Santos PS, Gonzaga MS, Araújo MA, Deschk M, de Siqueira CE, Floriano BP, Cancelli CH. Determination of the minimum alveolar concentration of sevoflurane in Holstein steers.
Vet Anaesth Analg 2023;
50:415-420. [PMID:
37407361 DOI:
10.1016/j.vaa.2023.06.001]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 06/03/2023] [Accepted: 06/05/2023] [Indexed: 07/07/2023]
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 ± 1.2 months and weighing 121 ± 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 × 10 ms followed by 2 × 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 ± 0.3%, which corresponds to 2.1 ± 0.3% at sea level.
CONCLUSIONS
Based on the proposed methodology, the MAC of sevoflurane for healthy Holstein steers is 2.1 ± 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.
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