Effect of PEEP on Subdural Pressure, Optic Nerve Sheath Diameter, Lung Compliance and Brain Perfusion Pressure

Study Overview
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Brief Summary
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We aim to determine the level of intraoperative PEEP that optimizes lung compliance without causing a rise in subdural pressure and if we can utilize optic nerve sheath diameter measurement as an indicator for ICP while optimizing lung compliance during supratentorial tumor surgeries.

Detailed Description
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Application of positive end-expiratory pressure (PEEP) during general anesthesia minimizes ventilation/perfusion mismatch, intraoperative atelectasis and postoperative pulmonary complications. PEEP application in intracranial surgeries is usually avoided due to the risk of raised intracranial pressure (ICP) leading to decreased cerebral perfusion pressure (CPP). Several studies examine the effects of PEEP on subdural pressure and CPP however none examine how lung compliance is affected at the same time. Ultrasound-guided measurement of optic nerve sheath diameter (ONSD) is an indirect indicator of raised ICP and there is limited literature on the correlation of ONSD and ICP during intracranial surgery. In this study, we aim to determine the level of intraoperative PEEP that optimizes lung compliance without causing a rise in subdural pressure and if we can utilize ONSD measurement as an indicator for ICP while optimizing lung compliance during supratentorial tumor surgeries.

Official Title
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The Effect of Intraoperative Variations in Positive-End Expiratory Pressure on Subdural Pressure, Optic Nerve Sheath Diameter, Lung Compliance and Brain Perfusion Pressure in Supratentorial Tumor Surgery

Conditions
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Supratentorial Neoplasms, Anesthesia, General, Optic Nerve

Intervention / Treatment
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* Procedure: PEEP variations


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Supratentorial tumor Elective surgery American Society of Anesthesiologist Class I, II or III Exclusion Criteria: Midline shift more than 5 mm determined by intracranial imaging Initial subdural pressure higher than 20 mmHg Requiring intravenous mannitol or hypertonic saline treatment before dural opening Congestive heart failure Pulmonary hypertension Sepsis Hypovolemia Obstructive or restrictive lung disease

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 70 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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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Interventional Model Description: After craniotomy, PEEP will be adjusted to 0 cmH2O, 5 cmH2O and 10 cmH2O for 5 minutes each to collect the data
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Supratentorial tumor surgery<br>Patients undergoing elective supratentorial tumor surgery under general anesthesia will be ventilated with positive end-expiratory pressures of 0, 5 and 10 cmH2O after craniotomy. | Procedure: PEEP variations<br>* Patients will be ventilated with a PEEP of 5 cmH2O during induction of anesthesia. After craniotomy, the PEEP will be reduced to 0 cmH2O for 5 minutes and data will be collected at the end of 5 minutes. Next, PEEP will be increased to 5 cmH2O for 5 minutes and data will be collected at the end of 5 minutes. Finally, PEEP will be increased to 10 cmH2O for 5 minutes and data will be collected at the end of 5 minutes.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Subdural pressure | 22G/ 0.9mm catheter will be introduced into subdural space after craniotomy and connected to the transducer for pressure measurement | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 
| Optic nerve sheath diameter (left and right) | Ultrasound-guided measurement with the linear probe. | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mean arterial pressure | Invasive blood pressure monitoring will be done. The transducer will be kept at the same level as the transducer for the subdural pressure, at the level of the external ear canal | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 
| Brain relaxation index | 1: dura is under the cranium, 2: dura is at the level of the cranium, 3: dura is above the cranium 4: dural pulsations ceased | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 
| Arterial blood gases | Arterial oxygen pressure and arterial carbon dioxide pressure will be recorded | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 
| Regional cerebral oxygen saturation | % - measurement taken with INVOS cerebral oximeter | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) | 
| Lung compliance | L/cmH2O - measurement taken from Draeger Dräger Perseus® A500 mechanical ventilator | Measurements will look at the change between 3 timepoints: at 5 minutes with PEEP of 0 cmH2O (T0), then at 5 minutes with PEEP of 5 cmH2O (T5), and finally at 5 minutes with PEEP of 10 cmH2O (T10) |