Fachbereich Veterinärmedizin



    Effect of retrobulbar nerve block on heart rate variability during enucleation in horses under general anesthesia (2014)

    Zeitschriftenartikel / wissenschaftlicher Beitrag
    Oel, Carolin
    Gerhards, Hartmut
    Gehlen, Heidrun (WE 17)
    Veterinary Ophthalmology; 17(3) — S. 170–174
    ISSN: 1463-5216
    DOI: 10.1111/vop.12061
    Pubmed: 23738675
    Klinik für Pferde, allgemeine Chirurgie und Radiologie

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    14163 Berlin
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    Abstract / Zusammenfassung

    OBJECTIVE: Analysis of any effect of retrobulbar block during ocular surgery on heart rate variability and oculocardiac reflex. STUDY DESIGN: Prospective study. ANIMAL STUDIED: Horses (n = 16) undergoing eye enucleation due to chronic ophthalmologic diseases. PROCEDURE: Eye enucleation was performed under general anesthesia. The horses were randomly assigned to the first (inhalation anesthesia only, n = 10) or second group (inhalation and local retrobulbar anesthesia, n = 6). The retrobulbar block was performed using 12 mL of mepivacaine hydrochloride 2%. ECG data were taken by a Telemetric ECG before, during, and after surgery. Heart rate variability was analyzed in the time domain as mean heart rate, mean beat-to-beat interval duration, and standard deviation of continuous beat-to-beat intervals. The frequency domain analysis included the low- and high-frequency components of heart rate variability and the sympathovagal balance (low/high frequency). The low frequency represents mainly sympathetic influences on the heart, whereas high frequency is mediated by the parasympathetic tone. RESULTS: All horses without a retrobulbar block showed a significant decrease in the heart rate during traction on the globe and pressure on the orbital fat pad for homoestasis (P = 0.04). Simultaneously, high-frequency power, as an indicator of vagal stimulation, increased significantly. High-frequency and low-frequency power in the retrobulbar block group increased in five horses, and heart rate decreased in only one horse. Both were not significant within the group, but there was a significant difference between both groups relating to the incidence of heart rate decrease occurring at globe traction. CONCLUSIONS AND CLINICAL RELEVANCE: Heart rate variability is a sensitive, non-invasive parameter to obtain sympathovagal stimulations during general anesthesia. The retrobulbar block can prevent heart rate decrease associated with initiation of the oculocardiac reflex.