Analysis of risk factors for venous air embolism in the semisitting position and its impact on outcome in a consecutive series of 740 patients

Abstract

OBJECTIVE Routine use of the semisitting position, which offers several advantages, remains a matter of debate. Venous air embolism (VAE) is a potentially serious complication associated with the semisitting position. In this study, the authors aimed to investigate the safety of the semisitting position by analyzing data over a 20-year period. METHODS The incidence of VAE and its perioperative management were analyzed retrospectively in a consecutive series of 740 patients who underwent surgery between 1996 and 2016. The occurrence of VAE was defined by detection of bubbles on transthoracic Doppler echocardiography (TTDE) or transesophageal echocardiography (TEE) studies, a decrease of end-tidal CO2 (ETCO2) by 4 mm Hg or more, and/or an unexplained drop in systolic arterial blood pressure (≥ 10 mm Hg). From 1996 until 2013 TTDE was used, and from 2013 on TEE was used. The possible risk factors for VAE and its impact on surgical performance were analyzed. RESULTS There were 404 women and 336 men with a mean age at surgery of 49 years (range 1–87 years). Surgery was performed for infratentorial lesions in 709 patients (95.8%), supratentorial lesions in 17 (2.3%), and cervical lesions in 14 (1.9%). The most frequent pathology was vestibular schwannoma. TEE had a higher sensitivity than TTDE. While TEE detected VAE in 40.5% of patients, TTDE had a detection rate of 11.8%. Overall, VAE was detected in 119 patients (16.1%) intraoperatively. In all of these patients, VAE was apparent on TTDE or TEE. Of those, 23 patients also had a decrease of ETCO2, 18 had a drop in blood pressure, and 23 had combined decreases in ETCO2 and blood pressure. VAE was detected in 24% of patients during craniotomy before opening the dura mater, in 67% during tumor resection, and in 9% during wound closure. No risk factors were identified for the occurrence of VAE. Two patients had serious complications due to VAE. Surgical performance in vestibular schwannoma surgery was not affected by the presence of VAE. CONCLUSIONS This study shows that the semisitting position is overall safe and that VAE can be managed effectively. Persistent morbidity is very rare. The authors suggest that the semisitting position should continue to have a place in the standard armamentarium of neurological surgery.

Resection of posterior fossa tumors in the semi-sitting position in children younger than 4 years of age

“…A total of 236 children who were operated on for a brain tumor in our institution over a 15-year period were screened for surgeries of posterior fossa tumors. Inclusion criteria for the present study were (1) surgery in the semi-sitting position and (2) age younger than 4 years at the time of surgery. Demographic and clinical data were analyzed retrospectively according to patients' charts and operative protocols.…”

“…Positioning the patient for cranial tumor surgery is one of the most important steps with a high impact for a successful operation. The semi-sitting position for the resection of posterior fossa tumors has a long history and is an alternative to the prone or the lateral position [1][2][3][4]. It offers several surgical advantages such as easier anatomical orientation, gravity-aided drainage of irrigation and clearer vision, less necessity for suction, avoidance of venous congestion by cerebellar retraction, and reduction of the need for bipolar coagulation [1,[5][6][7].…”

“…The semi-sitting position for the resection of posterior fossa tumors has a long history and is an alternative to the prone or the lateral position [1][2][3][4]. It offers several surgical advantages such as easier anatomical orientation, gravity-aided drainage of irrigation and clearer vision, less necessity for suction, avoidance of venous congestion by cerebellar retraction, and reduction of the need for bipolar coagulation [1,[5][6][7]. It also provides easier access to the aqueduct and to the pineal region especially in tumors located in the midline of the posterior fossa [5,8].…”

“…Nevertheless, the semi-sitting position harbors some risks, with the most dreaded being venous air embolism (VAE) and arterial hypotension [6,13]. VAE may occur in up to 38.6% [14] of surgeries depending on the measures used for its detection and its definition [1,5,6,12,13,15,16]. While the semi-sitting position has been abandoned in many centers because of its potential complications, there has been a renaissance, especially in European countries more recently [1,2,11,12,[17][18][19].…”

“…There is limited experience with the semi-sitting position in children [1,2,4,8,[19][20][21][22] especially in children younger than 4 years of age [1,8,19,23]. Such surgery is a challenge even for an experienced team with regard to the thinness of the skull for rigid fixation [24], the small bodies to be positioned [23], and the particular anesthesiological circumstances [19,22,25].…”