THE USE OF DEXMEDETOMIDINE IN PUNCTURE TECHNIQUES FOR DEGENERATIVE DISEASES OF THE LUMBAR

Objective: To analyze the results of the use of dexmedetomidine (D) in the treatment of patients with degenerative diseases of the lumbar spine using puncture techniques. Methods: The study included 77 patients who underwent surgical puncture for degenerative diseases of the lumbar spine with the use of alpha-2-adrenomimetic D: percutaneous laser denervation of the facet joints (n = 46) and posterolateral transforaminal endoscopic discectomy (n = 31). We assessed: the level of sedation using the Ramsay Sedation Scale (RSS) and the Richmond Agitation Sedation Scale (RASS); intraoperative dynamics of the cardiovascular and respiratory system parameters; the level of pain syndrome according to VAS. Results: A high intraoperative level of sedation was determined, with RASS -2, -3 and Ramsay III, IV; when transferring a patient to a department (in 90 minutes) this parameter was RASS 0 and Ramsay II. There were no significant changes in central hemodynamics and respiratory depression. The minimum level of pain was determined immediately after surgery, at 30 and 60 minutes after surgery, and before transfer to the department (90 minutes): 6 (4;9); 10 (8;12); 12 (9;13); 16 (13;19) respectively. The absence of the need for additional analgesia on the first postoperative day was verified. Conclusion: The use of D significantly reduces the level of pain, while maintaining the necessary verbal contact with the patient, and provides the necessary neurovegetative protection without respiratory depression or lowered hemodynamic parameters during the perioperative period. Level of evidence II; Prognostic Studies Investigating the Effect of a Patient Characteristic on Disease Outcome. Case series, retrospective study.


INTRODUCTION
Puncture methods for the surgical treatment of degenerative diseases of the lumbar spine are less traumatic and less painful methods of surgical correction when compared with traditional methods, enabling earlier return to activity and patient rehabilitation. 1,2 Spine surgeons do not properly take into account the degree of anxiety and the level of pain experienced by patients when performing minimally invasive surgical interventions. [3][4][5] The implementation of a safe perioperative period and the choice of drugs for anesthesia are aimed at the optimal combination of effective sedation with preservation of consciousness and controlled anesthesia. 6,7 There is currently a search for the optimum combination of drugs capable of providing these effects when performing minimally invasive spinal procedures without respiratory depression and intubation in the forced position. Nevertheless, when adverse intraoperative consequences occur, surgical procedures should be discontinued, the patient turned over, and the safety of the respiratory system ensured. 8,9 Also, when conducting surgical puncture treatment, it is important to maintain verbal contact with the patient in order to exclude iatrogenic lesions of neural structures. 10 As a result, insufficient sedation and analgesia are likely to occur, increasing anxiety and pain and the risk of cardiovascular complications.
Dexmedetomidine (D), an imidazoline derivative, is a highly selective agonist of alpha2-adrenoreceptors and has sedative, analgesic, anxiolytic, and sympatholytic properties. 11 The use of D provides a safe depth of mental sedation with no risk of respiratory depression. 12 Most of the drugs used as anesthesia in puncture techniques have several significant drawbacks: cardio-and respiratory depression, a short sedation effect, and the need for additional anesthetics and opioids. 13,14 To reduce the above-mentioned risks and optimize anesthetic support for the implementation of surgical puncture techniques for intraoperative sedation, D has been used since June 2017 at the Center for Neurosurgery of the Irkutsk Railway Clinical Hospital of the Russian Railways.
The purpose of this study was to analyze the results of the use of dexmedetomidine in the treatment of patients with degenerative diseases of the lumbar spine using puncture techniques.

METHODS
A single-center study was conducted. The results were evaluated of the intraoperative and postoperative course of 77 patients operated at the Center for Neurosurgery of the Irkutsk Railway Clinical Hospital of the Russian Railways in the period January 2018 to December 2019. Patients with degenerative diseases of the lumbar spine operated by percutaneous laser denervation of the facet joints (n = 46) and posterior lateral transforaminal endoscopic discectomy (n = 31) were included in the study. The inclusion criteria were ASA classes I-III, patient's ability to understand the visual analogue scale, and tolerability of all drugs used.
In all cases, multimodal anesthesia was performed: D was administered at a dose of 1 μg/kg for 10-15 minutes, followed by intravenous administration with infusomat at a dose of 0.4-0.7 μg/kg/h. Fentanyl was used as additional anesthesia, at a dose of 0.04-0.1 μg/kg/h. The patients' sex, age, height, weight, and body mass index were determined. The efficacy of sedation using D was assessed according to the RASS 15 and Ramsay 16 scales. Intraoperative dynamics of the cardiovascular and respiratory systems (heart rate and blood pressure) and oxygen saturation of hemoglobin (SpO 2 ) were evaluated, and the level of the pain was monitored, according to the visual analogue scale (VAS), before surgery, immediately after surgery, 30 and 60 minutes after surgery, and before transfer to the department (90 minutes).
Statistical processing of the results of the study was carried out using Microsoft Excel and Statistica 8.0. To assess the significance of the differences in sample populations, the criteria for nonparametric statistics were used, and the p < 0.05 was taken as the lower confidence limit. The data are represented by the median and interquartile ranges in the form of Me (25; 75). The following criteria of nonparametric statistics were used: Mann-Whitney (M-U) for intergroup comparison, Wilcoxon (W) for dependent samples, and Pearson's chi-square test (χ2) for binomial characteristics.

RESULTS
General information about the patients studied is presented in Table 1: the patients were mostly male, adults (35-60 years), with high nutritional status (body mass index > 25 kg/m2).
All patients were operated by the same surgical team. The median duration of surgery was 56 (43; 69) min. The use of D enabled intraoperative levels of sedation of RASS -2, -3 and Ramsay -III, IV to be achieved.
The intraoperative changes in the main indices of central hemodynamics are presented in Figures 1 and 2. During the dynamic assessment of the cardiovascular and respiratory parameters, there were no episodes of bradycardia (less than 10% of the initial heart rate), arterial hypotension (less than 10 mm Hg from the initial blood pressure) or decrease in SpO 2 values (less than 98%) registered.
Studying the need for anesthesia, it was found that after the intraoperative infusion of D on the first postoperative day, additional use of analgesics was not required in the vast majority of cases (n = 64, 83.1%). The use of D achieved a fairly high speed of recovery of psychomotor functions -at the moment of transfer to the department (after 90 minutes) the level of sedation corresponded to 0 on the RASS and II on the Ramsay. In such cases, the need for an extended stay in the intensive care unit is not fixed. No cases in our study required extended stays in the intensive care unit.

DISCUSSION
In the past two decades, puncture techniques such as denervation of the facet joints 17,18 and posterolateral transforaminal endoscopic discectomy have been widely used to reduce painful vertebrogenic syndrome. 19,20 Many spinal surgeons indicate the possibility of using local anesthesia in minimally invasive spinal interventions. 20,21 But in some cases, a low individual pain threshold and psychosomatic anxiety do not allow for adequate perioperative anesthesia, requiring use of general anesthesia. 22 In these conditions, the absence of verbal contact with the patient creates a risk of iatrogenic damage to the vascular-neural formations in the presence of anomalies of the latter, as well as due to a change in the normal anatomy in degenerative diseases of the supporting elements of the spinal column.
When performing minimally invasive surgery, not only are sedation and analgesia required, but also maintenance of normal hemodynamic parameters (blood pressure and heart rate). 23 Currently, propofol, benzodiazepines, and opioids are actively used as sedatives. Negative effects of their use include significant disorientation, respiratory depression and changes in hemodynamics. 14,24 In general, this study confirmed the effects of D that have been described by different groups of authors who have analyzed the course of anesthesia during various invasive interventions. 25,26 Unlike most drugs that act through the GABAergic system and cause dose-dependent respiratory depression, D has a sedative effect by means of the adrenergic pathway, and does not change the patterns of external respiration. 27 In therapeutic doses, D provides hemodynamically insignificant sympatholytic effects: it reduces the functional activity of the sinus node, has moderate vasodilation, which helps reduce the intraoperative stress reaction, and prevents the development of arterial hypertension, which is especially important in the presence of concomitant cardiovascular pathology. 28,29 D favorably affects the central nervous system: sedation is achieved without changing the bioelectric activity of the brain under conditions identical to natural sleep; 30 vasodilation is accompanied by an improvement in overall cerebral blood flow, without altering the intracranial pressure. 31 The antinociceptive mechanism of D is mainly associated with correction of the vegetative pain reaction. 32 Adequate anesthesia is a necessary condition for the safety of invasive manipulations, and insufficient anesthesia during surgery can be measured by the need for postoperative analgesia. In this work, we noted a significant decrease in the severity of postoperative pain, as well as a decrease in the need for postoperative administration of analgesics.
The study confirms the properties of D aimed at stabilizing intraoperative hemodynamics, while minimizing cardio-and respiratory depression.
In spinal surgery, experience in use of D is minimal, and is based on studies that emphasize the importance of early awakening of patients for assessment of neurological status. 33,34 In addition, after multilevel fusion, faster functional recovery and decreased blood cytokines and cortisol levels were observed in the group of patients using D, compared with the control group. 35 Thus, taking into account the insufficient amount of information on the use of D for vertebrogenic surgical interventions in the specialized literature, this work is considered relevant.

CONCLUSION
The study showed high efficiency and safety of intraoperative sedation with dexmedetomidine, enabling a significant reduction in pain while maintaining the necessary verbal contact with the patient.
The use of dexmedetomidine provides sufficient analgesia and neurovegetative protection without lowered respiratory or hemodynamic levels during the perioperative period.
Further research is required for comparative analysis of various multimodal anesthesia regimens for the provision of anesthesia in patients with vertebrogenic profile.
All authors declare no potential conflict of interest related to this article.    Median 25%-75% Min-Max After surgery CONTRIBUTIONS OF THE AUTHORS: Each author made significant individual contributions to this manuscript. VAB and VYG were the main contributors to the drafting of the manuscript. VAB, VYG, AAK, performed the surgery and anesthesia, collected patient follow-up data and gathered clinical data. AAK and MYB evaluated the data from the statistical analysis. VAB, VYG, AAK and MYB performed the literature search and review of the manuscript, and contributed to the intellectual concept of the study.