Internal Jugular Vein Flow in the Sitting Position

Overview

During neurosurgical procedures, patients need to be placed in sitting position for surgical access especially in surgeries in the vertex or posterior fossa. Due gravitational effect of sitting position the flow in IJV may be reduced. Venous air embolism (VAE) is a common complication of sitting position craniotomy and carries high mortality and morbidity. Venous pressure decreases as the head of the patient is raised above the heart. Hence, negative venous pressure in the cerebral venous system promotes entrapment of air in accidental opening of the sinuses. Common methods to prevent VAE in sitting position include increasing the venous pressure by either jugular venous compression and/or increasing the venous pressure by adding positive end expiratory pressure (PEEP). Both these methods can decrease venous return and can lead to brain swelling.. In addition, improper neck position can cause the kinking of the IJV which may lead to decreased venous drainage and increased ICP. This has been shown to be the contributing factor for intraoperative brain swelling and postoperative neck and tongue swelling leading to airway obstruction. Optimal brain perfusion is best in the neutral position of the head, but surgery cannot always be performed with this.

Currently, there are no studies that looked into the IJV flow in sitting position and effect of venous outflow obstruction on the IJV flow. Valsalva maneuver (forced inspiration with closed glottis) and /or compression of internal jugular veins (IJV) are the two commonly used physiological methods that can cause venous outflow obstruction. A custom made neck collar can be used for compression of internal jugular vein and previous investigations have used a similar device in a rat model to demonstrate the protective effects on slosh-mediated brain injury by increasing intracranial blood volume . While the collars have not yet been studied on people for their effectiveness at preventing concussions, many studies have looked at the effect of neck collars on both jugular compression and ICP.. The purpose of this study is to measure the venous blood flow of healthy volunteers by the use of an ultrasound and Doppler velocimetry in sitting position. the investigators will measure the IJV flow on both sides in sitting position at rest and at two conditions of venous outflow obstruction- 1. Neck compression using a custom made collar and 2. During 30 seconds Valsalva maneuver. This study will provide information on the cerebral venous drainage. This information will be very useful in planning and positioning of patients undergoing neurosurgical procedures and to prevent complications from the improper patient position.