ANI Parasympathetic Monitoring in Neurosurgery

Study Overview
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Brief Summary
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Surgery of large cerebellopontine angle (CPA) tumors (>2 x 2 cm diameter), with compression of the pons exposes the patient to inadvertent parasympathetic nerve stimulation (IPNS) leading to bradycardia and asystole. The analgesia nociception index (ANI) monitor assesses the balance between analgesia and nociception through the detection of parasympathetic tone. ANI >80 generally denotes excessive analgesia (EA). The main objective of this study was to determine whether ANI values for IPNS are different or the same as ANI values for EA. This study also aims at calculating the number of patients with IPNS and EA during surgery of large CPA tumours.

Detailed Description
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Bradycardia and asystole are potential life threatning complications during surgery of large cerebellopontine angle (CPA) tumors (>2 x 2 cm diameter), with compression of the pons.The incidence of such complications are unknown. One of the plausible mechanisms is inadvertent parasympathetic nerve stimulation (IPNS) due to the proximity of this cranial nerve to the CPA tumor. Monitoring parasympathetic nerve activity may provide further insight to the implication of this cranial nerve in the cardiac complications observed during surgery of large CPA tumors. The analgesia nociception index (ANI) monitor assesses the balance between analgesia and nociception through the detection of parasympathetic tone. Despite the abundant clinical reports about this index, to the knowledge of the investigators, only a few studies have been published in the neurological setting. Moreover, there are no data reporting the parasympathetic profile (measured by the ANI monitor) in situations of IPNS and EA. Are these profiles the same or different? Such is the main question this study thrives to answer. Understanding the behavior of parasympathetic nerve activity in this context could help provide the appropriate management strategy. In order to answer this question, participants undergoing elective large CPA tumor surgery were included in this prospective observational study. Standard cardiorespiratory monitoring including heart rate (HR) was done. Target-controlled anesthesia with Propofol and Remifentanil was guided by a bispectral index of 30-40 and an ANI of 50-70 respectively. Data was continuously recorded with event markers at the onset of bradycardia (HR < 45 bpm), asystole and the coincidence of ANI > 80 with Remifentanil site effect > 6 ng.ml-1 (defined as excessive analgesia).

Official Title
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Ability of the Analgesia Nociception Index Monitor to Distinguish Between Excessive Analgesia and Inadvertent Parasympathetic Nerve Stimulation During Surgery of Large Cerebellopontine Angle Tumours

Conditions
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Bradycardia

Intervention / Treatment
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* Device: ANI


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: patients undergoing elective surgery of large cerebellopontine angle tumors Exclusion Criteria: age below 18yr arrhythmia preoperative use of vagolytics, β-blockers and clonidine.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients with large CPA tumors<br>Patients with large cerebellopontine angle tumors (>2 x 2cm) undergoing elective surgery | Device: ANI<br>* ANI profiles during IPNS (bradycardia/asystole) or excessive analgesia. During surgery continuous monitoring of ANI, HR and Remifentanil effect site concentration was done and recorded. Event markers were placed at the onset of bradycardia, asystole and the coincidence of ANI>80 + Remifentanil >6ng/mL). ANI values of 1 min before and 1 min after the event were used for analysis.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Differences in instantaneous ANI (ANIi) values during bradycardia versus ANIi values when Remifentanil effect size concentration >6ng/mL | ANI, HR and Remifentanil effect site concentration were continuously recorded with event markers on the ANI monitor at the onset of bradycardia (HR<45 bpm) or Remifentanil effect site concentration>6ng/mL | ANIi values recorded at Day 1 only during surgery (duration: 4-6 hours) | 
| Differences in the area under the ROC curves between ANI values for IPNS and EA analgesia | ROC curves were built at different ANIi for IPNS or EA | ANIi values recorded at Day 1 only during surgery (duration: 4-6 hours) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentages of IPNS and EA cases | The percentages of IPNS or EA cases on the overall study population were calculated. | Cases observed at Day 1 only during surgery (duration: 4-6 hours) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Analgesia nociception index, Parasympathetic nerve stimulation, Excessive analgesia