**4.4 Monitoring of neuromuscular conduction**

Monitoring of neuromuscular conduction is mandatory for neurosurgical patients for reliable and deep relaxation because the surgical manipulations on the brain structures and cerebral vessels require absolute immobility and synchronization with apparatus of artificial lung ventilation for warning of the rise of intrathoracic pressure when the scull is still closed (dura mater does not open), especially in the patients with intracranial hypertension. Remember that potentiation of neuromuscular block is possible under the condition of water-electrolytic disorders, acid-base state violations, neuromuscular diseases, hypothermia. Control of residual neuromuscular

### **Figure 6.**

*Intraoperative hemodynamic monitoring during craniofacial block-resection (the image is taken from the private archive of I. A. Savvina). Non-invasive and invasive hemodynamic monitoring on the base of technology "PiCCO": monitor PHILIPS "IntelliVue MX 800" (A); monitor PULSION Medical Systems "PiCCOplus" (B).*

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

block is necessary for decision-making about the extubation of neurosurgical patients in the early postoperative period or the operating room. Musculus adductor pollicis and nervus ulnaris are the most often used for acceleromyography (registration of single twitch (ST); train of four (TOF); post-tetanic count (PTC)).

### **4.5 Intraoperative thermometry**

Intraoperative control of central (rectal, esophageal) and peripheral (skin) temperature is necessary for timely exposure of malignant hyperthermia during inhalational general anesthesia (sevoflurane, for example) and monitoring of balance between heat products and heat dissipation in the patient under the condition of general anesthesia with or without controlled hypothermia. Also, it is necessary when the neurosurgical operation is carried out on the anatomic structures of the third ventricle of the brain and the hypothalamic zone because neurosurgery may cause immediate water-electrolyte disorders and violations of thermoregulation [42].

### **4.6 Variational cardiointervalometry (heart rate variability)**

Variational cardiointervalometry is the noninvasive method of evaluation of the functional state of the cardiovascular system and general condition of the patients and healthy persons. The condition of the vegetative nervous system and mechanisms of regulation of heartbeat is estimated by some statistic, geometric, and special spectral characteristics including R-R intervals, HR, level HR, Baevsky tension index, the balance of the sympathetic and parasympathetic influences (LF/HF), index of centralization (IC), etc. [71, 72]. In neurosurgical patients when calculating the Kerdo index after anesthesia induction and after extubation of patients, a distinct tendency to the state of hypertension was revealed [41]. A significant decrease in heart rate variability was observed in patients with the voluminous formation in the posterior fossa with intracranial hypertension syndrome [50]. It should be noted that the perioperative results of monitoring heart rate variability were obtained using total intravenous anesthesia with the inclusion of α2-adrenergic agonist clonidine, along with dexmedetomidine, used as a component of neurovegetative stabilization in the structure of general anesthesia for neurosurgical interventions on the central nervous system [60, 65, 66, 70, 73, 74]. This method gives the possibility to estimate the prevalence of vegetative tone—sympathetic or parasympathetic or eutonia in neurosurgical patients under the condition of general anesthesia including patients with intracranial hypertension [47–50].

### **4.7 Method of photoplethysmographic evaluation of the perfusion index**

The value of perfusion index PI (N 4–5%) characterizes the volumetric peripheral arterial capillary blood flow [75]. An increase in PI is regarded as excessive perfusion as a result of redistribution of peripheral blood flow and arterioplegia. A decrease in PI values is an early and sensitive sign of adrenergic activity and peripheral vasoconstriction. This indicator is not so informative when assessing the adequacy of anesthesia during the neurosurgical intervention.

The criteria for the adequacy of anesthesiological maintenance in neurosurgery are a volume-stable, moist, pulsating, nonhyperemic brain [67, 70].


#### **Table 2.**

*Complications associated with the position during neurosurgical interventions on the posterior cranial fossa [67].*

### **4.8 Postural circulatory reactions under general anesthesia in neurosurgery**

Postural circulatory reactions under general anesthesia in neurosurgery are the most expressed when it is necessary to change horizontal position on the operating table to the operating position "sitting," pron-position, position on the side, lounge position.

Complications associated with the surgical position during neurosurgical interventions on the posterior cranial fossa [67] are presented in **Table 2**.

It is important to estimate the volemic status of the patient, and if the hypovolemia is obtained to start its correction with intravenous infusion of crystalloids (15 ml/kg) and colloid (5 ml/kg) solutions to avoid hypotension during seating of the patient.

### **4.9 Trigeminocardiac reflex in neurosurgery**

The central subtype of trigeminocardiac reflex arises during intracranial impact on the nerve root, central portion of the trigeminal nerve, gasser knot when deep activation of cardiac vagus branch, and depression of lower cardiac sympathetic nerve are discovered. Usually, it is manifested by bradycardia and arterial hypotension [68, 69, 76, 77]. **Figure 7** shows the giant trigeminal schwannoma (the image is taken from the private archive of I. A. Savvina). The removal of this tumor was

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

### **Figure 7.**

*Giant trigeminal schwannoma (shown by yellow arrow) on CT scan (the image is taken from the private archive of I. A. Savvina).*

### **Figure 8.**

*Pathways of trigeminocardiac reflex [69]: (A) long ciliary nerve; (B) short ciliary nerve; (C) ciliary ganglion; (D) optic nerve; (E) maxillary nerve; (F) winged ganglion; (G) mandibular nerve; (H) auditory ganglion; (1) gasser knot; (2) trigeminal nerve; (3) sensor nucleus of trigeminal nerve; (4) short internuclear fibers; (5) motor nucleus of vagus; and (6) vagus.*

accompanied by the central subtype of trigeminocardiac reflex (bradycardia and arterial hypertension as the variant of central TCR) [69, 77].

**Figure 8** shows the pathways of trigeminocardiac reflex [69].
