Effects of the Prone and the Sitting Positions on the Brain Oxygenation in Posterior Fossa Surgery

Study Overview
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Brief Summary
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The sitting or prone positions are used for posterior fossa surgery. Although the sitting position may cause hemodynamic instability, venous air embolism, it also provides optimum access to midline lesions, decreases intracranial pressure. The sitting position has not been only used in neurosurgery, it has been also used in the shoulder surgery. The sitting position related hypotension may reduce the cerebral perfusion pressure, therefore may cause cerebral ischemia. The sitting position related cerebral ischemia has been shown in the shoulder surgery. The non invasive cerebral oxymetry (INVOS-Covidien) has been used to measure cerebral oxygen saturation. Some studies has been done to investigate whether the sitting position cause cerebral desaturation or not in the shoulder surgery by non invasive cerebral oxymetry. The study results are controversial. It has been investigated that the effect of the prone position on the cerebral oxygenation in the spine surgery and the investigators found that the prone position may increase cerebral oxygenation. However, all studies have been done in patients without intracranial pathology. We speculate that due to the sitting position reduces the intracranial pressure, it may improve the cerebral oxygenation in the patients have intracranial pathology. Therefore we will compare the sitting and the prone positions effects on the cerebral oxygenation in patients undergoing posterior fossa tumour surgery by non invasive cerebral oxymetry. Method: 62 patients have posterior fossa tumour will include the study. Patients will divide to 2 groups according to the surgical position, the prone (n=31) or the sitting (n=31). Patients heart rate, mean blood pressure (MAP), cerebral oxygen saturation (SctO2), peripheral oxygen saturation (SpO2), BIS values will record before the induction of anesthesia. Five minutes after the standard anesthesia induction all values will record and it will accept as a baseline. After that all these parameters will record in each 3 minutes until the beginning of surgery. Mean while, more than 5 % reduction in SctO2 and more than 20 % reduction in SctO2 and/or MAP will record. As well as, if the SctO2 reduces than 55 and 60 %, it will record.

Detailed Description
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The sitting or prone positions are used for posterior fossa surgery. Although the sitting position may cause significant complications such as including hemodynamic instability, venous air embolism, paradoxical air embolism (PAE), pneumocephalus, peripheral neuropathy, quadriplegia and macroglossia, it also provides optimum access to midline lesions in posterior fossa and cervical spine, improves blood and cerebral spinal fluid drainage, decreases intracranial pressure, lowers airway pressure, and improves access to the endotracheal tube and ability to observe the face for signs of cranial nerves stimulations. The sitting position has not been only used in neurosurgery, it has been also used in the shoulder surgery. The sitting position related hypotension may reduce the cerebral perfusion pressure, therefore may cause cerebral ischemia. The sitting position related cerebral ischemia has been shown in the shoulder surgery. The non invasive cerebral oxymetry (INVOS-Covidien) has been used to measure cerebral oxygen saturation. Some studies has been done to investigate whether the sitting position cause cerebral desaturation or not in the shoulder surgery by non invasive cerebral oxymetry. The study results are controversial. It has been investigated that the effect of the prone position on the cerebral oxygenation in the spine surgery and the investigators found that the prone position may increase cerebral oxygenation. However, all studies have been done in patients without intracranial pathology. We speculate that due to the sitting position reduces the intracranial pressure, it may improve the cerebral oxygenation in the patients have intracranial pathology. Therefore we will compare the sitting and the prone positions effects on the cerebral oxygenation in patients undergoing posterior fossa tumour surgery by non invasive cerebral oxymetry. Method: 62 patients have posterior fossa tumour will include the study. Patients will divide to 2 groups according to the surgical position, the prone (n=31) or the sitting (n=31). Patients heart rate, mean blood pressure (MAP), cerebral oxygen saturation (SctO2), peripheral oxygen saturation (SpO2), BIS values will record before the induction of anesthesia. Five minutes after the standard anesthesia induction all values will record and it will accept as a baseline. After that all these parameters will record in each 3 minutes until the beginning of surgery. Mean while, more than 5 % reduction in SctO2 and more than 20 % reduction in SctO2 and/or MAP will record. As well as, if the SctO2 reduces than 55 and 60 %, it will record.

Official Title
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Effects of the Prone and the Sitting Positions on the Brain Oxygenation in Posterior Fossa Surgery

Conditions
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Infratentorial Neoplasms

Intervention / Treatment
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* Device: SctO2
* Device: BIS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Diagnosis of infratentoril neoplasms Exclusion Criteria: Stroke Diabetes mellitus Chronic obstructive pulmonary disease Anemia

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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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Randomized
Intervention Model: Factorial Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: The sitting<br>The sitting position Device sCtO2 Device BIS | Device: SctO2<br>* The non invasive cerebral oxymetry (INVOS-Covidien) has been used to measure cerebral oxygen saturation.<br>* Other names: INVOS-Covidien;Device: BIS<br>* Bispectral index<br>|
| Active Comparator: The prone<br>The prone position Device sCtO2 Device BIS | Device: SctO2<br>* The non invasive cerebral oxymetry (INVOS-Covidien) has been used to measure cerebral oxygen saturation.<br>* Other names: INVOS-Covidien;Device: BIS<br>* Bispectral index<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral oxygen saturation | After anesthesia induction cerebral oxygen saturation will record in each 3 minutes until the beginning of surgery | Change from baseline cerebral oxygen saturation up to skin incision |