The influence of orthostatic test (or verticalization) on the blood flow through the internal jugular and vertebral veins

Highlights. In the absence of venous pathology during verticalization, there is an increase in venous outflow both through the vertebral veins and through the internal jugular veins. In the absence of venous pathology, the internal jugular veins are the dominant route of venous outflow in clinostasis and orthostasis.Aim. To study the dynamics of venous outflow along the internal jugular veins (IJV) and vertebral veins (VV) during the transition from horizontal to vertical position.Methods. The study included 10 healthy women aged 24±2.91 years. Inclusion criteria were as follows: 1) optimal structure of the venous system, in which both of patient`s IJV are approximately symmetrical in cross-sectional area (CSA) and the intensity of the collapse, CSA of IJV exceeds CSA of the common carotid artery by 2–2.5 times, noticeable efficiency of valves during the Valsalva maneuver; 2) venous pressure (VD) in the brachial vein is 18–20 mm Hg. The exclusion criteria were: 1) a history of any disorders of cerebral circulation, symptoms of venous encephalopathy, vertebrobasilar insufficiency, compression of the neurovascular bundle when exiting the chest, arterial hypertension, any cervical spine pathology, hypertrophy and rigidity of the cervical and nodding muscles, 2) arterial pathology of brachiocephalic/intracranial arteries (stenosis, tortuosity, anomalies of the structure), 3) any cardiac pathology, 4) endocrine diseases. The study involved the method of triplex ultrasound with measurements of the cross-sectional areas of IJV, the diameters of VV, time-averaged mean velocity for volumetric blood flow (TAV) in clinostasis and orthostasis. Changes in volumetric venous outflow during verticalization of patients were evaluated as well.Results. In orthostasis, the mean CSA of IJV decreased from 0.862±0.043 cm2 to 0.19±0.024 cm2 , the mean TAV increased from 6.950±2.373 cm/s to 66,000±6.875 cm/s, the average volumetric blood flow increased from 5.952±2.006 mL/s to 12.425±1.559 mL/s. The mean TAV for VV during verticalization increased from 6,800±2.067 cm/s to 16,000±2.271 cm/s, and the average volumetric blood flow from 0.167±0.051 ml/s to 0.402±0.098 mL/s.Conclusion. In all cases, the volumetric blood flow along IJV dominated the volumetric blood flow along VV in clinostasis and orthostasis. In the absence of venous pathology, the dominant pathway of venous outflow in clinostasis and orthostasis are IJV.