Why the study?
Does sevoflurane affect sympathetic activity, somatosympathetic reflexes, and hemodynamics in anesthetized dogs?
Does sevoflurane affect sympathetic activity, somatosympathetic reflexes, and hemodynamics in anesthetized dogs?
Sevoflurane causes a dose-dependent depression of C and A delta nociceptive somatosympathetic reflexes and reduces MAP primarily through decreased SVR at lower concentrations, with additional cardiac depression at higher concentrations.
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Sevoflurane's effects in dogs should not guide human dosing; leaves open translation of dose-dependent reflex and hemodynamic changes to clinical anesthesia.
This study examined the effect of sevoflurane on spontaneous renal sympathetic nerve activity (RSNA), A delta-and C-fiber-mediated somatosympathetic reflexes, and hemodynamic changes in anesthetized dogs. RSNA, and A delta and C reflexes evoked by electrical stimulation of the radial nerve were observed in multifiber recordings of efferent activity in renal sympathetic nerves. Sevoflurane was administered at 1%, 2%, 3%, and 4% end-tidal concentrations for periods of 20 min. The mean A delta reflexes decreased by 20%, 39%, and 54% (P < 0.05 to < 0.01), and the C reflexes decreased by 38%, 62%, and 74% (P < 0.05 to < 0.01) at concentrations of 2%, 3%, and 4%, respectively. The relatively greater effect on C reflexes was significant (P < 0.05) and comparable with the effect of [micro sign]-opioids. There was no change in mean RSNA, heart rate (HR), and cardiac output (CO) up to 3% sevoflurane, but these decreased by 36%, 24%, and 13% (P < 0.05), respectively, at 4% sevoflurane. Sevoflurane 1%-4% caused a virtually linear reduction in systemic vascular resistance (SVR) from 7% (P < 0.05) to 44% (P < 0.05), together with a reduction in mean arterial pressure (MAP) that was significant for concentrations greater than 2%. The results indicate that sevoflurane causes a greater depression of C compared with A delta reflexes, and that the reduction in MAP was entirely due to a decrease in SVR up to 3%, whereas at 4% sevoflurane, reductions in sympathetic activity, HR, and CO also contributed its depressor effect. Implications: The relatively greater depressant effect of sevoflurane on C compared with A delta nociceptive somatosympathetic reflexes is similar to [micro sign]-opioids. The hypotensive effect of sevoflurane was significant at 2% concentration, whereas heart rate, cardiac output and sympathetic activity were reduced only at concentrations greater than 3%. (Anesth Analg 1998;86:1079-83)
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Ma et al. (1998) studied this question.
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