
• Support Opportunities: Scholarships in Brazil - Scientific Initiation