Semi-sitting Versus Supine Position in Endoscopic Skull Base Surgery (PosESS)

Semi-sitting Versus Supine Position in Endoscopic Skull Base Surgery (PosESS-Study) - Study Protocol for a Randomized-controlled Single-blinded Superiority Trial

This study is to prospectively compare the standard supine (control group) and the semi-sitting position (head elevation of 30°; intervention group) in endoscopic endonasal pituitary surgery.

The endonasal endoscopic approach (EEA) for pituitary surgery is standardly performed with the patient in supine position (SP). The semi-sitting position (SSP) is routinely used for the traditional microscopic transsphenoidal approach and also for posterior fossa surgery. The SSP results in lower intracranial pressure when compared to the supine position due to decreased venous congestion. As a result, intraoperative bleeding may be reduced, potentially leading to decreased surgical morbidity and improved surgical workflow. Studies during endoscopic sinus surgery have shown a significant reduction of blood loss when the patient is placed in a reverse Trendelenburg position with a head elevation of 30°. This study is to prospectively compare the standard supine (control group) and the semi-sitting position (head elevation of 30°; intervention group) in endoscopic endonasal pituitary surgery.

endoscopic endonasal pituitary surgery, endoscopic skull base surgery, intracranial venous pressure, venous air embolism

Patients will be placed in semi-sitting position. To achieve the semi-sitting position, the patient is placed in supine position. The operating table is then separated and flexed to elevate the torso (angle of 30°). The head, which is fixed in a head clamp, is slightly flexed to bring the floor of the sella right in front of the surgeon and gently rotated toward the operating team.

Intraoperative blood loss, calculated as follow: volume in the suction bag minus volume of rinsing water in Milliliters (ml). The surgery is divided into four steps: 1. endonasal phase, 2. osteodural exposure. 3. sellar stage and 4. skull base defect closure. For each step, the primary outcome will be assessed.

Frequency of interruption of the surgical workflow due to disturbing blood or a bleeding in the surgical field (number)

Frequency of interruption of the surgical workflow due to disturbing blood or a bleeding in the surgical field. This will be assessed by an independent blinded neurosurgeon, who will watch the operative video after the surgery.

MAP will be monitored during the whole surgery using the software Copra ©, which allows a continuous data extraction

Intraoperative assessment of the degree of descent or prolapse of the diaphragma sellae into the sellar cavity (class I to V, according to the classification of Abdelmaksoud et al)

Occurrence of a cerebrospinal fluid (CSF) leak during surgery (assessed by the operating neurosurgeon) (yes/ no)

Occurrence of a cerebrospinal fluid (CSF) leak during surgery (assessed by the operating neurosurgeon)

Surgical ergonomics assessed by the means of a standardized questionnaire. The surgeon will be asked to rate the intensity of neck and arm discomfort and the frequency of surgical flow interruption due to a suboptimal trajectory of the endoscope and the instruments due to the patient Position (1 = no discomfort, 2 = medium discomfort, 3 = high discomfort).

Inclusion Criteria: Patients with a presumed pituitary pathologies who are suitable for endoscopic endonasal surgical resection Exclusion Criteria: Patients with known hemorrhagic or thrombophilic disorders Patients with conditions associated with high central venous pressure: congestive heart failure, pulmonary hypertension, chronic obstructive pulmonary disease (COPD), interstitial lung disease, pregnancy Patients with poor cardiopulmonary condition (unable to perform 4 metabolic equivalents without stopping (climb a flight of stairs))