Comparison of Opioid Consumption During Target Controlled Infusion (TCI) Guided by Nociception Level Index (NOL) or Standard Care Undergoing Intracranial Tumor Surgery, Randomized Controlled Study

The study will be conducted on 50 patients aged between 18-75 years, with the American Society of Anesthesiologists (ASA) classification II-III, who would undergo intracranial tumor surgery after ethics committee approval (08/09/2020, 2020-15/15) and written consent from the patients. Standard monitoring (invasive arterial monitoring, 5-lead ECG, peripheral oxygen saturation-SpO2) and Bispectral Index Score (BIS) monitoring will be performed in the standard care group (SC; n=25), and NOL index monitoring will be performed in addition to standard monitors in the NOL guided group (NOL-G; n=25).

During TCI, propofol (Schnider) effect-site concentration (Ce) will be titrated to BIS score between 40-60 and remifentanil (Minto) Ce to standard hemodynamic parameters in the SC group and NOL index between 10-25 in the NOL-G group.

In all patients, Systolic, Diastolic and Mean Arterial Pressure (SAP, DAP, MAP), Heart Rate (HR), SpO2, BIS scores will be recorded before induction, intubation, head holder pinning, skin incision, muscle and periosteal dissection, craniotomy, dural incision, tumor excision, dural suturation, muscle and periosteum suturation, skin suturation, and interruption of infusions. In addition, NOL index in the NOL-G group patients will be recorded in all that time.

Hemodynamic parameters, to be administered propofol and remifentanil doses will be compared in two groups. NOL index changes before and after intubation, head holder pinning, skin incision and craniotomy, which are determined as severe noxious stimuli, will be compared with changes in HR.

Traditionally, the hemodynamic reactivity such as increased HR and blood pressure (BP), and/or nocifensive movements in the absence of paralytic agents are clinically considered for the assessment of nociception. The response to nociceptive stimuli is monitored as an increase in sympathetic or a decrease in parasympathetic tone (Guignard, 2006). The sympathetic response generates physiological changes such as increased HR, increased peripheral vasoconstriction, pupillary dilation, and changes in galvanic skin conductance (Guignard, 2006). As the understanding of nociception has grown in the past two decades, the industry has developed various nociception detecting devices based on some of the mentioned parameters.The only multi-parameter device is the Nociception Level (NOL) index (Ledowski, 2019). Evidence suggests the multi-parameter approach may be superior to the single-parameter approach for the assessment of nociceptive pain induced by tonic heat stimuli among healthy volunteers (Treister et al., 2012)