**4. General anesthesia and ANS: control and management in neurosurgery**

### **4.1 Anesthesia depth control (BIS monitoring)**

The key anatomic structures of the central nervous system (CNS) that contribute to the state of consciousness are—the brain stem, the pons, the thalamus (thalamic nuclei), and the brain cortex with their connecting neural pathways [56].

General anesthetics (propofol, sevoflurane, desflurane) inhibit the excitatory arousal pathways originating in the brain stem and pons or potentiate the sleep pathways that control them [57]. The brain stem and pontine nuclei have been known to be essential in maintaining cortical arousal and forming the so-called ascending reticular formation [57].

The most important task of an anesthesiologist during neurosurgical operation is to keep anesthesia depth sufficient for security vegetative stability of the patient

*General Anesthesia and Autonomic Nervous System: Control and Management in Neurosurgery DOI: http://dx.doi.org/10.5772/intechopen.101829*

### **Figure 5.**

*BIS-monitoring (rose line, BIS = 36) during general anesthesia (TIVA) in patient with brain tumor removal (the image is taken from the private archive of I. A. Savvina).*

under the condition of general anesthesia during neurosurgical manipulations especially on the brain stem anatomic structures, cerebral arteries (clipping of cerebral aneurysm), etc. For this purpose, it is necessary to use BIS monitoring. The main component of the BIS monitor is the bispectral analysis, which evaluates the phase relations from a single-channel EEG signal measured from the patient's forehead. The BIS index is a dimensionless number from 0 to 100. For neurosurgery, the optimal means of BIS index is around 40 so during total intravenous anesthesia (TIVA with propofol, opioid μ-agonist fentanyl) as inhalational general anesthesia (sevoflurane, desflurane). Control of the depth of TIVA during brain tumor removal (giant trigeminal schwannoma) is reflected in **Figure 5**.

### **4.2 Intraoperative antinociceptive defense**

Nociceptive stimulation during neurosurgical interventions on the brain, spine and spinal cord, peripheral nerves triggers activation of the sympathetic link of the autonomic nervous system, aseptic systemic inflammatory response [29, 34, 58]. As you know, the actual "pain" receptors are located in the skin, periosteum, and dura mater. Anticipating the development of such a scenario is possible when drugs from the NSAID group are included in the premedication scheme, in particular, ketoprofen, ketonal, lornoxicam [59]; the use of the technique of locoregional anesthesia in neurosurgery [60, 61]. There are both proponents of this approach and its opponents who associate the administration of NSAIDs in the perioperative period in neurosurgical patients with their negative effect on platelet aggregation and additional risks of postoperative hemorrhagic complications [59].

The concept of multimodal multicomponent analgesia in neurosurgical practice finds successful implementation in the form of proactive administration of NSAIDs at the stage of premedication (before the skin incision), locoregional anesthesia using naropin, at the stage of induction and maintenance of anesthesia—opioid analgesic (fentanyl) and α2-adrenergic agonist (clonidine or dexmedetomidine), when suturing a skin wound—paracetamol [53, 62–64].

On the main stage of the neurosurgical operation (brain tumor removing, cerebral aneurysm clipping, spinal hord tumor, AVM removing, etc.) antinociceptive defense is carried out with opioid analgesic μ-agonist fentanyl 3.5–5.0 mcg/kg/h + α2-adrenergic agonist clonidine 0.5 mcg/kg/h or dexmedetomidine 0.2–0.4 mcg/kg/h.

Neurovegetative stabilization with such a method and doses of drugs will be sufficient for cupping of central hemodynamic reactions during neurosurgery [65–69].

## **4.3 Hemodynamic monitoring**

Hemodynamic monitoring is necessary and mandatory part of intraoperative monitoring according to Helsinki Declaration on Patient Safety in Anesthesiology (2010). Noninvasive, invasive hemodynamic monitoring, on the base of technology "PiCCO,"—all options are used in neurosurgery—arterial blood pressure systolic, diastolic, mean (BP), cardiac index (CI), stroke index (SI), global end-diastolic volume index (GEDVI), stroke volume variability (SVV), left ventricular contractility index (LVCI), total peripheral vascular resistance index (TPVRI), intrathoracic blood volume index (ITBVI), extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI) [67, 69–71]. The choice of kind and volume of hemodynamic monitoring in neurosurgery is determined by the patient's condition (ASA classification), operation position, localization of brain tumor, supposed blood loss, etc. The level of neurovegetative stabilization is controlled on the basis of the evaluation of the hemodynamic profile of the patient and depth of anesthesia (**Figure 6**) [71].
