Background: The placement of subthalamic nucleus (STN) deep brain stimulation (DBS) electrodes can be facilitated by intraoperative microelectrode recording (MER) of the STN. Objectives: Optimal anesthetic management during surgery remains unclear because of a lack of quantitative data of the effect of anesthetics on MER. Therefore, we measured the effects of dexmedetomidine (DEX) on MER measures of the STN commonly taken intraoperatively. Methods: MER from 45 patients was retrospectively compared between patients treated with remifentanil (REMI) alone or both REMI and DEX, which are the 2 main standards of care at our center. The measures examined were population activity, such as root mean square, STN length, and number of passes yielding STN, and the single-neuron measures of firing rate and variability. Results: The addition of DEX does not affect population measures (number of passes: DEX+REMI, n = 68, REMI only, n = 154), or neuronal firing rates (number of neurons: DEX+REMI, n = 64, REMI only, n = 72), but firing rate variability was reduced. Conclusions: In this cohort, population-based measures routinely used for electrode placement in the STN were unaffected by DEX when added to REMI. Neuronal firing rates were also unaffected, but their variability was reduced, even beyond 20 min after cessation.
A 40-year-old achondroplastic patient underwent posterior spinal fusion under general endotracheal anesthesia. Anesthesia was maintained with isoflurane, and sufentanil, dexmedetomidine, and lidocaine infusions. Urine output increased from 150 mL/hr to 950 mL/hr the fourth hour. An increasing serum sodium, low urine-specific gravity, and increased serum osmolarity occurred simultaneously with the polyuria. Within 2 hours of discontinuing the dexmedetomidine infusion urine output greatly decreased. Within 24 hours all signs of the polyuric syndrome resolved spontaneously. Alpha(2) agonists block arginine-vasopressin release and action; however, a polyuric syndrome has not been reported in the human literature.
Based on these experiences, the authors' institution has adopted new guidelines in the setting of thoracic disc herniations that includes pre-operative optimization of volume status, placement of an awake arterial line prior to induction of anesthesia, use of MEP and SSEP electrophysiologic monitoring, careful selection of anesthetic, and aggressive maintenance of MAPs >110 % of preoperative values at all times prior to decompression of the spinal cord.
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